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Thread: Holding pins HIGH 24/7 - anything to worry about?

  1. #1
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    Holding pins HIGH 24/7 - anything to worry about?

    Thread title pretty much sums it up. I'm controlling a relay board where 4 of the 8 channels will be kept HIGH 99% of the time or more. This project will run 24/7... does that cause extra wear and tear on the MCU?

  2. #2
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    How are you controlling the relays? Unless you have an extremely small reed relay there has to be something between the relay and the MCU's GPIO pin, as those pins can't drive the relay coil's current requirement on their own.

    As long as whatever's sitting between the MCU and the relay doesn't require more than 10 mA, and the sum of current supplied by all pins is under 100 mA, then there's no problem leaving it on 24x7.

  3. #3
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    Perfect, thanks. The relay board is one of the popular opto-isolated boards on which the coil/optocoupler power can be provided externally. I did have to use a level shifter for the board's 5v logic, but its definitely less than 10mA to drive the 3.3v side of that.

    Thanks again!

  4. #4
    Senior Member+ MichaelMeissner's Avatar
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    Of course you need to verify that the relay can be used in 24/7. I would imagine most can, but it always helps to check the datasheet.

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