122-28176 Parallax Inc, 122-28176 Datasheet - Page 67

• Manufacturer Part Number: 122-28176
• Description: GUIDE STUDENT PROCESS CONTROL
• Manufacturer: Parallax Inc

Specifications of 122-28176

• Accessory Type: Manual
• Product: Microcontroller Accessories
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• For Use With/related Products: Propeller Education (PE) Kit
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant, Contains lead / RoHS non-compliant

The pushbutton circuit is termed Active-High because when the button is active
(pressed), the input state will be HIGH, a pull-down resistor is used to force the input
LOW (when the pushbutton is not pressed).
Challenge 3-3: Active-Low Pushbutton Circuit
Consider the circuit in Figure 3-9.
ACTIVITY #4: THE TRANSISTOR AS A SWITCH
The transistor revolutionized electronics and is the basic building block in both analog
and digital systems today. The Bipolar Junction Transistor (BJT) can be used as an
amplifier to take a small analog signal, such as sound waves hitting a microphone, and
amplifying that signal many times to be blasted out by speakers at rock concerts.
The transistor may also be used as a digital switch – ON or OFF. The BASIC Stamp and
the microprocessor that runs your computer system are two examples of thousands, or
1. This circuit is termed Active-Low. Why?
2. Does this circuit use a Pull-Up or Pull-Down resistor? Why?
3. Reconfigure your circuit to match, and test. Discuss your results.
Always check data sheets for the digital device in use. Different devices have different
input voltage and current specifications. They may be damaged by static electricity when
inputs are left uncommitted. Some devices may have internal pull-up resistors, alleviating
the need of adding them to the input. TTL devices will typically assume a HIGH state if not
connected, but this is not assured, especially during internal clocking or switching.
Figure 3-9
Active-Low
Pushbutton Circuit