Let's try to make an ESR meter (part 1: AC Signal)
I've stumbled upon this : https://ludens.cl/Electron/esr/esr.html A 100% hw ESR meter. The principle is simple enough : - Generate an "AC" signal - Go through a transformer to lower voltage/increase current - Measure the impedance across the capacitor to measure (and assume ESR >> Z at that fq ?) Let's do it with a MCU and a salvaged transformer from a 5v usb power supply. AC ? Since we are using a transformer, we NEED to use a AC source. DC will just heat the transformer. At first i used a sine oscillator made with an opamp, it sort of worked but was very unreliable in terms of replicating the circuit (gain was to be manually tweaked, its oscillation was changing, single fq ...) The 2nd try was with a plain square oscillator, driven by the MCU. It worked fine, but caused inductance effect on the transformer because the signal was square. The transformer output signal was very distorted. I could have used a CH32F103 or a GD32Fxx, which contain a DAC, but i al