The push button is normally closed, but opens when pressed. The push button will always have some residual resistance even when fully opened, which is something to keep in mind when designing circuits.
Push buttons are often used to:
- Add user input to a circuit: a part of the circuit will only function when the button is pressed
- In combination with transistors, circuits can be made where the push button only needs to be pressed shortly to make a longer action happen in the circuit
How does it work?
The tube inside the push button is initially kinked, so no air can flow through. As the button is pressed, the air inside the inner volume becomes displaced and pushes the two membranes outward. The tube is pulled apart from both sides, as it is connected to the two membranes on either side, and eventually it unkinks. Once it unkinks, it opens and air can flow through. When pressure is released, the volume returns to its original shape, the membranes move inwards, and the tube will re-kink, thus stopping air from flowing through.
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