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Old 20 May 2014, 01:05   #399
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Join Date: Mar 2012
Location: Norfolk, UK
Posts: 427
Originally Posted by kipper2k View Post
This particular buzzer is rated at 5v so you could actually power it from the 5v rail, The reason i tried the BC547 is because i had it handy, it switches on/off fast enough to allow the buzzer to get a good pulse of power to beep. I figure that attaching it to the 12v rail is not overdriving it too much considering the on time
I'd agree, except the duration of the step pulse is the *off* time. (Step is an active low signal.)

I did try the flat piezo buzzer with this ciruit and it didn't want to play.
Yeah that's what I found - and I think the reason is the storage time in the BJT, exacerbated by the tiny current through a piezo transducer and its capacitive nature.
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