Door Sensor With Counter




Introduction: Door Sensor With Counter

About: An electronics guy

This circuit consists of ldr which senses the light fron led fixed at the opposite side of the door.The seven segment display displays the no of interuptions in the led to ldr path.


1. IC LM324N (1 pc)

2. IC 7404 (1 pc)

3. 10 Kohm potentiometer (1 pc)

4. IC CD4026/33 (2 pc)

5. 7 segment display(Common Cathode) (2 pc)

6. 12V DC Source

7. Bread board (1 pc)

8. Connecting wires

9. Buzzer (1 pc)

10. LED (1 pc)

11. LDR(Light Dependent Resistor) (1 pc)

12. 10Kohm (1 pc), 100Kohm (1 pc), 270ohm (2 pc) resistors



CD4026/33 with 7 segment display

This circuit can be used in various projects where we require the counting. Like in doctors’ clinic or hospitals, in restaurants, in customer care offices where long queue is there and we want to stop the rush at the counter. This system is very effective where man power is less. In this you have to provide a token to the person and the person has to wait for its turn which can be displayed on the 7 segment display. With the help of this counter circuit we can maintain the silence and the person will also be informed about their turn.

This circuit is based on 4026, a Johnson counter IC commonly used in digital display. It has a 5 stage Johnson decade counter with decoder which convert the Johnson code to a 7 segment decoded output. This means it will convert the input into numeric display which can be seen on 7 segment display. It can be used for displaying analogue value, such as temperature with pic microcontroller, used for counting objects. It can be used in various applications like in 7 segment decimal display circuit, in clocks, timer etc. Advantage of 4026 counter-

* It contains counter and 7 segment decoding in one package.

* It can be easily interface with 7 segment types.

* Ideal for low power display.

* Operated at wide range of temperature from 5V to 20V.

* The big advantage of the 4026B counter IC is that it can drive a 7-segment display without eeding a decoder driver IC

Description To understand its working how we can interface 4026 with 7 segment display, first have to look on its pin diagram -(pin diagram given in equipments required part)

Now let us understand the working of individual pins-

1. Pin 1 or clock pin- It receives clock signals, and at every positive clock and counter advances one by one. You can provide clock with the switch, 555 timer or with the help of logic gates. In short high pulse on this input increments the counter. 2. Pin 2 or disable clock (clk inhibit) pin- 4026 counter advances one by one by receiving positive pulse at this time for this clock inhibit pin should be grounded. If it is connected to supply than counter advancement will be inhibited means there will be no meaning of clock pulse.

3. Pin 3 or enable display (En in) pin- It enable the 7 segment display to display the numeric value. It should be kept high for enabling the display. Mean output goes high when only when display enable is high.

4. Pin 4 or enable out- It Enables the carry out pin. In our circuit we have left this pin unconnected.

5. Pin 5 or divide by 10 output- It is used to complete one cycle for every 10 clock input cycle and it also used to cascade more IC's.

6.Pin 6, pin7 and Pin9 to pin 13 - These are 7 decoded output from a to g used to illuminates the corresponding segment of 7 segment display to display the digit from 0 to 9.

7. Pin 14 or not 2 output (UNGATED "C" SEGMENT) signals- They are not gated by the Display clock and therefore are available continuously. This feature is a requirement in implementation of certain divider function such a as divide by 60 and divide by 12.

8. Pin 15 or Reset pin- It is used to reset the counter. When it receives high it clears the counter and counting again starts from zero. One important thing reset pin should again made low to start the counter once again.

9. Pin 8 or ground pin and Pin 16 known or Vdd it should be connected to power supply.

To understand its working assemble the circuit as shown in circuit diagram -

It uses a 4026 combined counter and display driver IC which is designed to drive 7 segment display. When you press the switch S1 counter starts from zero and it advances one each time whenever pin 1 receives a positive pulse. When you press the switch for first time numeric 1 will display. Then you again press the switch numeric 2 will display, giving you second output. In similar manner 3 and 4 will display. When count reaches to 9 after that it again starts it counting from zero.

For resetting the counter to zero at any point press switch S2. For this pin 15 must be taken high and then taken low again. The table below shows sequence of how each segment glows after receiving clock signal.


LM 324 N is a quad OP-AMP ic. The LDR acts as a receiver, and the LED acts a transmitter. The 10Kohm POT is used for the adjustment of the sensibility of the sensor. The output of the sensor id fed into the circuit of CD4026/332 and 7 segment display. here we have used 2 7 segment display which can count from 0-99. When there is an interuption in the LED-LDR path the buzzer is on. In place of buzzer you can use LED also. As soon as there is an interuption the counter counts +1 which is visible on the 7 segment display .IC CD4026/33 is 7 segment decoder ic. Its pin configuration and details has already been discussed.The 100Kohm resistor is used to reset the counter.The 270 ohm resistor is used to control the light itensity of the 7 segment display. Instead of LED-LDR Sensor, one can go for IR Sensors or LASER or Ultrasonic sensor.

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    Rabia Latif
    Rabia Latif

    Question 2 years ago

    Can someone share the function/truth table related to circuit diagram for door counters?


    5 years ago

    Thanks for sharing :)