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Chris8
Visitor II
March 19, 2024
Solved

I/O circuit

  • March 19, 2024
  • 4 replies
  • 3793 views

Hey there , how can I find info to conect my STM32 with higher voltage devices , for digital inputs and outputs I have 24vcc and analogic inputs and outputs -10 to 10v, I want to conect they safely to not burn my chip.

    This topic has been closed for replies.
    Best answer by Peter BENSCH

    I have to hand it to you: you give a lot of details about your project and we have now a complete overview of all boundary conditions (irony = off).

    You will need matching circuits in any case:

    • for the analogue outputs, a circuit based on an operational amplifier, for example, which generates the desired voltage of ±10V from the analogue signal from the STM32 (0...VDD). Depending on your requirements (accuracy, thermal stability, drift, etc.), you will find plenty of ideas if you use your favourite search engine while searching for "'+3.3V' +to +'+-10V'", e.g. this one. The analogue signal can either come from the DAC (if the selected STM32 has one) or from a PWM output with RC filter. Above I wrote of VDD in general, as the STM32 can be operated not only with 3.3V, but also with 2.5V, for example.

     

    • If I have understood you correctly, you want to realise the digital outputs as npn at 24V. If you have no requirements for overload protection or similar, you can:
      • use logic level MOSFETs whose gates are controlled by the GPIO of the STM32
      • use npn BJTs whose base pin is controlled by the GPIO of the STM32 via a series resistor

     

    • If the digital inputs have to be protected inputs, you can interface the NPN Hall sensors e.g. with CLT03-1SC3 (1 channel) or CLT03-2Q3 (2 channels, same data sheet) to get the 24V levels converted to the voltage expected by the GPIOs.

    Hope that helps?

    Regards
    /Peter

    4 replies

    P
    Peter BENSCH
    Technical Moderator
    March 19, 2024

    Welcome @Chris8, to the community!

    As long as it is not clear which STM32 you have in mind, I have moved the thread to Other Hardware, as you need some kind of signal conditioning in the broadest sense.

    It is not entirely clear what exactly you want to do, among other things there are no details of which parameters are required in detail:

    • analogue inputs -10V...+10V?
    • analogue inputs 0...24V?
    • digital inputs 0...24V?

    For the inputs, additional details such as the required pulse strength for the input voltages or input impedances are important:

    • analogue outputs -10V...+10V?
    • analogue outputs 0...24V?
    • digital outputs 0...24V?

    Other important details for the outputs are e.g.:

    • maximum output frequencies
    • Output currents to be controlled
    • high side, low side, push-pull stages, etc

    As you can see, there are more open questions than you have expressed wishes. Can you go into more detail?

    Regards
    /Peter

    C
    Chris8Author
    Visitor II
    March 19, 2024

    I buy a STM32F411 and on digital inputs I ll conect +24v sensors , on analogic input -10 to 10v sensor ,  on digital outputs ll go to driver +24v digital input , and analogic output I want deliver -10 +10v for control a motor driver ( I want this signal analogic not pwm wave) frequncy of project is less than 10khz

    P
    Peter BENSCH
    Technical Moderator
    March 19, 2024
    • which type of interface does the digital 24V sensor use?
    • what type of driver is the one driving 24V outputs?
    • what input impedance needs to be driven at the analog output?
    C
    Chris8Author
    Visitor II
    March 19, 2024

    on servo driver is 10k ohms for analog

    Chris8_0-1710873447221.png

    4.7k ohms digital

    Chris8_1-1710873556726.png

    Im using NPN 24v festo hall sensors

     

    P
    Peter BENSCHAnswer
    Technical Moderator
    March 19, 2024

    I have to hand it to you: you give a lot of details about your project and we have now a complete overview of all boundary conditions (irony = off).

    You will need matching circuits in any case:

    • for the analogue outputs, a circuit based on an operational amplifier, for example, which generates the desired voltage of ±10V from the analogue signal from the STM32 (0...VDD). Depending on your requirements (accuracy, thermal stability, drift, etc.), you will find plenty of ideas if you use your favourite search engine while searching for "'+3.3V' +to +'+-10V'", e.g. this one. The analogue signal can either come from the DAC (if the selected STM32 has one) or from a PWM output with RC filter. Above I wrote of VDD in general, as the STM32 can be operated not only with 3.3V, but also with 2.5V, for example.

     

    • If I have understood you correctly, you want to realise the digital outputs as npn at 24V. If you have no requirements for overload protection or similar, you can:
      • use logic level MOSFETs whose gates are controlled by the GPIO of the STM32
      • use npn BJTs whose base pin is controlled by the GPIO of the STM32 via a series resistor

     

    • If the digital inputs have to be protected inputs, you can interface the NPN Hall sensors e.g. with CLT03-1SC3 (1 channel) or CLT03-2Q3 (2 channels, same data sheet) to get the 24V levels converted to the voltage expected by the GPIOs.

    Hope that helps?

    Regards
    /Peter

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