Introduction: Lemon Flashlight, My Electro-culinary Dish!

Picture of Lemon Flashlight, My Electro-culinary Dish!
Harness the power of fruit!  I give you the Lemon flashlight . It's the solution to the considerable worldwide energy problems that scientists have struggled with for so long. Powered by a single lemon, and with a brightness in a league of it's own, there's little stopping this flashlight from becoming a worldwide must have light.

Stuff you'll need:
  • Foil
  • Small piece of cardboard
  • LED (lowest voltage LED you can find)
  • Thick copper cable. About 2 foot long
  • Block of wood 15cm by 5cm by any thickness
  • Galvanized nails about 1.5" - 2" long  (MUST be zinc galvanized)
  • Small panel pins/nails
  • Drawing pin (could use nails if not available)
  • Sheet of Paper
  • Small pieces of wire
  • Steel wire wool
  • 2 litre plastic drinks bottle, or thin plastic

This instructable shows how to build a 5 cell version. I later built an 11 cell version in the hope of getting more light, but it's actually worse!. I guess the internal resistance of lemons is just too high.

Step 1: Strip the Copper Wire

Picture of Strip the Copper Wire

You'll need to strip the insulation off the copper cable so that you have nice bare copper wire.  Separate the strands of wire ready for the next step.

Step 2: Form Coils for the Plates

Picture of Form Coils for the Plates

To contact each lemon slice, you'll need a copper coil and two galvanized nails. . I started forming the copper coils using small tweezers until they were around 3/4" diameter then I just formed the rest using my hands. Leave around 3" of straight copper wire to attach to the nails.

You need to make 5 coils, and when you've done that you can attach the end of the wire to the nails, wrap around 3 turns around the nail. You want the nails to sit around 3mm away from the copper coil when they are finished.

Step 3: Nail in the "plates"

Picture of Nail in the "plates"

The plates are nailed to the block of wood. Nail two galvanized nails to the end of your block of wood about an inch away from the end. Using pliers, cut the heads of the nails off. This is so that you can push the slices of lemon into the plates easily.

Remove all of the nails that you twisted the copper wire around in step 2. You can now nail all of the copper springs in place. They are all nailed in line with each other about 5mm between the nails and the next copper spiral. As you nail each on down, cut the heads off the nails.

Step 4: Attach a Wire

Picture of Attach a Wire

Strip about 2" worth of insulation off a short piece of wire (any kind of insulated wire will do, about 10cm long) and wrap this around the two nails that you nailed on first.

Step 5: Make a Switch

Picture of Make a Switch

Take a piece of the thick wire you used to make the spirals, and form a small loop. This will be a pivot point for the switch. Form the rest of it in the shape shown in the photo's. There are two stop points for the switch made from panel pins (thin nails). One of the stops is a nail nailed onto the side of the wood and bent upwards. The other is just  nailed straight up around an inch away. Push a pin into the pivot point 

With the stop points complete, you can attached the other end of the wire that you connected in step 4. Then, push a drawing pin through the pivot point to allow it to pivot. To compete the switch, an elastic band is tied from the switch to the first nails that you nailed into the board. This returns the switch to the off position when not in use.

Step 6: A Reflector

Picture of A Reflector

I made a simple reflector to direct the huge amounts of dazzling light emitted from this device. It's made from paper covered in foil formed in a cone shape. I drew and cut out a paper circle around 80mm diameter,  and cut the same out of  aluminium foil. Tape the two together.

Then cut a straight line to the centre, and a cut a small 1cm circle out of the centre. You can roll it around now, like one of those protective collars vets give to animals to stop them injuring themselves even more. Tape the cone together at desired shape.

The reflector is attached to the wood using a small piece of cardboard that has and angle cut at the same angle as the reflector. This is taped to the reflector and to the wood.

Step 7: Plastic Insulators

Picture of Plastic Insulators

Between each cell there needs to be some little plastic separators to prevent the lemons touching each other. They are simply plastic squares cut from a drinks bottle about 50mm by 50mm.  These separators go between the copper coil and the nail that that copper coil is connected to.

