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.

Step 1: 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 (http://cgi.ebay.in/ws/eBayISAPI.dll?ViewItem&item=...)
  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 http://dushyant.ahuja.ws/2013/10/standalone-arduin...

<p>are all these components available in lamington road (Mumbai) ???</p><p>i intend to make same one for my mini project ... :)</p>
<p>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 evelta.com - they're mumbai based and deliver stuff. Have used them many times.</p>
<p>Awesome job! It's so useful for places with huge temperature fluctuations.</p>
<p>Thanks :-)</p>

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