Pedal powered generator diy

Pedal powered generator diy DEFAULT

Pedal Power Generator - Electricity From Exercise

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Curious about Human Power? Need some exercise? Trying to lose weight? Looking for a zero-carbon workout? Need inspiration? Researching technical information? Expensive electricity and gasoline making you nuts? You have come to the right place.

Every morning, I ride my Pedal Generator to generate electricity. The Pedal Generator I built and ride charges batteries, that run an inverter to produce v AC, that powers LED lights, the monitor on my computer, my cell phones, and charges my Roomba, my eGo Electric Moped, as well as many other battery-powered things. All Powered by Me. It is the most inspiring workout you can imagine, and it saves me money!

Become Part of the Solution - Build Your Own Pedal Generator

My Pedal Power History: 35 Years Researching the Power of Human Energy

The 12 Volt DC Pedal Generator you see on this site is a completely original invention. I built the first version of the 12v Pedal Generator in As an improvement over rudimentary bicycle generator and bicycle dynamo designs, I focused on efficiency and versatility. While a 12v bike generator is an alternative to my design, pedaling will be less efficient, and powering non-electric equipment may be difficult. A unique feature in my design was a 36" particle board disk with a groove routed in the edge that served as the flywheel and crankshaft for the permanent magnet 36 volt DC motor ( 12 ) seen at the upper right edge of the device. A small-pitch chain provided the power transfer system. The groove around the outer edge was lined with "rim strips" - thin rubber straps that prevented the chain from slipping and digging into the particle board. They are standard bicycle parts. The motor was obtained around from Northern Hydraulic, now known as Northern Tool and Equipment Company. It is a General Electric Permanent Magnet Motor, model 5BPA34NAA44, a very nice heavy-duty, ball bearing unit. I paid USD $29 for it if I remember correctly, and I still have it.

The bottom frame of the Pedal Generator was welded steel plate and channel, the crankset was an American Schwinn ball bearing set, a cotterless crank conversion spindle, alloy cranks and inexpensive pedals with toe clips.

The crankset had a steel chainwheel on it. I drilled some larger holes in the chainwheel and bolted the particle board disk to it. It was strong enough (fine Schwinn steel!) to hold the weight of the particle board disk and run true. I routed an oblong hole through the particle board disk for the "arm" of the crankset.

The seatpost and handlebar tube were standard galvanized water pipe. The generator/motor was mounted on a piece of 3/4 plywood visible in the motor pictures seen above, which was then bolted to the water-pipe frame.

The particle board disk was a key feature of this unit. The weight of the disk served as an excellent flywheel. Human legs and pedals create an extremely "peaky" torque curve, resulting in jerky motion and lots of stress on parts. The flywheel smoothes this all out by absorbing part of the energy on the power stroke, lowering peak torque, and releasing it on the "dead" part of the stroke, creating torque where Human legs/pedals cannot generate any. Another thing to remember is that Human legs do not like extreme stress. The flywheel allows the Human to avoid having to generate extreme pressure during the power stroke just to make it past the "dead" spots. Many "bicycle converters" lack the flywheel characteristic because tires/rims are designed to be so light.

Noisy but extremely efficient, I have powered 12v CHAIN SAWS directly (yes, while someone else cut wood with them) with this unit.(1) Pedaling position was similar to a bicycle. The seat is barely visible at the upper left of the photo, and the handlebars (dropped, as on a ten speed road bike) are at the upper right.

Burst pedal power output: 25 amps at 17 volts ( Watts) at 25 years old, and Watts at 52 years old, and Watts at 55 years old! Yes, I am in better shape than I was three years ago!

30 minute average output (back when I was in shape) Watts


A drill chuck threaded into the end of the motor shaft provided power for a flexible shaft drive. Drilling 1/2" holes through 2x4 fir with this arrangement was easy. The flex-shaft was rated at 1/2 HP (a commercial unit, about 3/4 in. thick - not a "dremel" type!!) and I was still worried that the torque would be too much for it.

For immediate electrical use, cigarette lighter outlets provided direct access to the generator output. I even had a small 12v toaster oven, and pedaled bread to toast more than once. For electricity storage I would charge a 12v Ah fork-lift battery. I could approximate the output of a small 10 amp battery charger.

Instrumentation consisted of a voltmeter and an ammeter, which together provided me with state of battery charge, output watts and somewhat of a "speedometer." The math needed to determine power output was easy: VOLTS x AMPS = WATTS. A 50 amp silicon stud diode mounted to a four inch square piece of aluminum sheet metal prevented reverse current flows (which would cause the motor to turn the flywheel, instead of the other way around!), and became satisfyingly warm after long sprints. It was mounted in the center of the aluminum plate visible in the first motor picture. For top efficiency (and safety), a switch was also installed to completely isolate the diode and motor/generator from the battery.

I had to be careful - I burned out several expensive 12v halogen bulbs powering them directly. If there was no voltage control, exuberant pedaling would fry the bulbs in short order. When the storage battery was connected, this was less of a problem because the battery tended to even out the voltage, but sprinting would still raise the voltage to the danger level.

I experimented with various non-electrical devices, connected directly to the chain with their own sprockets. I substituted a ball-bearing GPH Labawco type P pump for the generator, resulting in amazing water pumping capacity. The suction from the pump was strong enough to collapse the heavy wall 1 inch vinyl tubing used for the intake (radiator hose would have been better, with the wire reinforcement) and the output shot a stream of water about 25 feet across the street. A 5 gallon bucket was emptied using this pump in less than half the time it took a garden hose to fill it. I believe the pump was driven to capacity (1 gallon per second, emptying the bucket in five seconds) in sprints.

I also tried smaller pumps, including a MATEX rotary vane pump, with great success. I have had difficulty locating that brand recently (30 years later!), but Northern Tool & Equipment carries a pump that appears to be identical. And what a great price!

I never had a chance to determine how efficient the Pedal Generator was in converting mechanical energy to electrical energy, but I believe it was probably quite good. When it was running, only 4 ball bearings were turning, the only high-speed part was the armature of the motor, and I know from research that chains can be as high as 98+% efficient in power transfer. The permanent magnet motor was probably better then average at power generation, because it was designed to be efficient as a motor. In "reverse" tests, with the motor driving the unit with no load, the power consumed was less than an amp at 12 volts. This is negligible, and much of it was resistance loss in the motor windings, since the motor drew half an amp with no load connected to it.

Status: The Original Pedal Generator never broke down, and never wore out. I still have the motor and flex-shaft, but several job-related moves finally forced me to dismantle the unit, even though it was still in perfect working condition.

(1) Three things about the MINIBRUTE 12 Volt DC chain saw. One, I was in great shape and probably was generating over one horsepower in the sprint. Two, the branch/log was about three inches in diameter - not anything near the 10 inch bar length. And three, the saw was a 12 volt saw, so it was designed to be efficient. The literature from the saw said that the motor was a permanent magnet Bosch electric winch motor, which was a good match for the maximum output of the Pedal Generator. It was great to see the chips fly!

Human Pedal Power Potential: What is possible?

