Picture of How to Charge Any USB Device by Riding Your Bike
DC team.jpg
To start off, this project was started when we received a grant from the Lemelson-MIT Program. (Josh, if you're reading this, we love you.)
A team of 6 students and one teacher put this project together, and we have decided to put it on Instructables in hopes of winning a laser cutter, or at least a t-shirt.

What follows, is a compilation of our presentation and my own personal notes. I hope you enjoy this Instructable as much as we did.

I'd also like to thank Limor Fried, creator of the MintyBoost circuit. It played an key role in our project.

Jeff Brookins
Divine Child InvenTeam Member

Step 1: Our original intention...

Picture of Our original intention...
Our original project was to develop a product that used the Faraday Principle to allow runners to charge their iPods while they run. This concept would generate electricity the same way those Faraday flashlights do.
However, we had a problem. To quote my team mate Nick Ciarelli,

"At first we considered using a design similar to one of those shake-up flashlights and converting it so that a runner could strap it on for a run and have energy to charge their iPod or whatever device they use. The shake-up flashlight gets its energy from the interaction of the moving magnetic field of the magnet in the flashlight and the coil of wire wrapped around the tube the magnet slides through. The moving magnetic field causes electrons in the coil to move along the wire, creating an electric current. This current is then stored in a battery, which is then available to use for the flashlight bulb/LED. However, when we calculated how much energy we would be able to get from a run, we determined that it would take a 50-mile run to get enough energy to charge one AA battery. This was unreasonable so we changed our project to the bike system."

We then decided to use a bike-mounted system instead.
Share did you get the minty boost circuit?
sam5221 year ago

hello guys;

i have sun tracker
project, i wanted anyone can help me to know the specifications of my
supercapacitors ( my dc source voltage is 20 volt ) i need to have 12 volt and 1.2 amp from my supercapacitor


.... this supercap is hard to find... does anyone know of a source that will sell ONE ultracap at a time?

try alibaba.com one of thier supplier should be willing todo just that. heres a link 4 them
 I found the capcitor available in quantites of one at www.tecategroup.com/store/index.php
man... SO long it took me to locate these

BCAP0150 - 150F ultra-capacitor Mouser Electronics - yay!

i'll post more later.
skatrun2 years ago
very cool............
ctonks6 years ago
How do you handle surplus power?
name101 ctonks6 years ago
That's What the 140F capacitor was used for. In the graph explains that the surplus power is stored in the Ultra capacitor ~Name101
ac-dc name1016 years ago
Such a capacitor would store power, but will not "handle" surplus. When the load current drops the input voltage will rise and the linear regulator will be dropping more voltage, resulting in a higher heat level. You'd need far more than a capacitor to store the energy, something like a battery of a capacity high enough that it never reaches full charge, and yet this would be an additional drag on the bike, it should not be used because the whole circuit is wrong in the first place.
BC-45 ac-dc3 years ago
would a 3000 farad cap work?
PCfreak ac-dc6 years ago
7.2v RC Battery is Lightweight and ive used one in many applications
name101 ac-dc6 years ago
The way I see this design, The Supercapacitor was not meant to store "Large" amounts of energy but enough to keep the power consistent if the rider was to slow down or stop for a short period of time.. I agree a battery would be able to store a lot more energy than a Capacitor. but the capacitor is short term. Correct me if I'm wrong. ~Name101
ac-dc name1016 years ago
Of course, a supercap is short term. The problem is, a supercap doesn't have enough capacity to *buffer* for regular riding. That means that once the supercap is charged the voltage in the system rises and creates even more heat and loss with the linear regulator.

Let me put it another way. I don't revel in wasting energy but it's not so much a concern when something is AC wall powered. When you are peddling on the other hand, and a design has multiple forms of loss, energy conservation is really good, worth the time to do it right.

The problem was they didn't look at how to get from point A to point B, point A being a human being producing linear movement of a wheel, and point B, producing the desired charge, then finding the best way to get there.

Instead, they reused a design not just suboptimal for the purpose but contraindicated for the input and output.

The way this is set up it would be far better to just strap a battery pack onto a bike to recharge something, or of course to use a proper bike generator, a switching supply circuit that accepts (uses) input over the voltage variations that result from a bike generator, and and output with current regulation and the associated charge control chip complimentary to the battery type being recharged.

I appreciate this is beyond the ability of someone starting out, but at the same time this is what is great about technology today that we have ready-made ICs to do things difficult or lengthly to do with discrete parts. It is good to experiment but it is also good to see when it is redundant work, that each part of the problem can be seen modularly as how to get from point A to point B and that today we have great custom ICs to do these jobs (since when broken down into units, none of the things being done are new electronically).

I think it's great if they had no hands-on experience, to learn from building something like this, BUT to put it out there for others as an example of how to get something done, it is a poor one.
name101 ac-dc6 years ago
Well Personally am new to electronics.

I see that stepping down then stepping the voltage up again is a waste of energy. but when the power supply is so close to a LDO linear regulator I thought Providing consistent energy would be a problem.

You said "supercap is charged the voltage in the system rises and creates even more heat and loss with the linear regulator."

How is this so? I would like to learn from this experience.

I would like to learn how to make this as efficient as possible.

(I'm sorry about the short comment I wrote a big one but pressed cancel instead of post =( )

ac-dc name1016 years ago
With a variable input voltage (6V is not constant) an LDO will be a problem, but even if kept above the LDO regulated voltage it's still a very lossy circuit. With the supercap you are improving charging, but putting more drag on the rider to generate that charge, and by keeping the voltage higher it is continual drag instead of the voltage being allowed to drop below the critical level needed to power the rest of the circuit so the rider has no moments of relief. So it does improve the circuit but it does not meet a different goal in use on a bicycle, plus it adds a lot of weight. With a battery on the other hand, or really I mean a pack of series cells, they serve as a crude but effective enough form of regulation to keep the voltage at roughly the sum of the cells. There is some loss in doing this too, but not as much as use of an LDO. One thing that is not really clear is why either would be needed, charging doesn't have to continue at all moments necessarily. It could be good to even tweak the circuit such that applying the brakes bypasses a current limiter right after the motor so that during braking a higher % of power is produced and more motor drag, then less when not, but it would be a secondary issue, the primary one being that the better solution is none of these supercaps or batteries, to just use a wide input voltage, regulated output switching circuit. I'm not suggesting no capacitors are needed for that, but rather less capacitance, a smaller design with only the parts the regulation stage needs, also built more rugged (leaded parts like capactors don't like vibration much as you'd see on a bike, you can cement/glue/etc them in place or you can pick parts more immune to the environment).
name101 ac-dc6 years ago
Personally. I want to charge my device a constant as possible(GPS device). Once the Supercap is fully charged the Circuit will only draw the current needed to maintain the charge on the device. Correct? When I was doing the Research with my basic knowledge Something similar to this was perfect. I was aware of the energy loss through heat and converting the voltages 2 times is excess but the way I saw it was the voltages(form power source to USB device) are too close to use the LDO linear regulator. IF the hub generator produced 12v for example having a single Linear regulator would be perfect. Simplifying the circuit drastically. If the supercap was replaced with a battery pack for example would the circuit charge the batteries and would the batteries act like a capacitor? From my understanding capacitors have the advantage of being able to charge or discharge incredibly fast while if a battery had the same current draw the battery it self would be damaged. I completely forgot about the environment with my research. I must thank you so much with helping me here. ~Name101
ac-dc name1016 years ago
The generator voltage is not "close" to the LDO regulator necessarily, it depends on the load on it and of course gearing or friction wheel diameter, how fast it is spinning. A genuine 6V bike dynamo goes quite a bit above and below 6V even being designed for the task. That's why it's normally it's normally rated for wattage like 6W or 12W. I'm not saying it's terribly bad to have the supercap except it puts more drag on the bike at the worst possible time, getting started from a dead stop after having discharged. A constant charge isn't really needed, you only need to limit the max voltage and current within what the battery will accept. For example, suppose 20% of the time it wasn't charging, but the rest of the time it was charging at a high enough rate to compensate. The point that I'm attempting to keep drifting back towards is this needs to be seen as an accessory to bicycling, not the primary detail that matters so much as what factors are present while riding. Yes the batteries would charge like a capacitor, the point would mainly be that you can either: A) Have already charged them before the bike ride so they are a renewable portable power pack. B) Shut off the charging circuit before it drains them too much, then turn on again after having gotten up to speed so they aren't putting a high early drag on acceleration. You really don't want a linear regulator, not even an LDO. The voltage from a motor varies quite a lot, to always have it charging you will have to use something larger and create a great deal of heat as well as extra drag riding. The only way to have a small drop before the linear regulator is if you already had a wide input range switching regulator, but if you did then you wouldn't need the linear regulation stage at all. I have already outlined a much better way to do it, for good reason, that it should not be done a different way for bike powered use.
name101 ac-dc6 years ago
Oh. I'm starting to understand. Haha. I suppose I'll keep this in mind when I'm designing future circuits. I did throw myself into the deep end by starting with this projects with very little prior knowledge. Ill Look into what I can do.

