Hi Hood
That's definitely Index Debounce, I'm using pin 15 as the input on the bob, the wiring is shielded, actually its 4core shielded microphone cable, nice cable you can buy by the meter from Jaycar in Oz. The grounding of the shield is from one side only, the other is capped off as close as I can to the the opto, say 2" or 50mm. The grounds are all common as with the neg side of all power supplies all run from separate buss bars or points.
Ill include a couple of pics.
The only thing that I can think off at the moment, is my spinning disk is made from a CD, maybe reflection, refraction, or just do the locomotion (bit of humor here) but I have read that with the opto I'm using it makes no difference if its a reflective surface or not. I have painted my black anyway.
As I said in prior posts the BOB picks up without a problem every pulse sent by the opto, just mach cannot define it. Maybe I have to go for timing instead of index, maybe a different input pin would do better, maybe Peter Homman could shed some light on this its his bob's I'm using?
Cheers
katoh