Switching AC Motor Pump On/Off using Arduino

First, a little frustration - I recognise the high stress everyone places on safety while handling Mains power, and it cannot be overstated. But, for the beginner, there’s simply no resource (or so it seems) to start (once the danger has been understood, and fear drilled into our heads) working with Mains power.

I’m planning to operate two Iwaki motor pumps (data sheet) off a 110 V AC supply (tried dumb-switching on/off with 220VAC, as listed in data sheet, but the pump I have with me clearly states 110VAC only). My country has 220V AC as its mains supply, which I’m stepping down using a 500 VA transformer.

To switch the supply, I plan to put a 12VDC/10A - 230VAC 10A relay. On the Common port, I plan to connect the Live wire. On the NO ports of the four channel relay, I plan to use two ports, to put in the continuation of the Live wire, up to the respective motors separately.

The neutral wire would be connected separately to the motor directly.

To switch the relays, I’m using an L298 motor control board. The arduino, inputs power to an optocoupler, which powers on an L298 board. The L298 board then energizes the relay. The relay establishes continuity between the two pieces of the Live wire, and the motor switches on.

I only need to switch the motor on or off. Don’t need to control speed.

Does this sound right? Or do you think I’ll blow up the building? :slight_smile:

Thanks, attached is a schematic of the system from the relay to the motors.

What pump? A 500 VA transformer will handle only a small one.

That looks OK.

I assume you have the components already?

If you were starting from scratch, I'd recommend solid state relays. Solid state relays are easier to use because you can easily find SSRs that can be driven directly by the Arduino. And, since most higher-power SSRs have screw terminals, they are easy to use mechanically too.

A (maybe slightly cheaper) alternative is a relay board with a driver built-in. Or, the cheapest solution would be to make your own driver with a transistor or MOSFET.

The DC motor driver is "overkill", and you don't need optical isolation because the relay isolates the AC voltage from the Arduino.

My country has 220V AC as its mains supply, which I'm stepping down using a 500 VA transformer.

The transformer will draw some current when the pumps are turned-off. If that's an issue for you, especially if the pumps are run infrequently, you may want a 3rd relay to completely disconnect the 220V when both pumps are off.

Jremington - This is the MD-10N in the data sheet. Input power 18W, so I'm guessing my current draw would never exceed ~200 milliamperes (since I'm priming the pump separately by supplying water to it from a height of 12"). Should be safe, no?

DVDoug - You're right, I have all the components. I wanted to try with a pre-made four channel relay, before replacing it with an SSR. Once the first iteration works, I'll replace relay channel with an SSR. Eventually, I want to build my own driver, as you've suggested. On the overkill part - that's a scared first-time-Mains-Power-Tinkerer :) I'll get rid of the DC motor driver, optical isolation too. Thanks a big bunch for all of your suggestions!