00 to 99 minute timer using PIC16F628A microcontroller

Posted on Feb 6, 2014

A source code for a very simple PIC based digital timer. The actual hardware of the project isn`t with me anymore. I will rather demonstrate it using my DIY PIC16F628A breadboard module and I/O board. The complete circuit diagram along with the firmware developed using mikroC Pro for PIC compiler is provided in the article. As I mentioned earlier, the microcontroller used in this project is PIC16F628A running

00 to 99 minute timer using PIC16F628A microcontroller
Click here to download the full size of the above Circuit.

at 4. 0 MHz clock using an external crystal. An HD44780 based 16G—2 character LCD is the main display unit of the project where you can watch and set the timer duration using tact switch inputs. There are three tact switches connected to RB0 (Start/Stop), RB1 (Unit), and RB2 (Ten) pins. You can select the timer interval from 0-99 min using Unit and Ten minute switches. The Start/Stop switch is for toggling the timer ON and OFF. When the timer gets ON, a logic high signal appears on the RA3 pin, which can be used to switch on a Relay. The circuit diagram of this project is described below. I am using my self-made breadboard module for PIC16F628A and experimenter`s I/O board here to demonstrate this project. Since there is no relay switch in the I/O board, I am connecting the timer output (pin RA3) to an LED. When the timer starts, the LED is turned ON. As the timer duration is elapsed, the LED is turned OFF. When the device is powered ON, the microcontroller initializes the LCD display and shows the following message. The timer is initially OFF and so does the LED or relay, whichever is connected to RA3 pin. You can set time duration between 00-99 min (in step of 1 min) using the Unit and Ten tact switches. Each switch press will increment the corresponding time digit. When the desired time is set, press the Start/Stop switch to turn ON the timer. The RA3 pin goes high (LED glows) and the count down begins. When the timer is...

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