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I have a buzzer with an internal resistance of 16.5 ohms, which I have used with an arduino and it worked fine, so I assume it is 5v.

Can I connect a buzzer to gpio without a transistor, or would it damage the pin?

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How could I know? I remember using that buzzer with an arduino and it worked fine, so I assume it is 5v. – Euphorbium Aug 8 '12 at 11:12

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up vote 6 down vote accepted

The maximum safe current from a GPIO pin is only 16mA

3.3v/16.5Ω would be ~200mA, so No. Definitely not safe

You would need to add a series resistor of 190Ω or more to make it safe to connect and then the voltage across the buzzer will be only 0.26V, so very very quiet

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V=IR and all that... – Alex Chamberlain Aug 8 '12 at 11:46
Could @Euphorbium add a series resisitor? I don't know how buzzers work... – Alex Chamberlain Aug 8 '12 at 11:46
@AlexChamberlain, the buzzer would be very very quiet by the time the resistor was big enough – gnibbler Aug 8 '12 at 11:47

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