My buddy just bought an Illuminati32 FC board from Hobbyking for his new ZMR180 miniquad. The board is pretty sweet: Naze32, MWOSD, 35x35mm form factor, and only 20 bucks (on sale). It was really easy to set up, especially with the ZMR180 PDB that Diatone is shipping. The biggest problem is that there’s no buzzer output! A buzzer driver is one basic necessity every flight controller should come with. Low battery, lost models, and mode change beeps are pretty crucial to the operation of these miniquads. Luckily, it’s relatively simple and very cheap to add one onto this board. You’ll need:
- High gauge (>30) wire
- Fine solder and a fine-tipped soldering iron
- An NPN BJT (2N3904, BC557, etc)
- A 100Ω resistor
- Heatshrink tubing or tape
The built-in Naze32 (rev5 or greater) buzzer driver is a NPN transistor used in an open-collector configuration. There is a base resistor on the order of 100Ω used to set the drive current. PA12, or Pin 33 of the STM32 is used to drive the BJT.
It’s possible to do this BEAM style, with SMT components and a small piece of protoboard, or even a with small PCB (perhaps from OSHPark). We chose to do it with a little PCB that’s also got an ATTiny84 on it which controls some RGB led strip.
The hardest part of this is soldering onto the STM32, since PA12 isn’t broken out or used for anything else. See the below image to find the pin you need to solder to. Note that the text on the STM32 isn’t guaranteed to be upright, so look for the pin 1 marker!!!
You’ll need some fine gauge wire (30 gauge wire wrap wire worked well), a fine-tipped soldering iron, and a steady hand.
Once the solder connection is made, don’t hesitate to dump some hot glue onto the connection to keep it from being broken loose. Once you’ve got the connection to PA12, solder one end of the 100Ω resistor to the PA12 wire, and the other to the base of the BJT. Solder the positive lead of your buzzer to the flight controller’s 5V input, and the negative lead of the buzzer to the collector of the BJT. Finally, solder the emitter of the BJT to ground. Be sure to wrap everything in heatshrink or tape so that you don’t accidentally short anything out.
That’s all there is to it! Just plug in a battery without turning on the transmitter and the FC should issue the “no connection” beep if everything worked.