28123 Parallax Inc, 28123 Datasheet - Page 81

• 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

have two pins is because it needs stability. If the pushbutton only had two pins, those
pins would eventually bend and break from all the pressure that the pushbutton receives
when people press it.
The left side of Figure 3-2 shows how a normally open pushbutton looks when it’s not
pressed. When the button is not pressed, there is a gap between the 1,4 and 2,3 terminals.
This gap makes it so that the 1,4 terminal can not conduct current to the 2,3 terminal.
This is called an open circuit. The name “normally open” means that the pushbutton’s
normal state (not pressed) forms an open circuit. When the button is pressed, the gap
between the 1,4 and 2,3 terminals is bridged by a conductive metal. This is called closed,
and current can flow through the pushbutton.
Test Parts for the Pushbutton
(1) LED – pick a color
(1) Resistor - 470 Ω (yellow-violet-brown)
(1) Pushbutton - normally open
(1) Jumper wire
Building the Pushbutton Test Circuit
Figure 3-3 shows a circuit you can build to manually test the pushbutton.
1, 4
2, 3
1, 4
2, 3
1, 4
2, 3
1
2
4
3
Figure 3-1
Normally Open
Pushbutton
Schematic symbol (left)
and part drawing (right)
Figure 3-2
Normally Open
Pushbutton
Not pressed (left) and
pressed (right)