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Electrical switch Answered

I was wondering if theirs a type of simple cheep switch that would do this: electricity is turned on, a switch completes a second circuit but when original electricity is turned off the second circuit stays on. The first circuit gets power from an outlet but the second circuit runs on a battery But in diagram (I used paint it's the best I can do) I have both running on batteries. Dose any one know of an electrical component that would do this? Or is their any way I could build one for cheep? Thank you.


In advance of a reply to my first comment, how about using a latched relay? L

Look them up on the internet. Power flips the relay to one position, where it stays. Reverse power, or a second coil flips the relay back. Other types of relay act upon springs, so they default to the same positon when they are not powered. L

You better have some resistors of some sort in that project or else you will have quite a mess. (BTW Outlets give off 120V f you didn;t know)

Yeah I know, I have a lot more parts I just made a quick paint picture to try to show what I was trying to do.

Why won't a mechanical switch serve your purpose? what do you want to use this for? L

basicly an alarm clock that will force me out of bed to turn it off. yes i know it would be easy to just move the clock...

I know a guy who will have his clock go off and lie there through an hour of monotonous beeping. Then it stops. Have the clock trigger some music that you hate on the far side of your room. E.g. the demo function on a cheap keyboard.

That won't work anyway. I always put my alarm clock on the other side of the room, and I'm now capable of waking up, walking across the room, and hitting the snooze button every 7 to 10 minutes for HOURS before I actually manage to be awake enough not to fall asleep again during that "snooze" period. Sigh.

Basically Im looking for a system that when 1 thing is turned on another separate thing is turned on, and even if the first thing turns off, the second thing will keep running on its own power.


11 years ago

either a relay or a transistor can do this, you just need to connect the battery circuit so that there is a feedback to the gate of the relay/transistor - so that once activated, it keeps itself on. more specifically, connect one diode in series with power from circuit 1 (on the left) to the relay/transistor gate, and a 2nd diode in series with power from circuit 2 (on the right) to the relay/transistor gate. the diodes prevent back-driving your two power sources when both are on at once.