I work at a museum and would like to hook-up a light box to some kind
of switch that would have the box stay on for about 45 seconds and go
off. Any ideas?
I am assuming you want it to work like this: the user pushes a button,
the light box comes on, stays lit for 45 seconds, then turns off until
the user pushes the button again. I am also assuming that the light box
operates on regular wall-socket voltage from a regular wall socket, and
that you have someplace to put the control circuit.
If the above is true, then what you probably want is a "delay on break"
or "delay on release" relay. This is a relay (an electrically operated
switch) with an internal timer. There is a knob on top of the relay
that sets the time it stays on. These relays are usually designed to
plug into a standard socket, so you'd need to get a socket as well. You
also want to make sure you can get one that can be triggered by an
external (pushbutton) switch. You'll probably want to use a fairly
beefy pushbutton (like the ones used on arcade games) so it will last.
At the local electronics distributor, I can get a suitable relay and
socket for about US$65. Add another US$20 or so for a pushbutton, wire,
etc. The relay and socket will fit in a 3" (75 mm) cube. You'll have
a plug, a cord, the relay socket, the wiring to the light box, and the
wiring to the pushbutton.
If you're not familiar with wiring up things that plug into the wall,
get someone that is to help you with it. It's not that hard to do, but
the consequences of getting it wrong can be severe.
Matt Roberds