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The is my first attempt at a bike generator and I have made many improvements to the project. Check out my new instructable BikeGen for the new generator which recharges 2 AA batteries and powers the lights. BikeGen can also be used to recharge you cell phone or Ipod

I made this friction drive bike generator to power my head light and tail light. I got the idea and a lot of the info for this project from another great instructable personal powerPlant

I recently bought a bike to commute to work and around town and figured for safety's sake I'd get a light set. This is the light I got, Planet Bike 1200, but there are many options for bike lights. There are many instructables on bike lights too. My lights are both 3V, two AA's in the head light and 2 AAA's in the tail light, and the box said the head light will work for 4 hours and the tail light for 20 hours in blinking mode. While this is respectable it still requires some attention. I got this bike for its simplicity, single speed means I can just hop on and go, but replacing batteries gets expensive and complicates things to much. By adding the generator I can power the lights while riding.

Thanks to instrutables member aaronscottaugustinhotmail.com a schematic of the circuit is also available.

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fortepc5 days ago

to anyone who understands the electrical components better than I do, is there any circuitry protects against rolling backwards and outputting the reverse polarity from the motor?

pjax6 years ago
any advantage of using a stepper motor over a normal DC motor? i think this is the first time i've seen a stepper motor used as a generator...
Doug Costlow (author)  pjax6 years ago
I've only done a little research into this myself but for starters a stepper motor is brushless, so you don't have losses from friction like in a standard DC motor. This would be very small loss though. I've also read that steppers generate power at much lower rpm's then DC motors. This site, http://www.c-realevents.demon.co.uk/steppers/stepmotor.htm, claims 10 to 15 times slower rpm than a DC motor. I have not tried to run a DC motor with this generator so I have nothing to compare to though.
Nice project. Reading comments. Everything could be better but did they build one ? No. They bought one. I built one it was fun still works, but it charges two 1850 cells. Good job, man. If you added a constant current circut and a usb jack instead of the 12v ciggerette light power connector you could easly charge anything usb. and yeah a bit of weather proofing could not hurt. But put your name or nickname somewhere on you project on your bike, your good..
GTechno13 pjax5 years ago
Agreed, found the stepper with full bridges to be an interesting approach that may indeed be more efficient.  My suggestion would be to throw in a capacitor as well.
ac-dc GTechno135 years ago
LOL, no it is extremely inefficient because it is generating 30V and you lose 27 volts from use of a linear regulator.  That means only 10% electrical efficiency at best, you could randomly pick any other motor with lower output @ same RPM and have it more efficient.

However, a brushless motor will give longer life due to no brushes to replace, although selecting a motor with high quality ball bearings is another factor to increase lifespan.

Although use of a linear regulator is very simple for a beginner, it is the wrong circuit to regulate with a human-powered bike generator.  The better option would have been a buck switching regulator IC, followed by a LC (inductor, capacitor) filter.  Also to increase efficiency you can parallel two schottky diodes in the bridge rectifier.   Total circuit cost might be $5 more, but to get roughly eight times the efficiency and lower wheel drag it would be well worth it.
krawczuk ac-dc5 years ago
wow ,!!  NO REGULATOR ever made would have a loss of 27 volts..
max of about 1.5  volt loss.

or you could even buy a low dropout regulator,,,
kotlecik1 year ago
Wow, so nice! :D
jpoopdog3 years ago
a better way to go would be using two motors, and or two wheels. i myself am going to try to build one, thanks for the inspiration!
i know were talking about efficiency here, but why not add a digital readout and a power storage device? the digital readout could go on the handlebars so you can see how much power you have and could run more things. you could also add brake lights hooked up to a smaller switch for night.

very nice build!

