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This is a simple project of Line Following Robot Sensor Circuit Diagram. This Line Following Robot sensor or surface scanner for robots is a very simple, stamp-sized, short range (5-10mm) Infrared proximity detector wired around a standard reflective opto-sensor CNY70(IC1). In some disciplines, a line following robot or an electronic toy vehicle go along a predrawn black line on a white surface. In such devices, a surface scanner, pointed at the surface is used to align the right track. IC1 contains an infrared LED and a phototransistor. The LED emit invisible infrared light on the track and the phototransistor works as a receiver. Usually, black colored surface reflects less light than white surface and more current will flow through the phototransistor when it is above a white surface. When a reflection is detected (IR light falls on the phototransistor) a current flows through R2 to ground which generates a voltage drop at the base of T1 to make it conduct. As a result, transistor T...

Description Private branch exchange This project is aimed to make the low cost intercom system by which eight telephone lines can be interfaced with this hardware. Main card: In this card there is 89c51 micro controller is used. Micro controller is controller the DTMF encoder MT8870 and the Analog switch MT8816. SLIC card: In this card there is constant current source is used to activate the telephone. The lm339 is used to detect the hand off and hand on condition. There is same circuit are repeated because we have to interface the 8 telephone. Summary: When the telephone is hand on the output of the lm339 change, it is detected by micro controller that the telephone is hand on, then micro controller is make the analog channel by using the MT8816. the LM555 is used to generate the dial tone.    Circuit diagram Click on Image And Zoom  Author : Ashad mustufa E-mail: mustufa66@hotmail.com Source : http://www.electronics-lab.com