I got a question - I am considering to try using STM32F103 board in my project except of an Arduino Pro Mini. It needs 3.3V (or 5V over supply).
I would be operating it on RC plane, and I want to hook it to the FPV camera battery, which is a 3.7V LiPo from old Smartphone. All extension modules (NEO-6M GPS, HC-12 433Mhz Comm, and GY-91 Gyro/Compass/Pressure) have 3-5 V in specification, so should work. Can the STM32 handle the 3.7V safely, over the 3.3 port? Or could it be fed to 5V IN?
Or could it be fed to 5V IN?
No, you can't put 3.7V into the 5V IN, and expect to get 3.3V out.
You could use a zener diode between the + side and the 3.3V pin, to get about a 0.4V voltage drop.
Well, according to schematics it uses RT9193-33 regulator behind the 5V input, but as I understand, it would need at least 4.3V input... Dropping in a Zener is a good idea, but might be problematic due to non-constant discharge voltage.
I would probably need to use the main battery of my plane (6.6V 2S LiFePo4), and a stepdown voltage regulator... Or maybe get a 1S LiFePo4 cell instead of LiPo - it gives quite exactly 3.3V over 95% of discharge.
I would probably need to use the main battery of my plane (6.6V 2S LiFePo4), and a stepdown voltage regulator.
You can feed the 6.6V directly to the microcontroller. It's voltage regulator can take 6.6V.
Or maybe get a 1S LiFePo4 cell instead of LiPo - it gives quite exactly 3.3V over 95% of discharge.
Always a possibility, if weight isn't a problem.
I think I found a solution for my problem - I could use a Step up/down automatic voltage stabilizer, which converts 3-15V to a fixed 3.3V (called S09 module on Aliexpress). 0.6A max current should be more then enough for my purpose here. Just ordered a pair of these, to see how they work.