How to Build a Simple Countdown Timer Using the PIC16F84 Microcontroller

schema March 28, 2013

How to Build a Simple Countdown Timer Using the PIC16F84 Microcontroller

If you're just stepping into the world of microcontrollers, here's a perfect project to get your hands dirty: a countdown timer based entirely on the legendary PIC16F84. No extra timer ICs, just the microcontroller doing all the logic. Simple, educational, and—yes—it really works. And if you're anything like me, it might just save your pizza from burning in the oven!

🧠 What Is This Project All About?

This timer project allows you to set a countdown between 1 and 29 minutes. It uses two 7-segment displays—one for tens, one for units. Once you press a button to set your desired time, you hit another button to start the countdown. Every minute, the timer subtracts one unit until it reaches 0, at which point it triggers a beep to let you know time’s up.

Simple? Yes. Effective? Definitely.

🔧 Components Needed:

1 x PIC16F84 microcontroller
2 x 7-segment displays
2 x Push buttons
1 x Potentiometer (for sound control)
1 x Buzzer
Passive components (resistors, capacitors, etc.)
Power supply (5V)
Breadboard or PCB

⚙️ How It Works:

Button 1 (PORTA.2): Starts or resets the countdown.
Button 2 (PORTA.4): Adds 1 to the counter (only before countdown starts).
Potentiometer: Adjusts the buzzer's volume.
7-Segment Displays: Show countdown value from 1 to 29. Clever wiring lets four shared pins display the “2” digit properly.

Everything is managed by the PIC16F84, including time tracking, display updates, and output control. The microcontroller uses internal logic loops to mimic a 1-minute delay (or you can improve it using accurate timer interrupts if needed).

💡 Why This Project Is Great for Beginners

Teaches you how to interface with 7-segment displays.
Introduces basic programming logic for timers.
Helps you understand how buttons, delays, and loops work in microcontroller environments.
Doesn’t require complex hardware.
Bonus: You get a working kitchen timer by the end!

📘 Tips for Improvement

Use crystal oscillator for more accurate timing.
Implement interrupt-based timer logic for better precision.
Add EEPROM saving to remember the last selected time even after reset.
Upgrade to LCD display for fancier visuals.

📂 Final Thoughts

Building a timer using a PIC16F84 isn't just about managing time. It’s about learning how microcontrollers think and behave, one instruction at a time. This project is a great launchpad for further adventures into embedded systems.

And hey—if you save a pizza or two in the process, that’s just icing on the cake... or cheese on the crust. 🍕

Would you like me to also generate a schematic diagram image or the assembly code (hex file) for this timer?