NOTICE: Due to the large mass involved in moving roof segments, a secondary safety mechanism such as a mechanical slip clutch must be used with the drive motor(s). This will help prevent damage in the event that the roof binds or a limit switch fails. For safety the mechanical components must be designed such that the roof cannot be driven past safe limits in the event of an electrical failure. Please use extreme caution when opening or closing the observatory.
The controller card is shown below.
Dome Controller Circuit Card
The card should be mounted in a protected enclosure. You can use the four mounting holes, or if mounting on a non-conductive surface you can use stick-on Velcro buttons underneath the board. (Note: Velcro may not stick reliably if applied at low temperatures. Just use a small button of Velcro in each corner; otherwise you may need to apply a lot of force to remove the card, and you will run the risk of damaging it.)
WARNING: Use the supplied #4-40 screws, or other #4 or smaller hardware, when attaching the board. Do not force in screws that have threads larger than the hole. Using larger screws will damage the board and invalidate your warranty. Use appropriate spacers or standoffs to make sure the board electrical contacts do not touch metal.
WARNING: It is strongly recommended that a 10 amp in-line fuse be used for the battery connections, to prevent damage in the event that the wires are shorted or connected incorrectly. A shorted battery can be a fire hazard.
Important: The card must be installed in a suitable box or otherwise protected against direct contact with moisture. Moisture accumulating on the card can corrode the electrical circuits and cause the board to fail. Damaged caused by improper installation is not covered by the warranty.
The DIP switch is located just above the relays. Use the tip of a small precision screwdriver to set the switch positions. As shown in the picture below, OFF is to the LEFT, and ON is to the RIGHT.
The DIP switch must be set as follows:
Switch 1 (SHUTTER) must be set ON for roll-off roof controller operation.
Switch 2 (2 SHUTT) must be set OFF if you are operating two shutters (two roof segments), or ON if you are operating one shutter (one roof segment).
Switch 3 (AUTO CLS) should be turned OFF only if there is not risk of a collision between the roof and the telescope equipment. If the switch is OFF, then the roof will automatically close ten minutes after loss of communications with the computer. If the telescope must be parked before closing the roof, to prevent mechanical interference, then turn this ON.
Switch 4 (FACTORY) must be set OFF. It is only used when uploading new firmware and during factory test procedures.
Also please note that the auto-close feature is disabled when the roof is manually operated, and re-enabled when the roof is operated under PC control. This interlock prevents the roof from automatically closing every ten minutes if you are operating it manually.
Please note that some adjustments to these switches will be required during initial testing. Be sure to reset them appropriately once the testing is complete.
There are two green terminal blocks. Note that the terminal blocks can be unplugged from the board by gently pulling them out vertically.
The terminal blocks have the following connections, as shown from left to right in the picture above:
Large Terminal Block
|
ANT |
Not used |
|
ANT |
Not used |
|
GND |
Spare |
|
GND |
Spare |
|
GND |
Return for limit switch |
|
CLS2 |
Motor 2 closed limit switch (open circuit when roof closed) |
|
GND |
Return for limit switch |
|
OPEN2 |
Motor 2 open limit switch (open circuit when roof open) |
|
MOT2- |
Motor 2 winding (n.b. reverse wires if motor rotates wrong way) |
|
MOT2+ |
Motor 2 winding |
|
GND |
Return for limit switch |
|
CLS1 |
Motor 1 closed limit switch (open circuit when roof closed) |
|
GND |
Return for limit switch |
|
OPEN1 |
Motor 1 open limit switch (open circuit when roof open) |
|
MOT1- |
Motor 1 windings (n.b. reverse wires if motor rotates wrong way) |
|
MOT1+ |
Motor 1 windings |
|
GND |
Spare |
|
HOME |
Not used |
|
GND |
Ground return for Auxiliary inputs |
|
AUX2 |
Auxiliary close input |
|
AUX1 |
Auxiliary close input |
|
RIGHT |
Manual control switch Open Roof contact |
|
GND |
Manual control switch return |
|
LEFT |
Manual control switch Close Roof contact |
Small Terminal Block
|
BATT |
Battery terminal +12VDC |
|
GND |
Battery ground return |
|
+12V |
Solar cell +12V DC |
|
GND |
Ground return for solar cell |
These connections are shown schematically below. Each connection will also be described in more detail.
