Without a schematic, the best thing is probably to "start over" and build your own motor controller. ...Connect an H-bridge motor driver to the Arduino, add a little software, and you're done!
Or, maybe more than 'a little' software and maybe some additional hardware, depending on what you need.
I knew that there are digital potentiometer, but I was wondering if it's possible without this.
Since you want to control a pot with the Arduino, why are you opposed to that solution? (In practice there may some "issues", but functionally/logically that's exactly what you're asking for.)
Is your 24vdc electric motor reversible? if not, driving it from an arduino is very simple - probably much easier than interfacing to your existing control board
It all depends on what the pot does. It might just set a voltage (that's easy to do with an Arduino) but it might also set a current which makes it harder. There are digital pots BUT all I've seen have the limit that the voltage on any pin may not exceed Vcc. So again, depends on the circuit if this will work.
And yes, just replacing the pot with a voltage from the Arduino (which by the way isn't a variable voltage but PWM if you don't add components) may damage the controller or the Arduino if that's not what it expects.
I have another question: is it possible to use the DAC ( I'm using an Arduino Zero )output to simulate the
potentiometer.
The potentiometer acts like a voltage divider right? So with the DAC output is it possible to generate
a variable voltage output and connect to the pin on the mcu that drives the motor?Or could it be
dangerous ?
Thanks
Anything is possible, there's not much point speculating until we understand the board itself, and we
don't have those pictures or any information on it at all yet...
And yes, just replacing the pot with a voltage from the Arduino (which by the way isn't a variable voltage but PWM if you don't add components) may damage the controller or the Arduino if that's not what it expects.
He is using a Zero so it does have a D/A. However as it it then it is totall unsuitable for direct connection to your motor controller.
At best you need some level shifting circuits, like op amps, to get the signal to the right level.
