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I have a motor controller board that handles 24v and up to 60a and can be varied via a mechanical pot of 100k ohms. I want to replace it with a digital pot like an MCP41100 and control it with an arduino.

Can I expect the motor circuit with the digital pot inserted to be isolated and separate from the arduino circuit with the control portion of the digital pot?

Bottom line is its not working and I'm trying figure out why. Wondering if the two circuits are really one.

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    \$\begingroup\$ No, you cannot. You would have to analyze the circuit of the controller. It is possible that after having done so you will be able to use something simpler, like a PWM output with a filter capacitor. But in any event, you would only avoid galvanic connection to the motor driver (which depending on configuration and installation could have a live 'ground') by doing something like using an opto-isolated command path to an SPI digipot or simple PWM filter inserted into the motor circuit. \$\endgroup\$
    – Chris Stratton
    Commented Nov 7, 2015 at 20:35

2 Answers 2

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To figure out you should post the scheme. But in general you can replace mechanical potentiometer with digital, if you are sure the voltage and current are within maximum ratings of the latter. Also be sure to protect the digital potentiometer with shottky diodes to prevent voltage spikes, they may be lethal.

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  • \$\begingroup\$ First start with scheme or you driver. Diodes- later. \$\endgroup\$
    – user76844
    Commented Nov 7, 2015 at 20:40
  • \$\begingroup\$ Here's the link to the board. m.ebay.com/itm/301247561012?_mwBanner=1 \$\endgroup\$
    – user953175
    Commented Nov 7, 2015 at 20:43
  • \$\begingroup\$ I love red PCBs! But there is no scheme. \$\endgroup\$
    – user76844
    Commented Nov 7, 2015 at 20:47
  • \$\begingroup\$ Right I don't have a scheme. This is what I'm thinking: it's a switched pot that will have 24v across the switch when it's off and 24v used as power to the board. It's very small wires to the pot so I assume low current running through it. Therefore I assume the MCP41100 will handle. Dumb to assume but I'm a beginner. \$\endgroup\$
    – user953175
    Commented Nov 7, 2015 at 20:51
  • \$\begingroup\$ Also the board will be used to drive a do motor at 24v and up to 40a. \$\endgroup\$
    – user953175
    Commented Nov 7, 2015 at 20:52
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If the existing control is working like a pot instead of a rheostat and there's 24 volts on one end of it and zero volts on the other, then you can do this, as follows, in order to translate the zero to 5 volt output from the pot controlled by the Arduino into the zero to 24 volts the controller wants to see:

enter image description here

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  • \$\begingroup\$ gonna build it. Thx! \$\endgroup\$
    – user953175
    Commented Nov 8, 2015 at 16:52

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