There are many other possibilities that I can think of for this device. It is much more powerful than a hand crank generator. The efficiency and variable speed of the output are two features that can be exploited. Since it requires no fuel, and is not affected by time-of-day or weather, it would make an excellent Human-powered emergency generator, ready for any blackout. Here are some other devices that could be powered by the basic unit:
  • Pedal powered charging system for portable "Jump Start" systems. These devices feature lights, air compressors, battery chargers, power meters, 12 Volt DC outlets, and of course jumper cables. The Portable Power station in the photograph was purchased at Costco for $ It can be plugged directly into the 12 Volt DC output of the PPPM for charging, and then moved to wherever the power is needed. Add a small Volt AC inverter ( Watt) and you have everything you need for portable power. Run a laptop, TV, PA System, or any other small electrical device for hours from your stored energy. Real Goods sells an equivalent device that seems to be the next level up in quality and features (and cost, of course!).
  • Pedal powered backup generator for solar electric systems or other off-grid power systems. With the newly available white LED as a light source, a few minutes of pedaling would be enough to create hours of light.
  • Pedal powered biodiesel circulation pump or biodiesel transfer pump - direct drive, with no electricity and no battery. If you make biodiesel, and you wish to eliminate electric pumps from your biodiesel equipment, the Pedal Generator design is perfectly suited to circulate, agitate and then transfer a batch of biodiesel, and the power source is YOU!
  • Pedal powered washing machine (this is a tremendous workout, especially with the spin/sprint at the end!)
  • Pedal powered clothes dryer (when combined with a simple solar hot-air collector - such as your attic! - pedaling would tumble the clothes and circulate the heated air)
  • Pedal powered whole-house ventilation fan (15 minutes in the evening to cool off an entire house)
  • Pedal powered pump and watering system when combined with a cistern to store rainwater
  • Pedal powered emergency sump pump - keep your basement dry during a power outage
  • Pedal powered energy source to power astronomy equipment during stargazing. (A Human powered star party!) A PPPM in a pickup truck could provide a steady Watt 12 Volt DC power supply, quietly, and keep the riders warm at the same time. Switch riders frequently and you'll keep the all of the PPPM Human star party generators warm. Don't even think of starting vehicles during the event!
  • Pedal powered whole-house (central) vacuum cleaner - requires two people, of course
  • Pedal powered backup circulation pump and backup air pump for tropical fish, expensive pond Koi or other animals requiring small but constant energy flows.
  • Pedal powered generator, emergency bilge pump, crew-warmer and exerciser for marine use.
  • Pedal powered air compressor (compressing air takes a LOT of power, and is not very efficient. This would work for small jobs only, like filling tires, staple guns, nail guns, caulking guns, small hand tools - no jackhammers!!)
  • Pedal powered offset printing press, sewing machine (an ancient idea), hand tools (grinder, disk sander, buffer, drill, reciprocating saw, lathe), mulch grinder
  • Pedal powered public address systems, projectors, or amplifiers for music - Radio Shack has a perfect unit for this! A single rider could power two of these with 12 Volts DC direct from the PPPM. Musicians, your green, portable PA system is finally here!
  • Pedal powered Science Fair Project - anything from the efficiency of the unit, to the physiology of the rider can be studied. Human power generation is a vast subject with many possible areas of scientific exploration.
  • Pedal powered replacement for hand cranked generator - your legs are almost ten times stronger than your arms. Free your arms and hands for other tasks, like reading, knitting, or mousing!
  • Every safe room, bug-out bunker, fallout shelter and hidey-hole should have a PPPM pedal powered backup generator. In addition to keeping you warm, fed, illuminated, circulated, ventilated and connected with the outside world, it can give you something to do besides staring at the walls. And it is totally safe with no fuel, fumes, or dangerous voltages! (unless you need more than 12 Volt DC appliances) Don't leave your generator or solar panels out as an advertisement for mischief. The PPPM is the only power source you can have in the bunker with you.

Basically, any device that was hand cranked, foot-powered, or powered by a fractional horsepower electric motor could potentially be converted to pedal power.

Also note, if the base unit is being used to power an auxiliary device in addition to producing electricity, adding a solar panel will result in additional power from the motor/generator! That means whatever device you are powering would receive the combined power of the Human pedaler and the solar panel. This combination makes the best of both power sources, as efficiency would be very high, because the solar output would not suffer the losses of being stored and then extracted from a battery. Charging a battery and then extracting the same power is less than 80% efficient, and can be much worse. Direct utilization captures that wasted power.

Finally, keep in mind that a tandem setup for the pedals, with the pedals out-of-phase, doubles the power and smoothes out the power flow. Only one "flywheel" is needed, so this enhancement needs only a simple pedal/seat addition to the basic unit. With out-of-phase pedals, peak torque is not increased, so other parts of the system are not stressed. The torque curve for a complete revolution of the flywheel simply smoothes out, while RPMs stay constant, resulting in twice the power.

Latest News: Pedal Powered Prime Mover - Reborn

News: Sun Sep 14 PDT

Last weekend at TechShop San Jose I completely rebuilt the PPPM, after 10 years of hard riding. It has taken on the look of a Steampunk Project, except I am the power source instead of steam. The PPPM is a very interesting machine to see, and now that I have painted it and replaced worn parts it's ready for another 10 years of power-generating rides!

News: Sun Nov 16 PDT

The PPPM shared the stage with Tamara Dean, author of The Human-Powered Home. After the presentation, the PPPM was moved to the publisher's booth, where it became the only Green Energy powered display in the San Francisco Green Festival.

News: Thu Nov 18 PDT

The Christian Science Monitor interviewed me during one of my pedal-powered webcasts, and included the interview in an article about Human Power.

News: Thu Sep 18 PDT

The Mother Earth News printed an article on generating power with bicycle generators, and the PPPM was mentioned: Make Electricity While You Exercise. The author describes several different approaches to Human Power Generation, including a state-of-the-art design he invented and assembled for a friend.

News: Sat Aug 23 PDT

The San Francisco Chronicle printed a detailed article on the PPPM: Power From the Pedals. It's a fun article with a detailed diagram of the PPPM and its power systems, and a firsthand account by the author of how it feels to generate power.

News: Sat May 10 PST

After a long bike ride, I arrived at UCSC where I worked with a visionary Professor and an incredible group of students to construct FOUR PPPMs in ONE DAY! Here is a link to a photo album showing this unbelievable event:

PPPM Mass Production

The day ended with pizza, and a test of power output, of course!

News: Sun Feb 24 PST

Use this new interactive Circuit Builder Tool to see what kinds of equipment are needed to power various devices, from Television sets to Breadmakers.

News: Wed Aug 15 PDT

PPPM technology lit 15 lanterns in an enormous Oak tree at the Big Chill Festival at Eastnor Castle, UK.

News: Sat May 19 PDT

The PPPM is displayed at the Maker Faire powering a complete home office. I pedaled all day Saturday, generating Watt-hours!

News: Tue May 8 PDT

So far in , the PPPM has been on display at the Burning Man Green House event, Earth Day, and Springtime in Guadalupe Gardens. Record power was produced at Guadalupe Gardens: Watt-hours! See the PPPM Live!

News: Sun Dec 10 PST

PPPM designs and technology powered The Boycott Coca Cola Experience in London.

The PPPM is powering power the Wasteland installation at the Bates Museum by Artist Virginia Valdes.

