Velleman VMP502, User Manual

Page: 19 / 51

VMP502
V. 02
–
25/10/2019 19 ©Velleman nv
6.6 Buzzer
Required Hardware
•
1 x Raspberry Pi
®
•
1 x breadboard
•
1 x buzzer (active)
•
1 x PNP transistor (8550)
•
3 x 1 k
Ω resistor
•
jumper wires as needed
An electronic buzzer is widely used in computers, alarms, electronic toys, etc.
Buzzers can be categorized as active or passive. An active buzzer has a built-in oscillating source, so it will
make sounds when electrified. A passive buzzer does not have an oscillating source and will not buzz if DC
signals are used. Instead, you need to use square waves whose frequency is between 2K and 5K to drive it. The
active buzzer is often more expensive than the passive one because of multiple built-in oscillating circuits.
Here, an active buzzer is used. When the GPIO output is supplied with low level (0 V) by programming, the
transistor will conduct because of current saturation and the buzzer will make a sound. When a high level is
supplied to the IO of the Raspberry Pi
®
, the transistor will be cut off and the buzzer will not make a sound.