Step 8: Test an Led

Picture of Test an Led

Now you can test an LED to see if it works. Slice the lemon into about  5 pieces, discard the ends. Put the slice in between the plates.

Cut two pieces of wire about two inches long, strip the ends and attach a piece to each of the LED legs. Touch one of the wires the copper coil nearest the reflector, and touch the other wire to the copper on the switch. Does it light up ? If not try it the other way. If it still doesn't light up, there's either something wrong with your wiring, the lemons aren't juicy enough, or the LED is too high a voltage. The led I used lit up dimply at around 1.8V

If it's working, you can twist the wires around the last copper coil, and the straight nail stop on the switch.

Step 9: If It's Working!...

Picture of If It's Working!...

You can tape the LED onto the cardboard behind the reflector. It's finished now. With any luck, yours will be considerably brighter than my version. Test different LEDs and different lemons. Try adding a joule thief, experiment..  Have fun!

And remember, world domination of the lemon torch (flashlight if you're American) could happen at an moment! Be prepared.

Don't forget, you can use the sliced lemon in your favourite dishes even after you've run them flat....


h3idi (author)2010-08-11

When life gives you lemons, build a flashlight?

elephant1292 (author)2010-08-09

Nice. Does the lemon taste different after being drained?

Heh, it tastes the same ... Free energy! :D

bertus52x11 (author)2010-08-09

I tried to vote for you, but you're not listed in the contest??

scraptopower (author)bertus52x112010-08-09

I've not been approved yet, unfortunately. When the instructables staff get into work I'm sure they'll approve it. Thanks,

kcls (author)2010-08-08

Wow! I had to shield my eyes as to not be blinded from the massive amounts of light coming from that flashlight! Excellent job. Well illustrated, will vote!

scraptopower (author)kcls2010-08-09

LOL. I think this is probably illegal in some countries with it being so bright :D Thanks,

error32 (author)2010-08-08

Haha, I think this is a great instructable. Could be a great and fun project to do with kids to get them interested in electricity. This makes a much better show compared to the old '2 nails in a lemon powering something'.

astral_mage (author)2014-05-16

try using a capitor to bring up the voltage.

Yonatan24 (author)astral_mage2015-09-11

Capacitor? Maybe a Joule Thief would help

deviprasadnair (author)2010-11-07

thanks for the cool project . i made this for my sceince fair.again thanx a lot.but the one part i don't understand is the insulators between the lemon part .please explain it.

mayutsuki (author)2010-10-21

ummm.. did it actually light up? or is there a chance that it wouldn't light up?

hope for ur reply!

scraptopower (author)mayutsuki2010-10-22

Yes it did light up very dimly. There is a chance it wouldn't light if your lemons are no good, or your circuit is bad!

mayutsuki (author)2010-10-14

I like this!
But what's the lemon's role for lighting up the whole thing?

rsmaudsley (author)2010-08-15

"Remove all of the nails that you twisted the copper wire around in step 2." Is this "remove all the nails" or "Remove all of the nail *heads*"?

scraptopower (author)rsmaudsley2010-08-15

It's remove the nails from the coils you made in steps. They'll be facing the wrong way. But you also remove the nail heads too after you've nailed the coils in place.

spark master (author)2010-08-12

I like it, but have a question. shouldn't the nail NOT touch the copper coil ?

It should, in my opinion. It's like sticking a nail and copper in a lemon and then connecting it in series to another lemon. The copper in one lemon is connected straight to the zinc in the next lemon. Each coil and nail is like that.

I need to relook it over. It makes sense as you said it here, but not apparent(for me) in the actual instructable. I am sure the not seeing part is my error not yours. I do understand the concept though and that is what I thought you were going for. What confused me to no end was the copper connected to the nail itself, and the insulator sheets. The lemons can touch then metal cannot, although I believe in a car battery (wet cell) the acid is contained in X number of separate cells. When the price of lemons goes down I will ltry this, or use sponges and vinegar. I like instructables enough I may pay for it, eventually. It goes hot and cold with cool stuff . This uis pretty elegant for such an easy thing. sparkie

