At work, I recently moved into a new building, and, for some unknown reason, the regulation of air conditioning has never been working correctly. We have the choice between switching it OFF, and work in an oven at 30°, or turn it ON and see the temperature quickly falling below 18 ° C, regardless of the temperature selection. Fortunately, we have a remote controller that allows us to turn it on and off at will. As a result, we spend our day playing with the controller, trying to keep temperature within a reasonable range. Not ideal in terms of productivity, and also not a really healthy condition when temperature rise and fall of + – 5 ° C every 30 minutes.
As no one seems to be able to solve this problem, I ended up with an ugly but yet effective Do It Myself solution. I’ve put a new layer of hardware to override the failing AC software.
I use an Arduino to monitor temperature and activate a servo motor, tapped on the remote. It does the jobs of pushing the ON / OFF button in my place when needed.
At first, I was willing to develop a PC based electronic, but instead, I decided It would make a perfect first arduino project. And I totally fall in love with this board. The probe is a DS18b21 from Dallas, a potentiometer allows adjustment of the setpoint temperature, and a standard 2×16 LCD display controlled by 4 bits interface gives the feedback. As libraries were available for all components, the software did not take me over an hour to develop.
Despite of the ugly wiring on the breadboard, the system as been doing a very good job for several seems beginning of the summer, maintaining the temperature between 25.5 and office 26.5 ° C. The main downside is the sound of the relay and the beep of the AC every 5 minutes when the system switches ON or OFF.