DRAFT SO FAR

remember Grant’s email about taking apart the failed shutter

add note about how this shutter is different and only needs a short pulse to transition

make this a catch-all that describes the shutter cable, but points to other pages as needed (i.e. Galil TTL, scrambler timed shutter)

Table of Contents:

Introduction

A DB15 cable….

This LED is pointed at the fiber block within the HK spectrometer to back-illuminate the fibers. This allows the HK fiber viewing camera in the FIU to determine the locations of the HK fibers.

The LEDs are turned on and off at the PDU outlet using kpfpower for the appropriate outlet.

Relevant Devices

Relevant Functional Block Diagram

Cable Details

Pictures of Devices

Cable Details

Relevant Datasheets & Manuals

Notes on Failure (November 2022)

The trigger signals for these shutters operate differently than the other shutters. For these RS20 shutters they only require a pulse to transition (as described in the datasheet above). A sustained signal causes the shutters to heat up and eventually fail. This happened in early November 2022, when a hiccup with a software script caused the shutter pulse to remain on for many minutes. The temperature sensor kpfmet.SciSky_Scmblr_Fiber_End temperature sensor showed a temperature rise and then fall as the shutter failed. Software was then modified so that this situation could not happen again.

Grant Hill took the failed shutters apart, and noted that “At first I thought I saw molten slag but maybe that is just epoxy holding components in place? No burnt smell. The coil is hair thin wire but each end seemed intact and was still connected. In the pictures they are broken off because that was what it took to open it up. One of the pictures shows how you can only open it up a little way without breaking the wires.

I thought it was cool how the little triangular magnet allows the shutter to flip in/out on a trigger pulse and allows the bi-stable hold without having to apply a holding voltage.

When I looked under magnification I saw breaks in the coil wire part way round the loop so guessing that was the failure mode. I picked at one break to make it more visible. On the other shutter it appears that a strand of coil wire is visible glommed onto a component (a cap?).”