# Faraday For Fun: An Electronic Batteryless Dice

There has been a lot of interest in muscle powered electronic devices, due in large part to the success of Perpetual TorchPerpetual Torch, also known as battery-less LED torch. The battery-less torch consists of a voltage generator to power the LEDs, an electronic circuit to condition and store the voltage produced by the voltage generator and high efficiency white LEDs.

The muscle powered voltage generator is based on Faraday's law, consisting of a tube with cylindrical magnets. The tube is wound with a coil of magnet wire. As the tube is shaken, the magnets traverse the length of the tube back and forth, thus changing the magnetic flux through the coil and the coil therefore produces an AC voltage. We will come back to this later in the Instructable.

This Instructable shows you how to build an electronic, batterless dice. A photograph of the built unit is seen below.

But first some background --->
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## Step 1: An Electronic Dice

Instead of a traditional dice, it is nice and cool to use an electronic dice. Usually such a dice would consist of an electronic circuit and a LED display. The LED display could be a seven segment display that could display numbers between 1 and 6 as seen below or perhaps, to mimic the traditional dice pattern, it could consist of 7 LEDs arranged as shown in the second figure. Both the dice designs have a switch, which the user has to press when she/he wants to "roll the dice" (or "roll the die"?). The switch triggers a random number generator programmed in the microcontroller and the random number is then displayed on the seven segment display or the LED display. When the user wants a new number, the switch has to be pressed again.
azizs126 days ago

hi...may i know how many turn coil do you use......

50h9j2 years ago
This sounds impressive, but I am worried that the 15V is measured on an oscilloscope with high impedance and the current is measured on a short circuit, i.e. very low impedance. This flatters both measurements and gives no indication of actual power produced, particularly not sustained or average power over the cycle.
I have been looking at student wavepower converters that use such devices and I can't help thinking they are very low efficiency. This is reinforced by not finding any commercially designed machines with Faraday linear generators, of whatever they are called.
I would be interested if you could estimate the mechanical power input to your device and the electrical power output and come up with an efficiency. One way would be to power the device from an electric motor and mechanism of known efficiency.
Sparklesam5 years ago
The project is really cool, but u call it a batteryless dice. Real dice don't have batteries. Its a really cool idea, but what's the point when you can just use real dice?
5 years ago
-.- ... guess we'll call it batteryless electronic dice. as most of the things on this site the point is ... just doing it!
Gadre (author)  frenzone5 years ago
You could look at it this way: a traditional dice is batteryless. An electronic dice is not batteryless and this is a batteryless electronic-dice.
4 years ago
But no, a capacitor is a battery of sorts, so this is not batteryless
3 years ago
Respectfully, I know it has become popular to erroneously to refer to a battery, when they are completely two different items. Popular doesn't equal "battery of sorts", so this project use no battery. Yes it's "batteryless"
5 years ago
ur right. cool project gadre
5 years ago
It's cooler. And it's electronic and batteryless. Its not just batteryless.
Gadre (author)  Sparklesam5 years ago
OK :)
shylock6 years ago
I have batteryless dice, they are cube-shaped with dots on them. ; )
6 years ago
cube batteryless dice?? i would pay respect to see
Gadre (author)  stevenbelieven6 years ago
Yes, cube shaped battery-less dice. This is what Shylock is referring to. Photo from wikipedia dice.
3 years ago
Those are "analog" die. ;)
6 years ago
led to this application hahahaha it was all about led AS THIS MY GAME ON A LARGE SCALE !!! IN ASIA PEACE STEVENBELIEVEN4NOW
Gadre (author)  shylock6 years ago
Indeed. But it aint electronic!
nanosec123 years ago
Wow, just Wow....this is one of the best written instructibles I have ever read, and well documented with pictures as well. I love that you went into the history and theory, instead of just writing up a 'how to' Thanks

5 of 5 of course.

Nano
Gadre (author) 3 years ago
This and other 34 projects are now available in a book, published by McGraw Hill International: TinyAVR Microcontroller Projects for the Evil Genius.
Why don't you lock 2 magnets on the end of the tube and let the one in the middle to do the job? So you won't "crash" the magnets every time you roll.
revfnord4 years ago
I would love to make one of these inside a magic 8 ball with blue LEDs!!!

Love the tutorial, great job!
jornie4 years ago
how much is this worth if i would buy all the stuff?
knightowl4 years ago
Awesome build. Going on my "to make" pile for sure. also, good luck getting that thing through airport security.
sandman994 years ago
what does it do
godofal5 years ago
im olmost done!
but i forgot to order the pulse detector  diodes >.<
and i still  need to wrap the tube with that copper wire...