News: Sun Oct 8 PDT

The PPPM was the power source for a Demonstration of Incandescent vs. Compact Florescent light bulb energy use at an Energy Fair

News: Sun Sep 24 PDT

Today I tested a Farad Xpress Digital Power Capacitor, also known as an Audio Stiffening Capacitor, as both the power "smoother" and the voltmeter for the PPPM. The test was a complete success. I ran two different devices directly from the PPPM. One was an IBM ThinkPad T40 Laptop, and the other was a 12 volt air compressor.

The capacitor provided a real-time voltage display, and it stabilized the voltage and amperage being produced by the PPPM. When passed through a Targus 12 Volt DC converter to the laptop, pedaling was smooth and easy. With a comfortable seat the laptop could be pedaled indefinitely. The air compressor required more effort, especially when it was used to pump the tires on my eGO Electric Vehicle to PSI.

The capacitor was on sale at Frys Electronics for $ - a great deal considering it is both a capacitor AND a voltmeter. While it does not provide as much information as the Watt's Up I describe below, it does address two critical needs: voltage measurement and power stabilization. It's not in the same league as my Maxwell 58 Farad capacitor, but it costs 7 times less! It's perfect for a basic PPPM.

News: Wed Aug 16 PDT

The Pedal Powered Prime Mover is a hit in Australia! - Main BioSUB Site

News: July 31, , It has been one full year since I brought the Pedal Generator back to life. I have been riding that generator every day, and storing the power it produces in a battery bank. Motivated people from all over the world have bought plans to fulfill their own visions for Human Power. It's a success!

Previous News: On July 31, , I rebuilt the Pedal Generator, and I call the improved model the Pedal Powered Prime Mover, because it can do much more than generate electricity.

I built the Pedal Powered Prime Mover (base, frame and flywheel) in one day!

The design is similar to the early version in the picture at the top of this page, but I made a point of reproducing it in a way that would be friendly to a "do it yourselfer." The only tools I have used are: screwdriver, hacksaw, wrench, hand drill, and wood chisel. I finished it with only those tools, and all "off the shelf" parts. It's great to have the Pedal Generator back online, as the new and improved PPPM I.

I recently installed a power measuring device called the "Watt's Up" from (search for "battery analyzer") I think it is the best such device I have seen for this use. Disclaimer: I was so impressed with this device, I joined their affiliate program, and the link above goes to it. If you prefer to go directly to a different site,, visit This device provides a real-time display of volts, amps, watts, and other valuable and interesting information, such as peak output! It has become the "speedometer" and "odometer" for the Pedal Generator. Here it is in action! It's small, powered by the electricity it is measuring, and it measures in real time. In this display I am pedaling with no hands to take the picture, and the display shows an instantaneous output of Amps, Volts DC, Watts, and also shows that the peak output for that session was 51 Watts. The display cycles through other useful information, like total Watt-Hours and Amp-Hours produced in that session. It sure beats the old panel meters I had on the original Pedal Generator!

Pedal Power Movies and Specifications: The Pedal Powered Prime Mover in Action

Here are some movies of the PPPM I in action. One of the last issues I solved was a slight alignment problem with the flywheel. If you listen to the movies, that is the loudest sound. The final version of the PPPM I - which is used in the Ultimate Pedal Powered TV Movie - is MUCH quieter.

Some of the devices shown in the movies are powered by v AC through an inverter, some are powered from 12 volts DC directly from the PPPM I, and some are powered mechanically. No batteries are used in ANY of the movies!

Ultimate Pedal Powered Television: PPPM I, Watt Victor 12v DC to v AC inverter
  • 14 Inch Television: Short Movie, Long Movie, 12v DC 1 Farad capacitor
    (Note: the black bar on the TV screen is caused by unsynchronized camera and TV frame rates. The picture is actually perfect.)
  • 32 Inch Television 12v DC 58 Farad capacitor
Pedaling Effort: Light to Extreme, depending on the screen size ;-)

Pedal Powered Laptop Computer: PPPM I, AD-SDRW - Universal DC-DC Regulated Adapter, 12v DC 58 Farad capacitor
Pedaling Effort: Light to Medium

Pedal Powered Blender: PPPM I, 12v DC 58 Farad capacitor, 1, Watt 12v DC to v AC inverter
Pedaling Effort: Light to Medium

Pedal Powered Water Pump: PPPM I, direct drive to GPH Labawco type P ball-bearing pump, 6 gallons pumped during the movie
Pedaling Effort: Medium

Pedal Powered Trip Hammer: PPPM I, directly driving a 16 ounce (.4Kg) hammer through a 3 foot (1 Meter) swing.
Pedaling Effort: Effortless

Pedal Powered Fan: PPPM I, Watt Victor 12v DC to v AC inverter, 12v DC , MFD capacitor, Box Fan
Pedaling Effort: Moderate (Low Speed), Medium (Medium Speed), High (High Speed)

Pedal Powered Air Compressor: PPPM I, directly powering 12v DC air compressor, 15 PSI added during the movie (>65 PSI)
Pedaling Effort: A good workout. revolutions generated 30 PSI. Easier than a tire pump!

Pedal Powered Die Grinder: PPPM I, Watt Victor 12v DC to v AC inverter, 12v DC 1 Farad capacitor, 10,, RPM Die Grinder
Pedaling Effort: Light to Medium

Pedal Powered Vacuum Cleaner: PPPM I, directly powering 12v DC vacuum cleaner.
Pedaling Effort: Medium to Heavy

Pedal Powered LGB Garden Train: PPPM I, Farad Audio Stiffening Capacitor, directly powering an LGB G-Scale Train.
Pedaling Effort: Very Light - Moderate, Depending on Speed and Grade

The fun part of this is you can "feel" the effort the locomotive is making when it hits the grade. Controlling the speed of the train is easy - just speed up or slow down the pedaling. The Capacitor creates "momentum" electronically which adds to the overall effect. Is your consist a little too heavy? Don't just see the action, BE the action.

Pedal Powered Compact Florescent Light: PPPM I, Watt Victor 12v DC to v AC inverter, 12v DC , MFD capacitor, 60 watt equivalent bulb
Pedaling Effort: Very Light (sorry for the pun!)

Pedal Powered Biodiesel Pump (Methoxide Agitation and Transfer): PPPM I, directly powering Hypro 4 roller pump.
Pedaling Effort: Very Light (Agitate) to Medium (Transfer)

You may be wondering if it is possible to do more than one of these activities at the same time with a single unit. The answer is YES. The light, for example, could be combined with any of the other activities. As long as the rider can handle the extra workload, the Pedal Powered Prime Mover can deliver multiple outputs simultaneously!

One of the unique features of this design is that the Pedal Powered Prime Mover is not limited to generating electricity, unlike other Pedal Generator or Bicycle Generator systems. The mounting possibilities for pedal powered machinery are almost infinitely flexible. In the pedal generator movies above, where the Pedal Powered Prime Mover is being used directly as a pedal powered water pump for example, the generator has been removed and the new devices has taken its place. The flexibility is tremendous. In just a few minutes, you can change the Pedal Powered Primer Mover to a pedal generator, or to any of the other configurations you see in the movies. That means one Pedal Powered Prime Mover can serve a wide range of pedal power needs, including whatever you are thinking of right now

It is more fun than you can imagine to power things by pedaling, with just you as the "Power Plant." It's healthy, and it's green, sustainable energy. What would YOU like to power? Tell me here, and I just might give it a try and make a movie of the result.

Pedal Generator: Frequently Asked Questions

Over time, a number of questions have asked about the information on the page. Here are some Frequently Asked Questions and answers/opinions:
Do you have plans available?

