15-11-2014, 10:30 AM
Abstracts: As the name implies, what makes this device special, is that it can measure the rotational speed of a shaft without even touching it. This is very interesting when making direct contact with the rotating shaft is not an option or will reduce the velocity of the shaft, giving faulty readings. This device is built on an P89V51RD2 microcontroller, an alpha-numeric LCD module and a slotted opto isolator (MOC7811) to detect the rotation of the shaft whose speed is being measured. The new system attached with this project helps to control the speed according to the value entered using the key pad. The current speed of this system will display on the LCD. The speed of the DC motor is controlled using PWM technique. An H bridge is attached to this system can drives the DC motor. The idea behind most digital counting device, frequency meters and tachometers, is a micro-controller, used to count the pulses coming from a sensor or any other electronic device. In the case of this tachometer, the counted pulses will come from slotted opto isolator (MOC7811), which will detect any reflective element passing in front of it, and thus, will give an output pulse for each and every rotation of the shaft, as show in the picture. Those pulses will be fed to the microcontroller and counted. Here we are controlling speed, orientation and on/off of a dc motor using finger tips. When a switch in keypad interfaced with microcontroller is pressed ,it will make the control of the dc motor. The dc motor is controlled by the microcontroller using a dc driver circuit. The aim of development of this project is towards providing efficient and simple method for control speed of DC motor using pulse width modulation technique. The modulation of pulse width is obtained using microcontroller. There are several methods for controlling the speed of DC motors. The PWM based chopper circuit smoothly controls the speed of general purpose DC motors. To get desired modulation of pulse width as output, we have writer program in microcontroller according to the key being pressed. Here we are using a 12v DC Motor for controlling the speed and with a driver circuit using TIP transistors a DC motor of ratings up to 2 Amperes can be controlled. .