Changes between Version 2 and Version 3 of Hardware


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Timestamp:
Oct 2, 2021, 7:34:28 AM (4 months ago)
Author:
holtz
Comment:

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  • Hardware

    v2 v3  
    1515
    1616
     17== Camera ==
     18
     19QHY 600 installed in spring 2021, purchased from OPT (along with a QHY CFW-3 filter wheel). This is a CMOS camera that uses a Sony IMX 455 sensor, with 9576 x 6388 3.76 micron pixels. QHY software allows for 1x1 and 2x2 binning. Given the small pixels, the latter is used.
     20
    1721== Guider ==
    1822
    1923Because of concerns of too much back focal distance with FLI centerline and offset guider, guider moved to 6" finder scope spring 2021. Use Starlight Xpress, purchased Starlight Xpress Ultrastar Pro from Starizona summer/fall 2021.
    2024
    21 == Camera ==
    22 
    23 QHY 600 installed in spring 2021, purchased from OPT (along with a QHY CFW-3 filter wheel). This is a CMOS camera that uses a Sony IMX 455 sensor, with 9576 x 6388 3.76 micron pixels. QHY software allows for 1x1 and 2x2 binning. Given the small pixels, the latter is used.
    2425
    2526== Dome ==
    … …  
    3334
    3435Dome is controlled by ACP; don't connect to the dome in MaximDL. Note that the dome is set up such that it will automatically close if it does not detect a signal from the control computer; so if you're up there doing maintenance and open it to let some light in, make sure the computer is on so it doesn't close itself.
     36
     37=== Maxdome Card ===
     38
     39After suffering a failure of the dome control card we ordered a new card from Diffraction Limited. Upon installing it the dome immediately started to rotate endlessly. Pressing the stop button did stop the rotation, but only for as long as it was held in. Upon releasing the button, the dome began to rotate again.
     40After some posts to the support forum, and some tests, we eventually figured out what was going on. Our old cards are Revision D. The new card is Revision F. Between those two revision, Diffraction Limited changed how the cards work.
     41
     42In Revision D, the motor+ and motor- terminals are held at +12V (so effectively 0V across them). When a rotation is commanded, one of the terminals drops to 0V, giving you a difference of 12V across the two terminals and engaging the motor.
     43In Revision F they decided that holding the motor terminals at 12V is bad, just incase there’s a short somewhere. So now the terminals stay at 0V, and when a move is commanded the relevant terminal jumps to 12V.
     44If you simply have a motor connected across the terminals then there’s effectively no difference. In revision D you have a difference of 0V until you command a move, at which point one of the terminals drops to 0 and you get you 12V difference. In Revision F they two are at 0 until a move is commanded, at which point one jumps to 12V.
     45
     46However. We use a large motor to drive our large dome, so we don’t/can’t drive the motor directly from the card. We instead use the voltage from the card to trigger our large external relays, which then engage the motor. And this was wired up in such a way to expect 12V on the motor terminals, with 0v commanding a move. This was accomplished by a jumper on one of the connection block connections (on the back left of the rotation box), between the 12V connection and the relay connection.
     47Removing this jumper set the relays back to 0V and has them trigger when the MaxDome card motor terminals are at 12V (i.e. the new card behaviour).
     48It’s important to be aware of this behaviour for the future. We returned our faulty card to be repaired, and so now have a spare Revision D card (in the computer room downstairs). We’ll have to be careful about the wiring if we use it to replace a card in the future.
     49The dome shutter is still wired up to use a Revision D card, the rotation box is wired for Revision F.
     50
    3551
    3652== Weather ==
    … …  
    5167Horizon limiter: If the telescope gets too close to the horizon, the motor will shut off. It shouldn't be triggered in normal operation, as ACP Scheduler won't observe anything beneath 20° of the horizon. If it is, however, it requires a manual override to bring back; contact David or Jon about this.
    5268
    53 == Maxdome Card ==
    54 After suffering a failure of the dome control card we ordered a new card from Diffraction Limited. Upon installing it the dome immediately started to rotate endlessly. Pressing the stop button did stop the rotation, but only for as long as it was held in. Upon releasing the button, the dome began to rotate again.
    55 After some posts to the support forum, and some tests, we eventually figured out what was going on. Our old cards are Revision D. The new card is Revision F. Between those two revision, Diffraction Limited changed how the cards work.
    56 
    57 In Revision D, the motor+ and motor- terminals are held at +12V (so effectively 0V across them). When a rotation is commanded, one of the terminals drops to 0V, giving you a difference of 12V across the two terminals and engaging the motor.
    58 In Revision F they decided that holding the motor terminals at 12V is bad, just incase there’s a short somewhere. So now the terminals stay at 0V, and when a move is commanded the relevant terminal jumps to 12V.
    59 If you simply have a motor connected across the terminals then there’s effectively no difference. In revision D you have a difference of 0V until you command a move, at which point one of the terminals drops to 0 and you get you 12V difference. In Revision F they two are at 0 until a move is commanded, at which point one jumps to 12V.
    60 
    61 However. We use a large motor to drive our large dome, so we don’t/can’t drive the motor directly from the card. We instead use the voltage from the card to trigger our large external relays, which then engage the motor. And this was wired up in such a way to expect 12V on the motor terminals, with 0v commanding a move. This was accomplished by a jumper on one of the connection block connections (on the back left of the rotation box), between the 12V connection and the relay connection.
    62 Removing this jumper set the relays back to 0V and has them trigger when the MaxDome card motor terminals are at 12V (i.e. the new card behaviour).
    63 It’s important to be aware of this behaviour for the future. We returned our faulty card to be repaired, and so now have a spare Revision D card (in the computer room downstairs). We’ll have to be careful about the wiring if we use it to replace a card in the future.
    64 The dome shutter is still wired up to use a Revision D card, the rotation box is wired for Revision F.