I'd like to control the turn on/off of a NFw Series Centrifugal Water Pump 380-440V high voltage water pump using an Arduino.

I have searched for how control it, but I haven't found any ideas. Can you kindly give me a suggestion?


2 Answers 2


Try using a relay. I looked at the specification of the motor but couldn't tell if it was single phase or three phase but either way a relay is the best bet. I'd also try contacting the supplier to see what they recommend - at least this way you might get a circuit from them. Relay, single phase: -

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This uses a 12V relay but a 5V relay will do on a 5V supply. The output contact needs to be adequately rated for the supply and the motor i.e. correct voltage and current ratings. The brochure for the motor is inadequate - under "power" it says "electric" and I really do think it should specify what the power of the motor is on the website - maybe I missed it but, If you know what the power rating of the motor is then that's OK.

Remember this might be a three-phase motor and even if it isn't - do you have a 380V AC supply to hand - most folk don't so I'd proceed with caution before investing good money on this motor. If it is a three phase motor you need to have three isolated contacts available from the relay. You'll also need to be capable of wiring this unit in safely and correctly - also use a residual current circuit breaker to protect you and others.

Not a job for the faint hearted. You'll need to source the right relay (I can't tell from the brochure) and it's possible that the relay may need to activate the motor via a contactor that is suitable for the ac voltage and motor load current.

  • \$\begingroup\$ Your circuit should definitely show a diode across the relay coil (diode cathode to +12 V) to conduct the reverse voltage spikes when you switch the relay off... and depending on the relay coil and transistor gain at saturation, you may not be getting quite enough current to the relay coil with that base resistor. \$\endgroup\$
    – nekomatic
    Commented Oct 17, 2014 at 22:34
  • \$\begingroup\$ @nekomatic you are totally correct. This was an oversight on my part. \$\endgroup\$
    – Andy aka
    Commented Oct 18, 2014 at 0:36

Yes, relays are the best choice but use ULN2003, high voltage high current transistor darlington transistors with the relay and a diode on coil side of the relay to protect other components of the circuit from the reverse transient voltage.


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