_Scratch_4 years ago
My setup is quite pathetic compared to this, I have a weed whacker motor duct taped to the side of my my bike running against the wheel. I can get about 2 volts spinning it with my hand at least, and thats about 20 times slower than me riding.
Doug Costlow (author) 4 years ago
You can check out my newest version of this generator, which is able to charge USB devices, here USB Bike Generator 

Keep on the look out for a new Instructable I plan on posting later this summer. Its going to be a more robust design that incorporates a standard hub dynamo and USB charging. I plan on putting it to the ultimate test this summer when I ride 1700miles on the Fuller Center Bike Adventure
wagman454 years ago
this is just a general question. if i use a 24volt 280 watt, 15.4 amp motor as a generator, will that output 15.4 amps, 280 watts max? how does it translate when you use it as a generator? is it purely based on how much energy (RPMs) you put into it?
Doug Costlow (author)  wagman454 years ago
The output is based solely on the input power, you pedaling, and the efficiency of the motor as a generator. Your input is product of how fast your spinning (RPM) and how hard your pedaling (torque). You might be able to get 280 watts from the motor but you would be pedaling with over 300 watts(just a guess), this would be a pretty intense workout but still achievable.
Udon5 years ago
I have a question - what kind of stepper motor is it? I tried messing around with one (forgot how many wires it had), and I found that the coils "fought" with one another. i.e., one minute it was rolling smoothly, next thing I wire them together and get the motor resisting movement and low output voltage. How does it get done? A drawing would be really great. XieXie.
martzsam Udon5 years ago
A stepper motor is made to move by pulsing electricity through its coils. (usually performed by and oscillator circuit). They are usually used for machines that need high precision positioning. They are called stepper motors because they move in very small "steps" very quickly.
ilwgjh5 years ago

Ahem, I'm sorry to spoil the fun of you re-inventing "bike generator". (Though I like your project..).

I am Dutch and over here we have a lot of bikes ( 16 Milion people, 20 million bikes). Almost every bike has a "generator" on it to provide electricity for the lights. 6 volts if I am correct.

for instance: http://www.bike4travel.nl/product_info.php?products_id=625

You can buy them in standard (heavy trodding on the peddals), or High efficiency ones and cost between 6 and 60 Dollars.

Udon ilwgjh5 years ago
But where's the fun in that?
ilwgjh Udon5 years ago
Well, that's true. As I said: I like your project and it does look "cool". Please forgive me for spoiling your fun. I could send you one of ours, so you can do a test between the "old skool" Dutch design and your High Tech solution?
Doug Costlow (author)  ilwgjh5 years ago
I know that there have been electricity producing devices on bikes for a long time and I'm not trying to re-invent it, but it was fun to work on this and use it. I'm working on a third version of this generator right now and should have a new instructable soon.
I'll hold you to that. ^^ Using components in ways they weren't meant to be used isn't only "fun", but also a way to learn how to come up with simple solutions to complex problems. Using a stepper as a generator. Using an LED as a light sensor. Making fuses out of strands of wire. Is this inefficient? Maybe. Does it matter? Not in the least bit. It gives people access to technology and solutions that they normally would not have, or be able to afford.
ilwgjh Udon5 years ago
Give me an adress and I will mail t to you. I did not mean to make any "fun" of your work. I do just the same in my line of business. I too use existing technologies for purposes they were not invented for. ( You probably see and use some of my 'inventions' every day). Sir Clive Sinclair is one of my biggest heroes! I do however see my work as 'fun'. (Getting a company to have a meeting on a Sunday over a suggestion what to do with their technology is fun! It is really funny when the first comment is "He wants us to do what? Impossible!"
mha13635 years ago
kmpres5 years ago
Well done, but as others have commented, this could be refined into something better.  Unless you live in the desert, waterproofing is a must. Your circuitry will fail in short order, your generator a little later, from water and dirt contamination if you don't take this into account.  You can do this easily by using a project box with the lid sealed with a piece of rubber sheet cut from an old inner tube.  Encase the motor in a project box so it, too, is protected from the spray from the tire.  Also, the motor/generator is too big as you are wasting most of its output power as heat disipated by the linear regulator - good if your purpose is to give yourself more exercise, bad if you want to generate electricity with the least amount of effort expended.  I suggest you resize the motor and/or driven wheel so that the motor outputs about 10 volts at, say, 30 MPH, 5 volts at 15 MPH (give or take, these functions are seldom linear), so you'll have efficient light output at all but the slowest riding speeds.  You could compensate for slow speeds by adding a super-capacitor stolen from a cheap wind-up radio to augment the low power from your generator.  You might even get the light to satay on for 10 or 20 seconds after coming to a complete stop, such as at a traffic light.  This might take some experimenting but shouldn't be difficult.