Seriously, Thank you so much. =]

ac-dc name1016 years ago
To make it as efficient as possible, to start you would approximate an efficiency, perhaps 80% pulling numbers out of air. Next determine the required charge current for the device, and divide that by 80% or 0.8. Next determine the minimum dropout voltage for the regulation stage, some working familiarity with switching regulator designs helps a lot here, but just to pick a number a run with it until something more is known experimentally let's say 3V dropout across regulation stage. With this much info we know the minimum output voltage a generator will need, and can begin testing generators loaded to the desired output power (current times pre-dropout voltage) to see if they are sufficient. Once one at least capable of this output power is selected, the max and minimum voltage during riding with it powering the same load level will tell us the voltage range the switching subcircuit will have to accept. Next go to a website like Digikey if you don't have a regulation controller in mind yet. Browse through their offerings for a regulation chip capable of the input voltage variations and either fixed output for the device charging, or variable output with components you add to select the target voltage. Study the regulators example datasheet circuits as they provide the basic topology as well as reading any datasheet notes about precautions and requirements for it's rated functionality. Then you are ready to convert a rough sketch of circuit logic blocks into a schematic of electronic component values, and generate a PCB layout. Prior to that you probably also want to have selected a chassis for the circuit board, a vibration resistant mounting, and have therefore determined the dimensions of the PCB and keep-out zones for mounting hardware so you can plan the circuit layout around these dimensions. Obviously there's a bit more to it than described, but it is a start.
mulan20153 years ago
i'm curious to why the strap on shake-charger (original idea) didnt work?
Any help apprciated
I don't understand, why regulate down the voltage to then boost it up, it's nonsense!
lmaclean4 years ago
I have looked at the circuit and I can't see where to put the 140f supercapacitor. Can someone please help me?
importsonly6 years ago
JeffB you should try marking this item, make to usb ports one for a Ipod and one for the mobile phone, I know heaps of people that would buy a simple idea like this.. Good Job :)
not at over >$280 they wont you would be a moron to buy this lol

jeffB considering you have used a ridiculous motor for this project i think the constructive criticism off kagetsujki is quite apt.
if you don't want people to sit on top off a mountain criticizing then don't give them such a big mountain
that is cool would you be able to power a bike light
lovetoride4 years ago
I always wondered about charging my devices (I have a lot of them) while riding my bike.

I bought the Cycle Charger from www.econvergence.net/cyclech.htm because it has a USB port. It works well and starts charging at pretty slow speeds - around 8 mph.

I use it primarily to charge my Blackberry for work.

zoltzerino5 years ago
Why not use a smaller, cheaper, lower power motor and use a gearing system to increase it's RPM from the wheel rim? Similar to those wind-up torches with the handles. :-) Nice one anyway, but pricey.
The torch in question (one that I've dismantled) has a simple 4 diode AC-DC rectifier with a smoothing cap, this is somehow rut through a transistor, this seems to be enough to charge a little 3v button cell. With something a little more flashy, could this be notched up to 5v directly? With or without a Minty Boost.
hey look at what was done in the early seventies in this work on the pancake motor i'm trying to clean up the images but new to that line work
Pancake Motor (how it works).jpgPancake Motor (photo).jpg
here is gimp photo of a pancake motor
A 140F capacitor is just crazy.
i have seen 300 Farad caps
I've seen a 3000F supercapacitor on http://www.wima.com/EN/supercap_r_2.htm
add a transformer, hook it up to a coilgun and watch it blow up a HOUSE! :D
qwerty1565 years ago
Bad circuit, good idea. Take a 2 of those caps in series to make a ~5v Cap. so- Motor gives electricity 5v regulator gives 5v to Super caps. Caps give to deveice
The other thing with the shake up light idea, is that they tend to have a strong magnetic field, that may wipe the contents, or at least mess them up, on any Ipod or MP3 Player that has a harddrive. the flash based ones like the nanos, should be safer.
I dont think that magnetic field would be strong enough. You need a really strong magnetic field to damage data on an hdd, much more then people would think.
revhead wupme6 years ago
i have one of those shake it torch things and i pulled it apart and found that the magnet inside it was VERY powerful! i strugled to full it off the frige door, the only way i was able to get it off was to slide it off the edge of the frige. i dont know much about hard drives and such but it might be possible to corrupt the files with this sort of magnet.
wupme revhead6 years ago
Probably a neodymium magnet. But i still think not strong enough. You gotta remember that a magnetic field of such magnets loses drastical amounts of force when you increase the distance. Also harddrives are somewhat protected from magnet fields. I tryed with neodym magnets how much it actually takes. Now i dont remember what size the magnet was, and how strong he was, but a lot bigger and stronger then the once used in such lights. And the interesting thin, before i had data los... the motor failed completely from the magnetic field. Well ok, thats also a destroyed hdd then, but still interesting ;)
Hard drives have a powerful neodymium magnet within the drive as part of the control mechanism for the read head. They sit RIGHT next to the platters. Wouldn't THAT corrupt data too? It doesn't, your good.
Yeah, but might there be a slight possibility of the other magnet changing the position of the HDD head and making data go corrupt in a bad way ?
slight but the voice coil (the device that controls the arm) sits practically on top of the magnet. Any magnetic interference will have to change the magnetic field at the millimeter scale. I may set up a test with an old HDD if I can get my hands on one.
name101 wupme6 years ago
I put my Ipod classic on a "Magnet bender"(Used to bend sheet metal with the help of a magnetic feild.) While playing music... no hiccup at all.
well, probably doesn't hurt it, but just saying that its probably not a good idea for it to be around it for LONG periods of time. I had a cell phone get screwed up once from one of those
"not a good idea for it to be around it for LONG periods of time." I happen to agree with that :D I was just experementing with my iPod. If it broke i would take it back to apple and claim a new one on warranty claiming harddrive failure :P.
The magnet definitely wouldn't be strong enough to wipe the hard drive, although you might worry about the screen.
It takes a LOT of gauss to even slightly corrupt a couple of sectors on a hard drive.
adeb25 years ago
I agree with dirty valentine, a low dropout 5v regulator is much more efficient. I've build a unit to output 5 Volt 500 mA on USB cable to charge my Phone / GPS / PDA from a 6Volts, 3Watts HUB dynamo using just that. Of course with an additional bridge rectifier and a couple of capacitors. Have a look: http://www.arenddeboer.com/bike-mounted-usb-charger/
Shut Up Now6 years ago
all this electrical work is way over my head..when do people typically learn how to read schematics and work out big circuits...im just starting high school so thats why i am wondering..
That's about the right time. Start by getting books out of the library, and reading. Read up on anything electrical and electronic related, because it all helps. Take any courses that are offered in school; I did a correspondence course "Electricity 11" since it wasn't offered at my school. It gave me a good grounding in electrical basics. Horowitz & Hill's "The Art Of Electronics" is maybe the single best book. You just might find a PDF copy on a p2p network.
thanks guys, i hadn't even thought of the library. i will look into courses offered at my school in future years.
621.381 if they use that numbering system is where most of the electronics books hide. There will be others in the rockets/robot section nearby (past the automotive books). University/college libraries are good too, and they'll sometimes have bound copies of electronics hobby magazine back issues. If your own school doesn't offer a course like "Electricity 11", your state/provincial school system may do it as a correspondence or online course. (Like they do for kids that are home-schooled.) P2P networks are also infested with illegal copies of some electronics magazines. If you're not careful, you might find CDROM collections of entire years of Elektor. Or individual PDF issues of "circuit cellar ink", "Nuts and Volts", "Everyday Practical Electronics" aka EPE. It's just awful. Unless it's legal where you live. The Elektor back issues are good sources of high quality (usually professionally designed, so sometimes over-complicated) projects and information.
Most public libraries have access to databases of magazine and journal articles.  For example, I can find full-text articles from Popular Electronics in .pdf format, which I can then print, e-mail, or save to disk.  Ask your librarian for help.

