Instructables

440 Watt Regulated Pedal Power Bicyle Generator for iPod, Cell Phone, Portable TV or DVD player

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This bike generator design is good for running low power devices such as:

- An iPOD through a 12V Car cigarette lighter adapter like this one.
- Cell phone chargers
- Portable DVD player

You can use off the shelf parts from local stores to make this 296 Watt pedal power bicycle generator or buy parts from Amazon.com

Through volunteer efforts, 24 of these pedal power bicycle generators were assembled and used for charging cell phones at a 3 day event with 60,000 people attending a day. More Info here.

Any one who can use a drill, socket wrench, hack saw, wire cutters, and crimpers can do this project.

 
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Step 1: How It Works

Picture of How It Works
I hacked together a quick LabVIEW program and some sensors to hook up to the bike generator so you can get an idea of how it works. The chart below shows actual data while it was hooked up in the living room to our Sony play station PS2. The game being played is Harry Potter and the Goblet of Fire.

This test data shows Volts, Watts, Amps, Rear tire RPMs, and Heart Rate. The time period was about 3 minutes.

Note that the green line is actual wattage from the bicycle generator. When you first spin up the bike to about 275 revolutions per minute, about 5 seconds goes by while the alternator is developing a magnetic field, then the internal 14.8 Volt DC regulator kicks in and charges a 2 Farad capacitor.

This is the reason for the big green spike right at the beginning of the chart. After 2 seconds the capacitor is charged, and about 10 Watts of power is being consumed by an AC inverter which converts the 14.8 Volts DC to 110 Volts AC (The same stuff that comes out of your wall socket in your home).

Also note the red line showing that the voltage is stable at 14.8 Volts DC because the built in regulator is doing its job.

Next you will see where we turn on the Sony Play Station and the green line jumps up to 30 Watts.

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dermord4 years ago
so you have to ride to play?

That's right. You probably have to ride to play.

I would recommend a five amp fuse. Your calculations for 10 amps are correct, but the lowest rated part of that circuit is five amps. The fuse should protect the lowest rated part of the circuit. As an alternative, use two five amp fuses. Put one in line with each individual power port.
Milke19912 years ago
Does this bicycle could generate enough power for my pc? I'm trying to do this for a science fair.
ssleeper2 years ago
I must be missing something. What is the purpose of not having a battery? Aren't you just using a bike to spin the alternator instead of a Windmill?
Is the object to have a simple system to charge things and get some exercise.
I apologize but I am just starting to learn about alternative energy (I have alot of fabrication expierence) and am trying to learn how to design these things. I would like to be able to incorporate this idea into building a small windmill.
I like the idea of adding a flywheel or even using two recumbants for pedaling comfortably while watching TV.
ljfresh2 years ago
Does it matter what type of alternator to use? I can find 12 volt but the amps are different then 32.
Noblenutria3 years ago
Isn't it better to use a generator with permanent magnets?
Used this as a guide for my own bike generator. We are using it at SDSU as an outreach tool for sustainability and energy efficiency programs. Students love it powering the music at our farmers market and it was a big hit at our national conference.

Many thanks,
The SDSU Green Campus interns
forrest on bike.jpgIMG_1378.JPGIMG_1381.JPG
jj.inc3 years ago
small electronics, damn this could power my computer, excluding screens, and speakers.
nav_lexy3 years ago
What if you just plugged the generator up to a 12v 7ah battery. At 296 watts how long would it take to charge a battery?
Great idea...
vemsom nav_lexy3 years ago
1 W = 1 V * 1 A

A 12 Volt 7 Ah battery can store or deliver 7 amps at 12 volt for one hour. Or 12 volts at one amp (12 Watts) for 7 hours.

12 V * 7 A = 84 W

(84 / 296) * 60 minutes = 17

So. 17 minutes. :)
manuka4 years ago
I'm a great bike fan & applaud their whole earth engineering applications when normal electrical supplies are not available- lathes,grinders & sewing machines etc spring to mind. However I beg to differ about that quoted "100s of Watts" sustained power output. We humans are usually only good for ~50 Watts output over any length of time, & even this can become a pedaling chore. Prime condition athletes & Tour De France bikers can certainly pump iron, but "100s of Watts" can only be delivered for ~30 seconds by most people. You just need to conduct an energy physics "running up the stairs" experiment to establish this! Rather than pedaling to just charge batteries simply use a solar panel - PV prices have fallen to under US$5 a Watt. A typical 4 hour solar resource onto a 10 W panel will deliver 10 x 3600 x4 = 144 kJ with no effort at all ! That sort of energy could be used to later run a 100 Watt electrical appliance for 144,000/100 = 1440 seconds or ~20 minutes. Our feeble human energy levels are IMHO better used for more precise application & exercising - firewood chopping, gardening, lawn mowing, building a playhouse or home extension, playing ball games with your kids, rustling up a meal from scratch etc.
I ride a bike daily and have been tested for my poser output at the 8 hour, one hour and one minute levels. I'm not a racer just a very fit individual (I'm normally lanterne rouge in my local bike club's races) and I can do 150 watts for 8 hours, 220W for an hour, and 800 Watts for 1 minute. That one minute output requires several hours of recovery time before I can put out more than 75 W.
dhellew2 manuka3 years ago
A couple of suggestions to the project. While true that this isn't the best use of 'man'-power it is fun to try things anyway. The bike needs a flywheel. This gives the opportunity for intermittent rest periods so one can pedal longer.

