The MaxDome II controller boards have six indicator lights (Light Emitting Diodes or LEDs). Some LEDs have different functions depending on whether it is operating as the Rotation Controller or the Shutter Controller. The printed name is not always meaningful in both contexts, due to space limitations.
The functions of the LEDs are described in this table:
|
LED |
Rotation Controller |
Shutter Controller |
|
CLS |
Not Used |
Lower Closed Limit Switch |
|
OPEN |
Serial Port Activity |
Lower Open Limit Switch |
|
HOME |
At Home Position |
Upper Closed Limit Switch |
|
ROT |
Optical Rotation Sensor |
Upper Open Limit Switch |
|
LINK |
Induction Link Activity |
Induction Link Activity |
|
PWR |
DC Power On |
DC Power On |
The PWR LED turns on to indicate that power is present on the controller.
The LINK LED "warbles" when a message is being transmitted or received over the magnetic induction link between the two controllers. The Rotation Controller always starts the exchange (master), and the Shutter Controller responds (slave). If everything is working normally, two warbles will happen one after the other. This pattern will repeat every two seconds.
If the induction link is dead (e.g. broken induction "antenna" wire), the Rotation Controller LINK LED will warble once every two seconds, and the Shutter Controller LINK LED will not warble at all. If sometimes it works and sometimes it doesn't, then either the induction wires are installed incorrectly, or you have some kind of interference problem or other fault. Check the wires and if necessary contact Diffraction Limited for assistance.
The ROT LED blinks as the Optical Rotation Sensor sees the alternating white and black bands; it turns on for white and off for black. During dome rotation, this LED should blink steadily, turning on or off once a second or so. If it operates much more quickly than that, you may need to change the sensor installation. If it operates erratically, check the spacing and alignment of the sensor. Also make sure that the sensor is not shifting during dome rotation.
The HOME LED turns on when the home sensor magnet is near the sensor. If it does not light up, check the wires, and also verify that the magnet is not mounted too far away from the sensor. Note that the Rotation Controller will not actually recognize Home until the next tic of the Optical Rotation Sensor, so if the Optical Rotation Sensor is not working, the Home position will not be detected even though the LED illuminates.
When operating as a rotation controller, the OPEN LED is used as an indicator for serial port traffic. It blinks very briefly whenever a message is exchanged with the PC.
When operating as a Shutter Controller, the ROT, HOME, OPEN, and CLS LEDs show the status of the four shutter limit switches. OPEN and CLS refer to the lower shutter, and ROT and HOME refer to the upper shutter (ROT is open and HOME is closed). When the shutters are fully closed, CLS and HOME should be on. When the shutters are fully open, OPEN and ROT should be on. If the shutter is in an intermediate state, both LEDs for that shutter should be off. If both are ever on simultaneously, the switches are either wired incorrectly or are the wrong type (should be open circuit when actuated).
Check that the Rotation Controller board is powered up: the PWR LED should be illuminated. If it is not illuminated, check the power connections. They must be connected with the correct voltage (12V DC) and polarity. If using a Gel Cell battery, make sure it has charge (note that a trickle charger or solar charger may not have enough power to charge a completely flat battery).
Make sure the FACTORY DIP switch is turned OFF. (Cycle the power if you change a setting.)
On the Rotation Controller, the SHUTTER DIP Switch must be turned OFF; otherwise the board will behave like a Shutter Controller and will not respond to computer commands.
Check the OPEN LED. It should blink very briefly whenever serial port characters are received. Under normal operation, a very short blink will appear once a second. If the LED does not blink, check the cabling. Also check that the correct COM port is selected in the MaxDome driver setup (a list of COM Ports is available in the Windows Device Manager). The baud rate and stop bit settings are controlled automatically by the software, so no adjustments are required.
Check that the computer COM port is actually working. Some inexpensive USB-to-Serial adapters are very unreliable, and some have unstable Windows drivers.
If you need to use an extension cable, use a DB9 to DB9 serial port extension cable, available at computer stores. Do not attempt to use a different RJ-11 telephone jack style cable. Many of these cables have only two or four wires, not the required six, and the connectors can also be attached in two different orientations. Use only the supplied RJ-11 to DB9 adaptor; there is no standard for the wiring for these adaptors, and adapters from other equipment may not work (an Optec adapter will not work, but Meade and Technical Innovations adapters will).
Try swapping the rotation and shutter boards, to see if one is damaged. Note that the terminal strips are two-piece units. You don't have to unscrew all the connections; you can simply unplug the strip from the board. Don't forget to set the DIP switches.
Use the manual switch to rotate the dome. The ROT LED should be flashing steadily, with an on period of about one second, and an off period of about one second. It will turn on when the bright strip is under the sensor, and off when the dark strip is under the sensor.
