Engineering Console Upgrade - Oct 2001

The electronics in the carousel engineering console (CEC) have become increasingly unreliable and adequate spares for many components do not exist. The planned upgrade, which will shut the telescope down from 5-7 November, will result in a significant increase in facility reliability and maintainability. The CEC provides the logic for the roof and door safety interlock chain, is the main control for operation of the roof, doors and ventilation louvers, and contains electronics that condition the demand signal to the carousel drive system.

The CEC will be replaced with a modern Allen Bradley Programmable Logic Controller (PLC). The PLC can be programmed to duplicate the relay logic currently implemented in the CEC. In addition it provides an LCD display that will be much more user friendly than the existing system. The unit is a standard package already supported by JAC ETS with units in service controlling UKIRT dome and plant room systems.

Reliability of CEC controlled systems will be greatly improved as the current analog/digital discrete component system will be replaced in total by the solid state electronics in the PLC. It will also provide the capability to open the facility roof and doors, as well as control the ventilation louvers, remotely. This is an essential element of the future manned startup/remote observing JCMT operation model.

In concert with the CEC work, the slew speed of the carousel will be increased from the current .6 deg/sec to the original design value of 1.5 deg/sec. This will improve observing efficiency through a reduction in the overhead required to slew between sources. The control signal to the carousel will also be conditioned in a more rational manner through elimination of the redundant signal conditioning in the CEC.

Dean Shutt - Chief Engineer JAC

Click here for printable version.