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Industry isolated communication

ltomi91

Dear Everybody!

 

I search the best solution for the following problem.

I want to establish isolated communication between two devices. 2x 8 input and 8 output should be connected (one-way). First think the optocoupler, but it requires a lot of wires, and these devices are in a noisy, industry environment, so necessary the good interface, e.g. RS485. I was looking for any "target" IC, but could not find it.

I attached a picture from this situation.

 

Thank you in advance (and sorry for my english image ) !

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  • in reply to Robert Peter Oakes

    First of all, thank you the replys (also Michael) !

    Sorry the little information, but I did not know much about the situation. The voltage level is 24VDC, on both sides (1 robot and 1 CNC machine). I think the speed non time-critical (so no need a many MHz...). The distance I think some meters, but I inquire this.

    Edit: the distance is 25 meter.

  • in reply to ltomi91

    It would probably be worth building a parallel to serial adapter at each end to send the 8 bits down a differential pair (RS485), this will minimize noise and allow plenty of didtance to be covered (More than enough for 25Meters)

     

    you will need to drop the levels to 5V probably then into a shift register or a simple micro-controller with a serial interface (Arduino UNO would be a simple choice, or if your buyilding your own boards, base it on an ATMEGA328 so you can esily prototype it with an UNO at each end

     

    to go from 24V to the 5V, a simple opto isolator chip would work (4 channel device * 2 at each end). A RS485 tranceiver would be used between the two UNO/ATMEGA328s for the main comms

  • in reply to Robert Peter Oakes

    I am more skilled in the Microchip PIC microcontrollers (but I think this irrelevant).

    So the basic theory:

    - For the 8 channel use 1-1 MCU, and between two MCU use a RS485 interface.

    - In "Tx PIC" the program polling (or handle an interrupt) the 8 inputs, and if detected any difference compared to the previous state, then send the actual state on serial interface (trough RS485).

    - In "Rx PIC" the program received the serial data, and put that to output (8 pin).

    - ... and vica-versa.

     

    Opinion?

    Thank you!

  • in reply to ltomi91

    Exactly, and yes you are correct, any micro will suffice and if your familuar with PIC, then go for it, it will work as good as any other for this application

     

    In transmission you can try sending the byte, then the XOR of it as a check, that way there is no need for a return except for acknowledgement and as the serial speed can be fast, this will not impeed performance, this all depends on how improtant it is for 100% accuracy, other mechanisms can be imployed like a message ID etc added to transmission and the ack can be an XOR or other checksum of the entire package

     

    Regards

    Peter