Digital Count Down Timer using PIC Microcontroller




In this article, our author Mithun has developed a 0 – 99 min counter using PIC microcontroller 16F628A. So basically this is a digital count down timer ideal for engineering and diploma students for their project requirements. We have given complete circuit diagram of the digital count down timer along with full source code. In addition, photographs of the breadboard setup is uploaded.

diagram1

Every micro controller has a timer unit inside. A timer is nothing more than a time counting device fabricated inside the micro controller unit. A wide range of practical applications require a timer in action. For example, we need to turn a motor ON for 5 minutes and then turn it OFF as part of a particular project; how will we do that? A timer inside a mircocontroller unit aids us in implementing this perfectly. A timer can be used to count the 5 minutes exactly and the bits that get SET at 5 minutes limit can be used to program the controller to turn OFF some device(s).

I hope you got a basic idea about timer unit and its practical applications. We are going to make this project using an LCD display, PIC controller 16F628A and a 4 MHz external crystal to provide the necessary clock. We will be writing the codes using micro C.

In any project that involves an LCD, the first step is to initialize the LCD module. We have written detailed articles about interfacing LCD to an MCU before. You can learn more about Interfacing an LCD to 8051  and Interfacing LCD module to AVR controller in these articles. If you want to learn more about character LCD displays in detail, this tutorial on Character LC

D displays will be of help.

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Now, we need to configure relay and switches. The code snippet for the same is given below.

002

 

Here ‘sbit’ stands for set bit. You can do the same another way using “#define” command. This line means that  RA3 pin will be known as the Relay/ RB0 pin will be known as SS_Select etc.

Even though the project name “digital count down timer” sounds so silly, its operation is not that simple. We have given below a proteus diagram of the circuit to explain the project perfectly.

Analyzing the circuit diagram, you can see three buttons . One button is for Start/Stop function and the other 2 buttons for Units & Tens counting. We will configure our LCD module with display messages corresponding to the button configurations.

 

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