EDIT:
Second question. Is it possible to supply STM32 directly with 5V as in the picture or is it better to give 3.3v via VBAT?
STM32F401 and Servo
STM32F401 and Servo
Hi everyone. I don't know much about electronics, so I have a question. I have a servo that is powered by 5V. At the same time, I power my stm32 via a 5V pin. If I connect the servo in this way to stm32, will I not burn anything or do I need to use a converter? Thank you in advance for the answers for the layman;)
EDIT:
Second question. Is it possible to supply STM32 directly with 5V as in the picture or is it better to give 3.3v via VBAT?
EDIT:
Second question. Is it possible to supply STM32 directly with 5V as in the picture or is it better to give 3.3v via VBAT?
Re: STM32F401 and Servo
for stm32, the 5v input need to goto the LDO, normally it is the 5v pin on the board.
look in the datasheet
https://www.st.com/en/microcontrollers- ... 401cc.html
some pins are 5v tolerant, various are not e.g. the ADC pins.
to be on the safer side you may like to use a buffer such as 74HCT07
https://assets.nexperia.com/documents/d ... CT3G07.pdf
or 74HCT04 etc
https://assets.nexperia.com/documents/d ... _HCT04.pdf
or 74HCT245 etc
https://www.nexperia.com/products/analo ... CT245.html
this would also prevent missed triggering, as the voltage that STM32 can output is only 3.3v
the 74HCTxx chips are ideal for interfacing 5v circuits
edit:
if you can use an 'open collector' circuit, i.e. it is inverting, and you need to pullup with a resistor, uln2003
https://www.st.com/resource/en/datasheet/uln2001.pdf
can be used as well for a buffer
these worked like transistors, these are rather easy to get in the online 'flea' markets
https://www.aliexpress.com/wholesale?ca ... xt=uln2003
look in the datasheet
https://www.st.com/en/microcontrollers- ... 401cc.html
some pins are 5v tolerant, various are not e.g. the ADC pins.
to be on the safer side you may like to use a buffer such as 74HCT07
https://assets.nexperia.com/documents/d ... CT3G07.pdf
or 74HCT04 etc
https://assets.nexperia.com/documents/d ... _HCT04.pdf
or 74HCT245 etc
https://www.nexperia.com/products/analo ... CT245.html
this would also prevent missed triggering, as the voltage that STM32 can output is only 3.3v
the 74HCTxx chips are ideal for interfacing 5v circuits
edit:
if you can use an 'open collector' circuit, i.e. it is inverting, and you need to pullup with a resistor, uln2003
https://www.st.com/resource/en/datasheet/uln2001.pdf
can be used as well for a buffer
these worked like transistors, these are rather easy to get in the online 'flea' markets
https://www.aliexpress.com/wholesale?ca ... xt=uln2003
Last edited by ag123 on Tue Jun 14, 2022 4:08 am, edited 1 time in total.
Re: STM32F401 and Servo
I all depends on servo motor.
The ones I used had signal pin pulled to GND (and probably most of them are wired the same), so it's not supplying any power to MCU but they needed ~5V signal to work properly.
They work fine with Arduino Uno, but with STM32 I had to use transistors to supply 5V signal.
As to Vbat pin, it's for RTC battery, not for powering MCU.
The ones I used had signal pin pulled to GND (and probably most of them are wired the same), so it's not supplying any power to MCU but they needed ~5V signal to work properly.
They work fine with Arduino Uno, but with STM32 I had to use transistors to supply 5V signal.
As to Vbat pin, it's for RTC battery, not for powering MCU.
Re: STM32F401 and Servo
I would put a resistor (10K?) on the data line and find a 5v tolerant pin for that. just in case.
Re: STM32F401 and Servo
It will create voltage divider as signal pin in servo motor is pulled to ground.dannyf wrote: Tue Jun 14, 2022 12:05 am I would put a resistor (10K?) on the data line and find a 5v tolerant pin for that. just in case.
And if there a problem with 3.3V signal, you can figure out what will happen with much lower voltage.