28123 Parallax Inc, 28123 Datasheet - Page 273

• 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

10 kΩ
(1) Potentiometer – 10 kΩ
(3) Jumper wires
Building and Testing the Transistor Circuit
Figure 9-3 shows a circuit that you can use to manually control how much current the
transistor allows through the LED. By twisting the knob on the potentiometer, the circuit
will deliver different amounts of current to the transistor’s base. This will cause a change
in the amount of current the transistor allows to pass from its collector to its emitter. The
LED will give you a clear indication of the change by glowing more or less brightly.
Your Turn – Switching the Transistor On/Off
If all you want to do is switch a transistor on and off, you can use the circuit shown in
Figure 9-4. When the BASIC Stamp sends a high signal to this circuit, it will make it so
that the transistor conducts as much current as if you adjusted the potentiometer for
maximum brightness. When the BASIC Stamp sends a low signal to this circuit, it will
cause the transistor to stop conducting current, and the LED should emit no light.
POT
Vdd
Vss
√
√
Build the circuit shown in Figure 9-3.
Turn the knob on the potentiometer and verify that the LED changes
brightness in response to a change in the position of the potentiometer’s wiper
terminal.
100
100
kΩ
kΩ
Vdd
Vss
LED
P15
P14
P13
P12
P11
P10
P9
P8
P7
P6
P5
P4
P3
P2
P1
P0
X2
X3
Vdd
Vin
Vss
Figure 9-3
Manual
Potentiometer
Controlled
Transistor
Circuit