but i have the rest ready :)
Gadre (author)  godofal5 years ago
You could use normal rectifier diodes too (1N4001) without any problem. Give it a try.
4 years ago
well, i dont have a big lab :D
i have a 3 sorts of stuff lying around; resistors, capacitors, and LEDs

for the rest, i need to order everything if i need some specific thing...
Kidogo6 years ago
is the uF important?
5 years ago
Yes, very important.  Sparkfun has a 10F (10,000,000 μF!) 2.5 volt capacitor for ~\$5 (wire two in series for 5F, 5V).  I would highly recommend that.  But on a side note, I'd like to point out that dice is plural, while die is singular.
Gadre (author)  Kidogo6 years ago
A higher uF will keep the dice showing the number for a longer time. I have not tried with a capacitor smaller than 4700uF, but it would work anyway. I tried the 4700uF capacitor with my dual dice and it works for much smaller time.
Iridium75 years ago
do these things just pick any random number or something?
microman1715 years ago
Nice work :-) I like the way you have sorted out the 2 dice version. Will you be rapidly changing between the two displays (POV making it seem as though two dice) or one at a time? If magnet wire wasn't so expensive and hard to find in New Zealand, I would try this for sure! Would most likely use a PICAXE instead as that is what I use. Keep it up mate!
DIY Dave5 years ago
cool
cyborn955 years ago
This project is awesome but things need to be more descriptive. When building the circuit, I see resistors but you just call the resistors a pulse detector. I would like to build it but building the circuit is just too complicated. Also, in the intro you should put a complete list of what we need to build it.
Andruha11236 years ago
hi, it seems as you know what you are doing. I'm pretty new to this and have a question. Can i use yellow wire instead of the red one(magnet)? And do i have to use rare earth magnets? i bought (N42, Dia 3/8"X1/8", Axially Magnetized. Ni+Cu+Ni plated.) these magnets, would they work at all???thanks, looking forward to your answer, really wanna make this.
Gadre (author)  Andruha11236 years ago
1. By yellow wire you mean the insulation on the wire is yellow in color? If that is the case, then it would work just fine. 2. Your magnets are fine. Just make sure that the diamater of your magnet and the inner diamater of the tube onto which you are winding the coil are compatible. While the magnets shoudl slide freely inside the tube, having too much gap is not advisible. Good Luck!
5 years ago
Where can this wire be bought? Does it have to be insulated or can it be bare metal wound around? Is this type of wire in any household equipment that i could rip apart and scavenge? Thanks :)
Gadre (author)  alexgeek5 years ago
It has to be insulated. You can perhaps salvage such wire (make sure that the insulation is intact) from motors, transformers in mixers, grinders and other household equipment. Goodluck!
5 years ago
Thanks! If not, do many places sell it relatively cheap? Not found many good sites that sell it. Cheers.
5 years ago
5 years ago
I GOT MINE FROM AN OLD MONITOR. I FOUND THAT THIS IS THE BEST SOURCE.
6 years ago
here is the website and the specific magnet i bough, i'm thinking this would help. i bought 4 of them.
http://www.magnet4sale.com/product.php?productid=16394&cat=357&page=1
basqueman6 years ago
This looks awesome. I am all ready to go, but I'd like to get a PCB. Where should I go to order the PCB? If you ordered your through Eagle Circuits, can your board be recreated from the original order? I have never done this before.
6 years ago
Thats just a generic piece of PCB, or perf board. He just used jumpers, and solder bridges to create the circuit.
6 years ago
Yes, Initially a perf board was used but subsequently, I got PCBs made, you can see images of the PCB on the last page.
joinaqd6 years ago
awesome job dude...i had a flashlight like that..u gotta shake it to charge the 36mAh battery which powers a white led..good job!!
Carlos Marmo6 years ago
Wonderful work! Much Style! Congratulations!
Andruha11236 years ago
one more question, does it matter how long the coil is? i know you said 1500 turns, does it mean i can go the full length of the tube, of do i wind like an inch or 1 1/2 in the middle? thanks.
Gadre (author)  Andruha11236 years ago
Please allow enough margins at the tube ends so that the magnets can fully come out of the coil.
bhunter7366 years ago
Great Build! I want to make one. : )
Sandisk1duo6 years ago
cool!
andyhuntdesigns6 years ago
This is a great idea! I like the fact that it is powered/activated by shaking it, which almost simulates the act of rolling traditional dice. Then again, traditional dice themselves are also self-powered and battery free, so maybe this is a bit of extra effort...
6 years ago
My thoughts as well. Cool toy though. Over-engineering at it's best!
frollard6 years ago
I always used to program my TI-83 to be a dice generator that kept stats for when we played Settlers of Catan - why? because when we play at a given player's house, probability breaks, and we get 90% rolls in the 10th percentile of the bell curve. This project looks like a tonne of fun, and I have some long thin pcb material just waiting to be turned into something fun. Perhaps its time for me to delve into AVRs... I'm wondering if something similar could be built with simple digital logic.
papiya6 years ago
Ive actually seen this work and its a pretty cool toy to play ludo/snakes and ladder with..the best part is the dice never rolls off away..it still has the sounds of the rolling dice..and u can carry it whereever u go..it doesnt need any batteries
Polter6 years ago
Kool man!
downhilldman6 years ago
this is soooooooooooooooooo coooooooooollllllllllllllllll!!!!!!!!!!!!!!!!!!!!!!