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Tuesday, June 3, 2014

Fixed False Positives on HESA

Lately, I've been having a lot of false positives from the Home Environmental Sensor Array.  I finally decided to investigate the problem.

First, I thought that maybe there was some current in the enclosure itself.  So, I found an old power cord and used the ground wire to connect the enclosure to the ground screw on a nearby power outlet.  That would probably not pass code but I think it is effective.  However, that did not solve the problem.  The program running on the raspberry pi kept immediately detecting a circuit and shutting off the power.

Next, I thought that the connectors I used for the external wires were touching the metal of the enclosure and closing the circuit.  So, I removed the connectors from the case and just let the wires hang.  That did not solve the problem.

Finally, I disconnected the external cable.  This time, the program did NOT detect electricity.  I suspected the external cable.  I re-connected the external cable to the circuit and the program immediately detected electricity and shut off the power.

Short-story-long, the external cable has some kind of short in it.  Maybe some water got inside the plug.

I found an unused length of electrical cable for a lamp and connected it as the external cable for the HESA.  Now, it goes for days without any false positives.

The lesson is that I need a better detection cable.