Basically, it's the same thing only, you know, legal. :-)
:) I'm an engineer, and I never got a schematic reading course! You just grab some, and start to figure out what is what. Kind of like reading a map - most people don't get taught how, they just grab one, and figure it out! There are some courses on the standards used, but even they assume you can read the schematic, and focus more on the layouts and labelling. The best way to do it, is to start looking at the simplest schematics you can find, and try and figure out what it would mean in the "real" world. The best thing is to build a couple things from schematics - that drives the points home real fast. Radio Shack used to sell small project books (not sure if they still do), but that's where I started learning. They had simple, easy-to-build step-by-step instructions with simple schematics, and explanations of the schematics. I'd recommend them as a starter, even over more advanced books, because you can build directly from the schematic, and learn quickly!
As soon as you're ready! I think it's never too early or late to start... might help to have good teachers/experienced people who can help you, but you can learn a lot from books... pay attention in physics class, learn about electrons and electromagnetic fields (which requires vector calculus, you see why it can take a while). I think most people really begin to explore these ideas deeply in COLLEGE. But start whenever you get a chance, you can always learn.
Stubloke5 years ago
Hiya, i want to replicate this circuit for use on my bike, but im a bit confused. The step by step instructions mention components that are not on the circuit diagram, and also the circuit diagram doesnt show the ultracapacitor on it. Could you just clarify what components are needed in your circuit (not the mintyboost circuit). By the way im going to be using the mintyboost v2.0.

Any help would be much appreciated.

Thanks in advance
The supercap post ride charge is a fun idea but who would actually leave their ipod on their bike while not riding? security issues.
 if you are talking about how it charges even if you are not moving thats so if you are stopped it still charges, not to leave it on there when you are done
gamal kotp5 years ago
i am habye thank fo all
I've got the added task of recifying the output of the source, as it's actually an AC alternator, as opposed to a DC generator, or dynamo - which seems to be the subject of this instructable.

At least a couple of companies (Shimano being one of them) make these alternators which are built into the hub of the front wheel. Mine puts out a fairly steady 6vac at speed, but is slews to 0v at stop.

Has anyone addressed this previously?

I really like this instructable, but the circuit is not optimal. Stepping down from 6V to 2.5V with a linear regulator such as the LM338 is inefficient. In this case only about 42% of the power from the generator will make it to the Minty Boost circuit. The Boost circuit will have further losses lowering the efficiency down even more. The circuit will no doubt work but it is not optimal.

If the generator really puts out 6V, then a simple 5V output Low Drop-Out (LDO) regulator such as the Linear Technology LT1963A (http://www.linear.com/pc/productDetail.jsp?navId=H0,C1,C1003,C1040,C1055,P1879) could be used to drive pin 1 of the USB directly. In this case about 83% of the generator power would make it to USB device. The USB device would charge twice as fast, and the circuit cost and complexity is significantly reduced.

If the generator typically puts out less than 5V under load, a 5V output Buck-Boost converter could be used. This would provide for further efficiency improvement. I don't feel the added complexity and cost is justified if the generator can put out more than 5V under load though.
 I actually was thinking the same type of thing, but i am a newbie with all this stuff, I was wondering if a capacitor would be good tho, so that if the bike comes to a stop, the charging wont stop, i feel like that may hurt the battery to stop and go, is it?
I=C*dV/dt is the equation for a capacitor where I=current, C=capacitance and dV/dt is the change in voltage with time. rearranging the equation you get: C=I*dt/dV. If you are riding along and getting 6V out of the generator then suddenly stop, your capacitor will be charged to 6V. If a linear regulator is used as I suggested above It will start dropping out around 5V, and most LiIon chargers will stop charging around 4V. Thus best case you can only discharge the input capacitor from 6V to 4V (dV=2V). As for dt, that depends on how long you plan to be stopped. Lets assume you want to stop for 10seconds (dt=10s). Most LiIon chargers charge at 100mA or 500mA. I'll assume the best case (I=100mA). With this information we can figure out what size cap we need: C=100mA*10s/2V=0.5F. 0.5F is a REALLY big cap and would only buy you a best case stopping time of 10seconds.

