Resolved STT-8300M guiding problem

Discussion in 'STT Series' started by jliles01, Feb 21, 2018.

  1. jliles01

    jliles01 Cyanogen Customer

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    We've been using our STT-8300M camera & CCDOPS for the last 2-3 years with the Y- relay turned off with no problem. Polar alignment with our pier has been good enough, we turned it off due to stiction & backlash problems.

    Recently we turned it back on to use with another program and tried to calibrate. The Y- relay now does not seem to work. The new program does not have the option of turning off any relay. So we can't go further without calibrating.

    Using CCDOPS, while using "FOCUS", we pushed each button N,S,E,W and it did NOT move in the S direction. We unplugged the 6C cable from the camera, shorted out pin 5 to each of the pins 1-4, and the scope DID move in all 4 directions. So very confident the scope & the cable are good.

    LEDS on the side of camera DO come on when each button is pushed, and the scope moves in the N, E, & W directions, but NOT in the S direction.

    Using my multi-meter, we measured resistance between pin 5 (common) and pins 1-4. I've attached a PDF of what we found. The readings between pins 5 & 3 were jumping between 1008 ohms & open while the S button was pushed. The readings between pin 5 & pins 1, 2, & 4 were 42 - 44 ohms.

    I'm aware I'm reading through a solid state relay, and not just through dry contacts, but the readings don't seem to be right. They should at least be consistent between pin 5 & the other 4 pins.

    Any help would be appreciated.
     

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  2. Colin Haig

    Colin Haig Staff Member

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    Any chance you have the cable flipped to the wrong orientation?
    Autoguidercable2.png
     
  3. jliles01

    jliles01 Cyanogen Customer

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    We are using the cable provided. And it has worked in the past. But now, we can't get the scope to move in the Y- direction with the camera. We CAN by plugging the cable into the scope &7 shorting the proper pins.
     
  4. Doug

    Doug Staff Member

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    I'm not sure a multimeter would provide an accurate result, since you are looking into a phototransistor in the optoisolator; there might not be enough voltage to make a reliable measurement.

    A better approach would be to connect, say, a 5k resistor to +12V or +5V. Then use the multimeter to measure the voltage that results when the output switches on.
     
  5. jliles01

    jliles01 Cyanogen Customer

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    Ok, we'll try that.

    I agree that the multimeter readings may not be accurate. But I would think we would get a consistent result since we're reading through 4 identical optoisolators. Especially since the three that work are consistent readings, and the one that doesn't work has the strange reading.

    Now that Radio Shack is dead, I'll have to hunt for a resistor.
     
  6. jliles01

    jliles01 Cyanogen Customer

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    Ok Doug, I just want to be sure I'm following your instructions. I've attached a diagram of what I think you want. As soon as I can find a local source for the resistor, or get one delivered from an online source, I will test it.

    It seems to me that the camera would be built to a wide range of telescope mount specs, allowing for different mount drive voltages. But maybe +5V is the bare minimum that can overcome the internal resistance of the optoisolator, since you specified that voltage in your response. Dry contacts on a standard relay would allow any voltage to pass through. But we're dealing with optoisolators, of which I have no experience.

    But could you please comment on what I'm saying. There are 4 optoisolators, which I would assume are identical. Three of them give consistent readings through them with my ohmmeter, and those three work, allowing the mount to move in those 3 axis. One does not give a consistent reading, and that one does not work, the scope does not move in that axis when that one is activated. BUT, using the same cable and shorting out the common from the mount and each of the other 4 pins from the mount, allows the mount to move in all 4 axis. To me, that means the problem is inside the camera. And there's the fact that in the past, all four relays used to work. It's just recently that we found this one relay not working.

    A little background on me. I've been an electrician for 38 years. I'm a former HAM radio operator who had to have a certain amount of electronics knowledge to pass the license exams. I've installed Key telephone systems for a former employer. I do quite a bit of Ethernet wiring, terminating, & testing now. Tracing out wires through different connector pinouts is not new to me. Although this is the first time I've worked with optoisolators, I'm not an electronic novice.

