Really Basic Power On Question

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Bret Cahill

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Feb 16, 2021, 10:59:09 AMFeb 16
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This must be a really really common problem and the only reason it is difficult to find on youtube is the wrong search terms:


If a device has a power on button latch switch and you want it to turn on and off like a light bulb, i. e., when the power supply is plugged in or a relay connects the power, or for solar, when the sun comes up, is it a common solution to run a wire from the power supply through a cap and maybe a large drain resister in parallel then to one side of the latch switch?

The current would flow through the cap just long enough to set the latch switch before the cap is charged and stops the flow.

Then the device turns on and stays on until power is disconnected. The process can repeat after the charge drains off the cap.

First check the voltage through the on switch is the same as the power supply. (This will not werk on a lap top.)

I'd need some idea of the time it takes to latch and some thresh hold voltage for the latch to select the cap and resister. Maybe look at it on an oscilloscope.

Dan Purgert

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Feb 19, 2021, 7:50:43 AMFeb 19
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Bret Cahill wrote:
> This must be a really really common problem and the only reason it is
> difficult to find on youtube is the wrong search terms:
>
>
> If a device has a power on button latch switch and you want it to turn
> on and off like a light bulb, i. e., when the power supply is plugged
> in or a relay connects the power, or for solar, when the sun comes up,
> is it a common solution to run a wire from the power supply through a
> cap and maybe a large drain resister in parallel then to one side of
> the latch switch?

don't follow your description here at all. Are you just trying to
figure out a "simple" way to pulse a latching relay's coil long enough
for it to set?

Note that in order to reset a latching relay, one normally needs to
drive a secondary coil, or reverse the current flow in a single coil
model; so if I'm understanding your question properly, you're never
actually going to "unlatch" the relay.


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