14579Re: [cosmacelf] Re: OT: The Most Minimal Homebrew Computer [feedly]
- Dec 6, 2013The reader I fixed up used little spoked wheels. The wheels looked like those star shaped spring washers, but with only 5 or 6 spokes. When a hole comes along, the wheel sinks into it, when there isn't a hole, the spokes ride on top of the paper. I don't know what the contacts were made of, but they were still very shinny. I'm guessing they were silver contacts. There were a few set screws for the travel and spring tension, but I didn't have to adjust a thing... I built a circuit with a 555 to step the solenoid, some LED's to display the code and a PIC chip to convert to serial data for capture by a PC. I was very impressed how well it worked. It could read at full speed without errors. Full speed was as fast as the solenoid could go, which was about 40 characters a second (solenoid on for 20mSec and off for 20mSec). But it was very noisy! I should try to find some pictures of it for posting.
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