I have a pump that draws 60W at 12V.

I had a little old linear hobby power supply I was using to power it in the garden but condensation killed it. Not a surprise but I needed the pump working more than I cared about the PSU.

I have a couple of waterproof lighting transformers in the garage and thought I'd see if one would run it.

It doesn't say on the label, but I'm guessing they're switch-mode (?) and the only two discussions I've found on the web re. SMPS and motors says they should work.

Anyway, when I tried it, it just sounds like its 'buzzing' the motor on and off very fast, which makes sense.

I don't know what to buy to power the pump. SMPS seems completely dominant save for linear bench PSUs. Maybe a lighting transformer doesn't work because of some other reason and that a different SMPS will work??




1 Answer 1


A lighting transformer might just be a 230V AC (or 110V AC) to 12V AC transformer and AC won't work on a DC pump, it will rotate back and forth with 50 or 60 Hz.

So a SMPS will probably work. You can try if you have an old PC PSU lying around, those are SMPS as well.

As pointed out by Brian Drummond in the comments, if your lighting transformer is just an AC type (those will be pretty heavy) you can try and put a bridge rectifier with enough current handling capability (at least 5A) at the output of the transformer and hook up the pump to the output of the bridge rectifier.

The rotor should keep rotating smoothly as it will store momentum and bridge over those points where the output has too little voltage to drive the pump.

  • \$\begingroup\$ If the transformer's good and heavy, this is the answer. Then simply connect it to the motor via a 10A bridge rectifier... \$\endgroup\$
    – user16324
    Oct 3, 2015 at 19:12
  • \$\begingroup\$ @BrianDrummond will the inductance and momentum be good enough to keep it running smoothly? \$\endgroup\$
    – Arsenal
    Oct 3, 2015 at 19:32
  • 1
    \$\begingroup\$ Motors don't need clean DC : consider how smoothly a very similar "universal" brushed motor runs on AC. The rotor acts as a flywheel to store enough energy. \$\endgroup\$
    – user16324
    Oct 3, 2015 at 19:39
  • 1
    \$\begingroup\$ @BrianDrummond Yeah that makes sense, I've included your solution into my answer - if that's okay with you. \$\endgroup\$
    – Arsenal
    Oct 3, 2015 at 19:49
  • \$\begingroup\$ Lightning or lighting? :) \$\endgroup\$
    – BenG
    Oct 3, 2015 at 21:43

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