28123 Parallax Inc, 28123 Datasheet - Page 54

• 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

Figure 2-8 shows how the flow of electricity through the LED circuit is described using
schematic notation. The electric pressure across the circuit is called voltage. The + and –
signs are used to show the voltage applied to a circuit. The arrow shows the current
flowing through the circuit. This arrow is almost always shown pointing the opposite
direction of the actual flow of electrons. Benjamin Franklin is credited with not having
been aware of electrons when he decided to represent current flow as charge passing from
the positive to negative terminal of a circuit. By the time physicists discovered the true
nature of electric current, the convention was already well established.
Chemical reactions inside the battery supply the circuit with current. The battery’s negative
terminal contains a compound that has molecules with extra electrons (shown in Figure 2-7
by minus-signs). The battery’s positive terminal has a chemical compound with molecules
that are missing electrons (shown by plus-signs). When an electron leaves a molecule in
the negative terminal and travels through the wire, it is called a free electron (also shown by
minus-signs). The molecule that lost that extra electron no longer has an extra negative
charge; it is now called neutral (shown by an N). When an electron gets to the positive
terminal, it joins a molecule that was missing an electron, and now that molecule is neutral
too.
A schematic drawing (like Figure 2-8) is a picture that explains how one or more circuits
are connected.
engineers, and just about everybody else who works with circuits.
Appendix F: More about Electricity: This appendix contains some glossary terms and an
activity you can try to get more familiar with measurements of voltage, current and
resistance.
Voltage
Voltage
Current
+
-
Schematics are used by students, electronics hobbyists, electricians,
Vdd
Vss
Resistance
LED
Figure 2-8
LED-On Circuit
Schematic Showing
Conventional Voltage
and Current Flow
The + and – signs show
voltage applied to the
circuit, and the arrow
shows current flow
through the circuit.