INFRARED INTERRUPTION COUNTER USING MICROCONTROLLER AT89C2051

              In today’s world, there is a continuous need for automatic appliances with the increase in standard of living; there is a sense of urgency for developing circuits that would ease the complexity of life.Infrared interruption counter is a reliable circuit that takes over the task of counting number of interruptions very accurately. When somebody enters into the room, then the Counter is Incremented by one. The total number of Persons inside the Room is displayed on the seven segment displays. The microcontroller does the above job it receives the signals from the sensors, and this signals operated under the control of software which is stored in ROM.

The microcontroller receives the signals from the sensors, and this signal is operated under the control of software which is stored in ROM. Microcontroller AT89C2051 continuously monitor the Infrared Receivers, When any object pass through the IR Receiver's then the IR Rays falling on the receiver are obstructed , this obstruction is sensed by the Microcontroller. The buzzer will produce beep sound on every interruption.

Block diagram

Transmission circuit

                            This circuit diagram shows how a 555 timer IC is configured to function as a basic monostable multivibrator.  A monostable multivibrator is a timing circuit that changes state once triggered, but returns to its original state after a certain time delay.  It got its name from the fact that only one of its output states is stable.  It is also known as a 'one-shot'.

In this circuit, a negative pulse applied at pin 2 triggers an internal flip-flop that turns off pin 7's discharge transistor, allowing C1 to charge up through R1. At the same time, the flip-flop brings the output (pin 3) level to 'high'.  When capacitor C1 as charged up to about 2/3 Vcc, the flip-flop is triggered once again, this time making the pin 3 output 'low' and turning on pin 7's discharge transistor, which discharges C1 to ground. This circuit, in effect, produces a pulse at pin 3 whose width t is just the product of R1 and C1, i.e., t=R1C1.

Receiver circuit

                       The IR transmitter will emit modulated 38 kHz IR signal and at the receiver we use TSOP1738 (Infrared Sensor). The output goes high when the there is an interruption and it return back to low after the time period determined by the capacitor and resistor in the circuit. I.e. around 1 second. CL100 is to trigger the IC555 which is configured as monostable multivibrator. Input is given to the Port 1 of the microcontroller. Port 0 is used for the 7-Segment display purpose. 

List of components

 Microcontroller – AT89C2051

 IC – 7805

 Sensor – TSOP 1738 (Infrared Sensor)

 Transformer – 12-0-12, 500 mA

 Preset – 4.7K

 Disc capacitor – 104,33pF

    

 Reset button switch

 Rectifier diode – IN4148

 Transistor – BC 547, CL 100

 7-Segment Display

Flow chart description

  If the sensor 1 is interrupted first then the microcontroller will look for the sensor 2.And if it is interrupted then the microcontroller will increment the count

  If the sensor 2 is interrupted first then the microcontroller will look for the sensor 1. And if it is interrupted then the microcontroller will decrement the count.