Most likely any hand held electronics you buy today (cell phone, media player, etc) will have a LiIon type battery. LiIon batteries do not like to be overcharged. If overcharged they will start to loose capacity (best case) or can even burst into flames (worst case). The good news is that most quality electronics have built in protection circuitry that keep from overcharging the battery. I have not heard of any issues with starting and stopping charging. In fact some quality chargers do just that to measure the Equivelant Series Resistance (ESR) of the battery during the charging process.  Hope that helps. 
 thanks for the help...another idea...  if you havent already seen the 'contactless dynamo' bike light instructable, I was wondering if it would be possible to use that idea and your info to create a USB charger instead of with a motor...im not sure how much output voltage the contactless magent generator creates though, but I think this would be a better idea
Contactless induction can certainly be made to work. There are a lot of variables and I do not have much experience with this type of generator so I am not sure if the 'contactless dynamo' instructable will work in this application. My feeling is that the magnets turning at the rate of the wheel will be too slow and too far away from the coils to generate enough power.  FYI - it is really power that you are interested in and not voltage. My guess is that the peak voltage is probably high enough open circuit, but as soon as a load is applied (i.e. while charging) the voltage will collapse and charging will stop. To really make this work you will probably need an inductorless motor geared up off the wheel or chain to produce enough power to sustain charging.
gotcha...would they be good with just led lights tho? and maybe a stepper motor to charge?
Not sure, as I said I do not have much experience with generators, just a basic understanding of how they work. You would have to experiment or seek out knowledge elsewhere. Good luck.
Yey, constructive criticism! : ) would've been nice to have some from ac-dc.
Water Child5 years ago
I love this instructable, most likely ill be using it for life, anyway would it be illegal if i could use this fro my science fair project? there are no winners and no prizes its an elementary science fair for energy and i really lik this idea, i am a polite kid os i have to ask for your permission
advante5 years ago
It's hard to find the materials in this country which is one of ASEAN countries.
Cause I lived in Indonesia... If I go to an electronic markets where the items are in so many kinds, the electronic stores are traditional electronic stores (dirty, old building, simple). It sells LEDs, Voltage stabilizer, UPS, antenna, audio devices (not exclusive), transistors, transformator, etc.
advante5 years ago
I need 4.9 volt for my Sony Ericsson phone. Does it matter if over-voltage 0.1 volt? Cause 0.1 volt is matter for computer's processor. Please give a reply on externalleon@gmail.com
Jodex advante5 years ago
You CAN always charge with a lot higher voltage than your battery needs. BUT if you use enough big voltage your battery MAY explode. But couple of volts doesn't matter.. Except LiPos may be bit different.. Sorry for the words written with BIG letters : D
jules15 advante5 years ago
no man, thats fine
PCfreak6 years ago
your "PVC Pill" Just Gave me an Idea for a bike project Thx Ps. its not a pipe bomb either, to those that were probably thinking
kd0afk6 years ago
How about a parts list for the electronic components. And many of us can't afford a charging motor that costs more than our iPod, how about discussing using a bicycle generator.
Now please design one for my unicycle. Then ill be happier, still, good job.
lr10cent6 years ago
If I was going to do a motor, I'd consider one of the brushless motors used for electric model airplanes. They're really cheap now. Maybe $10 from some sources. What about putting a coil on the bike and a bunch of strong magnets on the wheel? If you set them up so the gap was very small, that ought to generate some power. I'm not sure how to evaluate the peak voltage, though. Maybe with a capacitor that's ridiculously high voltage, and a diode. Also, one could put a micro switch in the brake lever which would turn on the device only when braking. Even better, have a reed switch on the cranks with a delay, so the device would turn on whenever you weren't pedaling. I think this has real promise for a headlight generator, along with a big capacitor or a small battery.
I was thinking the magnet and coil thing myself. Although that may only work well at high speeds.
It wouldn't have to be all that high speed, I think. You can put the magnet pretty far out on the wheel, if you need to. Not sure about sizes, but you can count on something like 8 or 10 mph if you put it far out enough. I think that's comparable or larger than what goes on in some generators. If you look at some of the wind generator designs, I think it probably wouldn't be that hard to do. I think some of them have direct drive, and in a 15 or 20 mph wind the tip speed of the prop is probably under 100 mph, or certainly under 200 mph. If the generator has a tenth the radius of the prop, then you have similar speeds.
The rim of the wheel has a tangential velocity equal to the forward speed of the bike itself... think of the axle moving relative to the ground, then think of the ground moving relative to the axle, you see the tire (touching ground) must be moving at the same speed relative to the axle, as the axle relative to the ground. (You only even need Gallilean relativity for this, hehe.) So 20 to 30 mph?
Um, I think you're overlooking something. The coil has to be mounted on the bike, not the ground. And the magnet probably can't be right on the rim unless we also have disk or drum brakes. So you'll only see a large fraction of the bike's speed, not double that. And we'd like this to work even for people who ride slowly, or in the Midwest (i.e. without a bunch of high speed downhill runs). I average 12 to 15mph depending on the time of year and how much I've been riding, and I know there are slower riders. So let's say 80 percent of 10 or 12mph. That's how I got 8 or 10mph min. On the other hand, if you ride a minimum of 25mph, then you're right. For you. Perhaps if you revealed your real name we'd recognize you from the Tour de France?
Perhaps we could have a small wheel near the rim, and attach a magnet to it, so that the magnet spins inside a coil of wire...
Sounds like a regular bike generator, to me. Of course that means we know it would work. Or an inrunner brushless motor meets this description pretty well. But I've used bike generators that use a friction wheel to pick up power from the bike's regular wheel. They can slip when wet, and even when dry if not lined up right can cause problems by sliding, like, if they're against a tire, wearing away the sidewall.
knektek6 years ago
If i was going out cycling on a sunny day, why not attatch a solar panel?
Because a generator can produce more power for less money? A 2 watt solar panel is something like $50, and only does 2 watts under ideal conditions. And a sketch monkey might steal it off your bike if you leave it parked. A standard bicycle light generator will provide at least 5 watts, rain or shine, and since it is AC, you can use a transformer to efficiently convert it to a higher or lower voltage if needed.
False, a transformer (alone) is not even close to efficient conversion. Typically a transformer alone (if high quality and carefully selected, IE- custom made for the job at high cost) is about 60% efficient.
Transformers can be very efficient if designed correctly. Your typical wall-wart transformer is not very efficient (<85%) because resistive wire and cheep transformer cores are used. But good tranformers can be designed that are more than 90% efficient. http://en.wikipedia.org/wiki/Transformer Good transformer design requires knowledge and skill that is beyond most electronic hobbiests. I design power supplies for a living so I have significant knowledge in this area.

I disagree with your assertion that this project should not have been posted because it is not optimal. The great thing about posting to the world is the learning that is achieved by the comments that are posted. You yourself have provided many good comments that others have had a chance to learn from. This never would have happened if this project was not posted. Learning from mistakes can be the greatest teacher of all. Besides if every post had to be optimal there would be very few posts to this site (mine included).

Additionally you are judging this post to your standards. You obviously would have designed this project very differently and would not be happy with the project as designed, but these kids actually took the time to creat something that I have not doubt worked in the end. That was probably very rewarding for them and in itself worth all the time, cost and effort.

I applaude the effort of anyone who takes the time to post their project to the world. To do so makes you vonerable to the judgement of other, but allows other to learn from what you have done, as well as provide a feedback forum for learning and further improvements.
In this application, a transformer cannot be close to 90% efficient. No design will change this. Even switching PSU that use very high frequency and small transformer cores are seldom reaching 90% and we weren't talking about those. Linking to a wiki that does not consider the aspects of this project, as a kind of proof, is in error. The article itself is in error with the suggestion of 85%, I recommend you measure the efficiency of the best small transformer suited for this project, it will not be 85%. If you do design small mobile PSU, you should know this, or perhaps you are designing something else and just assumed? I did not claim the problem was it being "not optimal", the problem is it is far far from optimal, that it is simply the wrong way to get the job done. If you design PSU, you should know this plainly, but I am starting to think you don't design PSU and just made up that to seem knowledgeable on the topic. Remember that multiple other people had expressed similar concerns about the project, those who know are all drifting towards the same conclusion about dropping the voltage, then boosting it, and use of a linear regulator. However the circuit should have an inductive element, whether a transformer in the other sense of part of a switching circuit, but definitely not to boost voltage by itself. It would be far better to just use a basic AC dynamo with a voltage doubler, that would cause a duty cycle high enough a typical buck switching supply would suffice, and be smaller, lighter, and more efficient than a transformer alone, let alone the other losses like the linear regulation stage. There is certainly more than one way to skin a cat, but it can also be said there is a right way and a wrong way to do some things. It is important to weigh the merits of different designs, what penalties there are, because the end goal can't be just to charge something, it is to charge something riding a bike! As a learning exercise, this project was an introduction but now it is time to see it for what it is, not fit for the intended purpose due to what many here realize is an abandonment of the desirable attributes in both effect on the use of the bicycle and waste of power and size. As I mentioned previously the whole switching circuit would be lighter, probably smaller than only the heatsink needed for a linear regulator to keep it cool enough for longer term function. It also creates heat that has to be dealt with, a heat resistant chassis and/or potential to burn the rider. It's real easy to ignore such things, but when you put a project out there for the general public you have to think ahead about some kid building something and not understanding the consequences. That's why I mention them, because oversimplifying something is not always good, the goal of man should be to strive for the best result possible within reason. If it's worth doing, it's worth doing right.
Kryptik6 years ago
Why did you go with such an expensive motor? A DC motor out of a any small toy should generate enough power when spun.
infomet6 years ago
Dear Jeff, You need to grow up. Kagetsuki was right on and not offensive, in my opinion. Engineering is engineering and feelings don't count. This is a fine project, stupidly implemented. If you are going to do electronic projects, you should have a competent advisor involved. There are MANY little DC motors that would be fine, but you didn't bother looking for one. The bike dynamos are fine, but your rubber tired pickup wheel is better than their toothed one that runs on the tire. They usually have a latch to facilitate taking them off the wheel when not needed. The point here is that you have to DESIGN the wheel diameter/motor combination to produce the current you need at the speeds you expect to ride. This will dictate a fairly high voltage permanent magnet motor and a regulator to produce the proper charge voltage AND CURRENT. At high speed, you'll be wasting some energy because of the high voltage produced, but at low speed you'll still be charging. You also need a current limiter in the circuit, because really dead batteries will draw excessive charge current if placed across the normal full charge float voltage. No doubt the commercial charge circuit does all this, but it might be missed by someone starting from scratch. More importantly, the dynamos are AC generators, so using one would require a bridge rectifier before the voltage regulator. And what's the point of the supercap? If you are making short trips, it will indeed produce more total charge (although not a lot), but if the trips are long enough to charge the device, then it's redundant. BTW, this fine idea could be used to produce chargers for your laptop, portable radio, or TAZER gun, or flashlight, with minor modifications. Best wishes from a very old engineer with many mistakes to his credit So there you go. $10 motor/dynamo, 50 cent rectifier (maybe), $5 regulator parts, and $4.50 slush fund for extras or beer. Then you get a reasonable design, learn something, and maybe a beer.
name101 infomet6 years ago
I personally thought that the Supercap was used to keep the power consistent if the rider was to stop at a traffic light (for example). Dynamos can be brought in AC or DC versions I thought. ~Name101
owf6 years ago
This is EXACTLY what I need for my bike, but connected to a dynamo. I have the legendary Schmidt hub dynamo (a true marvel of German engineering) with unnoticeable drag, and would love a way to use that to charge any USB-powered device.
gabrielG26 years ago
Electronically talking, you guys project is overwhelming in size, you really don't need all that thing to make it happen... Starting by the wires and the filter capacitor on the power supply, and the regulator too! you could use thinner wires, a lower voltage filter capacitor, and a LM350 instead of a LM338. the power supply should be re-drawn too, by using a rectifier bridge to send DC to the DC-DC converter (the MintyBoost). anyway, the idea is really nice! nice job you guys did. Greetings from Brazil!
Cool project. I also participated in Inventeams back in 2006. We built the HEGU, the Hybrid Electric Generation Unit.
Hirtshals6 years ago
Their ia already a solution using a bicycle hub dynamo + cable, produced in Australia. http://www.pedalpower.com.au/ . I have used it with my Nokia N95 and it works well. It works with different devices.

