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Does anybody know whether it is possible to easily regulate the throughput of a DC water pump? E.g. one you would use for your pond or indoor fountain.

I would like to avoid lowering the duty cycle by switching on and off: one can get used to a continuous noise but a switched noise is irritating.

If I were to make an educated guess I would say that the pump uses a brushless DC motor. External leads are only +12V and GND.

So, would any of the following work without damaging / stalling the pump:

  • Switching with very high frequency, i.e. PWM
  • lowering the drive voltage statically
  • controlling permitted current draw

Which would give the best control over the throughput?

Note: the aim is to reduce the current draw and the noise of the pump.

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  • \$\begingroup\$ What pump? The MCP35x (branded version of the Laing DDC) has PWM control. Many other DC pumps can be controlled with voltage control. \$\endgroup\$
    – Shamtam
    Jul 8 '12 at 18:43
  • \$\begingroup\$ Do you wish to regulate the throughput with a control loop, i.e., will there be feedback? If not, if you're simply wanting to "set and forget", have you considered a non-electrical solution? For example, leave the pump voltage constant and return a portion of the pump output to the pump input through an adjustable valve. The electrical analogy would be adding a parallel variable resistance to a current source. \$\endgroup\$ Jul 8 '12 at 18:51
  • \$\begingroup\$ @Shamtam It is a no-name product. 12V 1.2A rotary / centrifugal / impeller-driven pump. \$\endgroup\$
    – ARF
    Jul 8 '12 at 19:28
  • \$\begingroup\$ @AlfredCentauri No, there will not be a control loop. - At least not regarding the throughput. Though there may be a control loop regarding a temperature variable that is dependent on the throughput. \$\endgroup\$
    – ARF
    Jul 8 '12 at 19:30
  • \$\begingroup\$ @ArikRaffaelFunke In that case, your best bet, IMO, is to just try a +12V PWM approach, or a voltage control approach. I would expect PWM to be harmless (but I'm not too familiar with PWM), and I know running a lower voltage than 12V will be harmless. I'd say try to find the starting voltage (start with a source at 0V and raise it until the pump turns on), then find out how much variation you get from the start-up voltage to 12V and work with that. \$\endgroup\$
    – Shamtam
    Jul 8 '12 at 22:07
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Buck regulator is basically a PWM with a filter. If you use a PWM switch with a high temp low ESR cap. than can handle ripple current, you can provide DC control of speed easily to maybe 30% depending on stiction.

Without knowing the details of your pump, my guess 1HP 72V 10Amp, I assume you can reduce to 75% V+ to cut the flow and RPM in half but noise depends on brushes, gears and bearings. DC is more efficient but noisier. YOu could consider sound proofing but not thermal insulating the motor.

Once you provide more accurate requirements, there are many creative ways to reduce the DC voltage. PWM , buck reg., add 500W Halogen Lamp in series etc etc.

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