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Tuesday, September 28, 2010

TS1 Test Fixture

Regular readers of this blog have seen a few of the automated test fixtures I have built.

Another fixture I built a few years ago monitors NEMA TS-1 output signals on up to 8 boards under test. TS-1 outputs are based on an open collector circuit configuration, producing a binary "low" or "high" condition. In simple terms these signals can be thought of as a "contact closure".

This fixture, as seen in the photos, contains a microcontroller and a couple "mux" boards for handling all the signals from two plug-in card cages. The TS1 fixture and card cages were mounted in a standard 19" rack cabinet. Each of the two card cages had a 33-conductor cable which plugs into the fixture - hence the pair of DB-37 female connectors seen in the top photo. These cables each handled 32 TS1 signals plus ground.

This device, as with the serial relay controller and the automated mouse movement emulator described in earlier blog posts, was controlled by a PC running LabVIEW software on Windows XP.

The box is an aluminum LMB enclosure; I used a dremmel tool to make the cut-outs for the DB-37 and DB-9 connectors, and a drill press for the round holes. The two large PCBs were made at an outside "board house", then populated by in-house assemblers. I mounted everything in the LMB enclosure and installed the chassis wiring. The smaller PCB - measuring about 2" x 2" - is the microcontroller board. The smallest PCB, connected to the microcontroller board via a ribbon cable, handles its RS-232 and power supply connections.

I built several of these fixtures for both engineering and manufacturing testing.

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