If it is not blinking, check that:
The black and white strip is visible to the sensor
The sensor is not too close or too far from the shaft. About 3/8" is usually optimum, although the optimum distance will vary slightly from unit to unit. Tip: to find the optimum point, adjust the dome so the white strip is under the sensor. Move the sensor closer until the ROT LED goes out, then move it farther away until the LED goes out again. The optimum is half-way between these two points.
Bright sunlight is not falling on the sensor
The sensor cable is not damaged (e.g. if not installed properly in a Sirius dome, the cable can get pinched as the motor assembly pivots)
If it still does not work, detach the sensor and try to detect a white piece of paper. You might also try swapping the Rotation and Shutter controllers (adjusting the DIP switches as required), just in case the controller is damaged.
Check whether the magnetic home position switch is working by looking at the HOME LED on the Rotation Controller board. It should be on when the magnet is near the switch. To check this, manually rotate the dome to the home position. If the LED does not illuminate, check the wiring and the magnet position.
Make sure that the motor tics are being counted. The home position is declared on the next motor tic after the home position sensor is triggered. If the optical sensor is not working, the home position will not be detected. If the optical sensor is working, the ROT LED should be flashing as the dome is rotating.
Make sure that both the Rotation Controller and the Shutter Controller PWR LEDs are illuminated.
Make sure that the SHUTTER DIP switch is OFF for the Rotation Controller, and ON for the Shutter Controller. Make sure the FACTORY DIP switch is OFF for both controllers. (Cycle the power if you change a setting.)
Try the manual open/close switch on the Shutter Controller. If the manual switch works but the computer commands do not, check the magnetic induction "antenna" on both controllers. The LINK LEDs on both the Rotation Controller and Shutter Controller should both be "warbling" twice (with a slight pause in-between) every two seconds. If not, check the induction "antenna" wires. At least one must loop fully around the observatory; otherwise the shutters may not work in certain dome positions. The other loop can be a shorter, but at least three feet long and at least one foot high. If a short loop is used, it must be located with the long side parallel to the other wire, as close to the other wire as possible. Try to avoid placing the loops in direct contact with ferromagnetic metals like carbon steel, as this might affect the magnetic fields. If you have insufficient signal and are using a short loop on one side, try making the loop longer and wider, or switch to a long loop around the whole dome.
If the manual open/close switch does not work, then check the limit switch LEDs. If the shutters are both closed, the CLS and HOME LEDs should be lit. If they are both open, then the OPEN and ROT LEDs should be lit. If the shutters are at an in-between position, the LEDs should be off. If the LEDs are in the wrong state, then the limit switch problem may be preventing any motor operations.
Open the ASCOM Dome Control Panel. Go to the Dome setup, and set "Report Partially Open As" to "Open Shutter". Connect the link. If the status shows Shutter Error, then the link between the Rotation Controller and Shutter Controller is not working. Check the induction antenna wires, and also check for any local sources of electromagnetic interference. Try turning off other devices to see if they are interfering with the link. (Be sure to restore the setting once this test is complete.)
Interference from other devices is extremely rare. The range of these signals is very limited, and very few devices use these frequencies. A continuously blinking LINK light may indicate interference from another device. Since the communications distance inside the dome is very short, a simple solution to interference may be to reduce the sensitivity of the wire loop. To do this, place a small resistor in series with the wire. The correct value may be determined by trial-and-error: large enough to remove the interference, but small enough to allow communications within the dome.
As of the time of writing, only the FriendlyRobotics® RoboMower is known to potentially cause interference, if the perimeter wire is directly adjacent to the observatory. To prevent interference, either locate the perimeter wire away from the observatory, or turn off the "perimeter switch" during observatory operation.
If the shutter motor does not stop when the dome is fully closed or fully open, check the wiring and positioning of the limit switches. If these are not functioning properly, the shutter motor will not stop correctly.
Make sure the upper/lower shutter motor wires are not swapped. The upper shutter should open first, and close last. If not, then swap the wires between the two motors.
If a shutter opens when it should be closing, reverse the wires to the shutter.
Repeat the detailed steps for commissioning the shutters in Shutter Controller Installation.
Check that the shutters can be operated from the ASCOM Dome Control Panel as described above.
Close both shutters. Check that the CLS and HOME LEDs are lit. If not, then the limit switches are not working. The status will not update properly until both LEDs are on (appropriate limit switches are open). Repeat this test with the shutters fully open (OPEN and ROT LEDs).
Command a Home operation from the ASCOM Dome Control Panel. The dome should turn to the right as seen from inside the dome. If it turns left, power down the controller and reverse the wires going to the motor.