Tag Archives: relay

AVR

AVR Project – Relay Timer with ATmega8 AVR MCU

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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.

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. Continue reading AVR Project – Relay Timer with ATmega8 AVR MCU →

AVR

Drive relay with AVR microcontroller

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To drive relay you need more than 20mA – the current can one pin drive. This is why you cannot connect relay directly to microcontrollers pin. To drive relay you need to connect simple amplifier made of one transistor.

Drive relay with AVR microcontroller

One important part of this circuit is the diode, which protects circuit from induction caused when switching relay.

This circuit is more general as instead relay you can connect any other load like lamps, DC motors if you need to control more than one relay, you might consider using ICs like ULN2003 or ULN2803. These ICs have Darlington transistors inside and can drive up to 500mA each.

iDrive relay with AVR microcontroller using ULN2003A

To switch on a relay in this case you need simply write ‘1’ to port pin. And current doesn’t exceed the allowed limit of microcontroller.

Sumber: https://www.scienceprog.com/drive-relay-with-avr-microcontroller/