Resolved Passing the STL-11000 power cable through the Astrosysteme ASA DDM85 mount

Discussion in 'Legacy Models - Community Support' started by Alan Brockman, Nov 7, 2020.

  1. Alan Brockman

    Alan Brockman Cyanogen Customer

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    I have a question regarding my STL-11000M CCD and how I can connect its power cable to my mounts' 'through the mount' power cable.
    I have a new mount, Astrosyteme ASA DDM85, but it does not have a hollow conduit for cables. Instead it has a 4-pin jack that connects to the back of the Dec axis as shown in the following image. There are 4 wires (2x pos and 2x neg) that pass through the mount allowing connection for a maximum of two separate 12V power supplies up to 6 amps.
    One other thing to note is that the wiring diagram for the power lack is incorrectly labelled. +12V is not on pin 6 and DC Return is not on Pin 3. Neither is connected.
    My question is this: Can the 2 +ve pins and 2 return pins from the STL-11000 power supply cable be joined separately together to connect to the single +ve and return wires to the isolated lines on the spiral cable? From the mount to the STL-11000 power supply, the reverse would occur.
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  2. Colin Haig

    Colin Haig Staff Member

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    Hi Alan, I had a look at these two manuals for the mount:
    9600010A-DDM85A user manual hardware.pdf
    wiringDDM85-with incremental encoders.pdf

    Short answer:
    Double up on the wires in the GALV cables. One pair for the +12VDC, one pair for the 0VDC.
    The internal wires in the GALV cables look a bit "skinny" to handle the load without a significant voltage drop and risk of overheating.

    I suspect an error in the labelling of the power connector in the STL manual.
    I suggest you check it with a voltmeter, or careful disassembly of the 6-pin male DIN connector on the STL power supply. There is one screw that holds it together.
    Some STL power supplies have 4 wires, some may have 6. In any case, all the +12V ones are connected together, and all the 0VDC ones are connected together.
    It's NOT two separate +12V supplies, just we doubled (or tripled) up the wiring.
    The DIN connectors are typically rated 2A per pin. So to handle 6A, 3 pins.
    Don't connect the metal shield to anything.

    Don't cut off the power supply DIN plug.
    Instead, use a 6-pin DIN Female to receive it.
    Solder as follows to the straight GALV cable that has Banana plugs. (Cut off the banana plugs one at a time):
    +12V pins to brown and grey on the GALV cable (cut off the Banana plugs)
    0V pins to black and yellow/green on the GALV cable.

    Then on the spiral cable, same deal.
    Test your cable with an ohmmeter.
    Then connect it only to the power supply and test +12V and 0V are where they are supposed to be.

    Solder a DIN 6-pin Male plug to the wires on the spiral cable.
    Test.

    From what I see here, the GALV connection at the base connects via an internal cable to the GALV connection on the dovetail adapter that the telescope attaches to.
    It does not specify the wire gauge provided through the mount. (e.g. 18 AWG or 0.75mm^2)
    This is odd. I suggest you contact them to find out how thick the internal wiring is, and any voltage/current limits. e.g. 12V at 10A.
    You mention 6A. I'm a bit doubtful.

    The wiring on the GALV spiral cable, and the GALV cable with 4 banana jacks looks pretty skinny. I'd ask them for the wire gauge and current capacity.
    There's always going to be some voltage drop over a length of wire. If it's too much, the camera will misbehave when the cooler is going on at 100% power and the filter wheel and any I2C accessories are running (eg AO-L/AO-X).
    West Mountain Radio has a simple and accurate Voltage Drop Calculator on their website:
    http://www.westmountainradio.com/find_cable_size.php
    8 feet of 18AWG wire will have a drop of about 0.5V at 6A. That's significant. If that wire through mount or the spiral cable is only 22AWG which is typical of those spiral retractile cables, then you're losing maybe 1.6V, which can make the STL unhappy.
    The bigger cameras like the STXL and STX would not operate.

    Don't blow up the camera ;-)
     
  3. Alan Brockman

    Alan Brockman Cyanogen Customer

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    Nov 7, 2020
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    That gives me a lot to think about but I really appreciate your digging and clarity of advice. I will do my best not to blow up my camera!
    Thanks so much, Al
     

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