Picture of Arduino controlled room heating system

The first thing that came to my mind when I started micro-controller programming was to set an automatic room heating cum humidifier system. Bangalore has a very confusing weather - especially for new-comers. The temperature is generally moderate, but nights can sometimes become very cold. However, on other days, the nights are warm and if you have a heater on - it becomes uncomfortable. Also, since the weather is generally moderate - automatic heating solutions are not available commercially.

Hence, one of the first projects I made on an arduino was a temperature and humidity controller.


  1. Controls a 2-relay board - one for a room heater and one for a humidifier.
  2. Checks the temperature and humidity every 10 minutes - this can be set in the code
  3. The algorithm is very simple - Switch off the heater if the temperature goes 1 degree above the set-point and switch it on again if it goes below the set-point. This is similar to most commercial systems.
  4. The humidifier gets switched on if the humidity is below 40% and gets switched off if it goes above 60%.
  5. Uses the EEPROM to save the preset
  6. Has one button that is used to change the preset - single click to increase the temperature by 1 degree, long press to decrease the temperature by 1 degree. The temperature circles between 25 and 30 degree centigrade.
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Step 1: Electronics

Picture of Electronics
  1. Atmega 328P-PU (without bootloader)
  2. 16 MHz Crystal
  3. 2 x 22 pf capacitors
  4. LM 7805
  5. 1 uF + 10uF Electrolytic capacitors
  6. 10k Resistor
  7. DHT11 Breakout Board or similar (
  8. 2 Channel Relay Board
  9. 1 push-button switch
  10. 16x2 character LCD
  11. 10k pot
  12. 9-12V 1Amp power supply
  13. Extension cord
  14. Wires
  15. General purpose PCB

Instructions for creating and using a "standalone arduino" can be found at


vrocks9 months ago

are all these components available in lamington road (Mumbai) ???

i intend to make same one for my mini project ... :)

dushu (author)  vrocks9 months ago

Not sure about Mumbai - but since I got everything in SP Road, Bangalore - I would assume that you should be able to get everything there. Otherwise try - they're mumbai based and deliver stuff. Have used them many times.

Awesome job! It's so useful for places with huge temperature fluctuations.

dushu (author)  Danger is my middle name9 months ago

Thanks :-)