OR-gate realization

To make an object counter we can use a simple dark detector circuit and a normal calculator. Pole and NO (Normally Open) terminals of a relay have to be connected to the two pins which are used to activate ‘=’ key of calculator. As we block the light falling on LDR, the calculator starts counting. For the calculator to work as a counter, we first need to press ‘1’ and ‘+’ keys. All calculators may not work as counter, you need to check with the following steps: a. First press 1 b. Then Press + c. Then keep on pressing = Each time when you press “=”, the calculator should increase the numbers and display 1,2,3,4… and so on. If your calculator displays “1″ every time you press “=”, then your calculator cannot be used as counter. In our circuit, we use relay to connect two wires of '=' key that eventually increases numbers on calculator. My project