Design/layout PCB board to allow D I/O to drive 250v ACrelay

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  prmurthyin

  The SSR can be moved towards SBC instead of doing all these things.
  Thanks

  over 1 year ago

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  TopGunPk

  Just one more thing Synrax.
  
  1) The TTL outputs, are they Logic-High or Logic-low ? Meanig, when you want to activate an SSR / Relay, do you pull the ttl line low or high ?
  
  2) the 25-pin cable connector you mention, is that an IDC connector Or a 25-pin D-SUB (like old RS-232C port) conector ? Can you give me a pin-out of the connector as to which pin has what signal ?
  
  I'll bid when you answer these questions. The PCB Layout will be done in EasyPCB, so i can send you the EasyPCB files as well as PDFs or Gerber.

  over 1 year ago

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  TopGunPk

  Noted Synrax.

  over 1 year ago

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  synrax

  Just to clarify, length of 20m will be from the board to be designed to the SSR. It will not be TTL signal. The TTL signal will be from the SBC to the "board to be designed" and this will be at maximum 30cm.
  
  The aim is to design a board to amplify and isolate the TTL Digital I/O from an SBC and drive SSRs located in different locations which could be up to 20m away.

  over 1 year ago

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  jsidev

  As my colleague TopGunPk noted, the solution parallel ribon-cable is not feasible. You will have a lot of subsequent problems. In such systems are used one master-multiple slaves RS485 half/full duplex serial communications. This topology use 4wire communication with multiple nodes and is best suited to galvanic isolation. Your SSRs become addressable and intelligent. You can fit in the proposed budget.

  over 1 year ago

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  TopGunPk

  Hello.
  
  20 meters of parallel ribon-cable to carry TTL signals is an overkill, worst what if multiple relays are to be switched ON and OFF, the high impedance and capacitance might be too much for your SBC.
  
  I can suggest annother solution !
  
  You will only need 4 TTL output lines on your SBC. These will be connected to a RS-485 line level shifter, producing 4 pairs of differntial signals (8 lines).
  
  These RS-485 lines can be taken upto 1Km (or approx. 4000 feet).
  
  These will terminate on the Relay board where a complimentary RS-485-to-TTL converter will translate them back into 4 TTL signals. These signals will drive a serial-in/parallel-out shift register-cum-latch.
  
  The output from these latches will be fed to the relay via opto-couplers / line drivers that can handle teh 12V relay coil switching voltage.
  
  
  I know this will add complexity to the circuit (and a little bit complexity to teh code on your SBC to shift out 24 bits serially), but the saving on wires and safety is huge.
  
  Compare 24 wires travellig 20 meters to just 8 wires that can go upto 1000 meters. Also, rS-485 is excellent in noise rejection from Back-EMF, switching and RFI noise.
  
  Moreover, you could daisy-chain such boards to add more relay outputs in future, with no hardware changing.
  
  Let me know if you would like this solution, so we can discus further before i bid. See the attached Access Database for info.
  
  Kind Regards...
  Zeeshan A. Noorwala
  Automation Engineering Solutions

  Attachment: DB1.MDB

  over 1 year ago

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