SDSS Trip Report
SDSS Interlock System Work
October 19-22, 1998

John Anderson and Glenn Federwitz
Fermi National Accelerator Laboratory
Batavia, IL   USA   60510

Bypass Enable Chassis

The interlock system bypass enable chassis has been modified to contain two key switches. The right hand switch functions the same as on the original module. This is used to bypass individual elements on the splitter chassis.

The left hand switch is used to bypass all stop switches at the same time. When this switch is activated, a strobe light on the bypass chassis and another strobe light on the azimuth stow light box on the upper level will begin flashing. In addition, all stop switches at the telescope will begin flashing.

Stop Switch LEDís

The individual stop switch LEDís have been modified to provide additional status information.

Stop Switch Logic

The low level axis logic has been modified to eliminate the possibility of inadvertently bypassing the telescope stop switches.

South Windbaffle Stop Switch

An additional stop switch was added to the south fork of the windbaffle and added to the low level axis logic.

Azimuth Telescope Clamp

Modified the high level logic to allow the alignment clamp to be used below 15 degrees. The clamp may still be used at zenith.  The clamp must be disengaged for the windscreen or telescope azimuth axes to receive a CW or CCW motion permit. This is to prevent LVDT errors from moving the windscreen with the clamp on and to prevent the telescope from attempting to drive against the windscreen.

AZ and ALT Motor Ready signals

For the telescope to have AZ CW and CCW permits, both azimuth motor 1 and 2 drive amplifiers must be ready. Any internal interlock trips on one amplifier will trip the other amplifier off. The same has been done for the altitude axis.

Windscreen CW / CCW / UP / DN permits

The windscreen soft inhibits now follow the telecope soft inhibits. If the telescope receives an UP inhibit, then an UP inhibit is sent to the windbaffle as well. The same holds true for Down, CW, and CCW inhibits. By implementing the logic in this fashion, the windbaffle will no longer follow an out-of-balance telescope past the soft limits to an out-of-operating-range position.

Hatch Switch and Dog House Door Switch

These switches were moved from Splitter chassis Slot 2, channels 6 and 7, to Slot 8, channels 6 and 7.

Lightning Protection

The Allen Bradley communications network now has lightning suppressors installed in the Interlock Rack, the windbaffle junction box, and in the azimuth junction box. This will help suppress any induced transients in the communications network between the PLC components. We will add a suppressor in the altitude junction box in the future. We were not able to move the telescope to a position that would allow for work in the altitude junction box this trip.

Comments regarding this trip report should be addressed to John Anderson at (630) 840-4973.

Last updated 11/19/98.