In continuation of the embedded control applications explained in Part 2, letís now examine the use of inbuilt functions of AVR ATmega8535 (such as output compare, ADC and UART) for various applications.
A tachometer is nothing but a simple electronic digital transducer. Normally, it is used for measuring the speed of a rotating shaft. The number of revolutions per minute (rpm) is valuable information for understanding any rotational system. For example, there is an optimum speed for drilling a particular-size hole in a particular metal piece; there is an ideal sanding disk speed that depends on the material being finished. You may also want to measure the speed of fans you use.
Here is an easy-to-construct temperature indicator-cum-controller that can be interfaced with a heater coil to maintain the ambient room temperature. The controller is based on Atmega8535 microcontroller, which makes it dynamic and faster, and uses an LCD module to display and two keys to increase or decrease the set values.
Electronic systems today incorporate a number of peripheral ICs that have to communicate with each other and the outside world. To maximise hardware efficiencyand simplify circuit design, Philips developed a simple bidirectional two-wire communication interface between components residing on the same circuit board. This interface is referred to as two-wire interface (TWI) or I2C (inter-integrated circuit).
Communication with remotely located automation systems is possible via the Internet. A physical communication port with a network is required for this communication. An Ethernet interface can be used for that purpose.
The AVR 8535 microcontroller and its new version ATmega8535 are versatile, high-performance but low-cost chips. This article series covers typical applications of this processor illustrating its power and cost-effectiveness in an embedded system.
In the first part of this article, we had described the main features of the AVR microcontroller and the hardware/software required for an AT-PROG programmer board interfaced to the printer port of a PC. Further, we explained the methods for message display on a liquid crystal display (LCD).
Digital wall clocks, table clocks and desk clocks with pointer or LCD display are readily available in the market. Here we present a clock that can be built in a small budget using AT89C2051 microcontroller. Additional feature of the clock is that the time display is visible even in the dark.
Here we describe a microcontroller-based dynamic display system using LED strip that can be used for advertising message display. The display works by flashing characters sequentially and then the entire text together.
A time-controlled switch is an automatic timer switch that turns an appliance ‘on’ for the desired time duration. After the preset time duration, the timer automatically switches off, disconnecting the appliance from the power supply.
Radio-frequency identification (RFID) is an automatic identification method wherein the data stored on RFID tags or transponders is remotely retrieved. The RFID tag is a device that can be attached to or incorporated into a product, animal or person for identification and tracking using radio waves.
This is a iBUTTON based secured system that uses a microcontroller. Whenever someone touches the iBUTTON using his own iBUTTON, the firmware inside AVR reads its unique ID and relay operates which in turn opens up the door.
The circuit that uses microcontroller AT89C51 can control four devices from a distance of upto 30 metres wirelessly. An LCD module is used to show the device number and preset control time at the transmitter module.
This is a circuit for a remote controlled 6 camera CCTV switcher that uses microcontroller, infrared module and other components to control the operation of 6 CCTV cameras. Controlling messages can be seen on a LCD module.
This circuit lets you operate your home appliances such as lights and water pump from your office or any remote location. The system also gives you voice acknowledgement of the appliance's status. It comprises microcontroller AT89C51, DTMF decoder MT8870, voice recording/ playback device APR9600.
This circuit uses a sensor for detecting a coin and a microcontroller that counts the coin and shows the count on 7-segment display. Once load switch is closed, a counter is initiated and power is given to the load until the counter decrements to zero.
This circuit controls a DC motor and can operate it in continuous, reversible or jogging mode in either direction. The speed of the motor, start up, stopping as well as time setting for forward and reverse running of motor can be set. A message is displayed on the LCD module to indicate the status of the motor.
This is a circuit for a microcontroller-based water level controller that turns the motor on/ off depending on the water level in the tank. The motor is turned off when voltage fluctuations or dry run occur.
This is a circuit for a microcontroller-based security system that can restrict access to a specific area. Only authorised persons are allowed to enter the area. The system locks out in case of brute forcing passwords and can be unlocked only by the Master User.