Andreas Hirtshals /Denmark
capricorn16 years ago
agreed. highly inefficient. the key is though that you don't get 6V the whole time. I think you should just be using a switch mode design that can take any voltage and output 5V. Any as in ~1-12, these circuits are easy to find online. This way, you would be at about 85-90% efficiency.
Why do you drop the 6v from the motor to 2v then bump it back up to 5v? Why not just charge 3 of the ultracaps in series then regulate it (or zener diode? USB devices are pretty tolerant...) down to 5v?
luvit6 years ago
you owe me a new ipod touch.
danlab luvit6 years ago
Why would he owe you a new ipod if you broke it...
ramakant7 years ago
can you tell me please how can i make a usb charger which can charge my phone from the duracell batteries/anyother thanks in advance
The charger you charge your phone with will have an output voltage listed on it. You simply need to match that output voltage. You can do this many ways, but the simplest is simply to use a voltage regulator. Most regulators give example schematics in their data sheets. A simple battery-regulator(with capacitors on input and output!)-output jack circuit consists of only a few components and should be simple enough for even an amateur to assemble. The problem here is if you are using non-rechargeable batteries you're probably going to be very dis-satisfied with the cost to performance ratio of this.
Hi again Kagetsuki, I followed your instructions, and the circuit worked well when connected to a transformer. I made my own dynamo and it has an output of 54 volts. I put in a diode to convert it to DC. However, when I connect the circuit to the dynamo, the voltage between the two drops down to 1.7 volts. pedaling also becomes a bit more difficult and the dynamo gets extremely hot. do you have an explanation and solution for this? Hoping for your most favorable reply. Thanks in advance!
Are you saying the dynamo was showing 54V when you metered it unconnected to the circuit? Or that it has a maximum rated output of 54V? Reguardless, one thing to consider is the fact you are dealing with fields here, and fields have some interesting physical rules. To illustrate this, take a look at a circuit called a "boost converter" (http://en.wikipedia.org/wiki/Boost_converter). Also consider that a large part of the dynamo is a very large coil system. Essentially when you have a coil feeding out into some sort of capacitative body, and that body has been completely charged at a particular voltage, the coil will increase its output voltage in order to release the energy from its collapsing field. This is a fairly simplified explanation of how it all works, but because of this measuring the voltage output of an isolated coil system usually doesn't indicate much other than the instantaneous voltage potential, which will decline instantly when the coil is connected. Because of this, the drop to 1.7V isn't necessarily unexpected.

As for pedaling getting harder, that's basically expected as you are now attempting to generate power at the same time. However, you noted the dynamo was getting hot, which indicates to me the dynamo is producing so much power and the attached system is using so little it is being forced to burn off the excess and furthermore since it can't pump any more power out of itself easily is imposing physical resistance. In other words, your dynamo may be too powerful! To diagnose if this is true, try adding a whole bunch of loads which will happily waste power quickly, such as lights (bulbs, not LEDs). If after adding those your pedaling gets easier and your dynamo stops producing as much heat then you have your solution at hand: add chargers, lights, etc. OR simply an external load to eat up the extra energy like a high tolerance resistor (maybe ceramic, perhaps with a heat sync).

