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Normally closed switch to discharge capacitor
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Moriambar:
Hi.

I'd like to have some kind of switch (normally closed) that drains a capacitor; when I apply a voltage to it the switch stays open and then the capacitor is allowed to charge. Removing the voltage, the switch closes and the capcitor is discharged.

I have 0-3.3V signals; the capacitor is also charged with 3.3V.

Can you help me choosing the right component for the job?

I hope what I said made sense
madires:
A relay?
Moriambar:

--- Quote from: madires on January 23, 2019, 03:06:28 pm ---A relay?

--- End quote ---
isn't it overkill? I mean, I was optimistic in a one-component solution, something like a transistor...
aheid:
Is it a large capacitor? Do you just want to discharge it, or do you want to discharge it through a specific circuit?

If you got a microcontroller, and if it's small and you just want to discharge it without special constraints, you could just put a suitable resistor between it and a GPIO pin, then toggle the GPIO between "output low" for discharging and "input high-z" (ie without pull-ups or pull-downs) for charging.
Moriambar:

--- Quote from: aheid on January 23, 2019, 03:42:42 pm ---Is it a large capacitor? Do you just want to discharge it, or do you want to discharge it through a specific circuit?

If you got a microcontroller, and if it's small and you just want to discharge it without special constraints, you could just put a suitable resistor between it and a GPIO pin, then toggle the GPIO between "output low" for discharging and "input high-z" (ie without pull-ups or pull-downs) for charging.

--- End quote ---
No basically I have no microcontroller and just a resistor to discharge it, connected to GND. All I want to do is basically have the + of the cap (between 100uF and 1mF) pulled down constantly unless I put a logic signal (3.3V or 0V) at the gate.

Thanks
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