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Topic: Pumps running when not connected to the Arduino (Read 180 times) previous topic - next topic


I have these 12V peristaltic pumps connected with my Arduino Mega via a IRLB8721 MOSFET. I have a 1N5819 schottky diode and a 0.1nF ceramic capacitor parallel to each pump.

When I haven't connected the Arduino with ground, to the circuit, the pumps start running.
Also, when I have the Arduino connect but not loaded with a sketch that declares the pump pins, the MOSFET's get really hot (some times the pumps start at a slow rate).

There is nothing wrong when I have everything connected and the pump sketch loaded; everything works. But I'm wondering if this is normal behaviour, or that I might have done something wrong?

I'm a beginner with al this stuff, so that's why I'm checking...


Add 10k resistors from pin to ground, to keep the MOSFET off if the processor is booting and has not yet set the pins correctly.
Read this page, first diagram.


Excellent! Problem solved! Thanks!

Very informative link :)

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