If after connecting extra loads the dynamo still gets so hot and it is still so hard to pedal tell me and I'll rethink the situation to see if I can figure out why and how to fix it.
Hi Kagetsuki, Sorry I had not been clear the first time. I really appreciate the time and effort you put into this. I’ve decreased the number of coils to the dynamo to lower the voltage output. Temperature then went down to a manageable level. I’m adding some diagrams and illustrations to try to explain myself more clearly. Figure 1 shows dynamo output (14v AC) Figure 2 shows the output with a diode (6v DC) Figure 3 shows the output with a diode and capacitor (15v DC) Figure 4 shows the voltage drop when the circuit is added (1.5v DC) Thanks in advance!
When you say you reduced the number of coils to the dynamo what is it exactly you are talking about? I may have been unclear, as the coils I was talking about were the coils within they dynamo. Does your dynamo have multiple leads perhaps? The voltages you are reporting in figure 1, 2, and 3 are all perfectly acceptable for this system, though I must ask did you take these measurements with a constantly moving dynamo or did you move the dynamo to charge then measure everything at rest? As for the voltage dropping to 1.5V after connecting the circuit, if you had the dynamo at rest then that's to be expected as your charger as taken the charge and used it. I'm a bit curious as to the layout of your voltage regulation/charger system, but instructables has shrunk the image too much to read it. Depending on the configuration of your charger you may be able to omit the diode, but from what I can make out it looks like you are connected primarily to a regulator and a diode would definitely not hurt in that case. Also, do you have any reports on how adding loads (like lights, etc.) in parallel to the charger affects the heat of the dynamo? Running the dynamo with the circuit connected and seeing if it is constantly using all the power you can throw at it would be a good idea, and if it is using all the power you throw at it then lack of power draw from the connected circuit would almost certainly not be the cause of they dynamo heat and thusly adding additional loads would not help the heat. If that's the case and the dynamo is still getting extremely hot there may be some separate problem. If you have a datasheet for the dynamo it may list a normalized pattern of the heat coming off the dynamo at different work units, checking the performance of your dynamo against those numbers will help you determine if your dynamo is operating abnormally/you have connected it improperly or if in fact it is operating normally and is supposed to be that temperature (some components, especially electro-mechanical and mechatronic will produce a lot of heat under normal operation).
Hi! 1. When you say you reduced the number of coils to the dynamo what is it exactly you are talking about? The coils within the dynamo. 2. Does your dynamo have multiple leads perhaps? Sorry, no. 3. The voltages you are reporting in figure 1, 2, and 3 are all perfectly acceptable for this system, though I must ask did you take these measurements with a constantly moving dynamo or did you move the dynamo to charge then measure everything at rest? Constantly moving. 4. As for the voltage dropping to 1.5V after connecting the circuit, if you had the dynamo at rest then that's to be expected as your charger as taken the charge and used it. I'm a bit curious as to the layout of your voltage regulation/charger system, but instructable has shrunk the image too much to read it. The shrunken circuit is actually the circuit designed in this instructable. 5. Also, do you have any reports on how adding loads (like lights, etc.) in parallel to the charger affects the heat of the dynamo? Adding a load drops the voltage to zero. And I only added a 5 volt bulb. 6. I tried increasing the voltage by winding up more coils in the dynamo then added a rectifier as described somewhere in this forum. I got a voltage of 130vDC but when I added the 5 volt bulb, everything dropped to zero. I read something somewhere about high voltage, no amps. Can you post a solution or point me to a site with a circuit where this was resolved? Believe me; I’ve tried looking to no avail. Sorry for the bother. I’m just starting to explore electronics, and beginning to really love it. Thought this was a good circuit to start with, plus a DIY dynamo. Thanks again for the prompt reply.
Basically it sounds like everything is performing properly then. The thing about the high voltage is that it is in fact a high voltage, as much as voltage is simple a measure of instantaneous potential. Common static electricity buildup that gives you a little shock is 10's of thousands of volts of instantaneous electricity, but it dissipates immediately and with basically no harm done (to us). The reason for this is while there is a large potential, there isn't a constant source to back that up. If you were to touch a 10kV source that was capable of sustaining that potential (in other words deliver a constant sustained current without dropping its voltage) you would most certainly be dead now. I guess you could think about it this way, voltage is the size of a truck. A very large truck can do some serious damage when it hits something. But just because the truck is massive doesn't mean it has enough fuel to really take it anywhere, it could have almost no fuel at all, like our static electricity, so it can only run so far as to tap you. Unfortunately for this analogy, our electric potential is disappearing as it gets used up, so it would be like the truck all the sudden shrinking as it runs out of fuel. Anyway, the voltage dropping is simply what happens when electricity from a non-constant source is used. In this case the voltage readings you are getting are sort of a fuzzy-math representation of the potential coming off the coils and, once connected, the coils couldn't hope to sustain that potential. The reason why is coils store energy as fields, when you measure your non-connected coils you are measuring a field which is basically just a bubble around the coil. Once the circuit is connected, that field collapses in on itself and as a result creates current (the energy collapses in on the coil and flows out into the circuit). With this circuit you generally don't want excessive field buildup as, even though the collapse generates a relatively weak force, microelectronics can be damaged by less force easily. In the end your most important measurements at this point will be based off the circuit fully connected and in operation. Which raises the question: have you hooked up the device you intend to charge and actually tried it yet? Did it work?
Hi, Unfortunately no, it did not work. I don't get any readings now whenever I put a load into it. Even the 5v light bulb makes the voltage drop to zero. Is there a way to sustain that potential? Thanks!
Well the voltage dropping to 0 means the electricity is being consumed completely. Sustaining a voltage potential should be as simple as continuing to generate power, in this case keeping the dynamo moving. Try hooking your circuit up to a fixed, reliable power source such as a set of batteries or a wall wart and see what happens. If the circuit turns on and begins charging then the circuit is either unreasonably demanding of power or the dynamo is not functioning properly. If you made it yourself it could be as simple as bad windings/windings crossing at weird angles (even at a single point). So, if it turns on with a dedicated power source then next thing I would try is a simple large hobby motor or something like that which is easily available (for cheap, if you are paying more for the motor than the cost of a reasonable lunch you are paying too much or buying something too fancy). If you can find a way to hook up the motor (on a bike, putting it at an angle with a ribbed rubber wheel against the tire wall) to get it spinning constantly you should be able to generate a moderate amount of power to at least test the circuit and determine if your dynamo is at fault. If the dynamo is not at fault/hooking the circuit up to a fixed power source results in a large drain with no proper activity then there is most likely a short or something is mis-wired. If that's the case start doing a walk-around with your multimeter to see where things are going wrong (try stepping around with the continuity test first to see if you can find a short).
Hi, Finally got around to looking for a short and found one :). I hooked the dynamo to a dedicated power source and it spun merrily, registering a voltage of 33vDC. Problem now is that when I add a load, the dynamo slows down, and gives out a voltage of 1.66vDC. Any suggestions? Thanks!
Again, that sounds somewhat normal. The slowing down is the dynamo working to actually push power through the circuit, which should be consuming it. What kind of voltage are you getting off the charger? If the voltage coming off the charger seems somewhat normalized, does the charger work when you plug in your target device (an iPod, was it?)?
Hi Kagetsuki, Would you have an idea on where to put the boostcap? Thanks
With a voltage regulator? Most 3 or 4 prong regulators require only small capacitors to operate. If you purchase a regulator, please refer to its data sheet to see what kind of capacitors should be applied and where. If you are using batteries to charge from then your input should be constant and you really wouldn't need a boostcap (super capacitor) at all. If you have an irregular input and wanted something to smooth that out, you would put the super capacitor on the output end of the voltage regulator. The reason for this is super capacitors have much lower voltage tolerances than their standard electrolytic brethren, and exposing it to an unknown or high voltage could destroy the super capacitor. In this particular application, for power profile issues I would recommend a large, high voltage tolerance electrolytic capacitor before the regulator than a super capacitor after it. In general most devices want either all their required voltage or none, and some do not deal with sagging well at all. A super capacitor after the regulator would sag or "brownout" each time it discharged, which depending on the application could be often. Anyway, to reiterate: if you have a constant input voltage from a source like a battery, you need only a regulator and a few small capacitors as indicated in the regulators data sheets (look at "sample applications" or "standard operation") . If you have an unpredictable voltage source then using larger electrolytic capacitors before then regulator (between the regulator and the voltage source) may be a better solution than using a super capacitor after the regulator. Side note: linear regulators can get hot and burn themselves out, a heat sink may be necessary for extended operation.
Thank you so much Kagetsuki!
An easy solution to the streamlining and weather proofing of the design would be to replace the generator that the team built with a dynohub, a genarator that puts out 6v and is built into the hub of the front wheel.
Shagglepuff6 years ago
140 Fared cap... ...wow...
dhymers6 years ago
Where did you get a boostcap ?! /me want.
1213441 dhymers6 years ago
Hi! Got mine from http://www.tecategroup.com/
Codemaster16 years ago
Is it possible to hook the supercapacitor to the ultracapacitor so you can have a fast charge to the capacitor time as well as a constant charge in the ultracapacitor?
can this charge my mp4 player but with the bike gen power generator. the bike gen is of he instrustables site...
bombmaker26 years ago
and how much are the supercapacitors
bombmaker26 years ago
do you have to build both of the circuits
Couldn't you purchase a bike hub generator (normally for powering headlights) and add an x voltage regulator ("x" being the voltage coming out of a USB port) and lead that to the USB adapter?
No, you have to use a capacitor as a 'buffer' so that the USB can get more constant power. The question here will be if the 140F (and one extra regulator) is overkill or inefficient.
surely that would defeat the point of most instructables...
good idea
Have you considered hand winding coils to be attached to the bike frame on either side of the wheel, and placing permanent magnets on the spokes? It may be possible to turn the wheel itself into the generator, this would be cheaper than buying an expensive motor. I've been researching alternate energy sources and a similar method is used in DIY wind turbines, though usually on a larger scale. It would be similar in design to the cheap bicycle speedometers that you can purchase at your local "mart" store. This would probably help to streamline the generator itself and reduce moving parts to practically zero. Imagine instead of the motor attached to the bicycle frame, only a small capsule containing the coil was attached to the frame. Check out DIY wind turbines for more information on winding your own coils, and possibly for your charge controller.
Seabeepirate, I was actually considering your idea when I searched for this instructable. I have a feeling someone could definitely change the frame into a Faraday-cage-like circuit and lead it through the tubing rather than on the outside. If so, this could be an awesome idea.
Kagetsuki8 years ago
I don't mean to be critical, but this instructable feels like a web adaptation of a high school science fair project. On top of that the cost of your design reduces the practicality greatly. The motor alone is worth well more than any bike I've ever owned. You could reduce the cost of the system by adapting an existing dynamo system. For instance the dynamos featured just a bit down on this page: http://www.cycle-yoshida.com/parts/light_menu.htm . A 6V 2.4W dynamo specifically designed and shaped for power generation from friction off of a bike tire rim for JPY1080 (less than US$10) should just suffice. And if it didn't modifications to your circuit should.

The circuit here also concerns me. Supercaps are great, but they have low voltage tolerances. To make up for this you regulate the voltage coming in. That basically jips you of a lot of the power coming off of that great motor which brings up a lot of questions regarding your design choices. Perhaps going with a big fat electrolytic capacitor and a dc-dc power IC would allow you to make better use of more of the power coming off that motor.

