Micro Buzzer signal lost low voltage alarm implementation discussion Ideas


Any info on how long shipping will take? :slight_smile:
I really want to try whether this works with a EMAX Femto. Would save another 0.6g.
It will probably take a while until these changes are in the hex-files you get via the configurator.


Should be here in a few days.
I’ll be back home on Friday for 5 days. Then next week on Thursday I have to leave to next hospital (rehabilitation center ) with my little girl.
I will keep you informed.


Can anyone who knows what’s going on post a quick summary? My application is an AcroWhoop V2 board. Questions are what is now the smallest beeper that will work with 1S even at 3.0V? Do you still need to solder directly off chip or can you use other output on board like LED or dedicated beeper pins? How to implement in BF with new code that just came out a few days ago?

I read the entire thread, but that has seemed to confuse me at this point due to the almost 2 years of posts.

Any help appreciated as I feel this is a huge need after looking last night for 30 minutes for a lost Whoop.


i am also wondering as well if i can use any 5v buzzer or if it needs to be a special one.
do i just ground anywhere or must it be on the ground in this pic?..

thanks so much


As far as I know you can use any gnd on the board e.g. bat gnd since they are all shared/the same/connected.
As for buzzers, just make sure it’s an active buzzer, not a passive one.


Just flashed an old scisky with buzzer (soldered to pin on stm32 chip) to Betaflight 3.1.6.
Everything works fine except the buzzer. Doesn’t make any sound.
If I flash back to AlienflightF1 from Nov 2015 (which was on before) buzzer works fine.

Is there a way to get it working with BF?
Maybe using resource command?
@las, @Chaotix any ideas?


Try typing resource in cli and see what shows for a buzzer pin, code space is getting tight on the F1 series now so it may have been removed or turned off by default.




resource BEEPER 1 A12
resource MOTOR 1 A08
resource MOTOR 2 A11
resource MOTOR 3 B06
resource MOTOR 4 B07
resource MOTOR 5 B08
resource MOTOR 6 B09
resource PPM 1 A00
resource PWM 1 A00
resource PWM 2 A01
resource PWM 3 A02
resource PWM 4 A03
resource PWM 5 A06
resource PWM 6 A07
resource PWM 7 B00
resource PWM 8 B01
resource LED_STRIP 1 A06

beeper is shown as A12.
Buzzer is soldered to PA12 pin of the chip (if I`m right). And now?


That should work. Maybe you need to turn beeper_inversion on or off?

Update on the external buzzer: I played around with the external buzzer yesterday (thanks to @chrisdo!) - could get it to make some noise via the LED_STRIP pad of the EMAX Femto. That required some changes to the code, but worked. Unfortunately my attempts to add a transistor to the mix and properly power the buzzer with 5V failed, maybe the transistor I was using was just not switching fast enough or something.


Will try to mess around with BF Scisky and buzzer. Right now I’m trapped in hospital again for some weeks.

Nice to hear you got those buzzers to make some sound.
Will contact you @las when I’m back home again sometime in May.


A little bit more success. Not happy yet (it’s not loud enough).
I’m currently driving it from 5V via a transistor - adding a “bleeder resistor” helped, but it’s not as loud as I want it - yet. Any experts here who know how to drive a piezo transducer properly?


All I know is you need to drive it high and low rather than just driving it high and letting it float. Hence the bleeder resistor helping.
The lower ohm the bleed resistor that louder it’ll be, at least for a while.

Driving it with a tiny 555 might be there way to go.

I’ve never had issue driving them with a microcontroller pwm output, but the ones I use can typically do 20-50ma output.


I’m driving it with the proper betaflight PWM code already - otherwise it would just not work.
Maybe I should use a FET instead of the transistor?

Possibly the buzzer at hand just isn’t very loud.


I was thinking more that the pwn port on the FC might not be able to put out the amperage to make a good sound driving it directly but would be driving both high and low, and the transistor, while it drives lots amps only drives high (pnp) or low (npn) but doesn’t actually drive the full square wave that the piezo needs.

It totally could just be a quiet buzzer though.


After some short research, it seems an inductor instead of an 1k resistor parallel to the transducer should do. Will try later.


Now that’s an interesting take on it, that makes perfect sense. Never would have thought of it, but yeah.

Please detail when you try it! Very curious on sizing and such.


Matek has a board for driving passive buzzer, the sound very loud, I can hear the sound clearly from 20m or more on the field, but it heavy 2g. We might have some idea by reference this board

It’s power from 5v, and generate sound by get signal from Buzzer (-) , not use Buzzer (+)

Sorry I get this pic from GB the components not show clear


Success. Buzzer is making noise. Betaflight MICROSCISKY 3.1.6.

Had to set beeper_inversion = on and beeper_od = off.

Btw. @las it’s the heavily modded one. Remember?

Am I right that you said it should be possible to run a FPV rig powered from the 4pin connector (UART) you installed?


@chrisdo another great result :grinning: