Building an OR gate

In this post we see how to build a logic OR gate.

It's actually really simple to understand.

Let's take a case where you want your car windows to wind up automatically, if either the engine is stopped OR the door is open (realistically you might not want that, but this is just a thought experiment).

We are looking at two states: engine running (true/false) and door open (true/false). Using "1" for "true" and "0" for false, we want the window to wind up if either or both are true.

So this is the truth table (v = OR):

Engine on v Door closed = wind up
Engine off v Door open = wind up
Engine off v Door open = do not wind up
Engine on v Door open = wind up

1 v 0 = 1

0 v 1 = 1

0 v 0 = 0

1 v 1 = 1

This also corresponds directly to English. "If my car door is open OR the engine is running, wind up the window, otherwise do not."

Here's the actual circuit and a video.
















 

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