Picture of USB Bike Generator
USB Bike Generator 062 small.jpg
USB Bike Generator 061 small.jpg
USB Bike Generator 065 small.jpg
USB Bike Generator 063 small.jpg
USB Bike Generator 059 small.jpg
The USB Bike Generator is a small bike mounted electricity producing device optimized to provide power for two USB ports.  There are so many small electronics that can be powered or charged from a USB connection it only makes since that people might want to do this while riding a bike.  The basic idea for the USB Bike Generator is to use a suitable stepper motor as a generator and a voltage regulator circuit to maintain the 5 volts needed for the USB ports.  In this instructable I will show you how to build this generator and through testing show that it is 70% efficient at converting the power from the generator to the power needed for the USB port. 

This is the third revision of my bike generator project, the first two can be found here http://www.instructables.com/id/Bike-Generator/ and here http://www.instructables.com/id/BikeGen/ I would strongly recommend that if you plan on building this USB Bike Generator you at least look over how these past to versions went together.

This third rendition of my bike generator project came about after reading some of the comments made about my previous methods. Specifically, one comment from member ac-dc stated that my decision to use a linear regulator to go from 30 volts from the generator to 3 volts to power the light was at best 10% efficient. Now since one of the interests I've had listed on my profile since I joined this site has been efficiency I decided to read the rest of his comment after wiping the tears from my eyes. Ac-dc suggested that buck switching regulator would be better suited for a bike generator like mine. I had no idea what a switching regulator was so I started to do some research and found out that ac-dc was right and that I could significantly increase the efficiency of the electronics I was using.

In my searching for switching regulators I came across this reference from Dimension Engineering, http://www.dimensionengineering.com/switchingregulators.htm.  They offer a good explanation of the switching regulators and even sell them. 

1-40 of 56Next »
yonatan246 days ago

You should feel that it is a bit harder to pedal with this because It has friction and takes some of your energy

It is a good idea to add an option to remove it, for example: when riding uphill so It would be easier...

ao'dell1 made it!1 year ago

Fun science fair proj for my nephew thanks!

Nick28cc1 year ago
What about adding a battery pack. that way you could have a more energy for other things after a long day's ride.
Doug Costlow (author)  Nick28cc1 year ago
Check out my previous version of this generator it charged AA batteries. I think either charging batteries or powering lights directly are two very good uses for a generator like this. Powering things directly gets harder because the power output is not consistent.
Nick28cc1 year ago
Maybe it is possible to install one of these motors directly off the rotation of the crank.?
Doug Costlow (author)  Nick28cc1 year ago
Yes, maybe with another chain connected between the crank and the generator. You've got to make sure your pedaling though to produce any power and the generator needs to spin much faster than the crank, so you'll have to figure out the gearing
How about mounting it on top of the luggage tray on the back? Cut a small window in it, to allow the stepper wheel to touch the tire from the top side. You could mount the stepper directly on that luggage tray. You will loose function of that luggage tray, of course :-)
mattblanks2 years ago
would two of these substitute the eight individual diodes?
Doug Costlow (author)  mattblanks2 years ago
Yes those bridge rectifiers are just like four diodes but in one nice package, so two of those will replace all eight diodes. Just hook the wires from each stepper coil to the AC input leads and then the positive and negative leads to the charger.
unnap2 years ago
thank you for the reply sir.

another question, can we replace it with a smaller motor having only two output terminals? i mean like a dynamo having two output terminals?

what will be the circuit configuration then if it is possible?

thanks again!
Doug Costlow (author)  unnap2 years ago
I'm assuming that by a motor with only two wires that this is a standard DC motor, not a stepper motor. In that case the rectifier diodes are not needed but using a DC motor can create other issues. You must be able to control and reduce the voltage produced by the generator, be it a stepper or DC motor, so that a controlled 5volts is delivered to the USB plug. With a DC motor this may require fewer electrical parts but will most likely be less efficient and produce less power.

I recommend using a stepper motor.
unnap2 years ago
sir, can we replace the stepper motor used in this project into a stepper motor having 5volts output and 1.1A output?
Doug Costlow (author)  unnap2 years ago
Yes, really any stepper motor that is a resonable size to mount to a bike in the fashion I have shown will work.
adrofig3 years ago
To someone who has used this, is the additional friction greatly noticeable?
Doug Costlow (author)  adrofig3 years ago
With this generator I noticed no drag while riding, but still the power was being produced. I now have a legit hub dynamo to compare to as well. When riding I still don't notice the hub but when I lift the front wheel off the ground and spin the tire by hand the drag is obvious. Both of these generators consume power on the order of a few watts, maybe 6 at most for the hub, but a normal rider can produce can produce anywhere from 150 to 250 watts. The generators power a small percentage of that and can be hard to notice but is still there.
Chowmix123 years ago
Can you explain to me why you used a stepper motor? i have a regular motor, and I want to use that instead so that with a 5 volt reg.
jwelbes4 years ago
"The rectifier, which is just 4 diodes..."

you're using 8 diodes. are you using 4 sets of two diodes connected in series, effectively making them one diode?
jwelbes jwelbes4 years ago
wait hold on. you made two seperate circuits, one for each USB charger inside your 12v car adapter. am I right? this makes more sense than my last comment. that would explain why your diagram you drew has only two wires going to your car adapter, but in your photograph there are 4 wires going to your adapter.
Doug Costlow (author)  jwelbes4 years ago
There are 2 rectifiers,each consisting of 4 diodes. A "rectifier" is just the combination of the 4 diodes in the pattern shown in the picture, nothing more than that. Two rectifiers are needed because there are two separate coils in the stepper motor. The positive/negative outputs of both rectifiers are connected to the 12v adapter and the adapter converts the voltage to 5v.
ah. two seperate coils. ok thanks!
jwelbes4 years ago
"Follow through the notes on the pictures to see how I connected all the parts together."