Thanks spark master. A car battery was my inspiration for this as it has many separate cells connected together. The separators are to stop the  lemons touching each other with I think will short out that cell (not sure).
I've added a drawing which might help:

Yep that makes sense. nail/lemon/copper nail/lemon/copper till you get thye voltage . If therer are separators in there they make each nail/lemon/copper a voltiac pile(battery) they are in series, (maybe .25-.5 volt each no load). put two or 3 lemons in same configuration , in parallel, to pump up the current capacity and the lamp might/should burn brighter. batteries under load (unless they are very big) will drop in voltage. raise the voltage and current availablity and you got better scenario. when the power comapny drops the voltage (brown out) your fridge and other compressors/motors will draw way more current, and the windings, not made for that current, (want more volts) will eventually smoke and flambe and the unit is dead. A lot of brown outs will eventually kill the thing and since it dod not happen in 1 single incidence, the power comapny will never pay. If they smoke your unit in 1 shot, you can make them pay for all the food and the unit, sometimes. I believe if you do not use the separators you get the equivilent of 1 cell but since all are in parallel, you get higher current. Again thanks for the update and great instructable

Kinnishian (author)2010-08-12

Hi, did you just choose to use slices to make it more compact? I remember making a large one before with entire lemons (4) and copper scraps (cheaper than piping) and zinc boat pieces (boat marina engines have various entire zinc parts). I don't think it was horrible, maybe you can check your voltage to make the light more suited (i got 2.5 volts or so). Obviously the current and capacity isn't amazing.

scraptopower (author)Kinnishian2010-08-13

I was hoping to get more voltage, the idea was to wire it like a car battery to increase the voltage, but keep it fairly compact so I didn't need a million lemons. It might increase the output with proper solid zinc. Maybe my nails weren't very good quality zinc and that's why the output isn't so good ?Thanks.

Kinnishian (author)scraptopower2010-08-13

I think maybe it was the galvanized nails, because galvanized is only a very thin cover of zinc (incidentally, made by the reverse chemical reaction that you're performing here) .

DannyBloom (author)2010-08-12

Hey, So a couple questions. Why only zinc galvanized nails? Also, how long do the lemons last to power this thing? Just until they dry out? Fantastic instructable. I wish I wouldve seen this earlier so I could vote for it.

scraptopower (author)DannyBloom2010-08-13

Thanks. From what I've read online, zinc is the best readily available metal for this, others will work but zinc gives the best output. Try it with different metals and let us know the output. It keeps working until the lemons dry out.

spark master (author)2010-08-12

could you draw this on paper simple block (ish) diagram?I can't see the circuit as in how it connects. Electric flows when the electrons are stripped from one side and through an acid (or base) go to the other side. Get copper nails and iron nails and th ebig copper coils (added mass). And do not reuse lemons on food, you will have metal contaminants. Still, very cool instructable

Kryptonite (author)2010-08-10

Have you tried a joul thief? Might help with the excessive of amount of light.

scraptopower (author)Kryptonite2010-08-10

I just tried it but nothing happens!

Kryptonite (author)scraptopower2010-08-10

Strange, I did it with a single lemon and got quite a bright light. Sure it's set up correctly?

scraptopower (author)Kryptonite2010-08-11

It could be the joule thief I used, it has more transistors than a DIY one, it's the emergency phone charger the I used in my thermoelectric generator. I'll have to make one and try that.

Kryptonite (author)scraptopower2010-08-11

I need to find the correct transistor to do mine.

depotdevoid (author)2010-08-09

I love the presentation, great instructable +5 stars!

twocvbloke (author)2010-08-09

Reading this makes me want a lemon meringue pie now... :S

Still, it's pretty cool, it's a rehash of that old idea of sticking a zinc rod and a copper rod into a lemon and getting electricity, only made more cool looking, cos without the lemons it looks like some misplaced NASA part or something... :P

yespotato (author)2010-08-09

i wonder if there is a dish or cake or some kind of food that u did this and it would be a good resturaunt idea.

celalboz (author)2010-08-09

wow again.., now make it light up and get 25mA

Doric (author)2010-08-08


About This Instructable




Bio: Scrap To Power - check out my website for more projects
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