Quote:
Originally Posted by eugenebrooks
What you want to do can be done with a relay, arranging that
the relay also provides voltage to the solenoid. When you hit
the button, the relay triggers and the relay then keeps itself
triggered until you break the solenoid circuit with a separate
normally closed switch.
Eugene
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Dr Brooks'
Relay suggestion is a classic design that goes from completely off to a simple latch that supplies power to the unit. Haven't seen that one since I worked on Telephone switching equipment in the days before calculators! But hey it's cool and simple and does the job and I'd go with that suggestion if you need to be completely un-powered while waiting.
The same basic design can be implemented with a flip flop latch arrangement or even a 555 timer but these need at least some power or a preset state for power on.
If you can have battery power then in the case of a PIC or Basic Stamp chip you could just have it looping until it see your momentary button and it can power everything else up.
Point is, there are many ways to do this but I think you need to give more details.
Best Wishes
Steve Alaniz