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Apr 04, 2015, 10:43 AM
I void warranties
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Need to make MW buzzer louder? Add a FET [diagram / how-to]


Hey guys, I've just added a piezo buzzer to my tricopter build but it wasn't loud enough (I found a random one in my junk bin, I probably would of been fine if I bought a nice new one sold for this job). Well anyway I decided to make it louder by adding in a FET so the pin wasn't supplying the power it used. I also plan to add indicator lights to the same circuit as a "find my crap when it crashes / gets lost" type of thing so it neded to be able to handle more current for that for sure (that'll need 700mAh).


I used this diagram I drew up real quick:

(note the buzzer is the half circle thing on the left, never needed to draw a piezo speaker before, had to google what the schematic symbol was lol)

As expected it works perfectly!
Multiwii piezo speaker with N-FET. (0 min 31 sec)


This would allow the use of multiple speakers orientated opposite directions or a speaker & lighting or whatever accessorie you want to activate with your gear switch (just tell the MW it's a speaker regardless). There is no current limit this way (other than what the FET can switch), but no concerns overloading the FC pin.

I didn't even have to remove the speaker that was already installed. If you do this don't forget that an N channel FET switches ground from a + signal so you'll have to reverse how you have the speaker wired; supply it 5V directly to its + leg, the POSITIVE signal from pin D8 goes to the FET gate then source is GND and drain is the speakers - leg. I used a 1kohm gate resistor (and no pull-down).

Last edited by Cereal_Killer; Apr 04, 2015 at 12:29 PM.
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