28128 Parallax Inc, 28128 Datasheet - Page 151

• Manufacturer Part Number: 28128
• Description: KIT BASIC ANALOG/DIGI PARTS ONLY
• Manufacturer: Parallax Inc

Specifications of 28128

• Accessory Type: ADC, DAC
• Product: Microcontroller Accessories
• For Use With/related Products: BASIC Stamp® 2 and Board of Education
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Chapter #8: Light Meter Gizmo with R/C Time
Constants
In this chapter, we'll be using concepts we learned in previous activities to develop a light
meter gizmo. Here is the list of gizmo specifications:
This experiment introduces a way of using a BASIC Stamp I/O pin to measure variable
resistance or capacitance. A number of sensors aside from the photoresistor vary in either
resistance or capacitance. A simple and straightforward way of measuring these
quantities can make interfacing with these sensors immensely easier.
In this experiment, we'll begin by building our gizmo, next we'll look more closely at the
measurement technique to see how it can be used to monitor variable resistance or
capacitance. Figure 8-1 shows a generic RC circuit that can be used to take RC time
constant measurements.
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•
•
The gizmo should beep every half-second.
When the light level in the room gets brighter, the gizmo should beep at a higher
pitch.
When the light level in the room gets dimmer, the gizmo should beep at a lower
pitch.
P15
220
Ω
Vdd
Vss
C
R
Figure 8-1
RC Circuit
For measuring
values of R or C