Introduction: Make a Pencil's Lead Potentiometer (Experimentations)

Picture of Make a Pencil's Lead Potentiometer (Experimentations)

Here is a really simple experiment in witch you will make a Kind of potentiometer (Variable Resistor) out of a sheet of paper and a graphite pencil (Lead Pencil)... Impossible you think? Check it out!

So first , What is a Potentiometer?
Its not very complicated, to make it short, it's a kind of resistors ( Limit the current flow) but its adjustable, so you can raise or lower the limit of the current flow.

I recently seen a video of MAKE Magazine (MAKE : Present The Resistor) on Youtube in witch they were doing something similar to this and thats where I got the idea to make an Instructables about how to make this simple Variable Resistor.So I have no credit for the idea, I just did an Instructables, to share it with you!

The Idea is to draw a band (with a Graphite pencil) on a sheet of paper ,the band of graphite will act as the Variable Resistor (Potentiometer) because the graphite conduct electricity but poorly.

Step 1: Material

Picture of Material
Here is what you will need to do your simple Variable Resistor and to test it:

Variable Resistor:
  • Sheet of paper
  • Pencil [You need a very soft one like 2B+ (Less may not work properly)]

To Test the Variable Resistor:
  • Multi-Meter
  • an LED
  • Alligator clips (2)
  • Source of power (9v battery is good)

Step 2: Draw the Variable Resistor

Picture of Draw the Variable Resistor

On the sheet of paper , you will need to draw a band about a centimetre wide and 5cm long and full it up with Graphite pencil. ( You can also try with longer band! ).

Step 3: Testing With the Multi-Meter

Picture of Testing With the Multi-Meter
To test your Variable Resistor with a Multi-Meter, you need to set it to the Ohm section(To test the resistance of the Graphite pencil), It work well with 2000k and anything in K.Put one electrode on each extremity of the band and look the resistance on your Multi-Meter, then get the electrode closer and closer and see what happen... Check the video!

Step 4: Testing With LED - Assembly

Picture of Testing With LED - Assembly

You can also test the Variable Resistor with an LED. Here is how to do it: First connect your 2 alligator clips to the 9V (one on each pole), then connect the Negative clip to the negative lead of the LED, and finally, bend the positive lead of the LED(Anode, the longest) so its easy to move on the paper and it gives good contact. ( If you don't have any alligator clips, you can replace them by normal wire, simply twist around the components to make the contact, or solder ) *Tips : If you don't know witch lead of the LED is - or + , test out with a button cell !

Step 5: Testing With LED - the Test

Now that you have your assembly, touch one end of the band with the other alligator clip and the LED lead on the other end of the band and slowly make the 2 connection closer and closer, see what happen... (*IMPORTANT* Avoid touching the LED lead directly on the battery pole or you can burn it up! You can also add a resistor in the circuit to avoid any damage of this kind) Check the Video! I made the Video a bit darker so can so the LED glowing! Explanation: The reason why the LED is glowing is because the current from the Positive pole of the battery ( Black clip) flow through the Lead or Graphite band and complete the circuit to the LED, result; the LED is glowing. Now the reason why the LED get brighter when you get the black clip nearest is because the Lead have some resistance [(Doesn't conduct electricity perfectly)(Measured in Ohm)]. So the closer you get to the LED, the less resistance the Lead provide you so more current go to the LED and make it brighter!

Step 6: Experiments!

Picture of Experiments!

Try wider or longer lead band or try other patterns and see what happen..! Try with other conductors like metals or anything else you know! Try with other kind of pencil (2H, 2B...) Try colouring lighter or darker for different result! Experiment, Experiment, Experiment ! and have some fun!!

Hope you enjoy !


EarlWallaceNYC (author)2016-01-13

This will help me in a few experiments.

hpatel8 (author)2011-07-25

cant you just use aluminum foil? Even though- nice experiment.

robot1398 (author)2010-12-28

very nice!!!!!!

nutsandbolts_64 (author)2010-06-11

Question: Would this work with the graphite replacements for mechanical pencils?

cardboarddude (author)2009-12-05

I tried this except i used a motor instead of a led but it doesnt work and I am sure that the motor works HELP!