YES! Follow the link below to order plans.

Why this design instead of a bicycle generator or a recumbent generator?

This design is simple and efficient. You will generate up to twice as much power for the same effort with this design compared to other bicycle generator designs.

Ok, but I see on the web other pedal generator designs claiming Watts, Watts, even Watts - and people posting they have "generated Watts" - or way more! Why all the different numbers?

Some sites quote MAXIMUM power output in an absolute all-out sprint, and some riders are not quoting actual electrical power generated at all. They are quoting "calculated output" from their exercise equipment meters that has nothing to do with real power generation.

I always quote REAL NUMBERS representing measured Amps and Volts coming OUT OF ME and going INTO A DEVICE or BATTERY. In other words, "real power output." Don't be fooled by the other numbers you see.

Do you have assembled PPPMs available?

NO! It is not cost-effective OR energy-effective to build the units and ship them. The best way to obtain a PPPM is to assemble it yourself, or find a local resource to assemble it, such as a Bicycle Shop. You will also be able to fix it yourself if you built it yourself.

Is there a recumbent version of the PPPM?

It is theoretically possible to convert the PPPM to a recumbent Pedal Generator. The image at the top of the page shows an early, working prototype of a recumbent version. In fact, the PPPM could be assembled for both upright AND recumbent use, and the riders could simply choose the riding position they prefer. The current plans do NOT contain instructions for this conversion, but a version of the plans is being written that will provide the details.

If I build the Pedal Generator, how do I power things with it?

Take a look at this Power Board I built for an Energy Fair for ideas. It shows how to wire 12 Volts DC through a junction box into an inverter with Ultracapacitors to smooth out the power, and both cigar lighters for 12 Volt DC appliances, and a power Strip for Volt AC devices. A 12 Volt DC Laptop Power supply enabled me to run an IBM Thinkpad directly, drawing only 20 watts. The Watt's Up meter shows how much power is flowing out to both the cigar lighter outlets and the inverter, in real time. You can power anything within reason with the setup shown. It's a great visual learning tool for educators to use in a classroom, too!

Here is a short movie explaining the inner workings of the Power Board. For mode information, check out the Interactive Circuit Building Tool!

Do you offer parts in a pedal power kit I could build myself?

No. All of the parts needed to build your own Pedal Powered Prime Mover are likely to be available locally. All you need are plans.

Would a car alternator work better for generating power?

No. Most automotive alternators have one ball/one sleeve bearing, a built-in power-robbing cooling fan, and they require external power to excite them at low-to moderate RPMs. They have never been designed with efficiency in mind, since they were attached to monstrous motors capable of producing orders of magnitude more power than the alternator required. They actually produce AC power, which subsequently must be rectified to DC to charge batteries. This step causes significant power loss in the diodes (around 5%). As I noted above, I ran power output around the diode and directly into the battery to avoid this loss. In addition, alternators are designed to run at extremely high RPMs (alternator pulleys are smaller than the driving pulley on the engine, meaning the alternator turns FASTER than the car engine. Look at your tachometer reading and double it. Whew!), and do not produce usable power until they are rotating quite rapidly, requiring high ratios of step-up from your pedals. A well-designed permanent-magnet ball-bearing motor, preferable one designed to squeeze every last bit of power out of a set of batteries, will easily beat an automotive alternator in efficiency, yielding % more electricity for the same effort.

Wouldn't gears help generate more power? And what about belts instead of chains?

Maybe. Humans can only pedal through a small speed range, about RPMs. Below that you can strain your joints, and above that efficiency falls off. There is a "magic" speed (different for every Human Being) at which they can generate maximum power. The proper gear ratio enables the Human to pedal at that speed. You may have noticed, though, that a Human's maximum power output can change quickly from fatigue, and slowly from changes in conditioning and age. The magic speed is always changing, so having a few closely-spaced "gears" or ratios may enable a better match of Human to generator. No matter what, though, gears don't create energy, they waste energy, so having fewer of them is always better. The same goes for bearings, even ball bearings. The pedal-power generator described on this page has very few of both, so it is very efficient.

Regarding belts, the transfer efficiency of most belts is less than chains. This is mostly due to flexing energy loss within the belt material and friction losses at the engagement points between the belt and the pulleys. Belts also work best when transferring low torque at high speed (the opposite of what a pair of legs produce!) which is why you do not see them on bicycles, for example. There may be some exotic, thin, high strength belts that could approach the efficiency of chains with the right design. For example, the "serpentine" belts used in modern automobile engines are much more efficient than the old "V-belts" from the past. Belts rely on friction to transfer power. Friction is bad. The best feature of belts is that they are quiet, so I can't say to avoid them completely. If you decide to use a belt to transfer power, use the thinnest, strongest belt you can find, and place only enough tension on it to keep it from slipping during use. I do not know whether equivalent "toothed" and "grooved" belts are equally efficient, but I believe the toothed belt has slightly lower friction losses. If I can ever find some real research data on the web I will link it in here.

I would rather use my bicycle in a stand and rig up a generator connected to the rear wheel, or convert an exercise machine by attaching a generator to it. Will you help?

I may, but I have all my attention focused on this design. I want to improve it, and make it even more efficient and easier to build. Every stand and exercise machine is different, and I can't invent a solution for each one separately. It's also impossible for me to work with equipment that I can't see, touch, or measure in any way.

If you are still interested, click on "Convert Your Bicycle" to the left.

Could I generate more power with my bicycle in a stand and a generator connected to the rear wheel?

No. You certainly can rig up a bicycle stand and hinge the generator against the back tire using a tension system. I don't think you will be able to generate more power than the PPPM does, and here's why:

To get an idea of how much energy is wasted in a bicycle power train, pick up the back end of a multi-gear bike, like an speed mountain bike, and give the wheel a good spin - backwards. See how long that much energy input can keep the machinery moving. I would be surprised if you counted more than five complete revolutions, unless you are testing a perfectly-maintained track bike.

With the same "push" the PPPM flywheel keeps spinning more than a minute. The difference is not caused by the flywheel - it's due to the rapid loss of the energy you put into the bicycle machinery due to friction. That loss will be a constant drag on YOU as you ride your bicycle generator. The PPPM design is simply more efficient.

You will also wear out your bicycle's tire, gears, chain, and bearings. If you have an expensive bike, you will be paying more than you think for your Human-powered electricity. If you have an inexpensive bike, it will be even less efficient!

If I pedal now and store the energy in a battery, can I watch TV later?

Of course! A Pedal Generator plus a battery is an interesting combination of technologies. Here are a number of different scenarios:
  1. If you pedal the TV directly, with no battery, almost all of the energy you create will go into the TV set. Very efficient.
  2. If you pedal the TV and have a battery attached to the system at the same time, the energy used by the TV will be used efficiently. If you pedal a bit more energy than the TV needs, the surplus will go into the battery. Due to battery inefficiency, you will only be able to get some of that surplus energy back. It could be anywhere from 70% to 90% depending on the chemistry of the batteries. If you wait a month to use the surplus stored in the battery, with some chemistries (like NiMH) you may find it has completely dissipated in battery self-discharge.
  3. If you pedal ONLY to the battery, with the idea that you will watch TV later, you will loose 10%% of ALL the energy you create in the manner of #2 above.

