Two channels? Why not implement this with a cheapy 7.1 channel card, and get all kinds of little flags? That would be pretty cool.

It can be a pain connecting your ‘physical’ project to your computer, but using your soundcard is a cool approach – especially if you don’t need any complicated logic on the receiving end.

I was.. and still am thinking about doing something like this with the Android phone. I had issues getting the signal to the levels i needed.. I should try it out again.

To clarify, when I say “low” I mean logic low, not music low. The pulse is high to low for Hitec and Futuba servos, but I think it is inverted for Airtronix and JR, so you may have to experiment.

Theoretically it should be at 50hz because servos are supposed to get a pulse every 20ms but I found that a slightly lower freq eliminates jitter. Also never pulse a servo at more then 50hz or you may damage the motor driver circuit.

Seems like a great hack for simple motion control on halloween props. Just use a voice recorder chip or mp3 player and put it on a loop. Of course I would probably use a cheap microcontroller but if you don’t want to program it would be an easy alternative. Outstanding hack.

I often use my line-input as an ADC for when I need to measure something.

Recently, I’ve measured the speed of my hometrainer by connecting the flywheel sensor directly to my line-input. By measuring the time between each pulse, I could calculate my current cycling speed. You can read about it on my blog.

also another mod is to use a high pass filter and transistor switch. this way the pc can generate >15 kHz outputs (sound cards often work up to 22) and the servo will react to it as if it were a lower frequency.

total parts count is under 10 for two channels.