A couple of years ago, I made a forever flashlight mostly out of old parts I found laying around.  This was the video I made of how I built it and how it turned out.


momoka.duw (author)2015-03-08

can I use any kind of magnet, sir?

cool project anyway :)

MagicTK (author)2014-10-19

I wonder if you were to use two or three separate coils along the length and wire them in parallel to the Bridge Rectifier, would that help build charge more quickly? I haven't tried it, so I am just wondering your thoughts.


could I use the capacitor in a disposable camera?

Probably but you want more Farads for longer term discharge. Most disposable camera capacitors are a special aluminum electrolytic capacitor, usually rated around 300V to 450V, capacitance in the 120uF to 330uF range. I would choose a supercapacitor like:
3.0v 20F

3.0v 50F

Or whatever voltage you needed.


thanks. because i have cameras in larger supply, i will just use a camera capacitor

manicmonday (author)2013-09-19

This is not near as easy as we are lead to believe. I tried this with 300 wraps, then 500, now 800 wraps before I ever got sufficient voltage. Also I tried it with 1 inch pvc and then found that 3/4 works better, and in fact I used my table saw to make a 1.5 inch groove 1/2 way through the pipe wall in the middle of the pipe so that the windings would be closer to the magnet. I recommend 28-34 gauge wire to make the winding smaller. Be advised that the smaller the wire gauge the higher the voltage, but the lower the amperage. Amperage = the actual power flow.

manicmonday (author)2013-08-30

I have a question or two: You didn't say where the poles of the magnet are. Are they on the ends, or the sides? Also, why did you use 1 inch pvc? The magnet fits much better into 3/4.


manicmonday (author)2013-08-08

Using a bicycle speedometer to count 300 wire wraps.

Connect the magnet to the pvc pipe, and the sensor next to it. Make the pipe so it can easily be spun in place.

Circumference of 26 inch bicycle wheel 81.64 (wheel diameter x 3.14)

1 mile converted to feet 5280
1 mile converted to inches 63360
1 mile converted to 81.64 inch units 776.0901519
4 tenths of a mile is this many 81.64 inch units 310.4360608

Keep spinning the pipe until the bike speedometer says .4 of a mile, and you have sufficient wire wraps.

manicmonday (author)2013-07-30

What would be the result of wrapping a single wire layer down most of the length of the pvc? Better? Worse? Not workable? Just curious.

Quantumagnet (author)2013-03-18

A question, Can you use other types of capacitors? If so, what farad?

longwinters (author)2012-12-29

Just one question, since no other storage component is listed, is the capacitor supplying the power for the run time?

Thanks for asking! Yes it is the only source of power

eyesee (author)2012-12-21


Dayus (author)2012-09-01

sorry, few laps with the copper wire was given to PVC coil and that should be the wire thickness???

The King of Random (author)Dayus2012-09-01

If you're asking about the wire, it's about 26 AWG and approx 300 turns around the PVC. The thinner the wire the better, and the more wraps the better! I hope that helps?

Dayus (author)The King of Random2012-09-01


The King of Random (author)Dayus2012-09-01

You're welcome!

Dayus (author)2012-09-01

hello you must be thick copper wire and how you have to give back?

The King of Random (author)Dayus2012-09-01

Hi! I'm sorry, but I don't understand your question?

DoctorDv (author)2012-08-31

This is so neat! Its a shame you missed the copycat challenge because this would have been a great entry!


I'm so glad you liked it! Thanks for your feedback, and I didn't know there was a copycat challenge until you mentioned it. Too bad, maybe next time :) Thanks again!

doodlecraft (author)2012-08-28

Hey Grant...I mean King O Random! Great running into you on this awesome website! I just won my first contest! Good luck in yours...they are a tad advanced for me! :) Wish we were still neighbors! :)

Hey Natalie! It's great to see you on here as well!!

Congratulations on winning your contest! Which one was it??

I hope you're getting to see much more of Mike these days? Tell him that after he left, I lost 30 lbs doing P90X and can do 28 chin-ups now! I can appreciate the hard work that goes into losing the weight!!

We miss you guys. Thanks for your message, and btw have you seen my other videos? I'm on YouTube at

See you around!

Penolopy Bulnick (author)2012-08-28

That's cool! Are rare earth magnets expensive or hard to get?

They sell them at Radio Shack but I would buy them somewhere else. You can get them online cheap, well at least cheaper than what you would pay in store. :P
Here is a cheap one I found that you can make an offer on:

Thanks for your info!

At the time they were pretty cheap. This was about 2 years ago. I think the price has gone up about 500% since then. I got them online so not hard to get at all :)

medossa (author)2012-08-28

Simple and it works :)
Good idea !!!

Thanks! It was a good project for learning simple electronics!

Misac-kun (author)2012-08-28

Great! I was thinking of doing it with a pen and a led, but the pen was too thin for the job, the capacitor was too large to fit inside (actualy just nanofarads was able to fit in).

A shake pen-light? That would be a cool idea! Yeah, sizing could be tough, but would be great if you pulled it off! Thanks for the comment!

About This Instructable




Bio: Random Weekend Projects
More by The King of Random:5 Ways to Start a Fire, Using Water How to make a Batarang like "The Dark Knight"How to Make Ninja Stress Balls
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