IR Digital Thermostat for FAN

Posted on Feb 6, 2014

Another feature of this circuit is that you can use the keys `1, 2, 3, 4` of a Philips TV IR remote to turn on or off three relays, The key `4` is used to turn on or off the over temperature alarm. package. LM35 can sense temperature from 0 C to 100 C but it gives analogue output the microcontroller does not understand analogue data, so ADC0804 (anal

IR Digital Thermostat for FAN
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ogue to digital converter) is used to convert it to digital form. This digital data is given to port 1 of microcontroller. (See the circuit diagram) this data is processed by microcontroller and temperature is displayed on lcd connected to port 2. The control pins of lcd are connected to port 0. port 0 also controls the relays and alarm. The ULN2003 chip is used to drive the relays because the microcontroller pins don`t have enough current to drive them. so relays cant be connected to microcontroller pins directly further more the relays are inductive load and reverse current is generated in them. Pin 1 to 7 are the inputs and 10to 16 are respective outputs. Pin 8 is ground and pin 9 is connected to the output of 7808 voltage regulator. The 7805 voltage regulator drives rest of the circuit. I used a standard buzzer driven by LM555 timer/Oscillator chip. The chip is wired as a monostable multivibrator and at its output (i. e. pin no 3) a buzzer is connected. Use any IR module and connect its Data out to pin 10 of microcontroller. The Relay connected to pin 13 of ULN2003 turns on when temp rises above 40 C so connect the fan to this relay. Use a standard pcb. A pcb file is included in the zip file it opens with a software called EAGLE You can download the demo version here its quiet simple and easy to use. So print the pcb on a glossy paper. now place the glossy paper on the pcb. The print should be on the copper side now use...

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