User Manual

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When a High lev el signal goes through an NPN transistor, it is energized. But a PNP one needs
a Low level signal to manage it. Both types of transistor are frequently used for contactless
switches, just like in this experiment.
The schematic diagram:
Principle: In this experiment, an active buzzer, a PNP transistor and a 1k resistor are used
between the base of the transistor and GPI O to protect the transistor . When the B17 of
Raspberry Pi output is supplied with low lev el (0V) by programming, the transistor will conduct
because of current saturation and the buzzer will make sounds. But when high lev el is
supplied to the IO of Raspberry Pi, the transistor will be cut off and the buzzer will not make
sounds.
Experimental Procedures
Step 1: Build the circuit (Pay attention to poles of the buzzer: The one with + label is the positive
pole and the other is the negative.)
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