Friday, December 3, 2010

Late Addition

I got an email late yesterday evening, requesting assistance for a rush update for the zombie project that would be shipping on Monday, according to what I was told earlier in the week. My customer had brought their customer in yesterday afternoon to inspect the system, and the end user asked for two additional relay outputs to indicate accept and reject conditions. While this wasn't a complicated addition at this late date (I've seen far worse), if anything can go wrong, it usually does, so I arranged my day accordingly, expecting to working late tonight.

In the end, it actually went a lot smoother than I expected and was home by 19:30. Most of the time for the additional wiring was spent figuring out the simplest way to do it. The software changes were simple but they triggered an discovered bug, which had me scratching my head for awhile, but it wasn't too difficult to fix. Wish that were true more often.

My customer was surprised when I suggested we buffer the outputs with real relays instead of directly using the digital output. The output is rated to 2A but it is a current source, not dry contact which is what most automation people expect. Also, 2A may sound reasonable but in the industrial automation world it's actually puny. I've seen a simple indicator lamp draw more current than that (yeah, it was bright ^_^). Better safe than sorry.

And so ends another busy week. None of the work involves any long term projects so it won't last much longer, unfortunately.

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