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  • PIC18F4620 MAX ->Matrix

  • Created: Feb 16, 2017

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This project is a simple countdown timer, which uses PIC12F683 microcontroller from Microchip Technology as the main controller. Also, this design utilizes MAX7219 for serial interface as well as an LED display driver. This countdown timer features a buzzer as an alarm and a 4-digit 7-segment display. The timeout condition is indicated by an audible alarm from a buzzer.

The timer is controlled through the two pushbutton switches (ADJUST, SET) . The ADJUST switch is used to set the timer, while the SET switch will start the countdown. These switches are both connected to GP4/AN3 pin, which is an ADC channel of PIC12F683 microcontroller. When pressed, these two switches give different analog voltages. When ADJUST switch is pressed, the input voltage to GP4 pin is 0V. When SET switch is pressed, the input to GP4 pin will be around 2.5V because of the voltage divider network composed of two 4.7kΩ resistors. If none of the switches are pressed, the ADC input is pulled up close to 5V. Therefore, based on the value of 10-bit ADC count, it is possible to detect and identify if any of the two switches is pressed. The buzzer is driven by a PWM signal generated at the GP2 output pin of PIC12F683. The display uses a 4-digit seven segment LED module which is driven by the MAX7219 IC.

In this design, the choice of using the PIC12F microcontroller is quite considerable because the PIC12F microcontrollers are handy 8-pin devices. This family of PIC microcontrollers are designed for small embedded applications that do not need many I/O pins. In this countdown timer wherein only few I/O pins are required, PIC12F683 is a good choice among other PIC microcontrollers.



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