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Make a Solar Panel using Diodes!by nevdull on June 4, 2010

Table of Contents

Author:   nevdull . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

License:   Attribution Share Alike (by-sa) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Intro:   Make a Solar Panel using Diodes! . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

step 1:   Silicon Diode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

step 2:   Test it for yourself . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

step 3:   Get Funky . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

step 4:   Final Thoughts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

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http://www.instructables.com/id/Make-a-Solar-Panel-using-Diodes/

Author:   nevdull

Author:  nevdull    AVR-based Network CombatGian is a microbial biochemist. He has a collection of 8-bit microcontrollers and a room full of computer junk that he believes talks to him. He is a sympathizerwith the Robot Overlords and is adroitly maneuvering himself to be in a comfortable position when the AVR global domination begins. He is also scared ofzombies.

License:   Attribution Share Alike (by-sa)

Intro:  Make a Solar Panel using Diodes!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, solet'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, asa fun project. 

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

step 1: Silicon DiodeA 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.  Theimage 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 DCvoltages, 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 instructablewe'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.

 

http://www.instructables.com/id/Make-a-Solar-Panel-using-Diodes/

step 2: Test it for yourselfGo 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 yourvoltmeter 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 Ihad 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 lateror 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.

http://www.instructables.com/id/Make-a-Solar-Panel-using-Diodes/

step 3: Get FunkySo 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 howsurface 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 ampor 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.

http://www.instructables.com/id/Make-a-Solar-Panel-using-Diodes/

step 4: Final ThoughtsI 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 youin trouble with your significant other.

Cheers!-gian

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http://www.instructables.com/id/Make-a-Solar-Panel-using-Diodes/

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Comments42 comments Add Comment

 quickshadow_2 says:  Jun 4, 2010. 12:51 PM  REPLYI noticed that your diodes are 200mA 100V ones, maybe that's why there is such a high voltage but such a low current gained from shining light on them0.1v=0.1% of 100v, so presumably, 0.1% of 200mA=0.2mA You may want to test both extremes, with 1A 50V diodes and 200mA 1000V diodes, thencompare the voltage and current achieved from either, to see whether this is true Note: In your instructable above, you connected 4 diodes in parallel, thatonly increases the current (X4) not the voltage, though with 1 diode (0.2 mA) your multimeter would be unlikely to pick-up the voltage reading, if i'm notwrong that's why you had to use 4 diodes in parallel. PLS DO REPLY, THANKS ^_^

 panic mode says:  Jun 10, 2010. 11:47 AM  REPLYtrying different diodes will have impact but the breakdown voltage of 100V and rated current of 100 or 200mA have nothing to do with it, it is the amountof light that falls on silicon. if you are experimenting, try ones that have lens (LED for example) or larger silicon die. you are right about breadboard, thosefour diodes are in parallel.

 saki_kawa says:  Jun 7, 2010. 3:07 PM  REPLYEhm.. diodes are non linear components.. so the proportion is wrong.. ;)

 nevdull says:  Jun 4, 2010. 1:23 PM  REPLYGreat ideas. I'll see if I have any laying about or maybe pick some up. As for the using four diodes, I actually used four diodes because that's how manywere in my hand when I grabbed inside my diode bin. Haha. I have, however, tried a few different permutations ie --|>|--|>|-- that probably makes nosense..and found between 4 and 8 to be the magic zone, although I've also gone to extremes as my PCB-gone-crazy-with-diodes pictures can attest. :)Thanks for the ideas on the different amp/voltage diodes!

 technicum says:  Jun 9, 2010. 12:19 PM  REPLYYou can also buy these diodes on Ebay. just search for "1N4148", there you can buy a 100/package for around $1,20 ;-)

 arihant says:  Jun 6, 2010. 6:02 AM  REPLYhow many diodes r needed for 2 v????

 nevdull says:  Jun 8, 2010. 5:37 AM  REPLYThat will depend on your configuration, type of diodes, etc. I think you'd need a lot of coverage area or try to to amplify what you get some way.

 abhinav.bejoy says:  Jun 6, 2010. 4:23 AM  REPLYthis is awesome....

 nevdull says:  Jun 8, 2010. 5:35 AM  REPLYthankee very much :)

