## Step 7: Build and Program the Yarn Dispenser's Circuit

When the correct signal is received, the yarn dispenser releases twelve feet of yarn (approximately the length of a half-lap around the track. You can reprogram the circuit as you wish to dispense any length.

Build the circuit in the diagram below, and program it with the provided code. I determined what twelve feet of yarn was by simply timing it with a stop-watch. The code runs the motor for that amount of time (converted into milliseconds).

For convenience, I built my circuit with an H-Bridge -- an IC chip that can switch the direction of a motor. The H-Brige's direction is determined by a toggle switch. Here is a tutorial about h-bridges.
So cool but I think you should add one of those guides to the spool of yarn like you see on garden hoses so this way it wont knot up on the floor and you can see the amount easier and of course wind it back up easier. <br> <br>Awesome products man keep it up!
you should knit a sweater from the yarn dispensed and wear it while you pace! lol
to notice and create around the inevitable unspoken anxiety that eats such a large part of our lives is a wonderful thing. Thanks for making.
Won't the length of the yarn dispensed change as the spool runs out? I would imagine that x-number of seconds dispensed from a full spool will yield a lot more yarn than the same number of seconds dispensed from an almost empty spool. Can you compensate for that in the receiver? Perhaps I'll go ponder it whilst I pace back and forth in my living room. :-) Very cool instructable!
you are so freaking cute.
I hope you don't have downstairs neighbors...
i was thinking the same exact thing. maybe some foam or spring underneath to cushion the tilt.
yarn makes me nervous.
Does the program account for the changing circumference of the spool of yarn? As the yarn is dispensed each revolution dispenses less yarn. It might be easier to dispense the yarn accurately with a feed mechanism consisting of two rubber rollers that pinch the yarn and feed it off a spool that just stores the yarn.
Your projects have a sort of whimsy about them that I like very much. For your next project, you should build a device that measures leg fidgeting and displays it in some physical way.
With a simple string-pulley-reel-dynamo system you could probably harness the heretofore unrealised energy source of human fretting :) For someone like me who is an incorrigible fidget there is probably a non-trivial amount of energy leaked this way- I'm sure I could charge an MP3 player from the rolling of my office chair wheels! Also, of course, kudos for the neat idea of quantifying worry and giving it a visual representation.