So - lets say it takes 60 Watt-hours to watch TV for one hour.

In scenario #1, you pedal at a 60 watt output for one hour, and watch TV for one hour.

In scenario #2, you pedal at, for example, 70 watt output, and watch TV for an hour while pedaling. The surplus (10 Wh) gets stored, but you can only draw 8 Wh back out of the battery, enabling you to watch TV for an additional 8 minutes, not 10 minutes as you might expect.

In scenario #3, you pedal at 60 watts for an hour with the TV off. Later you watch TV, and you discover the power is all consumed after watching 48 minutes of TV (80%).

In other words, if you pedal the TV directly for an hour, you need to maintain a 60 watt output. If you want to watch TV for an hour later, after pedaling, you will have to pedal at 70 watts for an hour to account for the power lost through inefficiency.

No matter what, you will be watching TV!

How much power can one Human Being create?

This is an opinion. I used to be a competitive swimmer, and for a number of years, I worked out 6 hours a day, swimming approximately 11 miles. Yes, 11 miles a day. If you pedaled that hard for that long you might be able to run one ordinary refrigerator for 24 hours. To make any kind of significant contribution to your energy supply, you must use the most efficient devices you possibly can. For example, a small refrigerator designed to be powered by solar power would be much more practical. For example, if you are prepared to use a slightly unconventional refrigerator there is a chance that you could power it with one good workout a day, and maybe even have some energy left over for other things. A rule of thumb: if the device was designed to be powered by batteries, even BIG batteries, you might be able to keep up with it.

If your electric bill shows KWH (kilowatt-hours), take the number, multiply by 8 (assuming you can crank out watts for an hour, which is very ambitious) and that is how many hours you will have to be in the saddle to create the same amount of power. Sorry, it can be depressing. The moral of the story: Using less power is as important, if not more important, than making more.

There are numerous sources of efficient appliances on the web. One place I like to shop is Real Goods, and of course I have spent time inventing my own efficient devices. The white LED light I built shows how technology can create new solutions to increase efficiency. Pedaling for an hour at the watt pace, with 80% efficiency of generation/storage/extraction, would create enough energy to run that light for hours!!!

You may be interested in the details of the effort and energy required to run the 12 volt appliances. I have compiled a Pedal Generator Energy Statistics page with the details.

Finally, here are some facts. Lots of people write to me and suggest that a more efficient method of capturing Human energy would result in a better power output. I am using this page for reference: Horsepower - Wikipedia. Here is the figure that matters:
1 horsepower = 33, ft/lbf/min = exactly Watts


  • A Human would have to lift 33, pounds one foot in a minute to generate one horsepower ( Watts output for one minute) - or, equivalently:
  • A pound human would have to run to the top of a 14 story building (12 feet/floor, about 4 seconds per floor, feet straight up) in one minute to generate watts of output, and would have to continue that pace to keep generating one horsepower. Lighter weight people would have to get to the top even faster to generate the same amount of power.
  • So - I dare you to generate watts/one horsepower, even for one minute ;-)
  • As you can see, even if we could capture Human output with % efficiency (we can't) you alone are not going to be able to run a refrigerator or air conditioner, or even a plasma screen TV directly by pedaling. No way. (Unless it is an unconventional refrigerator!!) However, with the combined output from multiple PPPMs, anything is possible!

Can I generate v AC? Can I run my electric meter backwards?

I don't recommend this! (Mostly, because it's illegal!) If someone were to replace the permanent magnet DC motor in a Pedal Generator (such as the one on this page) with a 1/4 to 1/2 horsepower v AC induction motor and pedal that it would result in an amazing thing. If the motor was hooked to the power lines and it was "pedaled faster than it wanted to go", it would start generating v alternating current. Beautiful sine wave AC. If it was creating more energy than your clocks, refrigerator, all those little square black power supplies you have plugged in around the house, your lights, and that watt stereo you are listening to while you pedal all use together, your electric meter would slowly creep backwards. However, that same motor would generate exactly 0 power if it is not plugged in to v AC.

For very light duty "off the grid" use of v AC, you can try pedaling your 12 volt DC generator into a large battery and hooking up an inverter (12v DC - v AC) to get some pretty decent v power. In general, plan on being able to pedal at the rate of about watts for half an hour or so, if you are in good shape. WARNING: You CAN'T use an ordinary inverter to "run your meter backwards"!!!! (Think smoke and flames!) If you are lucky enough to have a "grid tied" inverter that matches the output of the PPPM, you just might be able to send power back to the grid. However, read this before you consider a grid-tied pedal generator.

For efficiency, however, you are much better off producing 12v DC for a 12v DC TV (for example) than you are producing 12v DC to charge a battery to run an inverter to power a v AC TV. The UPS (uninterruptable power supply) for my website computer system can power the computer for about five minutes. The same battery (12v AH) would power my laptop computer for about 45 minutes. Everything (efficiency-wise) works FOR you when the device being powered is designed to be efficient (12v DC) and AGAINST you when it is not (v AC).

How do I know how much power an appliance requires?

Almost every appliance, motor, light bulb, etc. has a "Watts" rating. You need to know how many Watts the appliance uses while it's running. Keep in mind, some appliances, like air compressors and refrigerators, require a MUCH higher amount of power to start than they do once they are running. Others, like washing machines, use variable amounts of power depending on what they are doing at any given moment (pumping vs. agitating vs. spinning, for example).

The BEST way to know how many Watts an appliance require is to measure it! Here are several ways to measure power (Watts) used by devices:

How big should my batteries be?

If you are considering building a similar system, plan on using two batteries, and a simple switch which allows you to use one while charging the other. Flip this switch right before you begin charging to ensure that you are charging the battery with the lowest charge (the one most recently used). Also be sure to use a battery that is roughly equal to ten or twenty times your power output for a charging session. For example, if you crank out ten amps for an hour each time you charge, choose a amp hour battery. Larger batteries will simply loose charge through self-discharge faster, resulting is less efficiency for your system and more useless work for you.

What are "rim strips" and what did they do in the original Pedal Generator?

On the original Pedal Generator, I used rim strips on the outer edge of the particle board disk to keep the chain from slipping. They were exactly what you would use on bicycle rims to keep the spokes from poking through. The rim strips I used were for narrow 27 inch wheels. They were approximately one half inch wide. I had tried leaving the particle board groove bare, and there was no way to prevent the chain from slipping.

The particle board disk I used was too large for a single rim strip, so I used two strips end-to-end and glued together with silicone rubber. I overlapped the seam several inches. They are quite thin, so there was no noticeable "bump" going over the seams. I was also pleasantly surprised to find they prevented slipping completely, and there was no evidence of any wear on them for the life of the machine. Be careful when lubricating the chain, however. Keep the lubrication on (and inside if possible) the rollers, not on the outside of the side plates. I was very careful to not let the lubricants reach the parts of the chain contacting the rubber strips.

Where can I learn more about Electricity?

Learn about basic DC electricity here, and all kinds of electricity here.

  1. The most efficient way to use the power you create is not to create electricity at all, but to pedal power your (pump, fan, hoist, winch, drill press, grinder, sewing machine, etc.) directly through a mechanical connection.
  2. The second most efficient way to use the power is to pedal a generator to electrically power your (television, radio, floodlight, chain saw, laptop computer) directly, with no battery. Be careful about controlling voltage, or use a good regulator.
  3. The least efficient way to use your power is to generate electricity and store it in a battery, then extract it from the battery to power some device. Avoid this method in favor of methods 1 and 2!!

