Thursday, April 12, 2012

4 legged Push button: Working

4 legged push buttons are quite often used in circuits of embedded systems.

But some times , especially for beginners, it gets confusing to understand how should the button be connected and which leg is meant for which connection.

Here is small animation that tries to make the internals a little clear.

A 4 legged push button connected on breadboard can be viewed as shown below.

The legs 1 and 2 are shorted internally in the button and so are the legs 3 and 4.

So when the button is pressed, we are internally shorting all the 4 legs together, meaning, when the button is pressed all the 4 legs are connected to each other and when the button is not pressed, the legs 1 and 2 are connected to each other and 3 and 4 are connected to each other. (Please note the numbering is hypothetical and are not mentioned on the switches).

If it still gets confusing, we can use a multimeter to find out which legs are shorted internally.

Keep the multimeter in the mode where it beeps when shorted and just connect one pin of the multimeter to one of the legs and touch the other pin to all the other 3 legs. On touching which ever other pin the multimeter beeps that is the pair which are shorted and so is the other pair.

Hope using a push button becomes much more easier now .

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