28123 Parallax Inc, 28123 Datasheet - Page 272

• 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

ACTIVITY #1: CONTROL CURRENT FLOW WITH A TRANSISTOR
In this activity, you will use a transistor as a way to control the current passing through an
LED. You can use the LED to monitor the current since it glows more brightly when
more current passes through it and less brightly when less current passes through it.
Introducing the Transistor
Figure 9-2 shows the schematic symbol and part drawing of the 2N3904 transistor. There
are many different types of transistors. This one is called NPN, which refers to the type
of materials used to manufacture the transistor and the way those materials are layered on
the silicon. The best way to get started thinking about a transistor is to imagine it as a
valve that is used to control current. Different transistors control how much current
passes through by different means. This transistor controls how much current passes into
C (collector) and back out of E (emitter). It uses the amount of current allowed into the B
(base) terminal to control the current passing from C through E. With a very small
amount of current allowed into B, a current flow of about 416 times that amount flows
through the transistor into C and out of E.
Transistor Example Parts
(1) Transistor – 2N3904
(2) Resistors – 100 kΩ (brown-black-yellow)
(1) LED – any color
The 2N3904 Part Datasheet: As mentioned earlier, semiconductor manufacturers publish
documents called datasheets for the parts they make.
information engineers use to design the part into a product. To see an example of a part
datasheet for the 2N3904: Go to www.fairchildsemi.com. Enter 2N3904 into the Search field
on Fairchild Semiconductor’s home page, and click Go. One of the search results should be
a link to the 2N3904 Product Folder.
Download this Datasheet link. Most web browsers display the datasheet by opening it with
Adobe Acrobat Reader.
C
B
E
2N3904
B
C
E
Follow the link to the product folder, then click
Figure 9-2
2N3904 Transistor
These datasheets contain