# Value of the capacitor required for smoothing

I have been checking outputs for my energy harvesting device. I connected the schottky bridge rectifier for full wave rectification and then connected 2200 uF and 3300 uF capacitors for smoothing of the voltage.

simulate this circuit – Schematic created using CircuitLab

The direct output voltage from the motor is as follows:

When I connect them to Schottky diodes and C3 (2200 uF), It gives this reading with V_max at around 12 v:

When I connect to Schottky diodes and C1 (3300 uF), It gives this reading after smoothening with V_max at around 10 v:

How is this possible and how do I get the right smoothing capacitor for my required output voltage waveform? In this case, 2200 uF capacitor works better than the 3300 uF. I tried calculating using the formula, but I am not able to ballpark it to the estimated 2200 uF value:

$$q = I.t$$ $$C. \Delta V = I.t$$ $$C = \frac{I.t}{\Delta v}$$

• Strange how much the input voltage resembles speech. – JRE Sep 1 '16 at 12:03