# How to make dosing pump system more accurate

#### james211

Joined May 29, 2012
277
So I have an inexpensive dosing pump system I purchased, its an inexpensive chinese product. The software is OK, and the pumps were mediocre at best. I had four welco pumps here at home which are very well made japanese peristaltic pumps so I thought I'd swap those into this unit. The pumps run great but even with the calibration in the software, they aren't as accurate as I'd like. So my question is, is it possible to put a very fine tuning potentiometer between the board connection and the motor so I can fine tune the speed of the motor for more accurate dosing?

Max.

#### ronv

Joined Nov 12, 2008
3,770
The calibration is run via a program function that counts, in seconds, how long it takes to pump 100mL of fluid. The software then converts that information into how many mL/sec. What I don't like is that you cannot manually tweak that number.

Just out of curiosity, what would happen if one was to put a potentiometer between the board and the motor?
Seems like it should work pretty good. I think I would have counted revolutions, but hey.
Depending on how much current the motors take the potentiometer would probably smoke. And motors sometimes have a hard time starting with resistance in series with them as the start up current is higher than the run current. What you might try if you want to slow it down is a diode in series with the motor.

#### james211

Joined May 29, 2012
277
You know what, I spaced, when I was referring to a potentiometer, I was referring to these mini PWM controllers with a pot on it. My apologies, I dabble in this stuff.

So given that the computer turns on each motor port and basically just supplies power, I could in theory use that as the power supply to the PWM controller, and then plug the motor into the controller and slow it down that way?

Joined Jul 18, 2013
24,992
As per post #4 #7 #12.
They work pretty slick, I picked one up for evaluation.
Max.

#### kubeek

Joined Sep 20, 2005
5,772
Why would the rollers need to be geared? Or are you talking about something else?