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I'm working with a colleague to digitally control an old peristaltic pump using a digital potentiometer. The existing pump controller has a mechanical potentiometer and we are trying to replace it with an MCP4131-103.

Can anyone lend some insight on the types of questions we should be asking before doing a direct replacement? We have already burned a couple and I suspect we are wiring it incorrectly or using an under-rated IC. One measurement we already have is that the voltage across the A-B of the mechanical pot during operation is about 10V (from ground, I think I measured -40V on A and -50V on B, if that matters). Is that too much for this IC? Can anyone provide some pointers on how to proceed? Is there a better way to replace a mechanical pot than with a digital pot to allow for programmatic control?

Thanks in advance for the help provided. If I need to provide clearer details, please tell me some measurements/observations I can make about the current setup.

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Whoa, no wonder you're burning these: enter image description here

Essentially, you're feeding -40 and -50 volts to the pins PxA, PxW and PxB. Their absolute limit is rated at -0.3, up to VDD+0.3 volts. VDD can be up to 7 volts without damage, but the typical operating voltage is 5 volts.

There are a number digital potentiometers that can handle 10 volts, but you must make sure that you float them, if the pins you need to use really are at a potential of -40 or -50 volts. This is not necessarily easy to do.

Another alternative are motorized potentiometers.

You may get more solutions if you try to post the current schematic, maybe there's a way to bypass the potentiometer completely.

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  • \$\begingroup\$ "try to post the current schematic, maybe there's a way to bypass the potentiometer completely." - Full ack! \$\endgroup\$ – JimmyB Oct 7 '16 at 8:46
  • \$\begingroup\$ I hope to verify that those pins are indeed -40V/-50V (I may have gotten a bad reading). I'll try to post more/better details if I can. I really appreciate the feedback already. I thought that was probably the case, but needed confirmation. \$\endgroup\$ – Troy Weber Oct 7 '16 at 15:49

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