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Relay interface with Sitara AM335x Starter kit

Viswanathan T
Prodigy 80 points

I'm planning to drive a relay through a GPIO output from starter kit. This Relay requires input voltage of 5V for its coil. As main input supply (5V / 3A) is given to the starter kit, can I take 5V from Vbat & use to drive the relay.

If I need to increase the number relays to be driven, How can I calculate the voltage / current consumption in the starter kit design for each input & output.

Also from the starter kit design, I would like to know the spare GPIO pins available that I can use to drive the relays.

  • 0
    TI__Guru 62855 points

    You need to be careful using AM335x GPIOs to directly drive relay coils.  The current required to drive the relay coil needs to be less than the drive strength of the respective GPIO.  It is also very important to insure the back EMF from the coil does not exceed the maximum voltage overshot or undershot of the GPIO.

    In most cases an external transistor is used to drive the relay coil and a reversed bias diode is put across the relay coil to clamp the back EMF.

    The back EMF from relay coils can easily generate an Electrical Over Stress (EOS) event which can damage  semiconductors.

    Regards,
    Paul