Summary of Microwave Controller using ATmega8 – AVR Project
This article details a microwave and grill timer project built around an ATmega8 AVR microcontroller. The system features a 16×2 LCD for output, a buzzer for status alerts, and a seven-button keypad for user input. It utilizes two relays to control power for the microwave and grill functions independently. The hardware relies on a 5V regulated power supply derived from a 12V adapter, along with an ISP header for programming and a reset circuit for stable operation.
Parts used in the Microwave Timer:
- 16×2 alphanumeric LCD Module
- Buzzer
- Seven-button Keypad
- Microwave Relay
- Grill Relay
- ATmega8 AVR Microcontroller
- 5V Regulated DC Power Supply
- 12V Adapter
- ISP Header
- Reset Circuit (Pull up resistor)
The user interface has the following parts.
Output Device: A 16×2 alphanumeric LCD Module is used as the main output device. It can display numbers, alphabets and few symbols. It can show two line and each line can have 16 characters. The backlight enables the text to be visible even in dark.
A buzzer beeps when the system receive input from the user and the input is successfully processed. For example if the user presses 10 MIN button to increment timer by 10 min and this is successfully carried out the buzzer beeps. But if the timer is already at the maximum setting (90 minutes) the operation could be carried out, so the buzzer does not beeps.
This buzzer also beeps a few time when the food is ready (countdown is finished)
Input Device: Input from user is received by a keypad which has seven push buttons. The details of button is given below.
| Button | Function |
| Microwave | Selects Microwave mode. |
| Grill | Selects Grill mode. |
| 10 MIN | Increment timer by 10 minutes. |
| MIN | Increment timer by 1 minute. |
| 10 SEC | Increment timer by 1 sec. |
| STOP/Clear |
|
| START |
|
Controlling Relays
Their are two controlling relay
- The microwave relay: this controls power to the microwave function.
- The grill relay: this controls the power to the grill function.
Using the Microwave Timer
The first screen of timer asks you to choose one of the operating modes. You can choose from Microwave or Grill functions. Press the respective button on the keypad to choose the mode.
Hardware for Microwave Timer
The timer is built around ATmega8 AVR microcontroller. This is a very small single chip computer which runs a small program stored in its flash memory. This program provides all the functionalities of the timer.
Our microcontroller controls the LCD Module, the relays and the buzzer. It receives user input from the keypad.
MCU Core
Microcontroller chip requires a basic circuitry for functioning. This consists of the following parts.
- Power supply: This provides 5v regulated DC power to the microcontroller. It receives input 12V DC from a 12V adapter.
- ISP Header: In circuit programming header. Used to easily connect an ISP Programmer to upload programs to the Microcontroller.
- Reset Circuit: A pull up resistor holds the RESET pin of MCU to high state. This is required for normal operation.
For more detail: Microwave Controller using ATmega8 – AVR Project
- What is the main output device used?
A 16×2 alphanumeric LCD Module is used as the main output device. - How many push buttons are on the keypad?
The keypad has seven push buttons. - When does the buzzer beep?
The buzzer beeps when input is successfully processed or when the countdown finishes. - What happens if the timer is at maximum setting?
If the timer is already at 90 minutes, the buzzer does not beep even if the increment operation is carried out. - Which component controls the power to the microwave function?
The microwave relay controls the power to the microwave function. - What voltage does the microcontroller require?
The microcontroller requires 5v regulated DC power. - What is the purpose of the ISP Header?
The ISP Header is used to easily connect an ISP Programmer to upload programs to the Microcontroller. - How do you resume a paused timer?
You press the START button to resume the timer after pausing it.
