Current and voltage input for ST guiding chip and compatiability with modern mounts

Discussion in 'Legacy Models - Community Support' started by CrossoverManiac, Sep 6, 2020.

  1. CrossoverManiac

    CrossoverManiac Standard User

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    What is the current and voltage that an SBIG ST series camera inputs into a mount for autoguiding? Also, I know some of the older mounts match the wiring from an ST series ST-4 port but that later mounts are not wired up for it. Also, because the ground wires are different, would that cause an electrical issue with the mount or even damage mount circuit board?
     
    CrossoverManiac, Sep 6, 2020
    #1
  2. Doug

    Doug Staff Member

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    The autoguider interface doesn't generate any voltage. It pulls the pin down to the common pin voltage.

    Normally that would be ground, but on some older mounts it's not (most common example is the old Losmandy Digital Controller, which has a keypad scan strobe on the common pin).

    Newer SBIG cameras have an optoisolator, which means they will work with just about anything. The old ST series didn't have that, which is why they sometimes needed a relay box (e.g. for the old Losmandy controllers).
     
    Doug, Sep 6, 2020
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  3. CrossoverManiac

    CrossoverManiac Standard User

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    But is it possible for an incompatible autoguiding camera to damage a GOTO telescope mount circuit board?
     
    CrossoverManiac, Sep 7, 2020
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  4. Doug

    Doug Staff Member

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    Yes, potentially. What older mount are you using?
     
    Doug, Sep 7, 2020
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  5. CrossoverManiac

    CrossoverManiac Standard User

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    My mount is a Skywatcher EQ6-R. Originally, I had the ST-7 parallel port camera. Apart from issue with the pins, there was no indication of a problem. So I upgraded to the ST-8XE for photometry and the ST2000XCM for astrophotography. It was then I started having problems. First, my RA motor wouldn't run, at least until I unplugged the ST4 cable from the mount. Thinking it's a bad RJ cable, I just swapped it out for another cable but then the whole thing stopped working- the RA and DEC motors.
     
    CrossoverManiac, Sep 7, 2020
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  6. Doug

    Doug Staff Member

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    If one of the motor directions is permanently engaged, that means the cable is built backwards. You can put the RJ-12 connectors on in two different orientations, and if it's backwards it tends to permanently short one of the directions to ground. That sounds like the problem with the first cable.

    The second cable sounds like it simply isn't working - bad connection or something.
     
    Doug, Sep 7, 2020
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