28123 Parallax Inc, 28123 Datasheet - Page 227

• Manufacturer Part Number: 28123
• Description: TEXT WHAT'S A MICROCONTROLLER
• Manufacturer: Parallax Inc
• Type: Programmingr

Specifications of 28123

• Style: Book
• Title: What's a Microcontroller?
• Contents: Whats a Microcontroller? Text
• Product: Microcontroller Accessories
• Core Processor: PIC16C57c
• Flash: 128 Bytes
• Operating Supply Voltage: 9 V
• Board Size: 31 mm x 16 mm
• Lead Free Status / RoHS Status: Not applicable / Not applicable

Chapter #8: Frequency and Sound
YOUR DAY AND ELECTRONIC BEEPS
Here are a few examples of beeps you might hear during a normal day: The microwave
oven beeps when it’s done cooking your food. The cell phone plays different tones of
beeps that resemble songs to get your attention when a call is coming in. The ATM
machine beeps to remind you not to forget your card. A store cash register beeps to let
the teller know that the bar code of the grocery item passed over the scanner was read.
Many calculators beep when the wrong keys are pressed. Let’s not forget that you may
have started your day with a beeping alarm clock.
MICROCONTROLLERS, SPEAKERS, BEEPS AND ON/OFF SIGNALS
Just about all of the electronic beeps you hear during your daily routine are made by
microcontrollers connected to speakers. The microcontroller creates these beeps by
sending rapid high/low signals to various types of speakers. The rate of these high/low
signals is called the frequency, and it determines the tone or pitch of the beep. Each time
a high/low repeats itself, it is called a cycle. You will often see the number of cycles per
second referred to as Hertz, and it is abbreviated Hz. For example, one of the most
common frequencies for the beeps that help machines get your attention is 2 kHz. That
means that the high/low signals repeat at 2000 times per second.
Introducing the Piezoelectric Speaker
In this activity, you will experiment with sending a variety of signals to a common, small,
and inexpensive speaker called a piezoelectric speaker. Its schematic symbol and part
drawing are shown in Figure 8-1.
Figure 8-1
Piezoelectric Speaker
Schematic Symbol and
Part Drawing