Brief 74HC32 quad 2 input OR gate demonstration Push Button Switch and Light Dependent Resistor LDR signals

OR logic gates need to have one or more high inputs for the output to be high. If all of the inputs are low, then the output is low.

Basic electronics circuit fragments and simple circuits 23 Or logic gate switch 2N3904 NPN BJT and 7432 74HC32 IC based diagram by electronzap electronzapdotcom
Basic electronics circuit fragments and simple circuits 23 Or logic gate switch 2N3904 NPN BJT and 7432 74HC32 IC based diagram by electronzap electronzapdotcom

Making an OR gate with mechanical or transistor switches is easy. You simply give 2 (or more) possible ways to connect to positive supply when they are closed/on.

NPN Bipolar Junction Transistors (BJTs) wired as shown in the diagram, will drop about 0.6V from the output. They are wired as emitter followers.

The 7432 integrated circuit (74HC32 would most likely be used these days), has 4 individual OR gate circuits built into it.

The Light Dependent Resistor LDR example is demonstrated in the video below. It is not shown in the diagram.

Video:

Brief Circuit Schematics with Short Video List of Pages

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