You need to check how many volts your motor needs to run. It isn't working because doesn't have enough power

matroska (author)2010-01-21

A simple note to clarify, there's no such things as pencils leads actually made out of lead. Today it's only a mix of graphite and other stuff depending on the brand.

oscarthompson (author)2009-11-15

wait a minute... Wouldn't this only work with 'lead' pencils? Stationery store sell pencils with other type of cores...



No, because the 'other' cores are graphite, which is also conductive :P

dava_2 (author)2009-11-15

Nice, Very Nice!

MrLouque (author)2009-11-11

 Thats pretty sweet, good work

catfish23 (author)2009-11-11

 Excellent project, i will try it with some spare electronics parts.

Patented (author)2009-11-05

I dont care..

chosenone3 (author)2009-10-11

I've done almost same thing with white glue and the thing from batteries (black stuff) when it dries it has good resistance and when you apply water it becomes flexible ;]

Patented (author)chosenone32009-10-11


chosenone3 (author)Patented2009-10-12

well its almost the same thing it acts as a resistor but you have to play with amounts of "charcoal"(?)  and white glue to get desired results.

Patented (author)chosenone32009-10-12

Oh ok I get it!
But its not dangerous this black charcoal thing inside the batteries  ?

chosenone3 (author)Patented2009-10-12

I don't think it is but if it is you can use activated charcoal I think.

sodiumcanine (author)2009-10-01

GBT-11 Meter! Great model, Mine is nearly 6-Years Old A fuse here battery there has kept it going. McV

afatflatcat (author)2009-09-27

Christ on a bike. All this Paper Motor talk has me confused...

xitis (author)2009-09-22

doesn't work with me...

Patented (author)xitis2009-09-22

Are you sure your LED is working? did you try to switch the lead polarity on the battery? Check it out and send me back the result !

xitis (author)Patented2009-09-22

the LED is working fine...i tried it on direct lead and it is working but somehow it is not working on paper...

Patented (author)xitis2009-09-22

Ok than whats the pencil your using?

Patented (author)Patented2009-09-22

And are you sure you put enough graphite on the sheet( it need to be very dark , work better with the pencil i mention.

macrumpton (author)2009-09-05

if you draw a coil with a pencil and run a current through it does it create a magnetic field? Would it be possible to make an electric motor by drawing the coils?

killrsheep (author)macrumpton2009-09-06

only if you can draw a 3D coil.... and even if you somehow accomplish that (i would imagine it involves a lot of graphite and tons of thin strips of paper) graphite has a massively different resistance than copper does so my wild guess is that magnetic fields generated by a graphite coil are very very very veeeeeery low so in short... no, but it does get you thinking....

macrumpton (author)killrsheep2009-09-07

I imagined you would make the coil 3d by rolling or folding the paper after the pattern has been drawn. Perhaps the conductivity could be improved using the drawn graphite coil as an electrode (or anode I forget) to deposit a more conductive material, say copper onto it with an electroplating process.

BOOM5601 (author)macrumpton2009-09-16

I like the idea.

killrsheep (author)macrumpton2009-09-07

well yeah! that would be better but then it wouldn be considered a graphite coil...i was thinking last night of how could one accomplish a "graphite paper motor" and a lot of problems arised... say we make a dc motor with a colector on the rotor and some magnets for the stator.... i dont think we could fit enough graphite paper windings on the rotor to acomplish any significant torque (not even to move a rotor with zero load so say we make a... farfetched out of my mind "inverse dc motor" so we make a magnet rotor and we wind the stator (wich is a bigger pies so we might... just migt get enough windings) and say we would have to make another shaft to use as a collector for the stator to make a dc alternating current (jut in case we dont want to use any complex electronics.... after all we are making a very.... davinci-esque motor) and then comes the complex way wich is usin some sort of AC low voltage supply... wich is a bit crazier... a lot crazier!... theres a "simple motor design" somewhere around here, it just involves some "magnet wire" (im not sure of the technical english term) a D battery, a rubber band, a magnet and some nail polish i think....... maybe you could make one of those out of graphite... keep in mind tho that even the design that uses the magnet wire on that instructable produces just enough torque to move the "rotor"

killrsheep (author)killrsheep2009-09-07

then again... a solenoid is also an "electric motor" a linear one, and i think the coil design is quite a lot easier (im basically against the conventional electric motor bcuz you would need to wind the paper around a laminated core with a few slots on it ... wich just seems quite impossible to me) i think the coil is just a cilindrical coil so it seems like the ideal way to make some sort of solenoid... maybe a needle for the shaft... its lightweight and ferromagnetic so.... i think its worth a try

macrumpton (author)killrsheep2009-09-08

You could make the solenoid drive a crank and flywheel to get rotary motion.

