How to add a capacitor and switch correctly to piezoelectric circuit?

Am a hobbyist beginner with no prior electrical engineering knowledge (though can follow a basic circuit), so please bear that in mind when giving your valued advice! am following an instructable to build a piezoelectric circuit project.

The instructions say that the piezo elements generate AC and not DC so a bridge rectifier made of four diodes needs to be added, since the piezo elements will cancel each other's output if these diodes are not included.

6 piezo elements and 1 bridge rectifier is called for per piezo element to prevent this, however only one bridge rectifier is shown for 3 piezo elements in the instructions.

So far, I've followed the circuit below with 3 piezo elements and one bridge rectifier:

However, I'm aware that another 5 bridge rectifiers to be added (the other 3 piezo elements are underneath the white board I think). I'm looking for the following:

1) Can anyone describe the circuit diagram I should follow to include the additional 5 bridge rectifiers? here's the current circuit

I realize that each bridge rectifier should be connected on the silver wire connecting the piezos in the jpg, but then does that mean I need to connect all six wires from the rectifiers back to the - and + of the battery?

2) Can anyone describe/explain how to connect the circuit diagram with the rectifiers, capacitor + switch

3) An idea of what type of capacitor is best to use here (maybe a ceramic capacitor that can handle 100V, as it should be x3 the potential highest output which is around 27V? but may be incorrect)

• What is it you are actually trying to make? And does the instructable have a schematic? Commented Mar 5, 2016 at 16:55
• Hi I am trying to build the project from here instructables.com/id/Electricity-Generating-Footwear/?ALLSTEPS. The schematic is the same as in the pictures (couldn't post the link before since it only allows you to post two links max on basic account) Commented Mar 5, 2016 at 17:55

Without reading through the Instructable I think what you want is this:

simulate this circuit – Schematic created using CircuitLab

Figure 1. Multi-piezo rectification.

The piezo output will exhibit a very high internal resistance. Once they are loaded the output voltage will collapse. In practice the capacitor loads the piezo so that each piezo pulse will add a little charge to the capacitor. The max voltage the capacitor sees will depend on the rate of charge versus the rate of discharge.

simulate this circuit

Figure 2. Six-piezo rectification. All rectified outputs joined in parallel.

• Hi transistor, thanks for the schematic, however 6 piezo elements are required (the same circuit connected on the opposite side, the above shows the top side but not the bottom). How can I join these two circuits? Following the above diagram, would the opposite circuit be connected at points D3/D4, D1/D2 etc (obviously with diodes facing the correct way)? To clarify, there should be another piezo element under each one shown in the diagrams Commented Mar 7, 2016 at 5:55
• The other side of what of the white board? See Figure 2. Commented Mar 7, 2016 at 7:35
• Underneath the white board shown in the post there were more piezo elements. Thanks for the updated schematic. Commented Mar 11, 2016 at 20:06