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Please help me check my circuit schematic

Other Parts Discussed in Thread: OPA828, XTR111, OPA835, RCV420, TINA-TI, LM2596

Dear Engineer.

Since I have no previous experience in circuit design, I do n’t know if the design is wrong after completing the following circuit, so I came here to ask for help. The circuit is mainly based on the STM32F103VC single-chip microcomputer as the core, which includes 0-3.3V voltage to 0-10V voltage and 4-20ma current, 0-10V voltage and 4-20ma current to 0-3.3V voltage. The former is the 0-3.3V voltage of the DAC port of the microcontroller, and the latter is the 0-3.3V voltage input to the ADC port of the microcontroller. XTR111, OPA835, OPA828 and RCV420 are used in the circuit.

The four labels 0-10V OUTR, 0-10V OUTL, 4-20ma OUTR, and 4-20ma OUTL are pins for input to external devices. The four labels 0-10V INR, 0-10V INL, 4-20ma INR, 4-20ma INL is an external input signal.

BL1551 is an analog switch chip. When pin 6 of ENB is low, pin 4 is connected to A2; when pin 6 of ENB is high, pin 4 is connected to A1. We can determine which conversion the microcontroller is connected to by pressing the button or not.

Thank you very much for your help, please help me check the circuit for errors.

3730.board.rar

  • Hi,

    can you show a picture of your schematic? Do you have a TINA-TI file to share with us?

    Kai

  • Dear engineer,

     I'm really sorry that I don't have the relevant TINA-TI file. I want to send the picture out, but it's too blurry to see clearly. So I converted the schematic file into a PDF file. The PDF file is as follows.

    I apologize for the inconvenience. Thank you very much for responding to my questions during your busy schedule!

    board.pdf

  • Hi,

    is the solenoid valve driver circuit recommended by the manufacturer of solenoid valve? Is the resistor in series to the free wheeling diode used as "release adjust"?

    The LM2596 is a 3A-switcher. Do you need 3A? I would strongly recommend to add the "optional post ripple filter" shown in figure 32 of datasheet.

    The A_XT-1WR2 switcher is not strong enough to power all the +/-12V circuitry. Why not powering the XTR111 from +24V?

    The A_XT-1WR2 should have some noise and ripple filerting at the output. Datasheet also recommends input filtering to comply with the CE standards.

    Why not outputting 0...20mA and 0...10V at the same time? By this, the according switchers could be omitted and you would not run into trouble with the driver circuits which are NOT selected.

    A ground connection is missing at the 33k resistor and 470n cap of XTR111.

    The OPA828 and OPA835 are very fast. Why have you chosen so fast OPAmps?

    Is there additional circuitry for the OPA828 to isolate the output from capacitive loads (cables, TVS, etc.)?

    Kai

  • Dear Engineer,


    Thank you very much for your patience.

    The solenoid valve drive circuit is not recommended by the solenoid valve manufacturer. The diode 1N4007 and its resistance in series are to form a return circuit with the solenoid valve to attenuate the impact of the reverse current, thereby protecting the solenoid valve. Is there a problem with the circuit here?

    For the LM2596 chip, this circuit does not need such a large current, but this is chosen for the sake of insurance. Just like OPA828 and OPA835, because there is no selection experience, these two op amps were selected according to some performance parameters. The frequency of the signal is not high, probably less than 10kHZ. Will this high-speed op amp affect the signal after conversion?

    For the ± 12V power supply part, I plan to use the integrated power chip WRA2412S-3WR2. The single output current of this chip is larger than that of the previous chip.

    I will think again about the question "Why not outputting 4-20mA and 0-10V at the same time?" Thank you for your suggestions!

    I have modified your suggestion, but I don't quite understand what you mean by your last question. Could you please explain it?

    Thanks again for your patience!

    2337.board.pdf

  • Hi,

    there are several ways to provide the free wheeling. A simple diode might be used, a diode with release adjust resistor, a diode with zener diode or TVS in series to speed up the release, etc. I would ask the manufacturer which circuit he recommends.

    The OPAmps are ok, only a bit fast. This bears the risk of increased noise and increased susceptibility to EMI. It's always wise to keep your circuit as fast as needed but at the same time as slow as possible :-)

    Why don't you want to supply the XTR111 with +24V? The XTR111 designed for that.

    Your circuit only shows the naked OPAmps without any filtering and protection circuitry which is usually needed in an industrial design to comply with the CE standards (ESD, Burst, Surge, emission of radiation, etc.)

    Kai

  • Dear Engineer,

    Thank you very much for your patience.

    I'm currently consulting the manufacturer if they have a recommended circuit for controlling a solenoid valve. They haven't responded to me yet.

    The maximum supply voltage of this XTR111 chip is 44V, I have modified it to 24V in the circuit diagram. The power supply voltage of 12V was selected because the power supply voltage of the other circuit was also 12V. Thank you for your reminder!

    According to what I learned about filters, the circuit diagram of a 500Hz to 2KHz bandpass filter should look like this. The cut-off frequency of the high-pass filter f = 1 / (2πR1C1) = 500Hz, and the cut-off frequency of the low-pass filter f = 1 / (2πR2C2) = 2KHz. Select the value of the resistor and capacitor based on the two cutoff frequencies. Is there a problem with this design? Are there any issues to be aware of when choosing the value of the resistor and capacitor?Are there other better designs for the latter?

    Thanks again for your patience!

  • Hi,

    first, you should find out what your signal frequency range is. Also, think about where your product is used. Is it a home application or is it used in the industry? Is it used indoor or outdoor? This determines what sort of filtering and protection you need.

    Kai 

  • Dear engineer,

    Thank you very much for your patience. my circuit is ready for industrial and indoor use. The frequency of the input signal in the picture I answered earlier is 2KHz maximum and 500Hz minimum. So I am going to design a bandpass filter with a frequency range of 500Hz to 2KHz.

    Thanks again for your patience!

  • Kai, thanks for the support.

    Hello - if you have additional questions please let us know regarding the bandpass filter or the XTR111

    Regards,

    Joseph

  • Hi,

    I would do it this way:

    opa828_opa835.TSC

    Don't forget to spend the input of RCV420 an adequate filtering and protection scheme, too.

    Kai