I a using a MOT-B24400 motor which has a built in controller and only needs an external 5k pot to control the speed, plus power of course. I have this wired to a relay with a button to send a signal and engage the motor. Everything works when I use an analog pot. I was wanting to change it to a digital pot (MCP-4151) in order to "ramp" the speed up and down depending on a count coming into the pi. Without the motor attached, the digital pot changes values as expected. I have triple checked all the connections and believe that it is all right. I checked the motor pot connections and got 5vdc across the high and low with only power connected. Is there any reason this would work with an analog pot but not a digital pot?
connections (MCP4151-Pi/motor): 1-CE0, 2-SCLK, 3-MOSI, 4-GND from GPIO, 5-"high" on motor pot connection, 6-"wiper" on motor pot connection, 7-"low" on motor pot connection, 8-5vdc from GPIO