let's try and get this paper tape reader working. I have no control board for it so this is going to be interesting
here's a 4-phase stepper motor driver from another project. I actually got this working a while back, so I can move the tape precisely in either direction.
this is the illuminator. it shines light through the holes in the paper tape up into phototransistors
one red LED and the others are infrared. they appear faintly on my camera due to the filters in it
here's the sensor side. the cogged wheel pulls the tape through the reader
there's a switch at the back that senses if the tape clamp is in place or not. the optical sensors are on the right
the sensors are phototransistors. the emitters are all wired in common.
this is what 110110100110110 looks like. clock recovery shouldn't be that tricky because i control the stepper motor speed directly.
grabbed the clock from one of the stepper phase drive signals. easy!
built up a simple circuit with 8 LEDs so you can see the data scrolling by.
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i printed a new panel insert that has two BNC sockets on it (the original probes would have had captive cables)
the tricky part is that this oscilloscope has a 333K ohm input impedance instead of 1M like umm every other scope on the planet. fortunately someone designed a little conversion circuit...
in honor of Sim Wong Hoo, here's a quick historical review of the Sound Blaster! 🧵
but first we have to go back to their first sound card, the Creative Music System from 1987. (image credit: Bratgoul on Wikipedia)
this card has some special "CMS-301" chips. if you peel back the sticker, they have had their top marks removed. they're actually SAA1099 synthesizer chips made by Philips. Creative wrote music composition software for musicians on the PC.