AVR Project – Relay Timer with ATmega8 AVR MCU

Timers are widely used in industrial and domestic application for automating tasks. Microcontrollers can be used to design versatile and accurate timers with ease. Here I present a simple timer that can be used to turn on/off a load after user specified time.
AVR Project – Relay Timer with ATmega8 AVR MCU
The Timer uses a standard 16×2 lcd module for user interface (UI). User can set the time using a 3 button keypad.
After that Timer is started. While count down is in progress, the time left is displayed on screen.
The program use our LCD driver library more details of which can be found in here. Use avr-gcc + AVR Studio to compile.
The prototype was developed using xBoard MINI, a low cost easy to use ATmega8 development board. The program was burned to the MCU’s flash memory using eXtreme Burner – AVR Software and Hardware. A basic knowledge of working with different tools of AVR development is required, so please refer to following articles.

Using the Timer

The user interacts with the timer using 3 push buttons and the LCD module. The function of 3 keys are :-

  1. Select Key – Select Different items like hour,minute and start. It moves the arrow on screen to indicate which option is currently selected.
  2. Up/Increase Key – Increase the value. For example, select “minute” using “select” key and press this to increase its value.
  3. Down/Decrease Key – Same as above but it decreases the value.

When the timer is powered up the load is in off state. A welcome message is shown. Then you can set the time using the above buttons. After that move to “start” option by using select key. Then press any key to start the timer. Now the screen shows the count down and the load is powered on. When count down reaches 0 the load is turned off. The pictures and videos below illustrate the process.
AVR Project – Relay Timer with ATmega8 AVR MCU  Schematic
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