> http://cowshed.8m.com/trigger and tell me if there is any hope it'll
> work I'd be most appreciative

A problem with that circuit as it stands is that there's a good chance
the solenoid is going to cause a lot of noise on the PIC's Vcc. This
could lead to unwanted resets and/or strange behaviour

I'd suggest you supply the PIC's regulator via a diode. On the k of
this diode have a reservoir electrolytic, ie on the i/p of the regulator.
This effectively gives the PIC a supply that's isolated from the battery.
If the solenoid collapses or spikes the battery voltage it won't affect
the PIC

---------------------------------------------

Solenoids I use in mechanical clock ratchet drives, especially when
in Fast Forward, will do exactly this to a micro. They're pretty low Z
coils, around 4 ohms, and at 2Hz FF operation are a big load. On a
turret clock with 4 faces/drives, the only way to step or FF all of them
with a reasonable PSU or battery is to advance them in rotation. They
all have an isolation diode and a reservoir cap each, as well as the
protection for the PIC as above

---------------------------------------------

Last week I came across what I think might be another potential
problem. A circuit just finished has a PIC, LCD and 4 small (110
ohm coil) relays. When one relay in particular energises, the LCD
goes blank. The program appears to keep running properly, even
though you can't see what's going on. Only moving the LCD's short
ribbon cable away from that relay stops it happening. I'm sure the
cable/soldering/PSU is OK (spent an hour on it and replaced the
cable and relay's  transistor/diode) but there's something about the
wiring orientation.........

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