Finally, a simple spring and catch mechanism to press the driven wheel against the drive wheel (bike tire) and decouple them easily without having to use a screwdriver would be nice.  It would also save wear on your tire.
thepelton5 years ago
I was wondering if you could generate enough power to light a light, for even a flash, by having a coil run past a magnet without touching it, or vice versa.   Any ideas?
Alquimista5 years ago
Well for you project. I do not understand way you need to rectify the voltage, I believe that AC LEDs would light, and without loss of efficiency by rectification
 If there is already a rectifier in the bulb itself, then yes the one near the motor connection is not needed, however, IMO, I would still put them in just for safety measures.
I don't want to rain on anyone's parade but  I have doubts about the reliability of a stepper motor exposed to the elements, especially the elements to which a bicycle tire is exposed.  The motor should be housed in a water-tight box with the shaft sticking through a hole with o-ring seals to protect the bearings and windings from water and dirt that the bicycle tire will throw off as it spins.  Maybe a small otter-box could be used to house the motor and electronics.  Then all you need is a way to get the wires and motor shaft through the walls without compromising the seal.

It's a great project - just needs a little more work...

Maybe you could eliminate the shaft by mounting small magnets on wheel spokes and have pick up coil(s) mounted on the bike frame.  It wouldn't be terribly efficient but probably adequate to charge small batteries/capacitors to power the LEDs.

MattPendley5 years ago
Sorry for my ignorance, but what are the coil rectifiers for?
The coils are placed next to moving magnets, as the magnets pass you get positive and negative movement of electrons, first it pushes them down the wire, then it pulls them back.

A diode is a one-way valve for electrons.  A full-wave rectifier uses 4 diodes, 2 diodes for negative (one diode on each input), and 2 diodes for positive (also one diode for each input, but facing the other direction)

The rectifier sends only positive down one output and only negative down the other.  This makes the AC (alternating current) into DC (Direct Current).

Alright, makes since now.  Thanks!
greezus5 years ago
 i so wish i understood electronics & mechanics!!!

taking a trip around lake michigan this summer and this would be so handy- i'd mainly like one that would just recharge AA bateries- the gps eats 'em up quick!! but it'd also be nice to be able to charge my ipod too...

unfortunately, this is all greek to me. ugh. my brain seriously hurts. I DIY when & where I can, but unfortunately with this, i don't have a clue...

JordanaG6 years ago
When I was an exchange student in Sweden in 1995, my host family loaned me an old bike... it was probably at least twenty years old, and it had a light on it that was powered by friction from the tire. I wasn't very inquisitive at the time, so I don't know much about it, but I'm pretty sure there was no battery involved. The light was on when I rode, and off when I didn't.
 that was probably an old dynamo charger- they used to be really popular- now the company is making them in the hub of the wheel- totally cool!!
gordoflash6 years ago
Great idea, and I plan to do the same. You proved it works. My addition to the idea 1st -is to remove the circuit board, solder components together and cover with silicon so it becomes part of wiring. 2nd -add a couple super capacitors so the lights will stay on at intersections. 3rd -put the stepper motor closer to the hub, maybe screw a ring to the spokes for the motor to run on. Great work!!
 It's been a while since I did anything with capacitors.  How would you go about hooking these up?   I'm guessing in parallel, in line with the wire running to the light?
Read up on capacitors if your not sure as they can pack a punch if you short them.
Do not charge them with more voltage than they are rated for.
But they will take as many amps as you can peddle into them.
gordoflash5 years ago
2 supercapacitors 100F, 2.7volt in series, giving 50F at 5.4volts.
these are put in series to give you the voltage for your LEDs.
But you halve the charge capacity.
sean8825 years ago
 Great idea!  I plan on doing this by the weeks end.  I'm thinking I'll run one wire, negative, to the screw under the water bottle holder, giving the bike's chassis a negative charge, much like with automobiles.  Then I'll only need to run one wire to lights, maybe a small buzzer... possibly turn signals.
jwcheatwood5 years ago
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