Capacitor charge time

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Paultergeist

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Hello!

I know how to determine the charge time required for a RC circuit, but I have doubts about how to determine the charge time for a RC circuit with another resistor connected in parallel with the capacitor.

In my case, I have a 24VDC power supply connected to a 56K resistor which is connected is series to a parallel of a 3K3 resistor and a 1µF capacitor.

How can I determine the charge time of the capacitor in this circuit? I know that the voltage in capacitor, when fully charged will be around 1.336V...

If you didn't understand the circuit:




Thank you for your help!
 
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Use Thevenins theorem. Ignore the capacitor to begin with and look at the voltage source and resistors. They are equivalent to a 1.336V source with 3.116k resistor in series. So, the CR is 3.116k with 1uF.

Keith
 
Paultergeist,

as another simple method imagine that the capacitor would be charged already and let it discharge.
Thus, with a shorted input voltage both resistors act in parallel - and the time constant to discharge is identical to the time constant for charging.
 
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