Pedal Powered Prime Mover: Do-it-yourself Plans

Movie of David pedaling furiously on the rebuilt PPPM I

That's me above, on the rebuilt PPPM I. The DIY plans for constructing your own Pedal Powered Prime Mover are available for purchase ($USD50) below.

Online Magazine/Site Mentions:

Make: Television - I give the Pedal Powered Blender a whirl.
Planet Green - 5 Ways Going Green Can Help You Lose Weight (PPPM is #3).
Bicycling Magazine - High-Voltage Workouts.
The Christian Science Monitor - An electric workout through pedal power.
The Mother Earth News - Make Electricity While You Exercise
The San Francisco Chronicle - Power From the Pedals
Earthtoys Emagazine June - A PPPM Workout
Treehugger's Article on the PPPM
WorldChanging: Another World Is Here: BikePower! (Pedal Powered Electricity)
Make: Features the PPPM

Interesting References:

The Human-Powered Home - If you are looking for more information on all forms of Human Power - get this book!
Visit The BioSUB Project to read how the PPPM was used to generate power in a unique underwater habitat.
An excellent writeup giving details on a different design based on a bicycle and rollers.
A handcrafted masterpiece demonstrating unique construction.
Yahoo 12 Volt DC Power Group
Yahoo Human Powered Devices Group
Pedal Powered Grid Tied Inverter (PPPM-sized) Note: not tested by me!
Nifty Digital Voltage Meter and Socket Multiplier
12 Volt Appliances and Devices - Including LCD DVD/TV Combo!
P2 - Awesome!
AltE Kill-A-Watt database - how much power do devices use?
Modern Outpost, lots of interesting Personal Power Gadgets
Alternative Energy News
Cyclean, The pedal powered washing machine
The Easyseat - the only seat I used on my PPPM
Solar Panels, Inverters, RV Chargers
Many different kinds of Inverters
Tons of 12 volt battery and charging information
Every imaginable kind of 12 Volt Appliance

The 12 Volt Shop (UK)

Battery and power supply technical information

Joan Baez 'Rejoice in the Sun' - Silent Running

Home Power magazine is the Hands-on Journal of Home-Made Power. If you are interested in making your own electricity from renewable energy, alternative vehicles, or finding out the latest in related technologies and life-styles, then this publication can keep you up to date.

Waistlines Continue to Grow in U.S.

Free Energy from Magnets! (I don't believe in this, but if YOU do, off you go!)


Introduction: DIY Bike Generator

Using easily accessible parts, it is possible to build your own bicycle generator that will charge your cell phone! This instructable is an extension of this instructable made by our friends. Eventually, this bike will stand on its own in our student union, so our classmates can sustainably charge their phones off the grid!

The basic setup of the bike is as follows: the back wheel of the bike spins a DC motor via fan belt, the motor is connected to a charge controller, the charge controller charges a lead-acid battery, and the battery is then connected to an inverter. You can then plug your phone into the outlets of the inverter!

Basic Materials needed:

Bicycle Stand

Bicycle Frame with Back Wheel

12V Lead Acid Battery

DC-AC Inverter

DC-DC Battery Charger

24V DC Scooter Motor

Fan Belt

Fan Belt Pulley

Wires, Screws, Wood, and a Metal Rod

NOTE: We added more to our bike to make it run better, but these are the bare minimum materials to get it up and running.

Step 1: Assembling the Bike

We attached our bike system to a 2' by 6' piece of plywood. We used a bike stand to suspend and stabilize the back wheel. You can bolt the back wheel stand to the board, but we thought it was unnecessary since other portions of the bike were attached to the board. Our bike was donated with the front wheel off, so we built a front wheel stand. Make sure you have enough room on the board to attach the motor behind the back wheel!

Building the front wheel stand: The forks had a 1 cm diameter hole, so we found a one inch dowel for it to rest on. In addition, we took a " x 3" wooden beam and cut it into two " and two " blocks. We drilled a 1cm hole 1/2" down from the top of each of the 9" blocks. We then put the metal rod through the blocks and assembled the stand (see photo above). We added some washers and nuts to make the connections more secure. The two " blocks should be cut to fit tightly between the 9" blocks, as shown above. After building the bike stand, the front wheel should sit snugly on the blocks. Next, we screwed the lower " block down to the plywood. Finally, we attached the upper " block for stability. Now the bike stand for the front wheel is complete and should sit snugly on the rod between the blocks.

Step 2: Adding the Fan Belt to the Motor

We removed the tire from the back wheel using this video (make sure all the air is out of your tire). Next, we attached the pulley to our motor by adding a collar to the pulley and making it D-shaped. The pin running out side of the motor is in a D-shape so this allows the pulley to fixate to the motor and rotate the internal portion of motor smoothly. The screw holding it on is a left handed screw that goes on in the opposite direction of a normal screw allowing the motor to turn without having the screw come out. We then attached the belt to the wheel and to the pulley. Make sure that the motor is directly aligned with the back wheel. We screwed down the motor to the plywood base by having one person hold the motor unit as far back as possible while the other screwed it down, this insured maximum tension in the fan belt. The more tension we can get on the belt, the better it will work.

Note: Be aware of the direction that your motor is spinning in order to a positive and not negative voltage output. If it's negative, just switch the leads at your charge controller.

Step 3: About the Fan Belt Choice

The motor is rated at rpm, but riding at 20 mph is only rpm at the back wheel. Thus, we chose a pulley with diameter about ten times smaller than the wheel, so riding leisurely could give us higher rpm (about 10x increase). For practicality purposes we chose the thickest belt that could fit in the rim of our wheel. Our belt was rather long because it needed to be able to fit around the entire wheel and still have extra length to attach the pulley at the motor. Depending on what belt you are using, the motor could be mounted at various distances from the back wheel.

Function of Motor: This component is what is converting the movement of your legs on the bike into a DC voltage.

Step 4: Step 4: Motor to Charger

Purpose of Charger

The charge controller regulates the rate at which current travels into the battery. Ultimately, the charge controller prevents overcharging and draining of the battery, which will ruin the health of the battery. If the battery is overcharged then water electrolysis will occur, converting the water molecules into hydrogen and oxygen gas inside the battery. This will increase the sulfuric acid concentration in the battery and expose the internal plates to oxygen, quickly degrading the internal materials. Draining the battery will lead to sulfation, the crystallization of sulfur on the plates inside the battery. This will diminish the concentration of sulfuric acid in the battery and it will no longer be able to charge to its original potential.

Charger Properties

This charger can regulate the amount of current going to the battery, read the voltage that you are producing when biking, and the total amount of energy you have generated in one bike session. It will not give you the percentage of the battery charged, therefore (this is in the additional section) we have required that the user ride on the bike a set amount of time before the inverter will allow them to charge their device and that the user cannot charge the device if they are not biking.

The battery that we are using is a 12 V battery therefore the charge controller we chose can take us from 12V to 24V. The battery has a maximum charging current of A, therefore the charge controller should be put on a current output setting less than the max. Increasing the current that the charge controller is requiring will make pedaling harder. That’s a good reason why it’s good to keep the gear system on your bike, and not make it a one-speed!

