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I am trying to toggle an SRD-03VDC-SL-C (3V rated) relay with a Raspberry Pi GPIO.

When I put a wire to the Raspberry Pi 2B ground pin and the other to a 3.3V power pin the relay works (it clicks). I measured 3.28V with my multimeter.

Now, as the relay is confirmed to be working I want to toggle it via software by switching a GPIO pin. I confirmed that the GPIO switching is working with my multimeter: It shows 3.28 V when high and 0 V when low.

But when I connect the wire with the GPIO in high state it does not toggle the relay. How is this possible when both pins have the same voltage and how can I fix this?

Experimenting with the Raspberry I also observed the situation that I could set the voltage to 0 but disconnecting then made a difference. I would assume that in this case disconnecting would not make a difference.

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    \$\begingroup\$ A I/O pin cannot deliver the amount of current required to drive a relay coil (trying to do so can damage the device). Buffer the signal with a transistor. \$\endgroup\$
    – Unimportant
    Jan 1, 2021 at 17:49
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    \$\begingroup\$ Are you using a bare relay or a relay module? \$\endgroup\$
    – ocrdu
    Jan 1, 2021 at 17:49
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    \$\begingroup\$ Currently using a bare relay. \$\endgroup\$
    – Benedikt S. Vogler
    Jan 1, 2021 at 17:58
  • \$\begingroup\$ Measure the GPIO output while the relay is connected and add that to the question. \$\endgroup\$
    – user16324
    Jan 1, 2021 at 19:34

1 Answer 1

Reset to default
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A GPIO pin cannot provide enough current to a relay directly. Use the GPIO pin to drive a transistor, and use the transistor to drive the relay.

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    \$\begingroup\$ Thank you. This explains it. I will try that and if it works, accept your answer. \$\endgroup\$
    – Benedikt S. Vogler
    Jan 1, 2021 at 17:59

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