Timer Switch

[Dick Sexton]

I'm looking for a 110-volt spring loaded push switch that if someone
pushes the switch, that starts an activity, that the switch will not
work again for a set amount of time, say 10 seconds.

Any ideas?

 

[Chris]

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Dick Sexton wrote:

I'm looking for a 110-volt spring loaded push switch that if someone
pushes the switch, that starts an activity, that the switch will not
work again for a set amount of time, say 10 seconds.

Any ideas?

Hi,
Assuming we have some source of low-voltage DC available to us as well
as the high-voltage (I'm assuming AC but it really doesn't matter)
target, I would get a DPST or functionally equivalent switch. One of
the poles directly controls the target circuit. This is in series
with the normally-closed contacts of a single pole relay. The second
pole in the switch goes to the SET input of a monostable
multivibrator, calibrated for the requisite amount of time. The
output of the multivibrator is sent to the coils of the relay. The
multivibrator is powered by the low-voltage DC supply. When you push
the button, it momentarily makes contact and closes the 110-volt
circuit. It also activates the multivibrator, which immediately turns
on the relay and opens the 110-volt circuit. After the multivibrator
expires, the relay closes and the button is once again available for
use.

If, instead of a momentary pulse on the 110-volt circuit, you actually
need the user to press the button and have the 110-volt circuit stay
on for exactly 10 seconds then turn off, you'll want to take out the
normally-closed contacts and instead put the normally open contacts
in parallel with the switch. Thus, when the button is pushed, the
110-volts turns on, the multivibrator sets, and the relay turns on.
When the button is released, the relay keeps power flowing until the
multivibrator expires.

If you need something else, ask, but I'm not sure I'll be able to
figure it out.

- --
Chris
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