So, solar panels are made of silicon...diodes are made of silicon.  Have you ever wondered if diodes conduct current induced by light?  Sure you have, and so have I, so let's experiment and make a solar panel using 1N4148 (run-of-the-mill) diodes.   This is just a brief instructable, as the full construction is left up to you, intrepid reader, as a fun project. 

Check out the video below to see how much voltage you can get from just four diodes.

Step 1: Silicon Diode

A silicon diode is a two-lead semiconductor that gates current flow in one direction.  The symbol below shows how a diode is lined up with the schematic symbol.  The image was taken from http://www.gadgetjq.com/single_fire_tach_adapter_diode.jpg for copyright purposes.  Diodes are used in circuits that convert AC voltages to DC voltages, and also as voltage regulators, clamps, and multipliers.

Current flows in the direction of the arrow.  A few other terms of technical use are:

Forward-biased is when the anode is more positive than the cathode, and reverse-bias is the opposite:  the anode is made more negative in voltage than the cathode.

There are different kinds of diodes, too.  Pin diodes, germanium diodes, schottky diodes, rectifier diodes (p-n junction diodes) name most of them.  In this instructable we're going to work with silicon-based pin diodes, although if you're really curious I'd encourage you trying the different kinds of diodes to see how it all shakes out.

Diodes are pretty cheap.  You can pick up a pack of 50 from Radio Shack for around $3.


Step 2: Test It for Yourself

Go ahead and dig out a few diodes from your tacklebox, toolbox, bead drawer, or whatever you keep all your electronic goodies in and put them in parallel.  Connect your voltmeter to either side and take a reading in ambient light.  I get about 4-5mV in ambient light.

Next, grab your maglight and while still taking a reading shine a focused beam on the diodes and see what your voltmeter says.  In my configuration using the diodes I had at hand, I was able to get more than 100mV from four diodes.  That's not too shabby, especially if you're shuffling that voltage off to a capacitor to either save for later or to build up a larger charge to do something more useful, like light an LED (yeah, like that's more useful) or run your garbage disposal.

You don't have to worry too much about which direction the strip is facing as long as you face the strips all in the same direction.

Step 3: Get Funky

So you're generating voltage with your flashlight and a handful of diodes.....wow.  So what's next?  That's up to you.  You could cover a PCB with them and see how surface area corresponds to voltage, when you get diminishing returns, what the optimum diode to voltage ratio is, etc.   You could add in capacitors....throw in an op amp or even a charge pump and turn mV into V. 

I dropped $5 at R.S. and got two packs of 50 diodes and etched a PCB.  Your designs are endless.

Step 4: Final Thoughts

I hope I was able to share something new with you and that you now have a new-found love for green energy.  Don't get to crazy though; a rooftop of diodes will get you in trouble with your significant other.

