Billc wrote:The LM Gear pump uses a brushed DC motor. The speed control is done via PWM (pulse width modulation). By varying the duty cycle of the PWM you are able to control the speed of the motor. This is very different from the brushless DC motor control where the motor is commutated via a electronic controller. Just connecting it to a power supply will not work you must have some electronic switching, and in some cases some feedback also (usualy hall effect sensors). Then you are able to control the speed by varying the speed of the switching.
BillC

Dang, I almost understood all that! The gist yeah, not all the specifics. Been too long out of school and the field.

The radio controlled airplane modelers have been using brushless DC motors a LOT, in recent years. Speed controllers for such, are available from any decent hobby shop, and the big online stores will have dozens to choose from. As tech savvy as some of you are, you should have no trouble at all rigging up something workable... that you can then post-up detailed instructions about.

-Peter

I'm getting price quote for MGFR series from Fluid-o-Tech, I think they could be easy to setup at a home machine. But I could only tell after I try

Anyway, they seem to use a brushless DC motor with a embedded speed control (0-5V input) and 24V input for power. Bill probably know better than me! Have you tested this one, Bill?

Márcio.

Nifty looking pump. I must say, it has a marvelous size, but once you add in a power supply for it, the size advantage diminishes. The ability to control it though, that sets it apart. With the plethora of Arduino, PICaxe and other easy to work with micro controllers, we are entering a new age of custom electronics.

Mark

If my memory holds PWM is an A/C type of drive. Is the power supply rectified after the PWM section?
KDM

PWM is primarily used with DC power. Essentially the output of the electronic temperature control using PID software control is PWM. PWM is like turning on and off your light switch if you turn on for two seconds and off for two seconds then you are are 50% duty cycle with a cycle time of 4 seconds.
On for 1 Second and Off for 3 Seconds is 25%
On for 3 Seconds and off for 1 second is 75%
No Lower the duty cycle to 0.1 second (can't really do this with your hand). If you were at 50% you would only be using 50% power. Since it is flashing so fast your eyes would not detect the off but you would see a dim light. This is how they motor is controlled.

BillC