Controlling a 240 V water pump with Arduino

Hi Guys,

I'm tasked with controlling a small 240 V caravan pump with an Arduino. Any suggestions on the best way to go about doing this? Is the load too inductive to simply use a SSR. If so, what are my options?


I've been using SSRs with 240VAC well pumps for years without any problems. Here are some precautions for use with SSRs:

Thanks for the post! Very Informative. Do you mind if I ask you a couple other quick ones;

Do I need to protect the Arduino side of the circuit any further than the SSR already does?

Do you recommend adding a capacitor in to lower inductance at any point?

Should I use a fuse on the +240 V side?

I use no protection on the microprocessor side, just two wires to the control port from the output pin and ground. The SSR control port draws only a couple of mA.

Capacitance does not lower inductance. A small capacitor of the appropriate rating on the output side may help reduce switching transients, but follow the SSR manufacturer's instructions. I believe that most SSRs already have "snubber" circuits built in to the output.

Fuses of some sort are ALWAYS a good idea. I use standard double pole circuit breakers on the 240 VAC side, near the control circuitry and the pump. That way I can safely disconnect everything while working on the control system. But I never trust the circuit breaker until I've double checked for live wires, before working with high voltage circuitry. I had a couple of close calls early on and am still alive to tell about them.

Wow! Well Thanks for all the advice. Really Appreciate it. Sounds like I need to be EXTREMELY careful.

When you say you don't trust the circuit breaker until you've checked for live wires. Do you mean, visually?

Thanks again! Big help!

It just takes a few seconds to check for dangerous voltages and it might save your life.

After turning off the circuit breaker and visually inspecting it (sometimes one switch on a double pole breaker will not snap completely off, even if both handles are paired with a clip), I then use a multimeter on the 200 or 1000 VAC setting to check for voltages between every pair of wires on the "off" or "load" side and also between any wire and earth ground.

If you see a reading of a few volts, that usually doesn't matter -- the reading can be due to capacitatively induced voltages from nearby wiring and is usually extremely low current. BUT, in such a case I always short the offending wire to earth ground with a screwdriver to check for sparks!

In one case, while wiring a well pump, I got a bad shock off the protective ground (bare) wire coming from the house, and measured 77 VAC to earth ground. It turned out that the nearby utility pole had a faulty earth ground connection, which the power company had to repair. You shouldn't trust anything without verifying it yourself.