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Drawdio conductivity - possible solution
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Drawdio conductivity - possible solution

by sdowney on Tue Jul 13, 2010 4:54 pm

A number of posts describe the same problem I had - Drawdio works fine when touching both contacts on the pencil, but doesn't work at all when laying down graphite. Drawing with Drawdio didn't work - even with wetting the paper, washing hands, etc.

So, I tried experimenting with different pencils. I had success with the Pentel P209 mechanical pencil. It's about $8 (I already owned it for other drawing projects), but it works perfectly!

I also wonder if different types of paper (with different moisture content?) would have any impact?
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Re: Drawdio conductivity - possible solution

by adafruit on Tue Jul 13, 2010 5:32 pm

mechanical pencils do work much better, maybe checking to see if you're making good contact with the graphite on a normal pencil thru the thumbtak?

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Re: Drawdio conductivity - possible solution

by sdowney on Wed Jul 14, 2010 12:52 am

I thought about that Limor - even went so far as to saw off the tops of pencils so I could SEE the graphite rod.
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Re: Drawdio conductivity - possible solution

by TomS on Mon Jul 19, 2010 2:56 pm

I strongly recommend troubleshooting the pencil before worrying about the paper. If you can't hold the pencil in one hand and touch the graphite with the other and get audio, you have a Drawdio-to-graphite path problem. Try these steps to isolate your problem:

-touch both tabs on the PCB to be sure Drawdio is working
-hold the pencil and touch the top tab to make sure the "hand" copper tape is working
-hold the pencil and touch the tack or top copper tape to make sure that connection works
-hold the pencil and touch the graphite to make sure contact with the graphite is working

I initially had problems getting the thumbtack to make good contact with the graphite. I had an easier time when I switched the thumbtack to the side of the pencil instead of the top, but still had to hunt around occasionally.

I also had an easier time using B8 pencils from the art store down the street, instead of B2. The nice fat tip makes very dark thick lines easily.

My intuitive answer on the paper is that rougher paper will work better with less effort (if better means producing audio with longer lines) since it will pick up more graphite more quickly/more thickly, and the resistance of your line is related to the length and cross-sectional area of the graphite. I haven't tested this, though. Sometimes I have to wet the finger that I'm touching to the line to get the results I want too, the coin trick doesn't seem to do much for me.
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Please be positive and constructive with your questions and comments.