 saki_kawa says:  Jun 7, 2010. 4:09 PM  REPLYHi Nevdull! I spent the past year doing the same project.. before I start studying semiconductors! ;) Some warnings.. diodes are non linear components, sothe current is not proportional to the voltage. A little amount of voltage can generate a great current inside the diode! It's the way I burned my first 250mWlaser diode.. :( LEDs use current and potential gap to create a flow of electrons and holes, when an electron finds an hole falls into a lower energy level andfrees some energy producing a photon, so you have light. Different band gaps in the material of the p-n junction can generate different wavelength. Anhigher flow of majority carriers can increase the probability to electrons-holes crash. And the process can drive backward, but producing a very very littleamount of current. Why? Because the probability of electron-hole crash is very low. Only a little shape of the junction (the place where photons emission ispossible) is exposed to the light, and the material of the diode can use only some wavelength (blue leds use the green light and vice versa) (P.S.: in spaceyou could use UV led to gain maximum energy). So you are seeing a current generated from the minority carriers and some electron-hole recombination,very very little current. You can use it with a little amp op 741 as a photorevelator. Some lectures:http://en.wikipedia.org/wiki/LEDs_as_light_sensors#LED_as_light_sensor And an example from an Italian professor (Guido Pegna):http://www.pegna.com/page006.htm#18. DIODI LED Sorry for my English.. I hope to be clear enough! :) Hi all!!

 nevdull says:  Jun 7, 2010. 5:19 PM  REPLYsaki_kawa, hi! thanks for such a great post!! I appreciate your explanation of some of this stuff. As I (or the folks here) experiment more on this point,maybe we can pick some more of this knowledge out of your brain?! :) Your post has clarified some black holes in my knowledge and given me plenty tothink on. Feel free to post more or hit me via email. Thanks alot! -gian nevdull

http://www.instructables.com/id/Make-a-Solar-Panel-using-Diodes/

 saki_kawa says:  Jun 8, 2010. 1:33 AM  REPLYI'm here for everyone, if I can be useful! ;) Sorry but I made a little mistake.. when the light hit the junction, the probability of a photon to split into anelectron and an hole is low.. what I wrote wasn't right! If you have more questions, write me! If you will find a way to increase the electrons and holesproduction, I think you could go for a noble prize!..maybe in the space, with right wavelength.. but I think a new shape for the junction is nedeed.

 lxkarthi says:  Jun 6, 2010. 8:30 PM  REPLYHey, instead of using 1N4148, I have an alternate method and diode which will produce more power than this diode. There is some physics behind thisexperiment. I will be writing a post on this in http://techbird.wordpress.com or kelectronic.blogspot.com Check out my post after june 8 ,2010...

 Electron xxx says:  Jun 5, 2010. 8:24 PM  REPLYGREAT......THINKING.............i like .IT....

 godofal says:  Jun 5, 2010. 5:36 AM  REPLYebay's ur friend: 100 pack

 nevdull says:  Jun 5, 2010. 6:12 AM  REPLYYah, impossible to beat prices from Hong Kong/China on electronic components on ebay.

 godofal says:  Jun 5, 2010. 9:36 AM  REPLYyeah, if ur buying in surplus, ebay's the way to go :D i mostly just stock up on LED's, resistors, caps, diodes, transistors, and more of that kinda stuff,that's always handy to have.

 alex12349 says:  Jun 5, 2010. 6:58 AM  REPLYcan i use any other silicon diode

 nevdull says:  Jun 5, 2010. 7:58 AM  REPLYshould be able to, as long as it's clear...not a rectifier or opaque body. i haven't tried zeners, myself, though.

 reukpower says:  Jun 4, 2010. 1:00 PM  REPLYNeat idea! You can use certain LED's in the same way, and some transistors can be taken apart and used like this.

 nevdull says:  Jun 5, 2010. 5:31 AM  REPLYDo you know what type of LEDs? As for transistors, check out Nuno's comment below.

 ratgod says:  Jun 5, 2010. 3:43 AM  REPLYI agree, I've heard of some companies using LED's as ambient light sensors as well as indicators in the same circuit. Some of the old OC typegermanium transistors used to come in a glass capsule and were painted black so the light wouldn't cause this effect.

 panic mode says:  Jun 10, 2010. 11:54 AM  REPLYgeee, those are OLD, i should still have few somewhere... ;-) i used to scrape the paint off to use them as photo sensor but they have some greaseinside capsule - usually white, few of them ware clear.

 nevdull says:  Jun 5, 2010. 6:06 AM  REPLYGood point. My germanium diodes aren't black, but they are certainly opaque and not translucent like the schottky/pin/etc diodes, too.

http://www.instructables.com/id/Make-a-Solar-Panel-using-Diodes/

 carboman says:  Jun 5, 2010. 4:54 AM  REPLYReally dumb question. What would happen if you put something reflective such as a mirror or foil under diodes with diodes spread apart?

 nevdull says:  Jun 5, 2010. 5:29 AM  REPLYYou'll increase the voltage read across the diodes (if I'm understanding your question). I spent 30 minutes reflecting different light sources (LEDs,incandescent, fluorescent, UV, IR) off of a blank CD onto the diodes a few weeks ago. It also depends on how far apart you have them spread, whetheryou have them in series or parallel (my board-of-many-diodes has both series and parallel diodes in the same circuit). Go grab some diodes and play :)

 garywpalmer says:  Jun 4, 2010. 12:23 PM  REPLYCould you take your finished board with the 100 diodes out in full sun and check the voltage? Inquiring minds want to know.

 nevdull says:  Jun 4, 2010. 2:35 PM  REPLYThe PCB-of-many-diodes isn't an optimized design...it is a prototype I built after I started adding more diodes to explore the light-diode-voltagephenomenon.  in fact, it's got holes throughout where I've added capacitors (two), two potentiometers, a static resistor, etc.  So I don't think reading anyvoltage off of it would be representative of what a well thought-out design could accomplish, with that in mind from the beginning.  

