122-28176 Parallax Inc, 122-28176 Datasheet - Page 4

• 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

absorb the IR light and register as a high. The number of transitions is counted to arrive at the
RPM of the fan.
Recommendations
Not all inks absorb IR equally and some may be reflective to this wavelength of light. It is
recommended to use the data monitoring set of programs from Chapter 3 (DataMonitoring.bs2,
page 46, and the sic_pc_data_monitoring.spm macro) to test the reflection conduction with the 1
Cycle/revolution encoder wheel.
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Construct the circuit in Figure 4-18, page 117. For R
Do not power the fan yet.
Connect the Vin+ pin of the ADC (Pin 2) to the collector of the IR phototransistor.
Download and run DataMonitoring.bs2
Load StampPlot with the macro sic_pc_data_monitoring.
Position the fan approximately ½ inch from the opto-reflective switch with the 1 Cycle/revolution
encoder wheel.
Monitor the voltage when the sensor 'sees' the white vane and then the black vane. A distinct change
should be noted in the ADC's output from light (<1.4V) to a dark (>1.4V). Ideally, when seeing
reflection, the voltage should be near 0.3V due to saturation. When absorbed, the voltage should be
near 5V due to being in cutoff.
Based on results of prior experiments with varying resistances of R
adequate transition. If the detector appears to always be reflecting (low voltage), use markers or other
dark inks to color the dark vanes to limit reflection.
When proper transitions are noted, continue with Activity #6.
© Parallax, Inc. • Errata for Process Control v1.0 (#28176)
6
use 1 kΩ and for R
•
v1.0 5/22/06
C
C
use 100 kΩ.
, adjust R
•
Page 4 of 4
C
to achieve an