Originally posted by gambleb
Well I had a short time this morning to take my multimeter to the circuit and check it out. I'm starting to wonder about this diode I'm using. I was always taught that I diode is a short one way and an open the other. Is this not entirely correct because the diode that I have in my circuit has a resistance of almost 2Mohm (1.7M to be exact) and it is open in the other. Also the cord I was using has a 2 ohm resistance on either lead. Could those two factors be why it won't work at all? I still cant get the bars on the calibration screen to move at all.
thanks Brian
2 ohms on the lead almost certainly just means your multimeter is not very accurate at low resistances
. The measurements on the diode may or may not be o.k. depending on what voltage your multimeter uses for its resistance test (if it's not higher than the diode forward volt drop it will show up as a high resistance). Is it a 1N4148 or some other diode ? The readings could also be those of a zener diode, which won't work in there.
With it all plugged in and FMS running what DC voltage do you see between ground (pin 5) and each end of the diode ?
BTW, when you visited the FMS forums did you read the earlier threads in "Serial Interface" ? There have been plenty of similar questions relating to this same interface.
Steve