I don't see any notes on the pictures.
jwelbes jwelbes4 years ago
i guess I need to be a pro member...
could you use a car outlet power supply that has an AC plug and a USB plug instead of the dual USB power supply?
You mean an inverter?

Most things that you could run off a small dynamo would be DC anyway, so you'd be inverting up to 110/240 VAC then recifying down to DC for your phone/satnav/what ever charger with associated wastages.
traeblain5 years ago
Last question...but why did you choose to abandon the intermediate battery approach you used on your previous generation? I would think the battery could take the flaky charge gracefully, then you'd have clean output power to your devices and would correct for issue with the ipod charging reliability?
Doug Costlow (author)  traeblain5 years ago
I think a battery could be used but I would want something to protect it and whatever device I'm using. I wouldn't want to over charge it or drain it to low. That would require another circuit to control everything, which I might try in the future.
Well obviously more research is required before you start building a battery addon for this build but I would like to point out (if its not too obvious) that modern devices with lithium batteries have a set up that prevents over charging. Maybe hacking an old device to be your bike-battery would be easier than building your own circuit? Just a thought.
tomtortoise5 years ago
can you please make a simple schematic to better explain the rectifier wiring.
Doug Costlow (author)  tomtortoise5 years ago
Will this do?
thanks sorry for the late reply but i needed to make a mount first and get parts but i needed to use a different motor for my mount but the wires are weird. from the motor the order is orange, yellow, brown, green but when it goes to the white PCB mount plug it is yellow, orange, brown, green should i hook up the rectifiers in motor order or PCB plug order
Doug Costlow (author)  tomtortoise4 years ago
You should check the wires to find out which ones are connected to the same coil inside the motor. Get your DMM and set it to resistance than touch the probes to two wires. If you see a few ohms of resistance than those two wires are connected to a single coil in the motor. These are the two connect to one of the rectifiers. There are two coils in the motor that's why you have four wires. Don't go by color or connectors just measure and find out what it actually is.
mobby6664 years ago
With the right regulator you should be getting over 90% efficiency. Using a solar cell setup & a boost regulator should give you power to supliment your generator & reduce it's drag on your wheel. Look at BEAM robotics sites for other ideas about harvesting solar power. Nice
proelectron4 years ago
Great project! I might try this, but with a smaller wheel giving the required alternator speed. Surely the output of the stepper motor is pulsed and therefore could be stepped down using a small transformer?
varunmehta5 years ago
Rather than dismantling the whole male plug system (car style) on the USB charger and connect the wires, how about making a female receiver, like that in the car. You can plug this USB drive charger into it + if tomorrow you make a new enhancement or want to connect something new to it, you can reuse the same stepper motor and circuit to achieve it!
laznz15 years ago
http://www.nzherald.co.nz/technology/news/article.cfm?c_id=5&objectid=10657566 epic win!
traeblain5 years ago
I know this is why your previous generation motor didn't work, but I think there could have been better options than moving to a new motor (although I have not built this and don't know the ins-and-outs of your work). My first question is why not try a new wheel for the previous stepper motor? My calculations (assuming you're using a 700x23 wheel and tyre) simply using an aggressive inline skate wheel (47mm) you could move your target down to 12.9mph which is pretty good for casual riding. Not sure your target speed though. It may help to understand as I believe you got the last motor from an old printer? Where this one may cost a bit more money.
Doug Costlow (author)  traeblain5 years ago
The main reason I didn't want to reuse the stepper motor from the printer was that its voltage output was to high, which caused the regulator to become inefficient. I think the goal should be to first create the voltage you need, in this case 5v, and then try to develop as much current as you can at that voltage, to get the most power and efficiency. As far as a speed target, I wanted something that would maintain high efficiency over a large speed range. I didn't want to have a really high efficiency at one certain speed because then I would have to ride at that speed all the time to get the best performance. As far as the cost goes, I spent $10 on the new stepper motor from electronics surplus.com They have that same motor on sale on-line for $10 as well.
Ah, but that is the whole point of using a switching regulator. I don't know what is actually in your $1.00 USB convertor, but a properly designed switching regulator would allow you to transfer power efficiently and get more current out than you put in by operating with a higher input voltage. That is, with the proper switching regulator design including an input storage capacitor, you could use a higher voltage stepper motor to generate 12V for your convertor which would then step the voltage down to what you need. You see a tiny bit of that at the higher input voltages where you get slightly more current out than you are putting in. However, as it is now, you are barely getting enough voltage to make the switching regulator necessary. Based on the output voltages you list you would actually now be better off with the linear regulator - especially at the lower speeds. I suggest you try the old stepper motor with the higher voltage output with your new switching regulator. If you do this, make sure you don't get so much voltage that you destroy the switching regulator - I don't know what the input rating is although it is at least 15V if it is designed to operate in a car and probably more. Or try your new stepper motor setup with your older linear regulator. Additionally, you could get more efficiency by using schottky diodes for your rectifiers since they have a lower voltage drop than the 1N4001 diodes (0.4V vs 0.7V each)
Doug Costlow (author)  retasker5 years ago
Using the old stepper motor will not work, I know because I fried two of the regulators during testing. The MC34063 is rated at 40V and the new stepper motor puts out 30V unloaded at 3100 rpm. I think the high load of the dead battery is what caused the voltage to stay around 7V for the new motor, but I'm not quite sure how this works. At lower loads or lower output power the voltage will go up and the input current will decrease, right? But won't a higher load cause the voltage to drop even further because it can't compensate for the load? I guess my real question is what conditions are needed for max power output and what conditions are needed for max efficiency? Are they the same or is it a trade off.
1-40 of 56Next »