Well this is my first post, but I’ve been searching for days without a clear answer. I purchased a Micro Maestro and two 18v23’s. My intention is to power 2 fuel pumps using the Maestro to read a 0-5v input and adjust the speed of the two pumps. Obviously they are not servos, and they need to run continuously w/o interruption. I’m just now starting the code and it hit me that maybe the Maestro can’t do this? I see the servo command to output a position, but am I going to see hiccups in the output if I have two consecutive servo commands for two different servos and loop? Is there a better way to do this with the Maestro?
The main task the Maestro was designed for is to send out continuous (every 20 ms), precisely-timed pulses on all of its servo output lines. You should not see any hiccups in the output, and your motors should run continuously. What makes you think there would be hiccups in the output?
There “servo command to output a position” you are mentioning does not actually send a pulse to the servo, it just sets the width of future pulses that will get sent to the servo at a later time.
I guess it was a brain fart, nothing more than that. I managed to get a couple lines of code working to set the pump speed, so I burned through some gas and tires tonight and they worked great.
I still can’t believe those little servo drivers don’t need heat sinks but they seem to do fine. Do you think they are going to be OK for long-term use in an enclosure?
Are you referring to the Simple Motor Controller 18v23? The answer depends on how much current your motors draw and the PWM frequency you use (low frequencies generate less heat). In either case, the over-temperature response feature of the motor controller (which is enabled by default) should prevent the boards from overheating.
Sorry about that, I just looked at them and they are 18v25’s. I’m running on the 5khz freq, and each motor will draw a max of 18amps. I will only peak at that level for 10 seconds at a time. Most of the time they will just be cruising along at 75% duty cycle or so. Any advice for an enclosure would be appreciated. I was going to machine a box and lid from 6061 aluminum and put a few vent holes in it. Fans aren’t practical for something like this and I’m trying to keep it small. In a week of driving on 100 degree heat they haven’t overheated but they are basically free hanging in the truck near the battery for now. No air movement in there and the air temp was very hot though.
Unfortunately, we haven’t tested enclosing the Simple Motor Controllers. I expect it to be worse than your current setup, but it might be okay. If you try it, keep the over-temperature protection on and you will be able to see if it works without much risk of damaging them.
It sounds like that 18 amps might not be the stall current for those fuel pump motors. If they get jammed or right when they start up, they might be drawing significantly more current.