Adding a Capacitor or Zener Diode

Also, it is important to not overcharge the power controller by biking over its limit of 24V. You can add a zener diode with a breakdown voltage of 24V, so that if voltage is above 24V the zener diode will allow excess voltage to flow away from the charger.

In this setup we added a capacitor in parallel with the charge controller to assist in regulating the voltage generated by the motor. If we were to suddenly have Lance Armstrong hop on the bike and generate a voltage more than 24V temporarily, we can avoid a sudden overload to the charge controller by forcing a regular discharge from the capacitor.

Step 5: Step 5: Charger to Battery

Choosing your Battery

As we said before, you want to make sure that your battery is being charged at an appropriate current and voltage, well within the limits listed on your battery. Be sure to find a battery that your charge controller can charge or vice versa. The reason that you want to have a battery is so that you can store the energy that you are creating—so that you don’t have to bike constantly to charge your device and that you can bike without charging a device and store your energy for later.

Taking Care of your Battery

Make sure your battery is not moving when you are biking—sloshing around the liquids in the battery will add a kinetic energy variable into storage of your energy. It’s not a good variable. Your battery will output different voltages at different levels of charge. The voltage across your battery will be different when it is charging, sitting, and discharging; they will be about 14V, V, and 11 V respectively. Remember that these values will change over time (most likely decrease) as your battery ages and is being used. Degradation will occur. Be sure that if the output of the battery is 14V then you drain the battery so that it doesn’t overcharge.

Step 6: Step 6: Battery to Inverter

Purpose of AC Inverter

The current that comes out of your wall socket is alternating current (AC) rather than direct current (DC). The inverter converts the DC output of the batter to AC so that you can appropriately charge your devices. Also it provides the infrastructure to charge your devices, as in a plug and USB ports.

Choosing the Right Inverter

When choosing your inverter you want to be sure to make sure it give an output current and voltage similar to that of your typical wall socket, accepts a range of voltages similar to your battery, and the wattage that it can output.

Depending on the devices that you decide to charge (here we were interested in charging laptops, cell phones, and other small student devices) you need to make sure your inverter can output the right amount of watts. As a reminder, watts are a measure of energy required over a unit of time, joules per second. Appliances typically list the wattage that they require but to give you an idea a cell typically requires 5 watts and a laptop computer requires about watts. The inverter featured in this instructable has a capacity of watts.

Step 7: Making the Bike User Friendly

Our aim is to put this bike in our student union. Therefore we wanted to make this bike as user friendly as possible. A big obstacle we found was that the charge controller required you to press a button for 3 seconds in order for it to start charging. Although this is relatively simple for us to do, we felt like other users might not read the directions and think that they were charging even though they hadn't pressed start. The screen lights up which is misleading because it is technically "on", but is not charging. Therefore, we hacked our charger and will control it with an arduino instead to make the energy generation process user-friendly.

Step 8: Hacking the Charge Controller

Hacking the Charger: We took apart the charger by unscrewing the sides and popping off the top lid. We found that there was a ribbon wire connecting the 4 buttons to the circuit board. There were 5 wires on the ribbon wire, thus we thought that there might be one "reference" wire and the other four wires went to the buttons. Connecting the "reference" wire to any of the other four button wires was equivalent to pushing a button. We took a multimeter and tested our theory, and it was valid. To press a button, we should connect one of the wires with the "reference" wire. Next, we added wires to each of the five terminals where the ribbon wire used to connect to. The wires were led outside of the charge controller by drilling a hole through the side panel and pulling them through. These wires lead to our arduino shield, which will allow us to press the buttons and control the start button autonomously using a relay.

External Buttons: We used 4 buttons on our shield to recreate the buttons on the controller for testing purposes and in case we wanted to change settings on the charge controller.

Use of a Relay: We used a OMROM G5V-1 Relay to "press" the start button using our arduino. The image above shows how we connected each of the relay pins. The digital output pin from the arduino that is wired to the relay will signal the pressing of the button when it is set to HIGH. Two other pins on the relay connect to the start button wire and the "reference" wire, completing the connection. We had to connect one other relay pin to ground. For precaution, we put a diode across signal and ground of our relay because we don't want current flowing into our arduino when the digital output pin is switched to LOW (start button is off) . Now the arduino has the capability of pressing the start button autonomously.

Programming the Start: Although we know how to get the arduino to press start, we don't know when to tell it to do so yet. We would like it to press start for a few seconds after the user has been pedaling for about 10 seconds. How will we know a user is pedaling? We would like our arduino to read the DC voltage of our motor which will be present when a person is biking. However, our voltage is more than 5V, so our arduino cannot read it directly as it has a limit of 5V. We used this article to create an appropriate voltage divider to have the arduino read motor voltage.

A simple sketch of this voltage divider is in the picture above. I will include all the arduino code in another step. We used a K and 1K resister to scale down the voltage going into the arduino by a factor of 5. We've yet to pedal hard enough to get the motor to go above 17V, so we should be safe. Usually, we are outputting less than 15V from our motor. The voltage divider will go into an analog input in the arduino which will let the arduino calculate the motor voltage.

Psudo Code:

void loop(){



void startCharger(){

if (motorVoltage>12 && hasBeenOnForLong){

digitalWrite(relayOut, HIGH); //which really is equivalent to pressing Start


else if (motorVoltage>12){

//say it has been on for longer



//reset hasBeenOnForLong to the beginning



Step 9: Battery Voltage

We soldered an additional voltage divider to the shield in order to measure the voltage of our battery. We found that this was the best way to calculate how much our battery was actually charged. The output voltage of the battery is between V; decreasing as it becomes discharged. We found these tables which relate the output voltage of the battery to the battery state of charge in percent values for a 12V Lead Acid battery. We can make estimates from this graph, but we will further calibrate it later. Eventually we could add an LCD screen to readout the percent battery charge on our arduino. This readout can be coded by a lot of "if" statements simply structured as follows:



Because the battery only outputs up to 15V the absolute worst case scenario, we chose K and 1K resistors for our voltage divider. This divider works the same as our motor voltage divider. The picture above shows the resistors for the voltage divider on our board.

Note: Batteries degrade over time and the the capacity to which a battery can charge will change, altering the percent charge graphs.

Step Preserving the Battery

Lead Acid Batteries last a lot longer if they are not completely drained. Furthermore, we want to make sure users are generating electricity and not just charging devices from the battery without pedaling. We decided that we wanted users to bike for at least 2 minutes continuously before they were allowed to charge their phone. This idea turned out to be a little difficult, because we need something that can control a lot of current. We ended up employing a HUF MOSFET, which we be between our inverter and battery. When we signal the MOSFET with our digital output pin on the arduino, it will allow current to flow from the inverter to the negative terminal of the battery, thus completing the inverter/battery portion of the circuit. When it is signaled on, the MOSFET will act as though it is not there at all and the cell phones can charge normally. This is possible because the MOSFET we used allows a high current. However, we decided not to allow computer charging on our bike because that would draw more current than the MOSFET could handle. Furthermore, we were afraid the computer would deplete our battery. We are relying on some users biking just for fun without charging.

We will keep track of time since the charger pressed start and once two minutes have elapsed, we turn the MOSFET "on" by setting the digital out to HIGH. Here is part of the code:

String allowBatteryAccess(){
if(currentMillis-startMillis>(*)){ //if 2 minutes of time has elapsed

digitalWrite(allowBattery, HIGH);

return "Your device has started to charge. Keep Peddling";


return " "


Step Board Layout

We soldered all our components to a small board. Here is a color coded layout of how we attached everything. A lot of what we were attaching was to components off the board, so the names of these components are written instead. Attached is the untested Arduino Code for our board.

