I've somehow destroyed an Arduino, questioned my sanity, sacrificed several chickens, and finally, have the interface electronics from TNMOC's Armdroid now running. But, I'm facing what appears to be a timing problem as soon as the 74LS366 is inserted into the empty IC5 socket that enables the feedback sensors.
I was wondering why TNMOC's interface was missing this chip, because it doesn't make a great deal of sense when the arm has already been fitted with sensors. When you look back at the photographs it's quite obvious the previous owner bypassed the interface circuit and controlled the steppers and sensors from some other source. This is not the first time I've witnessed this when making a post-mortem analysis of a dead looking Armdroid.
Enabling IC5 and testing the same combination with my Armdroid interface circuit, everything is working as expected, so assuming I do have my facts correct, I will write up another day more information about the wiring up of these sensors.
I suspect the timing problem relates to the 74LS123 (IC4) Monostable Multivibrator and delay determined by the accompanying capacitor and resistor network. Testing this capacitor with my ESR meter in-circuit proved inconclusive, so I'll probably swap this out as soon as I have replacements available and try again.
Anyway, having spent many hours looking at the circuit board, decided I would take a break and start cleaning up the mechanics as everything is really dusty and dirty.... This morning I spotted a very subtle difference between my Armdroid 1 hardware and TNMOC's regarding the finger supports.
On the surface, the design of Armdroid 1 hardware didn't actually change a great deal after going into production, so this is worth a quick mention here...
Spot the Difference
As you can see in the following photograph - my Armdroid consists of an aluminium support flange for the three fingers:
|Finger Support Flange - my Armdroid|