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MIPC-1A driven from Hall effect sensors

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  • MIPC-1A driven from Hall effect sensors

    Hi, Since this combination proved itself very simple and reliable, I am expanding my machine with 2 more manuals. I use A3144 Hall effect sensors to trigger my keys and the grounding signal from the sensor goes into a MIPC-1A. I wired the A3144 with a pull-up resistor on output, as per its data sheet, all good. However, it would simplify my wiring a lot if I could omit those (61) resistors from the network. Anyone tried or knows whether it is possible to wire the A3144 output directly into the MIPC input? IOW, do the encoder inputs have internal pull-up resistors that would satisfy the Hall sensor specs? Or, as an alternative, where do I find the internal schematics of the MIPC encoder?
    Thanks, Ziggi.

  • #2
    I just checked the photo of the MIPC-1A online and see that it has pull-up SIL resistor packs for the inputs. One could use a multimeter to measure from any input pin to +5v to verify the exact resistance value, likely 10k ohms. Since the A3144 has open collector outputs I would expect it to work well with almost any pull-up value.
    http://www.nwmidi.com

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    • #3
      Thanks, John, for a quick an optimistic hint. I see the SILs now, but after measuring the resistances, an (open) input has about 24MOhm against the V++, and about 10k against the Ground. I wonder if those are actually pull-down 10k resistors. I need more investigation.
      Z

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      • #4
        The MIPC-1A installation manual covers how to change a jumper for pull-up or pull-down operation. The board comes set for pull-ups to +5v which is perfect for your application. It's always a bit tricky to get the proper resistance readings with all the other circuit components installed. Check the installation manual and also try powering up the MIPC-1A. You should see +5v on every input connection and grounding any input line with a test wire should generate a NoteOn. The MIPC-1A HV is an entirely different version made for higher keying voltages so be sure you look at the correct section of the manual for your board. The MIPC-1A manual is here: http://www.dtsmidisystems.com/upload...al_4-21-18.pdf
        http://www.nwmidi.com

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        • #5
          Thanks, I just re-read the pertinent sections of the manual, although I am familiar with it. My concerns are a bit different. Primarily, I am not sure how the A3144 will react to the connection without the resistor. If the MIPC does not provide the proper pull-up, results may be unpredictable. And now I found this in the MIPC manual:
          "NEVER CONNECT A +12 V COMMON BUSS TO THE INPUT TERMINAL OF THE MIPC-1A. ONLY A COMMON GND".
          This is exactly what may happen here, in the OFF state without the resistor, the "collector" of the Hall probe may be putting the V++ voltage on the input.
          Z

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          • #6
            In parallel, I posted a question to DTS, and just received a response:
            "The input pins of the MIPC-1A, each go to the inputs of a SN74HC541 and there is a 10k pull-up resistor on each input. The SIP resister packs between the 74HC541 and input pins are 10k. You should have no problem connecting the Hall Effect device..."

            Now I can safely rig a simple circuit to test.
            Z

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            • #7
              I'm glad DTS confirmed my information. Open collector circuits don't impose voltages on the next stage. That's why the word "open" is used. They can pull the input to ground but can never pull an input up to a positive voltage.
              http://www.nwmidi.com

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              • #8
                I just successfully verified the circuit. A direct connection from the output of the Hall probe A3144 to the MIPC-1A's input without the external pull-up resistor works flawlessly. Case closed and my wiring greatly simplified!
                Z

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