I was wondering if with the help of a low value resistor and a peak detector attached in parallel with the resisto i can measure the current peak of the charging capacitor, and then maybe send that value to a uC

 

1. You might be better connecting the sense resistor in the ground leg of the capacitor so the uC is measuring the voltage between the output of the peak detector and ground.

2. Also using the circuit you show the first 200mV or so fo the voltage across the shunt will produce no output because of the forward voltage needed by the diode. To solve that you can use an op-amp peak detector circuit as shown here: https://sound-au.com/appnotes/an014.htm

3. Having the sense resistor in series with the capacitor will raise its ESR and may affect the operation of whatever is inside the box labelled power supply.

 

1. You might be better connecting the sense resistor in the ground leg of the capacitor so the uC is measuring the voltage between the output of the peak detector and ground.

2. Also using the circuit you show the first 200mV or so fo the voltage across the shunt will produce no output because of the forward voltage needed by the diode. To solve that you can use an op-amp peak detector circuit as shown here: https://sound-au.com/appnotes/an014.htm

3. Having the sense resistor in series with the capacitor will raise its ESR and may affect the operation of whatever is inside the box labelled power supply.

I was already planning to use an op amp peak detector to eliminate the diode voltage drop.. but i didn't understood very well the first point, can u please explain it in a simplified way

 

The output of your circuit is across C1. The bottom of C1 is at the power supply voltage and the top is a little bit more than that. Grenerally an ADC measures the voltage between 0V and its input so here you would be using only a small part of the ADC input range and so losing a lot of resolution.

 

The output of your circuit is across C1. The bottom of C1 is at the power supply voltage and the top is a little bit more than that. Grenerally an ADC measures the voltage between 0V and its input so here you would be using only a small part of the ADC input range and so losing a lot of resolution.

So you are saying that the other lead of C1 must be connected to the gnd? Should I also unify the power supply gnd with the uC gnd?

 

The components from your original diagram should be arranged as below.

 

The components from your original diagram should be arranged as below.
View attachment 215671

Thanks for the help, I understand now

 

Thanks for the help, I understand now

For your further edification, you should also be aware of 2 other things about your original circuit:



1. The resistor & capacitor in series form a voltage divider.
2. The capacitor at the bottom is between ground and the rest of the circuit, so ground is elevated to the circuit. This is okay so long as nothing is then attached from the circuit to the bottom of the capacitor at ground. If you were to have connections from elsewhere in the circuit on both sides of the bottom capacitor, it would form a ground loop.

 

For your further edification, you should also be aware of 2 other things about your original circuit:

View attachment 215673

1. The resistor & capacitor in series form a voltage divider.
2. The capacitor at the bottom is between ground and the rest of the circuit, so ground is elevated to the circuit. This is okay so long as nothing is then attached from the circuit to the bottom of the capacitor at ground. If you were to have connections from elsewhere in the circuit on both sides of the bottom capacitor, it would form a ground loop.

So to fix that the schematic Albert hall posted is enough?

 

Albert's circuit should be good enough, replacing the diode with an opamp based precision rectifier.