Human-Powered Light--from my book, "Doable Renewables"

FeaturedContest WinnerContest Winner
Picture of Human-Powered Light--from my book,
For far too many people, an untapped energy source is close and personal: body fat. Exercise is a good way to get rid of that fat (or just to stay healthy) and we might as well use that exercise for some good purpose, like lighting a room.
This project takes human activity (winding a hand-cranked generator) and stores the energy in a futuristic way (ultracapacitors) to power a very efficient LED light. The human-powered generator is costly--perhaps your school can purchase one for the science lab.

Materials and Tools

Acrylic sheet, 12 x 12 inches, 1/2 inch thick (, Part # 1005001212)
Acrylic sheet, 12 x 12 inches, 1/4 inch thick (, Part # 1002050100)
4 solid acrylic rods, 1 1/2 inch diameter, 2 inches long (, Part # 5007524100)
6 medium screws
On/off switch (, Part # 22200)
Voltmeter (, Part # 2095040)
Human-powered generator ( Part # 454213)
Cable clamp
13 screws, 1/8 inch diameter, 3/8 inch long
12 ultracapacitors ( Part # BCAP0350-E250)
Wire (#22 stranded)
Fuseholder (, Part # 108792)
Acrylic tube, 1 inch outer diameter, 12 inches long (,
Part # 6013012100)
Halogen desk lamp (, Grandrick 20-watt Halogen Desk Lamp)
Wire cutters
2 wire connectors (, Part # 302666)
Wire nut
LED light (

Remove these adsRemove these ads by Signing Up

Step 1: Step 1

Picture of Step 1
Start by attaching four 2 inch long (1 1/2 inch diameter) rods to the 12 inch square, 1/2 inch thick acrylic sheet. Predrill holes in the base and the rods, but first practice using a piece of scrap wood. �Find a hole size that will just allow a medium-sized screw to slide in and out, then reduce that diameter by 1/16 inch. �If the predrilled holes are too small, the acrylic will crack when the screws are added. �Attach the base to the rods by inserting screws into the predrilled holes.

Step 2:

Picture of
Drill holes in the upper plate, a 12 inch square, 1/4 inch thick acrylic sheet, as shown on the template below.

Step 3:

Picture of
Insert the on/off switch and secure it with the mounting nut as shown.
Instead of the expensive "human Powered Generator" why not MAKE one from a dc or stepper motor & a crank handle ????
mathieulj4 years ago
@ End questions
1. Is it practical to use a human-powered generator to run an air conditioner?
2. How could you use a human-powered generator to limit someone's TV time?
3. How much power can an average human produce?
4. How long would you be willing to wind a crank or sit on a bicycle and pedal?

1. To cool a room: not even close. The average air conditioner's power requirements are way to high (Wattage wise).
To cool a person: something could be done with a peltier cell but it wouldn't be very efficient.

2. With a low consumption tv (modern small lcd for example) this is totally feasible.

3. 100-300 Watts (top of that scale being short term peak production)

4. Depends on the work load but if there are good shows on tv during the weekend, I could go all day long :).

As a word of caution, a short circuit across charged ultra-capacitors will result in molten metal flying out at high speeds (and possibly a small explosion if the capacitor's current ). As such, they need to be treated with respect to avoid injury/death (they can also source 800A). With this in mind, I wouldn't have any contacts outside the protective box. I don't think it was explicitly mentioned but for example in step 10, do not use a screw longer than the acrylic is thick. That way the is no charged conductors outside of the box (e.x. the screw tips).
The smallest 120 volt AC produced at 5,000 BTU uses a little more than 500 watts.
I found one manufacture in china, that sells a 12 volt DC unit, but it uses more watts compared to a 5,000 BTU 120 volt unit and is very expensive.

Now, what kind of TV does use the most power?
Glass tube type

It is the LCD.

