[youtube http://www.youtube.com/watch?v=P4-Wl0W1004&w=620&h=349]
Drawdio is a simple electronic sound synthesizer built onto a pencil! Designed by Jay Silver, then a student in the Lifelong Kindergarten group at the MIT Media Lab, the Drawdio circuit plays a musical tone with a frequency that varies based on the resistance between two points. The wire wrapped around the pencil handle is one point, and the pencil lead itself is another. When you hold Drawdio in your hand, your body becomes part of the resistive loop, and you can do all kinds of fun tricks, like draw yourself a piano and play a little tune!
The Drawdio circuit is based on the classic 555 timer chip. To save space on batteries, we’re using a more modern low-power version of the 555 that will run on 3 volts, but otherwise it behaves just like a standard 555. Wired like this, the 555 operates in so-called astable mode, outputting a continuous stream of pulses from pin 3. The frequency of those pulses can be controlled by changing the values of the resistors and capacitors connected to pins 2 and 7. Since the contacts are arranged to put the user’s body into the resistive loop, the frequency output by the 555 naturally varies depending on what she or he is touching. The transistor amplifies those pulses, which emerge from the speaker as audible sound.
Don’t you need to have a contact from the circuit board to the pencil lead on the top of the pencil for complete circuit?
I figured it out, I didn’t see all the steps. Please forgive my stupid-ness.
No problem! Asking questions is smart, not stupid! =) Sean Michael Ragan Technical & Toolbox Editor MAKE Magazine sean@makezine.com
is it okay to change the 570pf cap to a 470 pf cap? I cant find 570 ones from my source…..
Hi Bryan-
It will work but the frequency range will be higher, and 560pF is already a bit on the high side IMHO. I’d go with a bigger cap, if possible, rather than a smaller one. 680pF would be a better choice, if you can find it. If not, use two 470 pF caps wired in parallel (just twist the leads together or solder them through adjacent holes in the perf board). Capacitance adds in parallel so two 470 pF caps connected this way are equivalent to one 940 pF (470 pF + 470 pF) cap. I just tested it on my breadboard Drawdio with two parallel 560 pF caps (1120 pF together) and that sounded pretty good, so 940 should still be in the sweet spot.
Best-
Sean Michael Ragan Technical & Toolbox Editor MAKE Magazine sean@makezine.com
What part number is the amplifier transistor?, the radio shack package sells 3 different transistors in the bag but the 3 of them are for different porpuses
Hi Erick-
Woops, sorry! Look for a 2N3906. RadioShack doesn’t seem to sell them individually packaged.
Cheers-
Sean Michael Ragan Technical & Toolbox Editor MAKE Magazine sean@makezine.com
thanks
Great project! I think I will try and build it onto a Koh-I-Noor clutch pencil so that it would be refillable. (Will post pics if successful). Would it be possible to add a variable component so the tone can be adjusted?
Good question. You mean tone proper? Like the timbre of the sound? Or are you talking about the frequency range?
Oh sorry. I meant the pitch range of the sound itself. I assumed it was tied to the resistance of person and the graphite but was wondering if adding a pot somewhere could shift the register a bit.
Yes, absolutely. Might be a bit of a challenge to find one that would fit on the board, I think, but I haven’t really dug. If you could find a variable capacitor with a range of about 500-1000 pF to replace the 560 pF cap, that seems a theoretically ideal solution to me. Those are not easy to find, though, and I’m not sure even if you did find one it would be worth the cost or of a size you could fit on this build. I poked around on my breadboard just now with a 100K pot where the 10K resistor is now, and it really doesn’t add much variability. My next experiment (if I had the part on hand) would be a 1M Ohm pot or trimmer in place of the 270K resistor. If you check out the Wikipedia entry on the 555, under “Astable” mode, you’ll see there’s a formula for the frequency of the pulses and how it relates to the component values in this circuit. Sean Michael Ragan Technical & Toolbox Editor MAKE Magazine sean@makezine.com
Thanks. Will give it a try. I’m still a novice with circuits but smoking components is part of the game.
I built one!(on the breadboard still……..)but decided that such a small speaker just wouldn’t do so used an old tape recorder one(of course wouldn’t fit on a pencil,but that’s a minor detail :p )
Can you please tell which software you used to make this video?
(especially the animations with the board/components)
hi i am using an NE555 instead of TLC what changes are required in circuit to make drawdio???
I just built one with an NE555 but instead of the 3 volt AAA battery pack I just glued a 9 volt battery on the pencil. I also changed some component values but all you need to do is the 9 volts.
Anyone have a full parts list?
Just kidding it’s on the side. Sorry didn’t see it.
when I go to buy the speaker, How do I have to ask for?what’s the speaker name?
What would be the ideal method to amplify the sound. I want to hear a sound of grater volume.
I just started teaching my kids 9 & 10 electronics. This looks like a great starter project. I love the instructions and even the parts list on the side that links to the radio shack web site. Only problem is that some of the parts are not currently available online. It would be nice to be able to print a parts list to take to the local RS.
Hi, I am interested in guiding a few of my students to make this project as a school project and try to sell in my school. This way, the students will learn electronics knowledge and marketing skills as well. Is that alright? Thanks
how could i modify it to use a 9v battery? i cant find the low voltage 555
The only modifications you need to do are the ones you just mentioned – with a regular 555 chip and a 9v battery, the circuit works as is.
A substitution like this is the sort of thing that breadboards are made for – if you’re not sure if it will work, put the circuit together on a breadboard and if it works, solder away – if it doesn’t, experiment to figure out what the problem might be.
This is a great project for kids. I used it as a final project for an electronics class that I’m teaching for 2nd & 3rd graders at my kids’ school. In an hour-long class, with a snack break and a bit of time wasted on hopping out of their seats and running around, all the kids in the class were able to manage putting this together on a breadboard (the school won’t let me put soldering irons in the hands of 2nd & 3rd graders, and I’m not sure I’d want to anyway) within the class period.
Hi Bob! I´m from Argentina. I would love if you could teach me how you put this all together and which materials exactly did you use. I´d love to do it with my 5th graders. Please let me know!
In touch,
Gia
Gia,
My teaching notes for the class, currently run to about 15 pages, so this wouldn’t be a very good forum for trying to describe exactly what I did. The school librarian suggested that I should take what I learn teaching the class and write a book about teaching electronics to kids.
The main thing I did was to use the Velleman EDU01 kit as a basis from which to work, adding some material and taking away other material. For your kids, you could probably just use the Velleman booklet as written, and then after working their way through the book, they could build a Drawdio on a breadboard as a final project.
Are you willing to email the plans that you used?
Is there a kit for all this, or are the materials to be purchased separately?
http://www.ebay.com/itm/281383481236?ssPageName=STRK:MESELX:IT&_trksid=p3984.m1555.l2649
Drawdio Kit
http://www.ebay.com/itm/281383481236?ssPageName=STRK:MESELX:IT&_trksid=p3984.m1555.l2649
Will the Texas instruments timer work to?
What is the function of the isolating electrical tape, if your hand needs to make contact with the bare wire?
thanks for the project! this is my drawdio: https://www.youtube.com/watch?v=9ntKndysAAU. i skipped a bunch of resistors and stuff but it works great. also i used a classic 555 chip with two CR2032 batteries and that looks pretty cool
wich speaker did you use?
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