Hi every one,
I've seen quite a few methods here and there allowing us to estimate the value of a given capacitor with a somehow basic RC low-pass or hi-pass filter circuit.
In one example I found, there is a suggestion to vary the frequency such that the voltage accross the capacitor is half of the source.
Under these circumtances, it would be legitimate to conclude that the voltage accross the resistor and capacitor are the same. This is where the comparator comes in the picture. How interface the opamp with the RC circuit in such a way that when the equilibrium is reached, the output of the opamp is "flat".
Obviously, due to the nature of the opamps, a perfect match of Vc and Vr is pratically impossible, but if that could be done within few millivolts, I think that would be acceptable.
So ideally, a led would lit up if the frequency is too high and another one would be lit if the frequency needs to be increased. Having both lit or off would be acceptable, indicating that we're within the difference of few millivolts we've preset.
This is potentially not something too complicated, however I'm somehow uncertain where to start.
BTW, when the equilibrium is achieved, the formula sqrt(3)/(2*pi*f*r) would provide us with an estimated value of C.
This little circuit/project is simply to get more familiar with opamps and RC circuits and at the same time, give me the opportunity to create something that could be usefull, who knows.
Your help would be greatly appreciated.