Building the Arduino energy monitor - measuring mains voltage and current Example

I am buying the parts to build the example from this page Learn | OpenEnergyMonitor

The build calls for 2x 10uF capacitors, but I’m not sure which ones to buy as they have a voltage rating as well, what voltage do I need or doesnt that matter, also, Electrolytic or Tantalum Bead?

Also, there is the 33 Ohms resistor, as I will be running at 5v arduino. I have one, but was interested to know why the The EmonPi uses 22Ω burden resistors as that is also a 5v setup?

If you look at the circuit diagram, those capacitors are decoupling the 2.5 V midpoint voltage bias supply. The voltage rating needs to be greater than the voltage which the capacitor can possibly be subjected to, which is 5 V, and it’s good practise to go higher by a suitable safety margin. So 10 V (the lowest you’re likely to get) will be fine. We use electrolytic in the emonPi, emonTx and emonTx Shield.

No it isn’t - the Atmel 328P front end runs at 3.3 V.

Thanks for the quick reply Robert.

So with the 10uF capacitors would some rated at 25v for example still be ok? just that I actually have a few of those already from an old project.

Yes, no problem at all (as you’re presumably not constrained by size).