Simple counter using Calculator

This is very attention-grabbing idea of using calculator for counter. Using calculator is cheaper and less complicated then the circuit of counter. The components used in this circuit are easily available and can be assembled even by beginners.

Circuit Description of simple counter using calculator

Two leads from contact of the key “=” is taken out from the calculator. Calculator to be used should be are in which “1”, “+”, and “=” gives ‘1’ and each press of equal key after that would result in the increment of the number by ‘1’. The leads from the calculator are connected to two point of relay through switch SW1 as shown in figure of circuit diagram. The working of this project is base on the working principle of LDR, when the light fall on LDR the resistance becomes low which operate or activates the relay (RL1) with the help of relay driver transistor T1.

It is necessary to press “1”,”+”, and”=” keys to set counter and only then relay should be connected to the output leads from calculator. Here, potentiometer VR1 is used to adjust the sensitivity.


Resistors (all ¼-watt, ± 5% Carbon unless stated)

VR1 = 100 KΩ


T1 = SL100

D1 = 1N4001




RL1 = 6V/100Ω

SW1 = toggle switch

NOTE:- Memory function of the calculator can be used instead of using “=” keys. In this case leads are taken out from “M+” key and initially “1” and “M+” is pressed. This project is verified in “SANYO” calculator model CX8136NE and it worked well. If necessary to find out the number of counted object then press “MRC” key.



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One thought on “Simple counter using Calculator”

  1. Dear good people over there! Namaste!
    I want a circuit for coil winding machine with the calculator and relay to stop winding when a pre-set number of turns have completed by the winding motor. I am unable to interface the relay. Please help me.

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