Step Current Progress

Our board currently has the same functions as the charge controller before it was hacked with the arduino. We have the board wired up for the most part, but we need still need to attach a couple more components:

  • attach the battery and motor positive leads to the voltage divider
  • ground the other end of the voltage divider
  • attach the inverter negative lead to the drain of the MOSFET
  • attach the ground lead of the battery to the source of the MOSFET
  • attach battery ground to the arduino ground
  • ground the relay

These connections may be more difficult to create because the wires on the external components of the mortor and charge controller are much larger than the wires on our arduino shield. Once we get everything added we can test our code. We may need to fiddle with the timing of the start button and how long we it will be "on". The charger performs battery checks when it turns on so we might need to hold it down for as many as 8 seconds. We will check this once we get our board finished.

Step Future Ideas

Though our system works, there is a lot more to be done with user interfacing before it can be introduced unsupervised in the student union. We definitely should encase our electronics so that no one can touch them. We also would like to have a LCD display the can interact with the user showing how much they have charged the battery and their real time motor output voltage. We already have a clear plexiglass stand where people can put their homework reading. We plan to have instructions pasted to the back of this stand and mount the charge controller and arduino to the bottom of the stand.

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T.J. Proechel

I'm a cycling enthusiast, and when theweather is bad I use a bicycle trainer in my apartment. But riding to nowhere has always felt pointless. This got me thinking about how I could use my pedaling to produce electricity. By driving a generator with the movement of the back wheel, I figured I could run a lamp or charge my phone. Realistically, this wouldn't do much to cut my utility bills (or carbon emissions), but it would give my indoor riding a sense of purpose. Besides, I was curious to see what the project involved.

To skip ahead a bit, I ended up rigging my bike to a volt, watt electric motor, which I modified slightly to generate electricity instead of doing mechanical work. I used the motor (now, operationally, a generator) to charge a volt lead–acid battery. And, finally, I added an inverter to convert the battery's DC current into an AC current, which is what's needed to power anything you'd normally plug into a wall outlet, and to store power so you can use appliances even when not pedaling.

Pedal to Metal

I found a lot of the build details on Instructables, the online project-sharing community, where user saullopez52 had done basically what I had in mind. While interning at an educational startup in L.A., Saul Lopez developed the idea as a way to bring environmental technology projects to schools. He thought it would be a low-cost, fun way to provide students with engineering experience. "The exercise component was what made the project engaging," he says. Plus, he adds, "I like that the project has a lot of room for customization."

That's what I did—I customized. I found a combination single-speed/fixed-gear bike that worked well, thanks to its ability to hold a cog on either side of the back wheel. The chain on the right is driven by the pedals, while an added chain on the left spins the motor. On the side that's driven by the pedals, I used a freewheel, which rotates the wheel when I'm pedaling but allows it to keep spinning forward, without the chain moving, when I'm coasting or pedaling backward. On the left side of the wheel, I attached a fixed cog, which spins in the direction of the chain as long as the wheel is turning.

To keep the bike steady I dedicated a bicycle trainer to the project. A nice thing about commercial trainers is that you can easily detach the bike if you want to go out for a ride. But you can also build your own stand; you just need a setup that allows the rear axle to spin freely while raising the back wheel slightly off the ground. To get the bike stand ready for generating power, I removed the resistance unit, which is the spinnable metal cylinder that rubs against the wheel to mimic the feeling of riding on pavement. (Once you attach the motor, you'll also feel resistance as you generate a current, but it really doesn't take much effort.)

With the resistance unit gone, there was space to attach a wooden board extending from the rear of the bike, to hold the motor, battery, and inverter. Because I was using a narrow board (a 2 x 4), I needed to add a crossbar to hold the electrical equipment. (Note: Before attaching anything, you should measure how far the chain extends from the back of the bike. Position the motor so a chain from the left side of the rear hub runs parallel to the wheel, straight back to the motor. With a V-belt, you have to measure precisely; with a chain, you can add and remove links with a chain tool.)

With the motor screwed into the center of the crossbar, I positioned the battery and inverter on either side as counterweights for each other. That helped keep the bar parallel to the ground. I secured them with industrial-strength Velcro, which would hold up when I was moving the contraption around but allow me to fiddle with the parts.

Before linking up any of the electrical components, I tested the connection between the bike and the motor to make sure pedaling actually spun the motor shaft. The shaft of the motor I used is slightly grooved, and the chain gripped well. If you find yourself with a motor that refuses to spin, you can connect a cog to the shaft, guaranteeing that the chain will have a good grip.

T.J. Proechel

(Illustration by Phil Laughlin)

Going Electric

A motor is designed to spin rather than to be spun. So, when connected to a charged battery, it will want to draw power from the battery to turn the bike wheel. To prevent electricity from flowing the wrong way, I inserted a diode between the motor and the battery. A diode directs a current in only one direction, from the anode to the cathode; in my circuit, the anode faced the positive terminal of the motor, while the cathode faced the battery's positive terminal. I wrapped the ends of the diode around the motor's exposed wire and an alligator-clip-tipped test lead, which fastens to the battery, and insulated the connections with electrical tape. Then I wired the motor's negative lead directly to the negative terminal of the battery.

Ideally, the battery should be kept charged above 50 percent, but to prevent corroding it, don't continue to give it electricity after it's fully charged. To keep an eye on this I hooked up a multimeter to the battery terminals. Be careful to set the multimeter to the correct measurement—12 volts in the DC range (though, if that's not available, choose the next number higher than 12). I overlooked the setting on my first ride and the multimeter went up in smoke.

I also used a multimeter to monitor how hard I needed to pedal. To charge the battery I wanted the generator to put out 13 to volts. By keeping my eye on the multimeter as I rode, I was able to get a good feel for this. (In retrospect, it would have been worth it to buy a voltage regulator so I could pedal as hard as I wanted without feeding too much voltage into the battery.)

The final step was to connect the leads from the inverter to the battery. When choosing an inverter, make sure it can handle the maximum peak load you're anticipating. (Loads are measured in watts, which is a unit of power.) Since I wasn't planning to do anything more strenuous than run a watt lamp, I bought an inverter rated for just watts.

When it was all assembled, I pedaled my bike and the current flowed. Even better, if I had a few batteries on hand whose charge I monitored monthly, I could store up enough energy to power small electronics during a power outage. And, yes, the generator did make indoor bike riding fun. After a while, however, the rig made my apartment feel pretty cramped, especially since I already had two other bikes. Luckily, it caught the eye of a neighbor who had some extra space and who was happy to take the contraption. And now when I want to charge my phone while exercising, I know just where to go.

T.J. Proechel

A diode keeps electricity flowing from the motor to the battery instead of vice versa, as it normally would do.

T.J. Proechel

A second chain on the bike runs from the rear cog backwards to turn the motor.

T.J. Proechel

Where mechanical energy becomes the electricity that's stored in the battery.

T.J. Proechel

That electricity is converted from DC to AC by an inverter so it can power regular household appliances.

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DIY VIDEO 1 of 6 Permanent Magnet DC Pedal Power Bicycle Generator

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