I don't mind doing it for you anyway, if you like, but just wanted to say.  When I was outside it wasn't very sunny, but even so, I never read above100mV.  Also, I have eagle cad schematics of the board as I built it to explore the diode-solar-power thing that I don't mind posting, either, if someonejust wants some ideas.

In the meantime, here's a pic I just took outside (kinda hot, but not very sunny) with a mini-solar cell.  It was overcast when I took the pic.

Cheers!

 rocketman221 says:  Jun 4, 2010. 2:11 PM  REPLYThis could be quite useful for detecting light.

 Nuno says:  Jun 4, 2010. 2:05 PM  REPLYYou get very little current because the diode has a tiny junction area and it's not all exposed to light. If you want more current try an old power transistor likea 2N3055 (search the web).

 zaphodikus says:  Jun 4, 2010. 12:32 PM  REPLYI'm not sure that using silicon diodes in this way is totally new, it is nice to be reminded though of how fun the universe we live in is. I really love these"makes you think" instructables. My guess is that the finnished board generates around .6V in full sun , but only in the micro-ampere power level - so it is notgoing to really ever power more than a single led :-)

 Motta says:  Jun 4, 2010. 12:31 PM  REPLYI agree with gary... A pic with your finished PCB working would be great!

http://www.instructables.com/id/Make-a-Solar-Panel-using-Diodes/

 kelseymh says:  Jun 4, 2010. 11:08 AM  REPLYSo you get about 100 mV per diode from a focused beam (Maglite). If each one is less than 2.5 mm diameter and 5 mm long (the hole spacing on abreadboard), that's 8 mV/mm2, or a theoretical maximum of 8 kV/m2 for full coverage (assuming you wire them up in series to get the voltage to add).

Was there enough current output to measure with your Fluke?  In order to use this sort of structure for power, you need both voltage and current (duh :-).  Itwould be very interesting to know how this compares to "proper" (e.g., amorphous silicon) photovoltaic panels, as it provides a potentially practical route fortrue DIY PVs.

 nevdull says:  Jun 4, 2010. 11:18 AM  REPLYWell, the voltage isn't too bad, but the current is poor. On my PCB-of-many-diodes, there is hardly enough current to drive from one end to the other (thedesign wraps one long line around in half on the board). Maybe a voltage-current follower with a power transistor or something....ideas?

 kelseymh says:  Jun 4, 2010. 11:46 AM  REPLYHmmm...maybe. The thing is, if the current is too low, there just won't be enough total energy there to get anything out. Stupid conservation laws :-(

 nevdull says:  Jun 4, 2010. 12:28 PM  REPLYOh and as Bugs Bunny would say "I never studied Law." :)

 nevdull says:  Jun 4, 2010. 12:26 PM  REPLYSo even something like a source follower where you get a current gain but no voltage gain wouldn't gain us anything? And, I'm probably missingsomething very basic here, but if V = IR -> I = V/R can you increase V to get a larger I? Resistivity of the copper and resistance of the tracesshould stay (generally) the same (with I suppose the change in temperature), could a charge pump or buck boost increase V withoutoverincreasing R? I'm just sorta walking my wits here. It's fun to problem solve and then go actually build :)

 kelseymh says:  Jun 4, 2010. 11:06 AM  REPLYI'm curious about one thing. I would have thought the active diode material would be encased in some opaque coating (as good old resistors are). Do youhave to expose the silicon or germanium in order for this to work most effectively? Or am I mistaken about the packaging?

 nevdull says:  Jun 4, 2010. 11:20 AM  REPLYNope, it's just wrapped in glass. No exposing or special actions have to be taken. Throw a few diodes on the board, hookup your voltmeter, shine a light,and be amazed. I was surprised at how much voltage I could get from a few diodes. But like you mentioned before, drive is more of the issue here.

 kelseymh says:  Jun 4, 2010. 11:45 AM  REPLYThis is a really cool project. Thank you for putting this up, and thanks also for the quick responses.

 nevdull says:  Jun 4, 2010. 12:27 PM  REPLYI'm honored, thank you. I appreciate your thoughtful comments and dialog.

 jeff-o says:  Jun 4, 2010. 12:23 PM  REPLYWow, that's really cool. I never thought about using glass-encased diodes to generate electricity! Shame the current output is so poor. I guess I'll stick withregular solar cells if I need serious power.