Regulating flow small DC pumps

[Steven Bolgiano]

Main Question or Discussion Point

Using as an example a 12v pump typical of aquarium, to regulate flow is better to use a potentiometer or a closing valve to affect a rate of flow?

 

[YoungPhysicist]

Using as an example a 12v pump typical of aquarium, to regulate flow is better to use a potentiometer or a closing valve to affect a rate of flow?

A ball valve will be fantastic.
http://www.industrialvalvestore.com/sites/default/files/004-working-of-ball-valve_0.jpg

 

[Steven Bolgiano]

I tend to agree with that. But can someone tell me why a potentiometer isn't an effective way to adjust flow rates. I'm also curious why a brushless motor supposedly cannot be reversed flowed when the current is reversed,... Or at least that's what I've heard

 

[YoungPhysicist]

I tend to agree with that. But can someone tell me why a potentiometer isn't an effective way to adjust flow rates. I'm also curious why a brushless motor supposedly cannot be reversed flowed when the current is reversed,... Or at least that's what I've heard

Well, if there is a non-electric solution, it will always be a better one than the electric one,because electric ones tends to go wrong more often. But regardless of that, controlling a pump with a potentiometer is a great idea.

 

[CWatters]

I tend to agree with that. But can someone tell me why a potentiometer isn't an effective way to adjust flow rates. I'm also curious why a brushless motor supposedly cannot be reversed flowed when the current is reversed,... Or at least that's what I've heard

A potentiometer can be used for small brushed motors but the potentiometer may have to be rated to dissipate the same power as the motor. Might need a heat sink and cooling.

Brushless motors typically need an electronic means of doing the commutation. So it's not possible to use a single potentiometer in series with the motor to control the speed. However the electronics that does the commutation could be controlled using a potentiometer.

Many brushless motors can be reversed however the way you do it is different..With a small brushed motor you can typically just swap +ve and -ve and it will run backwards (possibly with increased brush wear). With a small three phase brushless motor, as used in model aircraft and model cars, you swap over any two of the three wires going to the motor. Alternatively some brushless motor controllers have a "switch" or link that reverses the commutation order making it spin backwards.

A lot depends what access you have. Do aquarium brushless motors have the controller built in? In that case it might not be possible the get access to the motor windings to swap them over.

 

[CWatters]

I should also add that the voltage delivered to the pump motor isn't the only thing that determines the flow rate. Changes to the input or output pressure will also change the flow rate.

If you need accurate control measure the flow rate and use a feedback loop to control the motor speed.

 

[berkeman]

Using as an example a 12v pump typical of aquarium, to regulate flow is better to use a potentiometer or a closing valve to affect a rate of flow?

How accurate do you need it? You also mention reversibility -- is that a design goal?

If you need accurate control measure the flow rate and use a feedback loop to control the motor speed.

Or use something like a peristaltic pump with stepper motor control (or microstepper motor control):

https://www.graylineinc.com/assets/images/peristaltic-pump-operation.jpg