Another possibility since this is for fun and exercise and not about the money why not add the solar panel too. Then perhaps us puny humans could go a few more miles. :-)

For a real challenge, put a car headlight on the bike and see how bright and how long you can keep going.... not long I assure you. Amazing how hard your car engine works for the small amount of fuel it consumes.
manuka4 years ago
I'm sure I've mentioned this before, but repeat that the average human is hard pushed to churn out even 50 Watts for any length of time. We're puny creatures after all -even using our "powerful" legs.  Although initially "fun" & perhaps sociable to group pedal away like this, it's however a waste of our potential!

There's almost always better things to do than static pedalling, especially intricate productive work with crafts, gardening, cooking, child minding or reading etc. Even go for a walk or bike ride!

Given the abundance now of solar PVs it's far "greener" to use (say) a ~5-10 Watt panel (costing  ~US$30-50 ) over a few hours to do the charging instead.
lalalaux manuka4 years ago
Waste of our potential? I think you're missing the point, and potential in this project.

Granted I wouldn't want to use one of these as my only source of power, that doesn't make it a useless idea. For instance, I can see one of these being great set in front of a tv, turning a mind numbing and unhealthy activity into something a little more "productive" while getting a bit of exercise.

Or you want to do something physical and the weather is nasty (because it's not always sunny). Or your rent and electric bill are both do and you only have the money for the former. Or.. I can think of tons of stuff you can do simultaneously while "static pedaling" (reading, singing or listening to music, having a conversation, etc). Maybe though, once in a while, it's nice to do something sort of meditative and not intensely mental.

Truthfully though, I'm so tired of this idea that people always need to be doing something "productive"! What is productive anyway? What if what I want to read instead of "static pedaling" is a gossip rag? What if I hate kids? Then it's not very productive or positive for me to be minding them, I would think.

I could go on and on and on, but I won't. And I don't mean to be offensive in any way, so please don't take it that way. I just strongly (I won't even go into the "puny" comment...) disagree with you .

I think Manuka's point is just that you aren't going to have any impact on your electric bill or total energy usage. 100 watts for 1 hour costs about 1 cent. Certainly it doesn't hurt anything if you were going to exercise anyway, you just shouldn't have the impression that you're going to save resources, etc. with a bicycle generator.
Photovoltaics are hardly green. That 5-10W panel will likely never repay the amount of energy that went into making it.

The bike would allow you to get some excercise while, say, watching some TV...which is more productive than just watching TV.

It also works at night, indoors, and on cloudy days.
I didn't read all of the comments... But a 1 wire GM alternator is a pretty common find at a junkyard. Why buy new if there's a used one that's clean and decent?
Tim Temple3 years ago
This is good and close to what I came up with.

But how about the other end of the circuit? Think 12 volt circuits. We need LED lights and even strings of LED lights. Heavy extension cords will conduct 12 volt electricity to neighbors so they can have lights at night, too. They can help charge the battery for the day. They become vested in common security as well.

When things go bad, this is useless for anyone living in a megapolis. The government will relocate the survivors.
DIY Dave4 years ago
So you don't need a charge controller to keep the alternator from overcharging the battery?
Any alternator with an internal regulator should already have that implemented, and even replacement external regulators also have the same protection. You should no more worry about overcharging the battery here as you should about overcharging the battery in your car.

Besides, it's more likely that you will tire long before this could be an issue, and car batteries are remarkeably-durable anyway, especially if you consider the harsh conditions they normally operate in.
Car batteries aren't all that durable at all. If by harsh you mean temperature extremes, they are only extreme to humans, not to a liquid (so long as it doesn't get below it's own freezing point), plastic, or metal.

Car batteries will be badly damaged if drained fully a few few times, will boil off liquid if overcharged. They are not very durable at all if not implemented properly, and don't even last very long at all if you consider the typical car battery might be drained only 5% of it's capacity about 5000 times before it fails in real world "harsh condition" use - this is far below full cycle capacity of a NiCd battery for example.
cool thanks
Dr.Bill5 years ago
I don't see a battery to energies the field coil. How do you do it?
bdwhaley (author)  Dr.Bill5 years ago
You don't need a battery because there is enough of a residual magnetic field within the alternator to allow it to start generating 14.8 volts after 3 seconds of fast pedaling. Watch it done on this video:

http://www.youtube.com/watch?v=bJFGEQRWxz8
Actually it's not residual magnetic field left (you may be thinking of older automotive generators), but because the alternator automatically uses some battery power to get one started, and with the mechanical power keeping things moving, it snowballs until it can sustain it's own field. Fortunately, it can start this reaction with as little as 1 volt.

