I have a DC motor that I’m trying to drive with an Arduino. The motor uses a PWM controller for speed control and speed adjustment on the PWM controller is made using a 10K analog potentiometer. Link for Data sheet is at the bottom. Because the motor is relatively high power (18V/27A), I’m looking to keep the existing PWM controller and replace the 10K analog pot with a 10K digital pot.
I picked up a Microchip MCP4131 digital pot. First I set it up with the Arduino and measured the resistance between pins 5 and 6 (PA and Wiper) with a multimeter. Cycles from 0-10k ohms with no problems. I then wired it up so that pins 5, 6, and 7 (PA, Wiper, and PB, respectively) directly replaced the analog pot and connected to the A, Wiper, and B terminals on the PWM PCB. Tried to show in the attached Fritzing diagram.
When connected to the PWM, the digital pot will not change resistance and the motor won’t run. I suspect this is because I am exceeding the maximum voltage specs for the digital pot. On the PWM PCB, terminal A of the analog pot is at +9V, terminal B is +2V, and the max current through the pot is 1.1mA.
Is this fundamentally the right approach, and I just need a different digital pot? Or should I be taking a different approach to the problem? I’ve searched for higher voltage digital pots but haven’t been able to find anything that can take the current. Closest seemed to be the AD5290.
Many thanks for any advice.
Wiring layout in attached Motor Control pdf.
Data sheet for MCP4131: http://dlnmh9ip6v2uc.cloudfront.net/datasheets/Components/General%20IC/22060b.pdf
Data sheet for PWM Controller: http://www.electronickits.com/kit/complete/motor/MX068-doc.pdf
Data sheet for AD5290: http://www.analog.com/static/imported-files/data_sheets/AD5290.pdf
Motor Control_bb.pdf (572 KB)