<p>Hello </p><p> I have try this system but not work properly , i was used 130 diodes this show 12 voltage but this temporary after the some time lose voltages and totally 0 voltage why ?</p>
<p>Hello </p><p> I have try this system but not work properly , i was used 130 diodes this show 12 voltage but this temporary after the some time lose voltages and totally 0 voltage why ?</p>
<p>Hello </p><p> I have try this system but not work properly , i was used 130 diodes this show 12 voltage but this temporary after the some time lose voltages and totally 0 voltage why ?</p>
<p>Hello </p><p> I have try this system but not work properly , i was used 130 diodes this show 12 voltage but this temporary after the some time lose voltages and totally 0 voltage why ?</p>
<p>Hello </p><p> I have try this system but not work properly , i was used 130 diodes this show 12 voltage but this temporary after the some time lose voltages and totally 0 voltage why ?</p>
<p>I have try this system but not with any circut board ,I was used 8 diode but it is not working; Does it not work without circut board.give me anwserplzzzz..........</p>
<p>Ummm</p><p>Did you ever hear about <strong><em>perpetuum mobile?</em></strong></p>
<p>I am very happy with this tutorial. Then I bought a couple of diodes and connect. Either in series or parallel both have been tried. But somehow did not happen anything. Under direct sunlight, or under lights.<br><br> 8 diodes connected in series with each other, then given light. then each end connected to a voltmeter. the result is no voltage.<br><br> 8 diodes connected in parallel with each other. Then given light. then each end connected to a voltmeter. the result is no voltage.<br><br> I hope you can help. thank you.</p>
Hi there,<br>Sorry to hear you're having problems with reading voltage from your diodes. Make sure your multi/voltmeter is set to mV or auto because you'll likely just get in the 10's to max 100's mV.<br>Good luck!
<p>Hi, with known V/A cell, how do you determine optimum diode size and reverse/forward bias? Per panel I'd like to use for shading bypass and another to prevent backward creep from batteries overnight</p>
<p>This was a very informative instructable and one of the only things I could find after work on the subject. Just this morning before work I tested a green led taken from a disposable camera with my voltmeter held up near a fluorescent bulb and it produced over a third of a volt. So I've been curious all day about the potential applications. Now a bit ago I read about the p and n connections in which they basically pollute the silicon crystals with differing metals on the p and n side. So I grabbed the only tiny diode (not light emitting) that I had and tested it in the light. I got close to half a volt. Then the thought occurred to me... what if I further 'polluted' each output end of the diode with differing metals? Would that cause greater flow? So I clipped a copper tube to one end and a piece of aluminum foil to the other and tested it again in light with the voltmeter. It jumped up to slightly over a volt! So now I'm more curious than ever and am also wondering why they don't make the diodes with one kind of wire on the p side and a differing kind of wire on the n side? Perhaps some do and if so I am unaware of it but that wouldn't be surprising because I'm fairly new to electronics. Anyway, I appreciate this instructable and want to thank you for furthering my curiosity. </p>
<p>u said u used 50 diode <br>what was voltage and ampere generated</p>
<p>It's a nice project.<br>I wanted to add it here, because nobody actually wrote anything about it (and some ppl might be confused by it!):<br>No, this is not a cheap or convenient method of creating electric power!<br>The amount of silicon used in diodes is very small and it is not specialized for creating electron flow from photons. You will go way cheaper (in means of Energy per dollar) and way more efficient (in means of space, time, components) if you just use solar cells.<br>My theory for the seeming limit of 100mV is, that every diode has a voltage drop of 0.5V as well, so this might be a border-effect, which wears of, as soon as you reach 0.1V... Not sure about it though.</p>
<p>Hi,</p><p>Thanks for your comments. I agree with you: diode energy harvesting can't compare to composite solar cells. This is definitely for exploring. As for the limit of 100mV, keep in mind that depending on the electron sinks and sources between the P and N junctions, you can well get diodes with voltage drops as little as 0.3 using a Germanium diode...but as far as I know, that's about it.</p><p>Thanks for the comment!</p>
value power plz
<p>its because of the light source or the heat?? Any other powerful diode that i can use besides 4148? i would appreciate if u have the complete circuit diagram for this project. </p>
I am not able to go beyond 4 to 5 diode connected in series and i was able to get 100 to 150mV. But going beyond that numbers of series connections i saw voltage drops to below 100mV which is confusing. Please let me know how to increase it to usable Voltage level..or give me website to refer.<br><br>Regards
<p>every diode causes voltage drop</p>
lost of power converted to heat.
<p>actually i m new here</p>
<p>i m very confused... can u please tell me exactly what we have to use , pn junction zener diode or silicon based diode ?</p>
great! <br>
thanks for join me.
I think you have used pn-juction zener diode .............Can I use a simple pn-juction diode . I mean as looks in this picture............
Yes, I believe you should be able to.<br>Good luck!
by connecting diodes in series or parallel is there any difference in voltage<br>
connecting them in series will increase the voltage, while connecting them in parallel will increase the current.
