Reading the voltage of an energy harvesting coil using Arduino ADC
At some stage you're going to have to rectify the signal to extract the energy so it makes sense to do it there, after the rectifier. Your problem is that you are working with low voltages so the diode drops become significant. I recommend that you go for higher voltage, lower current so that the losses become less significant. Of course, use Schottky diodes to minimise losses.







simulate this circuit &ndash; Schematic created using CircuitLab

Figure 1. Centre-tapped coil has only one diode in circuit at any time.

Use a centre-tapped coil so that one diode conducts on one half-cycle, etc. This is better than a single coil with full-wave rectifier as it always has two diodes in circuit at any time.

Add over-voltage protection to your ADC as you may get high spikes in the event of an impact / shock motion to the device.

Also, see William Bode-Tyrrell's answer to Increasing efficiency of a kinetic energy battery charger for some good calculations.