Initial Climate Controller Circuit

The idea for the climate controller was born out of frustration with the "thermostats" on automatic space heaters, which are really just a bunch of trash. Here are some problems:

  • The thermo sensor is close to the heater; I am usually not, especially if it is in my room. So, if I want it to be 70 degrees in the room, the heater may shut off when it is 70 near the heater.
  • I like to sleep in cooler temperatures, and would prefer it be warm when I get up. The timers on some space heaters either just turn them on, or will run them for some set period of time.

Long story short, I was inspired to buy a bunch of random parts and start hacking together some sort of Arduino Controlled Climate Manager. The device would take inputs of time, temperature, and humidity. The Arduino would crunch this data and some settings to determine if two relays should be on or off; one controlling a plug for a space heater, the other controlling a plug for a small humidifier. I'd also ideally like to use the humidifier's low water light to feedback into the system, or in some future iteration, trigger a little solenoid to refill it.

A basic sketch:

a basic sketch of the concept

Then, I ordered a bunch of parts; one of which was this cool, little, board mountable power adapter. I can send some 120V in and it will step it down and regulate it to the DC voltage I need to power the controller circuit. (RAC02-O9SC)

RAC02-O9SC power adapter block

The remainder of the key parts included a temperature/humidity sensor, an Arduino Uno, the LCD shield kit (for the user interface) and two relay kits (to control the switched devices):

arduino and lcd shield

one of the relay kits

Not pictured are power plugs and USB "pig-tail", plus the enclosure and various build materials.

Designing a Main Board

The plan is to enclose this in a little project box and 3D print the front and back panels to account for the various panel mount items; then provide springy push buttons to hit the micro switches on the LCD shield.

The relays came in kit form with their own little boards, and along with the power block, it seemed appropriate to make a single circuit board to contain all the components (plus, I really like etching my own boards). Additionally, the LCD break out shield can be attached to the Arduino with ribbon cable, and finally, I'll probably mount the Arduino itself onto the board as a shield of some sort, so everything is neat and tidy.

Depending on how things progress, I may even pull off most of the LCD kit parts on the the board as well, and run wire to the front panel.

The first order of business was duplicating the stock relay circuit and doubling it. I then created a part diagram for the little power block and added that to the schematic along with the recommended 330uF filter capacitor from the RAC02-09SC datasheet.

the start of the schematic

Next up will be finishing out the circuit design and planning out the PCB layers and routing. I'll be etching it at home along with some UV hardening solder mask.

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