1. Arduino learning notebook -- Button experience www.juvtamll.com ( a company supply PCB Prototyping, PCBA service, sell modules.) The button is a commonly used key, normally used to connect or disconnect the circuit, so as to control the the motor or other equipment. The buttons have a variety of appearance. This experiment is used for this kind of miniature keypad, 6mm, as shown below. Look at the back of the button, it has 4 pins. When the button not be pushed, No. 1 and 2 are connected, 3 and 4 are connected. When the button is pressed down, all the pins will be connected. We use button to control the led. The general situation is install the button series in the led circuit, however, it’s too simple. We use the indirect way, the button judge output voltage from the circuit. If the voltage is greater than 4.88 V, output high level to the LED circuit, whereas output low level. ...
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