I understand this comment isn't necessarily a positive one, I do feel it is constructive. Good engineering comes from the realization of bad engineering. Flaunting bad engineering and furthermore using it to promote yourself, as you seem to be doing here, offends me.
Yes...thank you a EE geek...
I believe you intended to use "an" rather than "a" in that sentence. And as English text has no inherent expression of tone I'm completely incapable of determining if you are being sarcastic or genuine. The use of trailing periods implies sarcasm to me, in which case I question why you would rather not have someone with specialized technical knowledge criticize a poor design with a self-serving presentation. If however you were genuine with your statement, then my response is "no problem!".
sounds like someone has a stick up his/her(?) bum. i think this is a great instructable. bit too expensive for my pocket, but none the less, instructive. if kagetsuki wants to shine some light on those less fortunate of his/her great knowledge, feel free to remake this with your mods and post your own instructable so that we may benefit, o great one.
I described how you could do this for under $20 in the post at the top of this page. 1. Get a proper bike dynamo (just take the bulb out of a bike lamp or spend some money on a hub dynamo). 2. Hook dynamo up in parallel to a fairly high tolerance capacitor. 3. Add a voltage regulator after the capacitor. 4. Add a larger capacity (but lower tolerance) capacitor on the output side of the voltage regulator. 5. Hook up to IPod If you are ever displeased with the performance get more capcitors to place between the dynamo and regulator. Depending on how the iPod handles variable voltages and brownout conditions you may need a bunch of capacitors if you are making frequent stops. I'd write my own instructable for this, but I own neither a bike nor iPod. The fact that this can be replicated and very likely out-performed by a blatantly simple system less than 10% of the cost does in fact irritate me. Using the last page of the instructable as some sort of personal PR irritates me as well. The fact that anyone would want to replicate this without knowing they would be using a blatantly over-expensive solution and relatively inefficient solution depresses me.
JeffB (author)  Kagetsuki6 years ago
Kagetsuki, Your presence in this Instructable has deteriorated rapidly. I appreciated your constructive criticism, but your continued attacks will not be tolerated. You claim to be against personal PR, yet you do nothing but promote yourself. I have stated multiple times that this system was built as a concept and under a timeline by high school students with no background experience, get off your high horse of "specialized technical knowledge," no one else appreciates it. If you don't feel like making an Instructable, you don't have to mention it. I don't own an iPod either and I probably won't remake this system. You act as if I care about what irritates you, I don't. But if you're curious, your constant attacks on this Instructable irritate me to no end. Sincerely, Jeff
Kagetsuki JeffB6 years ago
I'm sorry I've offended you so much. In the future I will refrain from such direct criticisms of your work, and will no longer comment on your instructable. I hope that some day you may understand the point of view through which I made the above comments and look back on this and forgive me. Thank you, and sorry.
so...... with kagetsukis "suggestions" have you found a cheaper way?? this seems like a great idea!! i also like seebee pirates idea of turning the wheel itself into a generator. (i was actually going to do that in metal shop, make a battery system rechargeable by bike :D)
JeffB (author)  Kagetsuki6 years ago
You should realize that I wasn't offended by your technical criticism, it was your attitude.
cdubnbird6 years ago
what's a good motor to use if i want to spend $50 or less? - and still get the most out of it?
Use one of those rechargable bike generators. You know, those thingies you attach to a wheel and that power a light bulb......
im going to make this without the minty boost to trickle charge my batterys for my cold cathode under lighting on my bike
I think I'll make one of these with sort of a windmill design with the rotating magnet in a coil wire field. I'll also hook it up to my phone and what ever else device
jester_rob7 years ago
so basically if someone had already purchased one of the battery usb charger units they could simply determine the voltage it ran on, use a voltage regulator to step it down to that amount, and simply wire it in instead of the batteries?
This is probably one of the best instructables I have sen yet and you got a grant... awesome. The circuit you designed was awesome, simple, and got the job done. Although, I think the other circuit may have been slightly overdesigned.
cspannos7 years ago
So would anyone know how to adapt this to make it run off of a hamster wheel? I know that sounds crazy, but I came across this http://www.ananova.com/news/story/sm_1513938.html and thought it was fantastic. Would someone be interested in creating an instructable for that? Kagetsuki, you really sound like you know your stuff... you wouldn't happen to be a hamster owner by any chance? I doubt I would be so lucky...
-Aj- cspannos7 years ago
if you want a cheap n easy dynamo, just use a small electric motor. get one of the small 3-12v ones would work, slap a diode in series( so the motor powers the batteries, not the other way round, dont want to turbo charge your hamster wheel!) then hook it directly up to the NiMH battery pack. just stick a small rubber wheel on the motor shaft and fix it down so it rubs against the outside of your hampster wheel i dont think this will charge very well though, as the little guy wont be wanting to run for hrs on end i doubt, even for treats! but thats about the easiest way to do it if you wanted to. probably better off using a solar array
n4zou7 years ago
This is too complicated and expensive! All you need is a standard bicycle dynamo, 4 Ni-MH batteries, 4 1N5818 diodes, and a USB connector. The Ni-MH batteries will regulate dynamo voltage due to high impedance as voltage approaches 5 volts topping out at 5.2 volts, well within USB requirements. The batteries also absorb excess current as recharging current thus regulating and filtering power for the USB device plugged into the USB connector. S1 selects the headlight circuit or USB charging circuit. Center off position prevents slow discharge with the bike is parked or electrically disconnects a hub dynamo. Here is the circuit.
garote n4zou7 years ago
An excellent, excellent simplification. I have a few questions: 1. What happens when you go down a large hill? Will you damage the batteries? Is there danger of damaging the USB device? And, if you've been riding for a long while and the batteries are fully charged, do they stop acting as regulating/filtering components for the USB device? 2. Is there a particular bicycle dynamo you could recommend?
n4zou garote7 years ago
The impedance becomes so high in Ni-MH rechargeable batteries that it becomes impossible for the dynamo to produce more than 5.2 volts due to it's claw pole design. Going down a hill very fast will not damage the batteries at all. Most all USB devices have a charge indicator. Simply disconnect the device from the batteries and if it indicates fully charged just leave it disconnected and set S1 to off. When the device needs to be charged again just plug it back in and switch S1 to the USB circuit. If your Ni-MH batteries need recharging you can rapid recharge them by switching S1 to the USB circuit and engage the dynamo if it's a tire driven type. This will allow full 500mA of recharging current. 500mA happens to be the suggested current for rapid recharging of Ni-MH batteries. How nice it that! Just look at the battery package for recharging time, calculate how much time is required to recharge the batteries at 500mA, reset your cycle computers trip time and when the required recharging time is displayed your batteries will be fully charged. If your batteries are fully charged you can prevent an overcharge condition by simply disengaging the dynamo for a while and allow the USB device to draw down the batteries. If you need your headlight such as entering a tunnel simply switch S1 to the headlight circuit allowing the batteries to power/recharge the USB device. Depending on the AH capacity of the batteries this may allow running the headlight for several hours and your USB device to operate on it's internal and USB circuit batteries for several hours as well. Any standard 6V-3W dynamo will work perfectly. I use a tire driven bottle type dynamo on my touring bike and a hub type dynamo on my road bike when involved in rides that span day and night. Both work well with the circuit above.
Kinnishian7 years ago
I had a nice (well, not in the sense that it was very praising) long comment here. But then I accidentally hit cancel, instead of post. BUT ALL IS NOT LOST. My comment was almost identical to Kagetsuki's (I realized afterwards) In constructive criticism of price (with the exact same suggestion of using a dynamo designed for bikes), science fair style, and the slight offense at the overall instructable. On a different note: A dynamo bike piece was what william kamkwamba used to generate energy from his makeshift windmill!
Sandisk1duo7 years ago
se where did you guys get such a powerful capacitor?
I Love this, it would be really cool if someone built a set of amps that could go on your bike then you could also charge that with this, I made an old fm am radio into an ipod amp and it only ran off 3 aa's
Oh my god! I've done that exact thing before! I must post an instructable about it!
JeffB (author)  TheCheese99218 years ago
Yeah, its definitely possible. We could even remove the MintyBoost and adjust the voltage regulator to get the desired voltage. The LM338 will go from 1.2 to 28 volts, if I recall correctly.
No idea what you just said, but it sounds AWESOME!!
he said you can power amps!
I'd sure like to see that as an Instructable, or know how it's done.
Nirjuana7 years ago
Wouldn't it be much more simpler to replace the MintyBoost circuit by using a low-drop (6v) regulator and filter it off?
guyfrom7up7 years ago
this seems like an extremeley expensive way to make this. The 140F capacitor? 140F!!!!
Uh, you non EE types every hear of Buck, Boost & Step Up Converters? Linear regulators, LDO's and PMU's?