The controller card nominally requires +12VDC for operation, but will operate between 8V and 14V. Both the charger and battery inputs have built-in 10 Amp fuses, which automatically reset once the overload is removed.
When idle, the board draws about 1 mA. When transmitting a magnetic induction message, it briefly draws about 10 mA. When the motor is operating, the current draw is determined by the motor used.
The battery drain by the controller is minimal, so the battery should be sized to provide sufficient power for the motor during expected operation. A standard 12V, 6 or 12 Amp-hour gell cell battery is usually sufficient. Using a battery supply also ensures that the large inrush currents generated when the motor starts up will not cause the power supply to droop.
The solar charger should be sized to fully recharge the battery during a single sunny day (30W is usually sufficient). Please note that high latitudes it may be necessary to use a larger solar cell, to ensure adequate charging during the short winter days. Optimize the angle of the solar cell for the worst-case month (December in the Northern Hemisphere, June in the Southern Hemisphere).
There are two identical motors control sets; one for the Motor 1 and one for the Motor 2 (optional).
Important: Motor 1 opens before Motor 2, and closes after Motor 2. This ensures the roof segments always open and close in the same sequence. In some designs, the roof segments must be sequenced in a particular order; be sure to connect the motors appropriately. Carefully double-check the sequencing when testing the system.
Once the motors are connected, you must test them to ensure that all limit switches and motors are wired correctly. Make sure that the limit switches are open circuit when the shutter is at the limit, and closed circuit when not at the limit. If you are using magnetic "burglar alarm" style switches, this is known as a "Normally Open" switch (i.e. open circuit when magnet present).
The test procedure is as follows:
Power off the Controller (if no switch is available, unplug the power terminal block from the board).
Referring to the DIP switch settings above, configure the board as a Shutter Controller, with one shutter operation only (2 SHUTT switch ON), and disable the automatic close feature (AUTO CLS switch ON). We don't want the shutter to be actuated unexpectedly!
Apply power to the Controller.
Now check Motor 1. Briefly switch the manual control switch to Open (Right input terminal connected to ground). The roof segment should start to open. If it goes in the wrong direction, reverse the wires to the motor. If the motor does not move, check the limit switches and wiring. The open limit switch must go open circuit only when the Motor 1 roof segment is fully open. The closed limit switch must go open circuit only when the Motor 1 roof segment is fully closed. When the roof segment is in a middle position, both LEDs should be off.
Now hold down the switch until the shutter fully closes. When you get near the end, be ready to let go of the switch if the limit switch fails to work. If the switch is working properly, the roof segment will stop moving when you hit the end. If the limit switch fails to stop the shutter, check that it is actually tripping, that it is wired to the correct terminals (CLS1 and GND), and that the wires are intact. Also bear in mind that it is possible to have both the motor direction and the manual control switch direction wired backwards, in which case the limit switch will appear to not work because the controller is expecting the other switch to actuate.
Now try to fully open the roof segment, and verify that the open limit switch works correctly.
If you have a Motor 2 roof segment, proceed to test it as follows:
First, open the Motor 1 roof segment fully. Then set the DIP switches to enable the Motor 2 roof segment (two shutter operation), and cycle the power to the Controller on and off (briefly unplug the power terminal block).
Now try to open the roof. If the Motor 1 roof segment is not already fully open, it will open first. If the Motor 2 roof segment starts going in the wrong direction, release the switch and reverse the connections to the motor.
Continue operating the Motor 2 shutter until it reaches the fully open position. Again, while approaching the end position, be ready to stop if the limit switch fails to operate. If necessary, correct any problems with the wiring or positioning of the limit switch.
Now start closing the roof. Once again be ready to stop if the roof segment fails to stop at the closed limit switch, and readjust the switch as required. Once the Motor 2 roof segment is fully closed and the limit switch engaged, the Motor 1 roof segment will start closing.
Run the roof through a couple of complete open/close cycles, to ensure that they cycle in the correct order, and that the limit switches are working reliably.
Review the DIP switch settings again, to ensure that they are set for normal dome operation. If you change the settings, cycle the power to the board to reset it.
The shutter may be commanded to close by an external device, by pulling either the AUX 1 or AUX 2 input to ground (GND pin).
Do not use this feature if there is any risk of mechanical interference between the telescope and roof, since the roof may close at any time without warning
The AUX inputs should be left unconnected if they are not being used.