Charging-Discharging Capacitor

Thread Starter

aacbh

Joined Feb 9, 2018
4
I have an application where I charge up a capacitor from a DC source.
I only want the capacitor to discharge into a load if the DC source charging the capacitor increases and then goes to zero. I have considered just using an upper threshold for the source voltage and trigger off that, but since the DC + source can vary I wanted to add the condition that the source go to zero to activate the mosfet. Both conditions need to be true.
I do not have another power source Circuit.jpg available to power ICs, such as a comparitor, so it needs to be done with diodes, caps, etc

Any suggestions for a circuit? The capacitor will discharge to the load thru a mosfet so I would like to supervise the discharge from the mosfet. This is only a very short duartion discharge of the capacitor into the coil of a latching relay.

Thanks for all the help!
 

ericgibbs

Joined Jan 29, 2010
14,168
OK,
Give me some details of the working voltage and the relay coil resistance.
Also some idea of the pulse width you want from the relay drive.

Any other information about the project will help.
E
 

Thread Starter

aacbh

Joined Feb 9, 2018
4
The working voltage will be approx 0 to 5V.
The latching relay coils are about 64 ohm. I have not settled on all the components yet. Just looking for the methodology on how to accomplish this. The capaitor will need to store enough energy to drive the latching relay coil. This is a minature signal latching relay. The DC+ source that charges the capacitor will be available for plenty of time prior to the action requested.

THX
 

ericgibbs

Joined Jan 29, 2010
14,168
OK,
5V/64R is approx 80mA.
A 2N2222 transistor will be suitable.
How do you plan to start the pulse, is it a push switch or a micro controller output pin.?

E
 

Thread Starter

aacbh

Joined Feb 9, 2018
4
OK,
5V/64R is approx 80mA.
A 2N2222 transistor will be suitable.
How do you plan to start the pulse, is it a push switch or a micro controller output pin.?

E
Your .gif file causes an error. I do not have an external way to trigger the mosfet. I want to trigger it when the source DC+ rises and then goes to zero after that. THX
 
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