Shutter Controller Installation

Controller Board

The controller card is shown below. Note that the Rotation Controller and the Shutter Controller boards are identical; a DIP switch is used to configure each board to rotation mode or shutter mode.

Dome Controller Circuit Card

The card should be mounted in a protected enclosure. For Sirius Observatories, it will slide into the slot intended for the original (non-automated) motor relay card. For other types of installations, 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.

DIP Switch

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 shutter controller operation.

Switch 2 (2 SHUTT) must be set OFF if you are operating two shutters, or ON if you are operating one shutter.

Switch 3 (AUTO CLS) should be turned OFF if the shutter can be operated at any dome position. If the switch is OFF, then the dome will automatically close ten minutes after loss of communications with the Rotation Controller. If the dome must be parked before operating the shutter, 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.

*The Rotation Controller also has a similar safety feature. It will command the shutter to close if it loses communications with the PC for more than ten minutes. It can be configured to Park the dome prior to operating the shutter, providing an auto-close safety feature without the risk of a mechanical collision with the shutter mechanism. The Rotation Controller is usually powered by a trickle-charged Gell Cell battery, so it will continue running after the PC loses power.

Also please note that the auto-close feature is disabled when the shutter is manually operated, and re-enabled when the shutter is operated under PC control. This interlock prevents the shutter from automatically closing every ten minutes if you are operating the dome 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.

Wiring

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

Small Terminal Block

These connections are shown schematically below. Each connection will also be described in more detail.

Power Supply Wiring

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 shutter 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).

Magnetic Induction "Antenna"

The magnetic induction "antenna" is simply a loop of wire that runs all the way around the dome, and connects back to the controller. The wire generates a very low frequency (8 kHz) pulsating magnetic field, which induces a small voltage in the other controller's wire. The pulsations encode low bit-rate digital data, which is transferred back and forth every two seconds.

Note that only one wire needs to run the full diameter of the dome. Usually the base wire runs the full diameter, to ensure good communications in all dome positions. The upper wire usually only needs to extend about 3-4 feet to provide a reliable link. If this arrangement of the wire is used, return path of the wire must be kept at least one foot away from the other side of the loop, as shown in the diagram.

Motor Control Wiring

There are two identical motors control sets; one for the upper shutter and one for the lower (optional).

Important: The upper shutter is Shutter 1, and the lower shutter is Shutter 2. Shutter 1 opens before Shutter 2, and closes after Shutter 2. In many dual shutter designs the upper shutter overlaps the lower shutter to provide a better weather seal, and operating them in the wrong sequence can cause them to bind. Carefully double-check the sequencing when testing the shutters.

Once the shutters 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 both the Rotation Controller and the Shutter 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 Shutter Controller (do not  power up the Rotation Controller, to make sure that it does not send any commands).

Now check the upper shutter. Briefly switch the manual control switch to Open (Right input terminal connected to ground). The shutter 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 upper shutter is fully open. The closed limit switch must go open circuit only when the upper shutter is fully closed. When the shutter 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 shutter 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 shutter, and verify that the open limit switch works correctly.

If you have a lower shutter, proceed to test it as follows:

First, open the upper shutter fully. Then set the DIP switches to enable the lower shutter, and cycle the power to the Shutter Controller on and off (briefly unplug the power terminal block).

Now try to open the shutters. If the upper shutter is not already fully open, it will open first. If the lower shutter starts going in the wrong direction, release the switch and reverse the connections to the motor.

Continue operating the lower 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 shutter. Once again be ready to stop if the shutter fails to stop at the closed limit switch, and readjust the switch as required. Once the lower shutter is fully closed and the limit switch engaged, the upper shutter will start closing.

Run the shutter 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.

Auxiliary Inputs

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).

The AUX inputs should be left unconnected if they are not being used.

Important Note: The AUX inputs on the Shutter Controller will not park the dome before closing the shutter. If you need the automatic park feature, use the AUX inputs on the Rotation Controller only.