    And I have not looked at the warranty for this camera, and don't care. I will pay to get it fixed. From my testing, it seems pretty obvious that the camera is the problem. But I'm not infallible. I would like your confirmation that my reasoning is sound, and will do additional testing as suggested. I don't want to send the camera in for repair if it doesn't need it.Please let me know if the diagram I attached is what you are looking for. Meanwhile, I'll find a resistor.

    Thank you.
     

    Attached Files:

  7. Doug

    Doug Staff Member

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    Sorry but that diagram is wrong. You need to provide +5V through a resistor to the pin, and then measure the pin when you switch the output on and off. When on it should be close to 0V, and when it's off it should be 5V.

    Here's my version:

    guideport.jpg

    Yes, it is possible that the optoisolator is damaged. It's also possible that it's still okay but has slightly different response to your multimeter test, which doesn't really apply sufficient bias to the phototransistor. This quick check might save you having to send back your camera for repair. Or it could prove that the part is damaged.
     
  8. jliles01

    jliles01 Cyanogen Customer

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    Thanks Doug. And you said earlier I could use +5V or +12V. 12V would be easier to get.

    We might have resistors at our shop. We're an electrical contractor, not electronics. But sometimes we have some for End of Line applications. I'll check in the morning.
     
  9. Doug

    Doug Staff Member

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    Digikey.com if you can’t find one.
     
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  10. jliles01

    jliles01 Cyanogen Customer

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    Doug, here are the results of my testing.

    I found enough resistors to series together to give me 3120 ohms. I used one & two 6V batteries to give me 6V & 12V. I hooked everything up per your drawing, including grounding the negative terminal.

    At 12 V:
    Pin 1 12.3V OFF .1V ON
    Pin 2 12.3V OFF .1V ON
    Pin 3 6.6V OFF 6.6V ON
    Pin 4 12.3V OFF .1V ON

    At 6V:
    Pin 1 6.6V OFF .1V ON
    Pin 2 6.6V OFF .1V ON
    Pin 3 0V OFF 0V ON
    Pin 4 6.6V OFF .1V ON

    Does this help?
     
    Last edited: Feb 25, 2018
  11. Colin Haig

    Colin Haig Staff Member

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    Hardware failure... you'll probably want to contact Bill @ sbig dot com to send in for service.
     
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  12. jliles01

    jliles01 Cyanogen Customer

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    Thanks Colin. No reflection on you, but I will wait for Doug to confirm it. I'm also gonna wait a couple of months until the weather turns against us here in central Florida. We can use the camera without the Y- axis working, been doing it for 2-3 years now.

    We calibrate with CCDOPS knowing that axis is turned off. It's when we started trying to use SBIG CONTROL that we noticed that axis wasn't working. SBIG CONTROL doesn't have a way to turn off individual axis relays, so we couldn't complete calibration. It would "tell it" to move, and it didn't move. So we couldn't complete calibration and don't even know if the rest of the program works.

    When the rainy season starts, about the end of April and we can't image anyway, I'll send it in for repair.
     
  13. Doug

    Doug Staff Member

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    Yes, there's clearly something wrong there. It will have to go in for service. What is the camera's serial number?
     
  14. jliles01

    jliles01 Cyanogen Customer

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    Thanks Doug.
    Serial # is T14030641.

    When I send it in, should I remove the self-guiding filter wheel and just send the camera?
     
  15. Doug

    Doug Staff Member

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    Please check with Bill on that.
     
  16. Bill

    Bill SBIG Service and Repairs Staff Member

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    jliles, send me an email, bill@sbig.com and we can arrange to have it come in.

    -Bill
     
  17. jliles01

    jliles01 Cyanogen Customer

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    Doug, Bill. Colin. Thank you very much.
     
  18. jliles01

    jliles01 Cyanogen Customer

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    I don't know how, or even if I can, label this thread as "resolved". But thanks to all who have commented and helped us with this issue.
     
  19. Doug

    Doug Staff Member

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    I've marked it as "Resolved".

    Glad to help. I'm sure Bill will get you sorted out.
     

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