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Topic: High current sensing and safety (Read 406 times) previous topic - next topic


Hi there,

I am driving two large actuators that at peak load will draw 3.6A each. So far they have gone no where near this, but at stall they can also draw 15A. I was originally going to use two separate DPDT relays to control each individually, but realized I would rather just signal them both at the same time. As such, I am using a 5A relay and 2 TIP120 transistors. Nothing has broken so far, but I would like to be able to sense the current and very quickly switch it off if it becomes too high.

From some basic search I found I can sense the current with a resistor by looking at the voltage. However, I am wondering if I can really sense and shut off the power fast enough before something gets fried?

Ideally I should probably buy a 10A relay, however then I cannot use the TIP120 and am unsure if there is any difficulties in using a higher current relay, as the TIP120 seems pretty standard.

Thanks guys!



Use a current sensor as they introduce virtually zero series R.


You can then monitor the current and turn off in time.



Make sure your code is always reading the relevant pin - you can use comparator(s)
to convert an over-current condition to a logic level you can read with digitalRead ()
which is quicker than analogRead().
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]

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