Hello all,

After connecting the decoupling caps across the 5V and ground pins of each IC, I found that the uC still stalled!
I then used a scope to measure the potential at the Vcc pin of the uC and the output pin of my 5V voltage regulator.
I found that when the first pnumatic piston is energised (after all of them had been de-energized) a 14 to 16 V peak-to-peak spike appeared on the pins, even though the 5V regulator was present.
The same did NOT appear on the PIC board!
I then realized that in my cct the 110V used to energise the pistons was provided by the very same power supply that ( after the appropriate regulation ) powered my digital system.
In the case od the PIC board, the 110V used to energize the pistons was provided by a seperate power supply from the one that powered the digital system , as a 110V power supply was not provided on that board!

I therefor put the problem down to the "inductive kick" mentioned on page 1 of AP-125 - "Designing Microcontroller Systems for Electrically Noisy Environments"

With that being said, does anyone have ideas on how to overcome this Noise without using a seporate power supply for the 110V pistons!
I was thinking of connecting a Zener diode across the 5V input!

Thank you for your time
sun