122-28176 Parallax Inc, 122-28176 Datasheet - Page 61

• 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

Saving digital input is performed within the routine to read the ADC, in an attempt to
read both the ADC and digital input at the same time. The ADC value and the digital
value may not track perfectly depending on how quickly the analog level changes.
Challenge 3-1: Reversing the Potentiometer Supply Voltage
What has changed when rotating the potentiometer? Explain why this change has
occurred. (Hint: Refer to Figure 3-3a, and consider what occurs when Vss and Vdd are
swapped).
ACTIVITY #2: NIGHT-LIGHT PROCESS
The input of the BASIC Stamp changing between HIGH and LOW at a fixed voltage can
provide a simple means of control using analog signals. The input simply needs to go
above and below the threshold level for the controller.
In this activity, a photoresistor will be added to the bottom of the variable resistor in the
ADC circuit from Activity 1. This modified circuit creates a light-controlled voltage
divider input to the BS2 for control of a light (the LED) at a certain level of darkness.
Parts Required
Circuit from Activity #1 (Figure 3-1 on page 46)
(1) Photoresistor
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Modify the circuit as shown in Figure 3-4 by adding the photoresistor between
the potentiometer and Vss. Do not modify the ADC or LED portions of the
circuit.
Re-run the program DataMonitoring.bs2, if needed.
Close the Debug Terminal.
Run StampPlot macro sic_pc_data_monitoring.spm.
Connect and plot.
Allow the photoresistor to be exposed to ‘daylight levels’ of light.
Adjust the potentiometer for a daylight voltage of 1.0 V.
Note the direction of rotation needed to achieve an increasing voltage.
Reverse the Vdd and Vss connections to the potentiometer.