I'm glad to see more people getting on board with this idea, because countless trillions of watts are lost to heat on exercise-bikes worldwide every day. By actually harnessing this power, it decreases the carbon-footprint of a person/household by a great deal.

Kudos to you for posting this project, because exercise bikes are stupid when they aren't actually salvaging that lost power. 100 Captain-Planet points to you, and a bonus 5 internets for intelligent design in the project.

As a suggestion, you could try weighting the wheel (making sure it's centrifugally-balanced, of course), because while it may take a little more energy to get it up to speed, it would actually reduce fatigue dramatically, having only to maintain the momentum. As a well-seasoned ex-cyclist, I can assure you that you will feel the difference while you are on it. It's much easier to maintain momentum than to sustain it without mass. That's part of why engines have flywheels.

Awesome project, I love it.
ncoded5 years ago
This is such a useful article, perhaps not 'now' but probably for the future! Would it be possible to put this guide together into a .pdf for download? Also, is it possible to boil water using a similar type method?
bdwhaley (author)  ncoded5 years ago
Hello, just curious, but why do you want it in a pdf? Also yes, you can easily boil a cup of wate in it. It might take you about 5 minutes for a cup of water. The hard part would be to find a 12 V heating element, or hot plate. Brad, pedalpowergenerator.com Brad
The Instrucatables website automatically makes a pdf of every instructable. After step 45 you will see a pdf has been created. I like pdfs because I can add it to my CD of useful things to make when the big "power down" comes. After all, you wouldn't be making a bicycle generator if you didn't think there was a need for an off-grid (or no more grid) source of electricity. No grid means no Internet and no chance to view this instructable.
Just saying...why put it on a CD if there's a power down coming? haha excellent article though. I'm curious about the inefficiencies of using a car alternator though. Don't alternators lack permanent magnets, and therefore isn't some current going to be wasted by the alternator itself to create a magnetic field inside of itself?
The lack of permanent magnets does not necessarily equal loss. Alternators are "self-exciting", and once excitation of the core has started while mechanical power is maintained, there is no longer any need for a PM (permanent-magnet) because the field is self-sustaining. PM's are vulnerable to vibration and sometimes cracking (which instantly turns one magnet into two), and that itself would actually cause more loss.

Permanent magnets are used in smaller motors as a cost-saving measure mostly, and in larger motors it is because of their particular characteristics that make them most effective for the job. Unless you need the specific properties of a PM motor/generator, an alternator is actually the preferable choice.

The biggest inefficiency of any motor/generator/alternator is the air gap between the stator (field/stationary coil) and the rotor (rotating coil). In automotive alternators, this gap is very small. PM motors cannot possibly have a gap so small because the cost would be economically-prohibitive.

The small (and I do mean small) difference in efficiency  are negated by the intelligence of the design. DC motors generate higher and higher voltages the faster you spin them, requiring bulkier and tougher voltage regulators, which will introduce electrical loss. With an alternator, when it starts to generate too high a voltage, it takes the magnetic field away until the voltage drops to within limits, well before getting any higher than 18 volts, instead of a DC motor, where you would have to hold back as much as 300 volts, and the way many regulators work is to dump this to a resistor to be burned-off as heat.

At the end of the day, the alternator is the better choice, for simplicity, durability, and functionality.
I live off-grid so my home-made electricity can power my PC.
ctonks bdwhaley4 years ago
 Hey Brad,

we have a human power tea and toast stall that uses about 10 people to make tea.. pretty efficiently too. 

Colin

peater ncoded5 years ago
Regarding boiling water, doing it using an electric heating element is inefficient and uses a lot of power. If you want to boil water off grid you'd be better off using a woodfired 'rocket stove' or similar, rather than your own energy. If you're a meat eater you will effectively be burning animals to make a cup of tea...
Can me and my physics group use this as our science fair project? (thats if we can get it 2work lol) It is sooooo kewl!!!
bdwhaley (author)  lil_agelu4life6 years ago
Sure, But I would recommend using the permanent magnet DC motor as a generator and make a floating ball go up and down using an AC Yard blower. People really enjoy that. The plans for doing the Permanent magnet DC Motor / generator are here:
http://www.scienceshareware.com/build-your-own-generator-bike-trainer-stand.htm
ctonks bdwhaley4 years ago
 Hey Brad,

can you tell how you hook up the AC yeard blow to the DC generator.. I can see some many applications for this. Thanks Colin (electricpedals,com)
Actually most electric leaf-blowers will run on DC just as they are, since an ac induction motor cannot generate the speed needed. They usually use permanent-magnet or series-wound (universal) motors, so as long as there is no speed-control (just on/off), you can just plug it in as it is. If there IS a speed-control, you will have to bypass it because DC will instantly destroy it and possibly cause a short/fire.
sirant4 years ago
Great project! I remember 25 years ago a similar thing at a kids science camp that should have been implemented into common practice. They had a bicycle powering a television.... Imagine if all televisions in north america were bicycle powered.... There would certainly be a far smaller weight propblem per capita!
But your idea is awesome too. I'd love to have a cike to commute on that charged my electronics as I went...
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