I have tried using a digital pot (MCP4131) but it is acting erratically
PWM is digital so it will pass-through an optical isolator
How did you isolate that?
Hi all, I would like to use and Arduino to replace the 0-5V 10K analog potentiometer that is currently used to control the speed input on a DC motor controller. Additionally, the Arduino and the 0-5V speed control input must be isolated. I have tried using a digital pot (MCP4131) but it is acting erratically (I suspect the current is too great because the 4131 is getting very hot). I do not have any current ratings on the 0-5V speed control circuit. I have also used a PWM signal from Arduino to mimic the voltage on the wiper, which works well, but does not solve the isolation constraint. Any thoughts on where to go from here? Best, stueveone
Additionally, the Arduino and the 0-5V speed control input must be isolated.
Presumably the motor controller is not cleanly isolated from the mains supply, hence the isolation requirement for the potentiometer.
Digital pots are not isolated at all. If its getting hot, its probably fried. There is no easy way to do this isolated, you need to know more about the motor controller, in particular what voltage it uses on the pot, whether it has open-circuit and closed-circuit failsafe modes on the potentiometer connections. The receive side needs power from the controller circuit too of course.
You've posted no details of the motor controller, this is the primary piece of information required.
Hi,Can you post a diagram of how you have the Arduino, what model, and the digital pot and motor controller please?Can you please post a link to data/specs of the motor controller?Tom....
Why dos it have to be isolated? That's rather unusual.
You may find something here. It is about a similar problem of replacing an isolated motor controller potentiometer using a pwm method:https://forum.arduino.cc/index.php?topic=511067.5
When I was sending a PWM signal straight from the Adruino, the only way I could get the motor controller to work is if I also connected the 0V signal from the motor controller to Arduino ground.
This worked on its own and controlled the speed well. However, after connecting a display to the Arduino, whenever the motor went from off to on, it would reset the display.
@6v6gtI am trying to digest your recommended post, thanks for sending BTW! Do you have a final schematic that you got to work? I am not sure where the PNP transistor should go. I would also be interested to see how you omitted the power supply circuit, seeing as I have a 5V supply already provided with the speed control circuit?Best, stueveone