Hi,
I want to power a small watering system. The watering will be provided by 2 water pumps RS-360SH. They don't need to run parallely. From measuring of the pumps I know, they draw about 1,7A at running (dry) and a bit over 3A at start.
Should I use 5A PSU, or will be the 3A PSU with some larger capacitor enough?
I would like to power from the same PSU also the arduino and relay board.
Measuring the dry current is not relevant since the current probably will be larger with the pump working. So use the 5A in order to have some margins
Some PSU's will reset if overcurrent, others won't (but might not be rated for it).
Which supplies are you thinking of - as always post the link to the datasheet(s) since
otherwise you'll just get guesswork.
The thing you need to do is measure the motor's stall current (or equivalently the winding
resistance), so that the highest current draw is known (not guessed).