Hi, I have a remote control that opens the garage doors when a button is pressed. I wish to do this remotely so have shorted the appropriate button and a voltage will be applied across the battery terminals when I need the remote to operate. This works fine. I do though need a way to cut off the applied voltage after say 2s as I need a short pulse rather than continuous operation. Whilst I could buy an adjustable timer, is there a simpler way? Thanks.
Do you mean to turn off the "voltage ...applied across the battery terminals..."?
There's nothing simpler (for this function) than a bought time delay relay; you just plug it in.
But, if you want to design and build something just for fun/education, go for it! :-)
Cheers! Rich
-- More than likely. What voltage are you applying across the remote's battery terminals and how are you doing it now?
You could connect the power through a capacitor, with a bleed resistor. The capacitor charges up and the voltage across the remote goes to zero... and when power is removed, the bleed resistor discharges the capacitor before the next cycle.
I'm wondering why you can't just use a momentary switch in series with the battery for the remote. The duration of the pulse would just be the length of time you pressed the button. But you may have something in mind that is not apparent in your post. In that case, read on.
Assuming a 9V battery for the remote:
+9 ---+-------+------o--- | | ^---o----- +9 to remote | [R3] | | | +---[Relay]---+ o | | | PB +-----|
Arrggh! There's a connection from PB to gnd in the schematic that should not be there. Here's how it was supposed to be:
+9 ---+-------+------o--- | | ^---o----- +9 to remote | [R3] | | | +---[Relay]---+ o | | | PB +-----|ehsjr:
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