Instructables
Picture of Drawdio!
Drawdio: A pencil that lets you draw with music! - The Drawdio kit was designed in collaboration with Jay Silver based on his original design.

When I first saw the Drawdio at Maker Faire I knew it would be a great project for beginners: A lot of fun with instant gratification! Essentially, its a very simple musical synthesizer that uses the conductive properties of pencil graphite to create different sounds. The result is a fun toy that lets you draw musical instruments on any piece of paper.

  • Runs on a single AAA battery for many hours (even 'nearly dead' batteries will work)
  • Use any pencil - mechanical or plain. The kit comes with a 2B pencil, the softer the lead the better
  • Ridiculously fun for all ages

Video!

The best way to see how Drawdio works is to watch a video...

Here are some videos from JJ Silver himself! These videos are of an earlier revision so it looks a little different






Here is one of me playing with my kit right after building it

Credits

The Drawdio kit was designed in collaboration with Jay Silver & based on his original design!
 
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Step 1: Design

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Electronic_Amplifier_Push-pull.png
How does it work?

The Drawdio kit is pretty simple compared to most electronic projects.

We will go through it one section at a time, please refer to the schematic

Power supply

The first part to understand is the power supply, which keeps everything running. The power source is a single AAA battery which is held in a plastic container that is soldered to the PCB. There is also a switch S1 which can connect or disconnect the battery from the rest of the circuit. Finally there is a large electrolytic capacitor C4, which is used as a 'bypass capacitor'. This means that it goes across the AAA battery and smooths out any ripples that are caused from power surges (like when the drawdio makes noise!)

The Oscillator

The heart of the kit is a TLC551 chip, which is a low voltage version of the famous LM555 timer chip. This integrated circuit is specifically designed for creating timers and oscillators. The original LM555 needs at least 5V to run (which is more than 3 1.5 batteries!) so we are using the 551 which can run as low as 1V. Its a little more expensive but makes the whole thing fit on a pencil.

One of the more popular ways that '555s are used is as a 'astable multivibrator' which is another way of saying an oscillator. The frequency of the oscillation is set by 2 resistors and a capacitor. The chip slowly feeds current into the capacitor until it is full and then, likewise, slowly drains it out. The resistors set how fast to fill and drain the capacitor and the size of the capacitor indicates how long it takes before it fills.

This system is pretty much identical to Japanese water fountains, as this video shows:



Except its all with electrons instead of water molecules and capacitor C1 is the 'bucket'. The water fountain oscillates maybe once a minute (1/60 Hz). But electrons are so much faster, a '555 can oscillate at thousands of Hertz, which means it can make audible sound. (Human hearing tends to range from 20Hz to 20000 Hz)

f = 1.44 /(C3 * (RA + 2 * RB))

C3 = 680 pF = 0.00000000068 F
RA = 10000 ohms
RB = 300000 ohm to 1000000 ohm (1 Mohm)

In this case, we use two resistors RA and RB but also have an 'open connection': two tabs at the end of the PCB. If the two tabs are shorted with a piece of wire, then the frequency of the oscillation is 3500 Hz, if instead there is a resistor of 1 Megaohms between the two tabs, the frequency of oscillation is about 1000 Hz. You can use a calculator to do the math yourself using the formula above

Instead of a 'everyday' resistor between the tabs, however, we use something else - the conductivity of the human body and graphite! The human body has a resistance similar to a 200,000 ohm resistor. Graphite has resistance of about 1 ohm per inch when its in the form of a pencil lead. When its spread out on a piece of paper, the resistance goes up a lot, up to a megaohm for a few inches of 'drawn resistor'

Amplifier

The 551 can create audio-frequency oscillations but it is not powerful enough to play them on a speaker, just like an MP3 player needs an amp to play music on large speakers. That's because the 551 was designed mostly for digital logic, not for low impedance (8 ohm) audio outputs. So we will use a Class B 'pushpull' amplifier, which uses two separate transistors to amplify the sound.

