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14579Re: [cosmacelf] Re: OT: The Most Minimal Homebrew Computer [feedly]

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  • joshbensadon
    Dec 6, 2013
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      The 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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