This infrared object counter can be installed on the front door to count the total number of people entering any place. For example, it can be used at train stations or at bus stations to count people arriving by day or week.
The meter uses a pair of infrared transceiver and a simple and inexpensive calculator. It works even in the presence of normal light. The maximum detection range is about 10 meters. This means that the transmitter and the receiver must be installed (on opposite pillars of the door) not more than 10 meters away. No focusing lens is required. If an 8-digit calculator is used, the counter can count up to 99,999,999 easily, and if a 10-digit calculator is used, the counter can count up to 9,999,999,999.
Powered by a 9V battery, the transmitter circuit (see Figure 1) comprises IC 555 (IC1), which is wired as an astable multivibrator with a center frequency of approximately 38 kHz and two infrared (LED) light emitting diodes (LEDs). The receiver circuit (see Figure 2) is powered by a 5 V regulated power supply, built around transformer X1, bridge rectifier comprising diodes D1 to D4 and regulator IC2. It uses an infrared receiver (IR) module (RX1), optocoupler (IC3) and a simple calculator.
When the switch S1 is in the 'on' position, the transmitter circuit is activated to produce a square wave at its output terminal 3. The two infrared LEDs (IR LED1 and IR LED2) connected to its output transmit modulated IR rays thereto frequency (38 kHz). The oscillator frequency can be adjusted using the preset VR1.
In the receiver circuit, the TSOP1738 IR receiver module is used as the sensor, which is commonly used in color televisions to detect the IR signals transmitted from the television remote control.
The IR-transmitted IR beams LED1 and LED2 fall on the infrared receiver module RX1 of the receiver circuit to produce a low output on its pin 2. This keeps the transistor T1 in non-conducting mode.
Now, when someone enters through the gate to interrupt the IR beam, the receiver module IR produces a high output pulse on its pin 3. As a result, transistor T1 leads to activate IC3 and its internal transistor cuts the key '= 'Of the calculator to advance the count by one.
Both the transmitter and the receiver can be mounted on any general purpose PCB. Place the transmitter and receiver about one meter away.
For calibration, press switches S1 and S2 followed by the 'on' key on the calculator. Now press the '1' and '+' keys sequentially to get '1' on the calculator screen. Then place a piece of cardboard between the transmitter and the receiver to interrupt the IR rays twice. If the calculator counts '2', the counter is working correctly for that range. Repeat this procedure for higher ranges as well. If there is a problem, set VR1.
For installation, turn off the transmitter, receiver, and calculator, and mount the transmitter and receiver on the opposing pillars of the main entrance door so that they are facing each other correctly. Mount the calculator where you can easily read it. Connect IC3 pins 4 and 5 through the '=' key connections on the PCB of the calculator.
Now turn on the transmitter and receiver by pressing switches S1 and S2, respectively. Then turn on the calculator and press '1' followed by the '+' key on the calculator to initialize it. Now your accountant is ready to count.
The calculator reads '1' after an interrupt, '2' after the second interrupt and so on.
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