And the TV with least Power consumption?
I am not 100% sure, but I would say it is the glass tube type.
My 27'' glass tube type uses 40 watts ( 2 years old )
My 32'' LCD uses 200 watts. ( 1/2 year old )

Anyone has a wattage for a comparable size LED tv  between 27'' and 32''? That would give us a good comparison.

Our family went to the science center and they had a small 5'' black and white Tv and a little fan that was powered by an generator hooked up to a exercise bicycle. I tell you, after 5-10 minutes I had enough and our kids did not even last that long.

jeab_993 years ago
Hi, mrigsby.
I'm jeab and respect to your idea.

This is a great project. I like it. Two last years I try to make electric from water ,I use copper piece and silver piece dipped into glass water it make 0.8-0.9 volt. I use my little knowledge about electric make circuit in series until 12 volt. And connect with red LED. It light for about 24 hour when the time past it  low light . When I change new water I have bright light again. I changed from LED to motor electric but it not move. I thing not enough current.

Today I saw you project I think If change from your generator to Battery from water.
I want to know It will make a light or not? how long the light will bright? Can Battery from water push motor electric move or not?

last I'm sory about my English.
This is my fail project Battery from water.
If you have more time please try to my question.
I want to try make it.  but I not have knowledge  about electric.

Thank you


MikeTheMaker (author)  jeab_993 years ago

You are correct that your battery does not have enough current to run a motor.

If you attach your battery to a rechargeable battery (a 1.2 volt cell--positive on your battery to positive on the rechargeable battery) the small current from your battery should slowly charge the rechargeable battery.

After you have left your battery on the rechargeable for 24 hours, the rechargeable should run a small motor for some time.

Thank you for your reply. I will try with rechargeable battery .
Good one ,
ryanmercer4 years ago
Nice, too bad I don't want to pay $560-565 to have some light... the hand generator is $550 by itself!
leblebija4 years ago
How many volts is the hand-held generator? Can it be used for car amplifier capacitor of 2,000,000 micro farad?
MikeTheMaker (author)  leblebija4 years ago
12 volts (around 14 volts peak) and it wlll charge 2 farads in 30 seconds or so.
arulseh4 years ago
Interesting project. I would however recommend removing the first two sentences from your intro for a couple of reasons. One, it seems to imply (in my opinion) that this device is powered by body fat, when in fact chemical energy stored in ATP is being converted to mechanical energy - whether or not the replenishment of ATP will affect fat stores will depend on many factors (more likely the mass of muscles being used would increase if you used it a lot). And a second minor point is that everyone has body fat, just that some of us have more than we need (BMI).
fidibiri4 years ago
If the generatos is rated at 12V aprox, the capacitors at 15V, if wou connect 12 capacitors in series the voltage on each capacitor will be 1V aprox, and a divided total capacitance. For adding the capacitance (charge capacity) of the ultracapacitors they should be connecten in parallel. Am I wrong? is there another reason for getting them connected in series?
MikeTheMaker (author)  fidibiri4 years ago
The capacitors are actually rated at 2.5 volts each--that's why I have two banks of capacitors (six in series in each bank). The six in series gives me the needed 15 volt rating, the second group adds to the capacity.
Ok, that explains it all. Nice ible, like it because doesn't use batteries...
And the answers:

1- No, the AC systems remove the heat generated by people form a room, if you'r exercising you'll produce more heat thus requiring more AC power...

2- You'll get tired of watching TV by exercising...

3- Between 1/4 and 1/2 horsepower

4- 40 min daily, rated at ~1/4hp (200W) enough for my 40" LCD TV.
robot7974 years ago
if you add an rectivier you can turn the crank eter way and it will still work

and if you use a stepper motor you will have more gain
rockyt4 years ago
A video would compliment the instructable nicely. you know, just to see it in action.
Musicman414 years ago
Idea, a tv that is powered only by a bicycle. Wouldn't watch much tv, but would get good workout.
It could be done, but I think it would need to be a small flat screen with LED back lighting. I mean really small unless you're lance Armstrong.