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Old 23 May 2014, 00:10   #424
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Join Date: Mar 2012
Location: Norfolk, UK
Posts: 561
Originally Posted by kipper2k View Post
Here is an updated buzzer mod, uses a 5v buzzer now connected to the 5v rail ...

1 x BC547 or similar bipolar transistor
1 x 1k resistor
1 x magnetic type buzzer (Digikey # 668-1373-nd

A couple of criticisms, though:
According to the datasheet on the digi-key page, the buzzer you've specified there is only rated for 3v. No problem if it's only getting momentary pulses, but it's not: STEP is active low, so unless I'm misunderstanding something here there's 5v across that buzzer for 99.9% of the time.

The buzzer's own resistance is also very low (only 20 Ohms according to the datasheet) so again, bearing in mind STEP is active-low, and thus there's voltage across the buzzer while it's idle, the power draw is quite high. (I hope the DC resistance of the buzzer is somewhat higher than 20 Ohms, but the datasheet only specifies "resistance" - the datasheet of the other buzzer you used specified impedance and DC resistance separately.)
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