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Interfacing with Allen Capture System

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  • Interfacing with Allen Capture System

    I've been planning for the next phase of working out how to get the combination action of my Allen to interface with Hauptwerk. I have tested the stop mechanism, and I found that if a current is going to the middle pin of the three pin solder connections at the bottom of an individual stop (thin green wire), then if the stop is selected and the pulse is activated, it will pull it up, and do nothing if it is already up. If the stop is not selected, and no current is going to the middle pin, then the current pulse will pull it down. Otherwise, it will leave it down. The first and the third pin appear to be where the current pulse goes in and out. So, my plan is to wire each middle contact to the pins of a MCP23017 I/O expander. The circuit only draws ~4 mA, at 5V, so I think the MCP23017 should handle it fine. I have a small Nano Every, which has the I2C pins, so that is what I will use to connect to them. To activate the pulse for the combination action, my plan is to wire one of the Nano Every pins to a relay, then to ground. On the other side of the relay, my plan is to wire the leads of one of the current pistons that activate the capture action pulse. I decided to separate the capture action from the Mega I'm using for keying, since I don't want the capture action program and slow MCP23017 pins to slow down keying. My plan is to totally separate Midi input on the Nano Every from the Midi output on the Mega, and to use the mega to read the state of the stops and pistons and send them to Hauptwerk via MIDI out, and the Nano Every to read MIDI input stop state messages coming from Hauptwerk.

    My questions have to do with the relay. I have some 5V 10 amp relays coming. I will test the leads of the switch I'm planning to use to make sure it isn't too much for the relay, and if it is, I'll buy some automotive relays. However, I'm wondering how long to switch over the relay for in the Arduino program? I thought I could start short, say switch the pin to OUTPUT and HIGH, then delay for 50 micros, then switch back to INPUT, and see if it is enough to trigger the pulse, then keep increasing until it works, but anyone more familiar with how the Allen capture action operates would save me a lot of trial and error. Given how thick the wires are, I'm wondering if the full current going to the stop mechanisms also goes through the control switches. However, I'm not sure if there is a circuit in the capture action power supply to limit the duration of the pulse? Is anyone is aware of whether the capture action does in fact limit the duration of the pulse? Also, any thoughts about pros and cons of my circuit design would be appreciated! Thanks in advance!

  • #2
    Knowing the model and number of stops you plan on supporting would helpful. The current draw can be quite substantial. Activating my combination action causes the house lights on the same circuit to dim. Keep in mind that with the Allen system, current is applied to one coil of every stop even if that stop is already in the desired state when a combination is activated. For example, if the stop is up and the combination calls for the stop to be up, current will still be applied to the up coil of that stop. I don't recall the voltages involved, but they are in the 40 - 50 vdc range. The no longer available Zuma solution for DM capture systems as well the DM solution under development by John Kinkennon leverage the Allen Capture supply for this purpose. I would not consider using a relay for this purpose.
    -Admin

    Allen 965
    Zuma Group Midi Keyboard Encoder
    Zuma Group DM Midi Stop Controller
    Hauptwerk 4.2

    Comment


    • #3
      Thanks Admin. I have a MOS-2 225 RTC with 54 stop tabs. My thought was not to use the power supply directly, but to interface the Arduino with an existing piston to trigger the capture action. I agree if the full current goes through the switch a relay may not work, but surely there is a way to trigger the pulse without needing to go through the full voltage?

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      • myorgan
        myorgan commented
        Editing a comment
        Larason2,

        I would think that in order for the stop tabs to move on your organ, it would STILL require the same amount of voltage to turn the stop on or off. I do know that on Allens of that vintage, moving stops are required to change the registration. It may work differently on Allen's blind capture organs, but moving stoptabs and/or drawknobs will require the full voltage.

        Michael

    • #4
      Since it's a DM system, you should use the existing Allen Capture Power supply. There are four banks of outputs that drive the stops and those are triggered by a logic level signal. At this point in time, I'd be waiting for John Kinkennon s solution, but if you want to do it yourself, I think you'll find some information on how to do this on his project website. I believe there's also a discussion on interfacing to the supply on the Forum as well. Search on Allen Capture Power Supply.
      -Admin

      Allen 965
      Zuma Group Midi Keyboard Encoder
      Zuma Group DM Midi Stop Controller
      Hauptwerk 4.2

      Comment


      • #5
        Let me remind everyone that my code is available on www.kinkennon.com right on the home page until I get around to making some web site updates. The code is for the Teensy 4.1 which is a relative of the Arduinos with some improvements so 95% of the code is Arduino. Technically it is Teensyduino.

        Set the green wires to the logic level you want. 0v sets a stop to turn on and 5v sets it to turn off. To cause the stops in a division to actually move pull N1, N2, N3, or N4 low from an open collector device for 50ms. Each Nx on the capture supply pulses voltage to one division of stops. I connect to the stops through a 1k resistor.

        I used the 23017 devices with Allen stops for years and it's a great choice.

        As an aside my "pistons boards" for the J80 connection are finally with DHL and on their way from Hong Kong.
        http://www.kinkennon.com

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        • #6
          Thanks for your reply John! That’s very helpful. I feel like I should be patient and wait for your boards though, especially since they will allow me to keep the original function, which was one of my project goals. It’s good to know if the capture board ever stops working I have a backup though! Thanks again for all your help.

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