slowing down an aquarium water pump?

Go To Last Post
13 posts / 0 new
Author
Message
#1
  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

I have a simple $10 water pump (probably AC motor since runs from mains) that I would like to slow down, maybe even assign some control for the RPM. How can I do that with this type of motor?

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

I guess you wont know until you start pulling it apart. Would assume you could just add a potentiometer to get RPM control.

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

No.

If it is a simple line powered motor with no brushes (ie, not a "universal" motor), then the shaft speed is fixed to the line frequency. To control the speed, you will need to build an inverter that generates a variable frequency "sorta_sine" to power the motor. Its not so easy.

Jim

Jim Wagner Oregon Research Electronics, Consulting Div. Tangent, OR, USA http://www.orelectronics.net

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

You can reduce the speed of induction motors by reducing the voltage, such as with a resistor, capacitor, or phase control ("dimmer"). Torque falls of rapidly with reduced voltage so stalling becomes a problem if you go to far. Since you have a pump, using feedback from a pressure transducer to control voltage via a phase control can give you pretty good flow control. As a practical solution to reducing flow, you might just put a valve on the pump's discharge line. This eliminates the stalling problem and centrifugal pumps generally do not care if flow is restricted.

Tom Pappano
Tulsa, Oklahoma

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

One solution is to turn the motor on/off periodically. Sort of a slow motion PWM.

If this is a brushless induction motor then You really can adjust the speed by limiting motor current but the adjustable range is far from great. The adjustment is also hightly non-linear.

Some of the "simplest" motors are only designed to run with that fixed speed so trying to control their speed is not even possible.

A very simple frequency converter can be done by omitting half waves from the AC. This has to be done symmetrically to avoid AC buildup on the motor. For example omitting every other half wave yields half of the frequency. You need to investigate WHEN to turn on/off the switch - it is NOT on the zero crossing because of the phase lag created by the motor.

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 1

Probably there is no motor at all. Simple membrane pump with solenoid on 50Hz.

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

johnfound wrote:
Probably there is no motor at all. Simple membrane pump with solenoid on 50Hz.

Actually I can take the top of the pump off and see the shaft with the "propeller" at one end.
The problem is that the motor is housed inside an epoxy which was casted all over it making it impossible to see any electronic components (if at all present) or the motor assembly itself.

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

If this is an airpump, is there any reason you cannot attach a T adapter at the end, and a variable valve on one stem to bleed off excess pressure?

If you want to get really fancy, you could stick a chamber there, with a pressure sensor and a vent valve.

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

The "propeller" is known as an impeller in this type of pump.

You can restrict the flow-rate and the motor will just waste power but otherwise come to no harm.

So you are really stuck with a variable frequency drive, intermittent pumping, or continuous flow with a bleed or restriction.

The first option is not viable for a $10 pump.
Perhaps a $5 pump will give you the desired flow-rate.

David.

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

Quote:
So you are really stuck with a variable frequency drive, intermittent pumping, or continuous flow with a bleed or restriction.

And variable voltage drive

Tom Pappano
Tulsa, Oklahoma

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

It would be useful to know the end application.  Is it indeed for aquarium use?  If so, as already mentioned, simple petcocks are a standard accessory to limit air flow.

 

But if for another use -- then give more details.  We have a family of apps that require a couple PSI.  I found DC-powered "pumps" from ink-jet printers that are quite quiet, not expensive, and work OK.  We actually use a pressure sensor to close the loop and turn the pump on/off as needed.  Can be used for pressure or vacuum.  E.g.

http://www.ebay.com/itm/DC24V-7W...

http://www.ebay.com/itm/4pcs-lot...

 

You can put lipstick on a pig, but it is still a pig.

I've never met a pig I didn't like, as long as you have some salt and pepper.

Last Edited: Mon. Sep 25, 2017 - 01:54 PM
  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

Lee, eight-year-old thread.  Spam was deleted, hence the 'refresh'

"Experience is what enables you to recognise a mistake the second time you make it."

"Good judgement comes from experience.  Experience comes from bad judgement."

"When you hear hoofbeats, think horses, not unicorns."

"Fast.  Cheap.  Good.  Pick two."

"Read a lot.  Write a lot."

"We see a lot of arses on handlebars around here." - [J Ekdahl]

 

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

joeymorin wrote:
Lee, eight-year-old thread.

lol -- never noticed.

 

 

You can put lipstick on a pig, but it is still a pig.

I've never met a pig I didn't like, as long as you have some salt and pepper.