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I have motor on my Arduino Motor Shield that draws <500mA when running and maximum 1A when stalled. I want to add some form of stall protection so that when the motor stalls the power is removed and the host system is alerted.

I have a three-level host system: a Raspberry Pi sending high-level instructions to a Arduino Mega 2560, that traces states of the motors that is hooked to several Unos and controls them using basic digital commands. The interrupt should be raised to both Pi and Mega 2560.

What is the best way to implement that? Is a comparator and pot a good idea?

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  • \$\begingroup\$ A circuit of how you control the motor would help including voltage power levels and IO voltages that control it. \$\endgroup\$ – Andy aka May 30 '14 at 10:24
  • \$\begingroup\$ @Andyaka I am using standard Arduino Motor Shield, power comes from 12V lead-acid batteries and one single motor is used. If the method of detection is confirmed I will use a open drain design, eliminating voltage converters. \$\endgroup\$ – Maxthon Chan May 30 '14 at 10:39
  • \$\begingroup\$ "arduino motor shield" isn't a definition of the circuit in my book and what you use now is probably irrelevant to someone wanting to answer the question. \$\endgroup\$ – Andy aka May 30 '14 at 10:43
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Though not the most efficient method, you can use a small resistor in series with the motor of the order of few milliOhm and sense the voltage across the resistor. When the motor is stalled, the current will be very high, so using that you can devise the cut-off amperage.

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  • \$\begingroup\$ How to sense that voltage bidirectionally? The motor is H-bridged. \$\endgroup\$ – Maxthon Chan Jun 4 '14 at 15:39

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