If you run the pump 1/2 speed for 7 hours versus full speed for 3.5 hours, which way uses more energy?
I believe in a DC system they would both use the same power (ohm's law P=IV; P:power,I:current, V:voltage). The voltage is fixed at 12. I'm assuming half speed would use 1/2 the current but there may be more losses one way or the other. Anybody confirm this?
DC motor speed control has always been about adjusting the voltage.
I googled around and found your motor control.
PWM - A Pulse Width Modulated controller is the animal you have. Good choice.
I googled a bit to find a pictorial example of what's happening here.
Not the best, but it will do. Only one that showed the complete 0% to 100%, and a few things in between.
Consider OFF to be 0VDC and ON to be 12VDC.
To make this real simple, look at the square wave at 50%. You will notice that the ON time and OFF time appear to be equal, which they are. Also remember that the ON time is 12VDC and the OFF time is 0VDC. What your motor is seeing is the average value of the ON time -vs- the OFF time, which at 50% is 6VDC. If the ON time was 75%, then it would be 9VDC. Follow? Pretty neat trick
You cant measure this with your meter because it happens at such a high frequency, and the peak voltage is 12VDC, so that's what you get for a reading on your meter. This takes some fancy stuff to actually measure.
Your diaphragm pump is a type of positive displacement pump. DC motors are generally considered constant torque animals, which means they are going to try maintain their design torque thru their speed range. That can be a whole new can of worms based on motor and pump design.
My guess is that if you cut the speed in half, you could possibly see ~45% power consumption over the 50% you reduced it to (~5% less). 7hrs at half speed would most likely use less juice for a while until resistance builds and increases the pressure, which is directly proportional to power.
Constant Torque in a Constant Horsepower application, generally you might be able to gain some efficiency with DC by tweaking and tuning it, but not even close to the efficiency you get with AC.
Two thumbs up from me tho! I like it!!!