Hello sir..It's an awesome project....I am very interesting about this project and want to make one for me. You write &quot;You could add in capacitors....throw in an op amp or even a charge pump and turn mV into V. &quot; but I am very new here and don't know how do I do it. Can you please give me a diagram? Thank you
what you need to do is add a joule thief to the circuit. because then you have 3 volts &gt;:-)
Good Idea .... May i have circuit diagram please or the web site where i can go though for it?
That's an interesting thought. :) There are some charge pumps that operate on a very low voltage and if a joule thief circuit could boost to 3V, the charge pump could easily make that 6V or 9V, although I think the current would severely suffer. Thanks for the comment!
yes the current would suffer but if it didn't, some charge pumps can turn 3v into 12v and then you just need an inverter to make that 240v.
I bought five 3&quot;, 5&quot;, and 7&quot; LCDs at dirtcheap prices the other week from my local surplus electronics shop and put together a few CFL inverters for the backlights, but much to my chagrin it still required a -24V on VLED and all the charge pumps I was willing to buy (ie not over $5) couldn't invert more than 10-12V *and* perform a boost (although I saw a few more expensive ones that could and found a nice voltage tripler pump), but figured how to string them together to get <p style="margin-left: 40.0px;"> V<sub>out</sub> = 2D - (2 * V<sub>in</sub>)</p> <p> I wonder, though, how much of an AC&nbsp; voltage swing you'd get if you're pushing, say, 10 uA.&nbsp; Sadly, I'm not sure it could even meet the charge pumps I<sub>in</sub> requirements.&nbsp; It would be interesting to see if you could get 120 or 240 VAC from it, though.&nbsp;</p>
It is kinda funny....in the 80's i used to scrap out old tobe radios for copper ans other metals. I found that those old selenium rectifers also produced electricity when exposed to light. I used to 4 or 5 volts from 3 or 4 of them hooked togather. But back then their wasn't much use for these electricity producers. <br>Foe those of you who do not know what these are, they were square pices of metal. Usually about 3&quot; by 3&quot; and about 1/32&quot; thick. They were stacked with spacers between the plates and anywhere between 6 and 10 plates per rectifer. Now you can replace then with 1n4004 diodes. <br>Dave
how many volts did you get in the PCB panel?<br>
with my configuration I was only able to raise a few hundred millivolts. :-\
I believe that it is so far out and crazie that is just beautiful man!!!!!!! Cheers!
hey thanks!<br>Cheers!
This is great,<br>I used only 2 zener diodes (I think 5v, but not sure) and got up to 2 V in parallel and even 3 V in series, though I did not manage to light up an LED. But I am planning to try buying more of these diodes and making a whole PCB full of them or something and see how much power I can get. I'll let you know.
That's awesome! I'll be curious to know if you ever manage to light up that LED. Keep us posted on your progress and feel free to post any schematics/pics/etc to this instructable.<br>Cheers,<br>/nev/dull
Well, I am sorry that I took so long, but finally I tried and bad news, with about 20 diodes in series or parallel the voltage is not even as much as I had got before (I am afraid they might sold me slightly different diodes in the shop, there they make confusion sometimes). I might try again, but not very soon, perhaps in a few weeks.
No problem. Too bad it didn't source more voltage. Maybe a new design might help if you're tinkering out with it again! It's always fun to try new setups, I think. Thanks for the post!
Well, I forgot to mention that the diodes had to be almost touching the light source (I used a 15watt CFL bulb), so perhaps it's not that great, but I will still try. I'll also post a picture most probably.
lol, it neva crossed my mind that a zena diode could be used to generate current :P but it makes perfect sense since it does contail n-type &amp; p-typ semiconductors. I have so many of them at home, so gonna start as soon as I get there! Yay, excitement ^_^
This is a good use for clear glass diodes found on discarded circut boards in older computers and other devices. The semicondutor junction will only convert a small part of the visable spectrum to electrical current because of the band gap potential of the PN junction. So a diode or infared LED will have a peak output in red light , a green LED will only output in blue light , a blue LED output in ultraviolet light . It takes red, green and blue light to produce white light so a white LED has an output voltage of about 3 volts in full sunlight because it can convert most of the visable spectrum. The output current of a single diode or LED is too small to power anything however if an electrolytic capacitor (2000 mfd 10vdc) is connected for several hours in full sunlight a small amount of energy can be collected. For maximum output the diode or LED must be aimed at the light source and any size large capacitor will work.
how many volts did you generate with the pcb shown? I would like to charge a 12v lead acid battery, I would like to know if it is remotely possible.
i generated a couple hundred mV but there are other configurations that could probably get you more. however, i dont think it would have the current to push as a recharger unless you used some intermediary caps or something, or again, changed the configuration of parallel and serial connections.
ok, thanks. I did some calculations, and it was not very efficient, but a good idea anyways. :D
May I know what your calculations were? =)

About This Instructable




Bio: Gian is a computational biologist and is the Managing Director at Open Design Strategies, LLC. He holds a BA in Molecular/Cellular Biology and an ... More »
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