killrsheep (author)macrumpton2009-09-08

yeah that seems like a better way to go, id try to make a very long coil with a very lightweight shaft.... the logic behind that is that i doubt a small scale solenoid would produce much force to move a mechanism, and a linear coil can be made in just about any size with no problems also the shaft so, yeah id try that, make a huge coil and a large lightweight shaft Hey, here's a thought! just so we stop guessing around... make the electromagnet experiment with a paper graphite coil... y'know the experiment where you use a nail, some insulated wire and a battery to make an electromagnet, only this time use a graphite coil... thats one easy way to compare the magnetic field's achieved by both means (wire and graphite)

macrumpton (author)killrsheep2009-09-08

Good Idea! I will try to do that tomorrow.

macrumpton (author)killrsheep2009-09-08

I think for simplicity's sake a permanent magnet on the shaft and stationary coils is the way to go. An ac power source like a wall wart (one with ac output or you could remove the rectifier diodes) would make it so you did not need any kind of switching mechanism to change polarity of the magnetic field. It might even be possible to have no permanent magnet and have another coil on the shaft with the dc power coming in from the two ends of the shaft. I am having a hard time visualizing what shape the coil(s) need to be. Keep in mind the coils can be printed on both sides of the paper.

killrsheep (author)macrumpton2009-09-08

of course it would be possible... theoretically, but still... let me see if i can explain the way i see it... We need a LOT of windings, on a strip of paper with a very very "impractical" small width, and since we need lots of windings we need to overlap more than twice (wich is what you get if you draw on both sides), that can be accomplished by overlapping layers of paper, but a new problem arises, you have to protect and isolate the coils from erasin or shorting each other or most likely both, wich requires some sort of insulation coating... now back to the "why we would need small widths... a rotor coil doesnt go around the shaft... it goes length-wise, inserted in some slots in the core , i really dont see how can we manage to insert a ring of insulated paper (wich by now turns out to be bulkier and more expensive than insulated copper wire) in a core with at the very least three slots and also achieving a small air gap between the rotor and stator it seems a bit easier to wind the stator, since its bigger, but i still dont know if it would create enough magnetic field... we "are" using a resistive path i really didnt go into it before because it is fun to imagine further than that, but id think there is a noticeable impact on magnetic field when using a resistive path

Kaiven (author)2009-08-27

Interesting.. It could be fitted in a small rotating cylinder, kind of like a light dimmer. That would be useful, but does it create heat with too much current? Will the paper catch fire? :P I saw some light dimmers that were pretty expensive just for me to play with electronics, but this could be helpful for small motor gadgets an doohickeys.

Patented (author)Kaiven2009-08-27

Hey, that seem a very good idea to me! (make a permanent potentiometer)And it would be very helpful and cheap to do! I am going to give it a try, and I give you news!

Kaiven (author)Patented2009-08-27

Ok :D Make an instructable if you can!

Patented (author)Kaiven2009-08-27

I will for sure!.. If it works!!

Kaiven (author)Patented2009-08-27

Good luck! :D

BOOM5601 (author)Kaiven2009-08-28

The only problem would be that pencil leads contain clay, and this could create heat.

Kaiven (author)BOOM56012009-08-28

That's why I asked if the paper would catch fire :P

BOOM5601 (author)Kaiven2009-08-28

Time bombs ;)

Kaiven (author)BOOM56012009-08-28


killrsheep (author)Kaiven2009-09-08

it should work much like tracks on a pcb rite?..... i mean the wider it is the most current it can handle, i think the "pick ups " have to be wider too

macrumpton (author)Kaiven2009-09-08

or make a circular track on a disk.

sageserver (author)Kaiven2009-08-27

light dimmers dont use resistance to dim the lights they use 3 transistors inside them and they work becuase of the ac current thats put into it.

robotkid249 (author)2009-08-28

Hopefully in the future we have circuits boards made of paper...

BOOM5601 (author)robotkid2492009-08-28

Scientists are currently working on a way to print silicon and other parts directly onto paper. It would make stuff cheaper, but would ruin electronics as a hobby.

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