As indicated above, this is slightly theoretical, because I know what physically failed in my circuit, but I can only surmise what happened inside the devices. However, during the diagnostic process, I discovered another flaw in the design of the circuit; the 'Chinese copy' DuPont contacts are quite unreliable. Both female and male contacts are poor, but for different reasons (maybe it's the same reason (**** metal)), but the end result is different:
- Male contacts - I've been using male contacts to screw into the terminations on the Motor Drive Board, but the metal is quite brittle and the slightest movement once they are clamped down causes the tip to break off. The bought-in contacts were not like that, but I have to crimp a female contact onto the other end.....
- Female contacts. These are OK the first time they are used, but once the cable end has been removed (for access for example), they are no longer reliably retained on the pin (they just fall off). The bought-in contacts were not like that, but I have to crimp something to the other end at the moment.
There are obviously alternative approaches:
- I could only use ends that have been made up by the manufacturer of the bought-in wires. This would make the wires super long, like the first Interface was.
- As 1 above, but solder the other end to the Header Pin on the Veroboard. This can't work where both devices have header pins as part of their construction, although I could solder to the pins in the DC/DC Converter. I wouldn't want to solder to the pins on the A/D, Motor Drive Board inputs or the Pi.
- Something else.
All ideas welcome.