See Pics... in a 3mm 10SON format for $2...

" The ultracapacitor stores energy to continuously charge the USB device even while the bike is not in motion. "...uh then isn't this better implemented with a rechargable "Battery"... and a batteries are cheaper. USB devices draw less than 500mA peak. Less when charging...So any 4 cell NiMh give unregulated 4.5v for over 2200mAH. ~ 4 hours between charges and can be had for a few dollars in bulk...
Damn, I just realized that myself. And it's got a limit of 2.5V.... I just came back to this to see if it was updated by the author in any way to make it at least reasonable... but no. On a somewhat related note, I received a solar cell as a sample recently and to check it out I slapped together a simple circuit to output USB level power. I used a 5V (max 1A) regulator (which has an operating range of 3V+ if you pair it with some caps to run the internal charge pump, which I did), a USB jack, 4X 3300uF 50V caps which I got in a value pack, and a power diode. The same setup with a rectifier instead of the diode would be a much better solution to the charge circuit and wouldn't cost more than $5US..... You can use the money you saved on more/different capacitors and a real dynamo that you can affix to your bike.
wrencher698 years ago
You might try using a VSS (vehicle speed sensor) found on most 1995 and up Ford vehicles. Used in the transmission tail section on rear wheel drive vehicles. Perhaps you could adapt its gear to a wheel?It puts out about 5v I think...hope it helps
beartoe8 years ago
Most of the standard bicycle dynamos are alternators, running 6v, 3W, so 500 ma is right at their operating efficiency. I don't recall if this setup required a rectifier or not on the "front-end" circuit. But If you're willing to build up a wheel, you can find a brand-new Shimano dynamo hub for about US$85-90. And much cleaner and simpler. Of course, you couldn't charge your USB device AND run the lighting system. Maybe this is a good idea -- at night the bicyclist ought to be concentrating more :)
beartoe8 years ago
I wonder if you could use a "proper" hub-dynamo for this purpose such as a Schmidt Nabendynamo or a Shimano. What kind of amperage is required to run the USB circuitry?

Look at this page
The dynamos you linked would probably work much better than this solution. Motors aren't always the best generators. Ideally, you want a high torque low speed motor if you want to generate electricity, but even then they may not be ideal. You also need to consider the orientation and fixture of this motor vs the dynamos you linked. This motor requires friction to move it, and in a natural world you're going to loose or miss out on a lot of possible energy because of that. Not to mention wear may be fairly quick. As for "amperage", that's all handled in the power regulation portions of the circuit. The lines from the motor/generator will fluctuate, but the energy first hits the capacitors which then feed into the voltage regulator which will provide a steady voltage source and a predetermined maximum current as long as it has enough power to drive it. From there they have the whole thing connected to that "minty boost" circuit which will handle the supply to the USB terminal. If you were asking how many amps USB devices usually require that depends on the device. If I'm not mistaken you can pull something like 500mA off the bus. I don't know how much current an iPod sources to charge off a standard bus, but I'm assuming the minty boost circuit can provide enough to satisfy it.
diegugawa8 years ago
also, you can buy a switching regulator, and play either 5 or 12 volts. 12 volts to connect it to a small light, or the 5v that is use it for every USB device. The switching reg. you can order it online as a sample (means free), or buy it for 8 dollars. Using a little of imagination (and reading about it) you can figure it out what you can do with the SR., besides it's really small and you can adapt it very easily. The motor you can adapt it directly to the wheel. Even when is still spinning the way that we see it, is not 100% efficient. But if you connect it in the axis, will work better. You only need a ~15v motor, the SR makes the rest of the work (believe me, take a look). It's a nice instructable though. But I think it's cheaper if you can get the parts that way. That is my suggestion.
ac-dc8 years ago
This is just crazy (wrong way to do it). The motor is unnecessarily large, expensive, unnecessary addt'l drag on the wheel and the following linear regulator in the circuit wastes tons of power and generates unnecessary heat. A couple of other options might be Shimano's generator hub, or to use a purpose-designed circuit instead of tacking these parts after a mintyboost. For example Maxim's MAX1634, though there are other of this type, large input tolerance (variable frequency mode) switching converters with 5V output. By selecting the motor and friction roller size appropriately (if not gear driven which would tend to waste less power as friction) you can hit the required voltage curve vs speed for the input to the switching regulator and for the rare times when speeding down a steep hill at high speed a shunt regulator could burn off extra voltage or pseudo-shut would be fed into a second regulator stage for a voltage:current conversion to be fed back into the regulator input (schottky diode isolation as needed). I just can't recommend that anyone build this bike charger circuit as is, there's nothing positive about it. You might as well just grab an equal weight 5V battery and strap that to the frame, as it would hold multiple times as much power, could be replaced quite a few times (if it weren't rechargable) for the cost of all these parts (especially the motor). Above all, the two things you really shouldn't want to do are to use a linear regulator at all, or a transformer (unless a tiny lower loss type as part of a switching regulator subcircuit). I don't mean to be mean, but if you're peddling away on a bike it out to be as lightweight and efficient as possible, and a lot cheaper is nice too.
JeffB (author)  ac-dc8 years ago
I don't mean to be mean either, but if you had read the full Instructable you should have noticed "We decided to stick with our Maxon 90, which was a beautiful motor, even though its cost was $275. (For those wishing to build this project, a cheaper motor will suffice.)" We only used this motor because we had it available and we had deadlines to meet for June 1. We wanted to make the concept work, then streamline and rework everything.
ac-dc JeffB8 years ago
I read the instructions. The motor is only half the problem, as having such an inefficient design requires a larger motor to meet any particular charge rate, which makes that motor inherantly more expensive and/or larger, heavier, and more drag on the wheel (rider effort). On a bike, these factors are really important.
JeffB (author)  ac-dc8 years ago
Yes, I do realize that and am currently looking into your suggestions, especially the circuit portion. Thanks.
LasVegas8 years ago
It would help if you were to add sources of the parts used. It would also be proper, IMO, that links to sources, such as the MintyBoost were included. I can't find specs on the Maxon-90 motor you're using. If an AC motor were used, with an output of ~6v, a 1:1 transformer with a secondary center-tap and a couple of diodes could double the current supplied into the supercap without so much going to waste through the regulator. Hint: For improved visibility and potential of this becoming a Featured project; Add, before the first picture in the Intro, a photo of the completed project.
JeffB (author)  LasVegas8 years ago
Thanks for the advice, I'll be adding the sources as soon as I can grab a few minutes of time. As for the advice on the AC motor, I'll look into it. I'm not that familiar with it and I think I could probably learn something from that. Thanks!
LasVegas JeffB8 years ago
It wouldn't take a big transformer since you aren't dealing with a lot of power. I've attached a schematic about how the transformer would be inserted between the generator (motor) and regulator circuit.
Picture 1.png
How would you know if it has become a featured project? Does Instructables tell you?
pfmia8 years ago
It sounds great but i can't see the 140 F capacitor in the schematic, I think it must be connected between the lm338 voltage regulator and the minty boost
JeffB (author)  pfmia8 years ago
Sorry, I uploaded the wrong diagram! I'll have it fixed as soon as I find the original.