Sunday, August 14, 2016

Crash, Burn, Rebuild Air Conditioning Control

Remember when I rebuilt the air conditioner thermostat in the farm kitchen / fermenting room? Well.. yea...  sometimes things dont work out so well.. that one  sort of.. exploded.

The mistake was.. while the relays inside the temperature controller were large enough to handle the load, the actual connectors are not. After running flawlessly for a few months, one of the connectors overheated and the eventual result was... disaster.

So yesterday after deliveries I rebuilt the controller into a more robust unit... another  temperature controller just like before but  I added optoisolators to handle the compressor / heater load.  Should work beautifully. The whole thing is mounted inside a plastic storage bucket for safety (with ventilation holes cut in the sides).

Completed unit, installed and running

Here is a top view, you can see the two optoisolators, one on the left and one on the right. one does cooling and one heat.

side view showing hte heat sinks on the optoisolators. you can also see the vent holes up the side.

Here is the fancy schematic (hand drawing) of the wiring.

This is a gret temperature controller for projects, capable, cheap, accurate. 

And.. last years model after the accident

As you can see, the connector on the right end overheated and melted, shorting out he unit and blowing the fuse. 

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