08/28/2014 22:52
PIC12F675 is a fully functional 8 bit micro controller in eight pin package. The PIC12F family is very similar to microchip popular PIC16F devices and with the same instruction sets. The PIC12F675 is featured with a internal 4 MHz oscillator factory calibrated with in ±1%, six i/o pins and other peripherals like timers, ADC module etc.
PIC12F675 and few more components are used to make this project. BT136 – 600D is logic level triac from NXP semiconductors® are intended for general purpose bidirectional switching and phase control applications. These devices are designed to directly interfaced with microcontroller or low power gate trigger circuits. The device can be trigger in all four quadrants but it is better to avoid the fourth quadrant which has higher gate trigger and latch currents. This circuit used quadrant two and three to trigger the triac which can handle a load current up to a maximum of 4A.
The remote control has a total 21 keys, and the keys “0 to 9” are used to control fan speed, “0” will be turn off the fan. The key “CH-” can also be used to turn off, while the key “CH+” is to turn on. The +/- buttons can also used to increase/decrease fan speed respectively. The previous/next keys are used to increase/decrease time respectively with one hour step, and a maximum of 8 hour can be set. The timer will be disabled when the time decremented to zero. The timer can be turned on/off using the “PLAY”/“EQ” keys in the remote, and it will be disabled automatically when it reaches the set value (i.e. when the fan turned off by the timer). No timer adjustments are possible, if the fan is not running. The eeprom also store the time values, so when enabled it starts with the last value. The timer is enabled while pressing previous/next in the remote, it will not change the time value for the first time. The two push buttons (SW1 and SW2) can also used to increase/decrease fan speed.
The LED is lit while it accepts the commands from the remote control. It also used to display the remaining time if the timer is running. The number of blinks represent the remaining time, and it repeats in every six seconds.
Circuit Diagram:
The PCB is designed with Eagle software can be used to build the project. The circuit, pcbs and hex file for programming PIC12F675 are available in the download link . Please take care not to erase the internal oscillator calibration constant, which is written to the last location program memory. The Microchip® Development Tools maintain all calibration bits to factory settings, or if you are using IC-Prog, it will ask you before erasing.
The circuit can be tested with a 12V AC (instead of 230V AC) supply from a transformer, and connecting a 10 Ohm, 0.5W resistor parallel to the capacitor C6. The output (i.e. between 'N' and 'Hot out') may connected to a LED through a 1.2k resistor, instead of fan. Now use remote or keys to test the circuit functions, like speed (LED brightness will change), timer etc. After testing you can put the circuit in actual situation, but please remember to remove the 10 Ohm resistor.
password for rar: subham's electronics cw$24
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