Serious Apprehension

Today is the day I will close my eyes, cross my fingers, and press a button.

Old and New PLC's
The old and new programmable logic controllers installed in side the control cabinet.
If all goes well, 700 tons of steel and aluminum will move at that button press. the Keck 2 dome will rotate and I will be able to breathe again. There is just a little apprehension here. Replacing the controller that commands the motors and brakes has been my major effort for the last couple months. A great deal of time has been spent testing and retesting the software in the new controller.

Further tests will open and close the shutters. If anything this part is even more worrisome. The controller is responsible for releasing the brakes on the shutters. If the brakes were to open without motor power the shutters will be able to simply run downwards.

Fortunately they will not fall, but they can run downwards to the hard stops rather quickly. There will be a tech stationed at the shutters with a finger poised over the e-stop button during these first tests. The button blows the dome main breaker, which removes power from the brakes, causing them to close.

A brain replacement is fraught with opportunities for error. Currently the old and new PLC’s sit next to each other in the cabinet, installed last week. Monday morning I will remove the old one and slave the I/O cards to the new controller.

Then the testing begins.

Author: Andrew

An electrical engineer, amateur astronomer, and diver, living and working on the island of Hawaiʻi.

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