This is pretty much the same thing in your stereo, except your stereo has enormous transistors with gigantic heatsinks so that it can drive large speakers.
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ravenking2 years ago
Wow. This looks like fun. Can the pitch be changed to have deeper sounds?
Arduino Guy3 years ago
Hi, I made the Drawdio, and it makes an extremely high pitched noise, and It doesnt matter what resistance it makes the same sound, but it has to have a resistance to make the noise. What can be wrong? could some flux residue cause this problem ot some short? thanks
I measured the frequency on pin 3, it was 6.5 KHz, under 10Mohm resistor if that helps, by the way it worked perfectly on a breadboard.
I measured the frequency on pin 3, it was 5.3 KHz, while shorted. please help me make it work.
I fixed it, when i finished soldering i put the 555 timer into the socket, but when i needed a longer sense wire i soldered it without removing the ic, therefore these problems were solved by changing the 555 timer ic.
opulido3 years ago
anyone know how i can print this using the toner transfer method?
Oblivitus5 years ago
I received a 6.3 volt capacitor (the blue one on your parts list) from adafruit industries in the mail but the one that you show is a 10 volt. Will mine still work for this project? Also, do I need one or two of them?, because you stated 1 for quantity here on your parts list but show two of them on the next step. And is an on/off switch absolutely neccessary?, because I didn't receive one of those in my kit either. Lastly, I received only one transistor, you show two. What should I do?
6.3 V cap will be ok since you're gonna work with a 1.5V battery ...
(the voltage on those electrolytic caps is the maximum you can use them with)
senseisean4 years ago
The materials shouldn't cost more than $20 (US).. Looks like the priciest item is the copper foil tape, and you might be able to shop around a bit to find a decent deal.
denilsonsa5 years ago
So simple... and so great! Congratulations! Question: how would the contacts be connected to a mechanical pencil? Do you have any photos of that? I was thinking and thinking and couldn't find a good way. By the way, what kind of mechanical pencil? 0.5mm, 0.7mm, or another one thicker? Suggestion: Please add extra warning to NOT solder the battery holder with the battery in place. The soldering heat might damage the battery and maybe the battery could explode.
Try soldering to the metal tip that comes out the end of the tip of the mechanical pencil.
Hey,
I have some notes on this on the Drawdio website here
http://web.media.mit.edu/~silver/drawdio/make.htm

The basic trick is to attach one side of the circuit to a *metal tipped* mechanical pencil. I like 0.7mm but try a couple out and see what you think. You can test them before even mounting: just draw a line and touch (or clip) one side of the drawdio to the line... then hold the other side with your hand and touch the other end of the line with your hand.
Ah, I forgot to add: 1 Volt could be potentially dangerous if you had an open wound on both fingers while using this (allowing blood to contact the graphite and the copper foil) unlikely, but a warning, as the current could pass through your heart.
i use 5 volt but why 555 do not work?
?
it is long time ago. And it was solved.
cool!
.Unknown.4 years ago
So ground is the positive of the battery?
No, ground is always the negative.
Right,...I must've misread the battery in the schematics
Wait, is this at the Faire every year? Sadly, I won't be there this weekend. I was there today, but no drawdio :(
haha this reminds me of my theremin
merseyless4 years ago
the best thing is, i have all the parts in my "parts that i probably shouldnt have bought" draw! definatly going to make this.

Is the main IC a bog-standard 555 timer?
WOW!! I just looked at the videos for the first time. This is fantastic!! Can't wait to try it out at the maker faire! maybe even build it. :D
cyan_shadow5 years ago
Hi! What is the price of all the parts and do you where can i get them if i am not in the USA (cause i`m in Bulgaria)?
adafruit ships internationally :)
sputnick5 years ago
The C3 value in the calculations doesn't match the schematic :/
Noticed the same thing on ladyada's site.

I'm using TS555C with a coin cell battery and I'm only getting low hz almost none changing static :(

Not sure what that could be...
question from utter newb. like i dont know jack.
but if i bought the kit how would i add a line out type deal so i could put it through guitar pedals and computer effects and the like.
thanks
jook
oooh a line in too.
teehee
zoltzerino5 years ago
Sorry Adafruit; I am going to make this using the Veroboard method because it will cost me around 15-20 GBP to ship it to me whereas I can build it for less than 5 GBP.

What sort of component ranges can I have (do the caps have to be spot-on or is there leeway?) I think I have most of the components already apart from the 551.  Can I use a AA cell rather than a AAA? If i simply whack a bigger battery in and change it to a 555 will there be any issues?

etc. etc. 
?
gameboy7oa5 years ago
It sounds like a dentist drill......
these're kinda annoying? doesn't anyone else think so, hah.
spacecappa5 years ago
do u know if i could buy it pre made

Oblivitus5 years ago
Do you know of a way to change the pitch of the sound?
jaxter1845 years ago
my C2 has 681k on it... P.S., This is awesome
finaly tictactoe is funner then ever (im tired of always tieing)
Thanks a lot I have always wanted to make one of these but didnt want to buy the kits, is it possible you have a schematic to make one of these on a veroboard as i cannot purchase a PCB nor make one. Thanks again
Instructions on using stripboard (Veroboard) with link to the schematics if you can't get hold of the kit.
http://www.2ne1.com/drawdio/
pmac935 years ago
I bought all of the parts from the links you provided, but when they arrived I realized you linked to an 18pf capacitor instead of 680pf. Is this correct?
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