122-28176 Parallax Inc, 122-28176 Datasheet - Page 168

• 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

As can be seen in Figure 5-13, the discharge time is approximately 4 seconds, which is
not too far off from the predicted time, taking into account sampling rate and tolerances
of components used. Also note that the discharge time, or time constant, of the RC
network did not change significantly whether starting from 255 or 125. The response of
the circuit is not dependent on where it started.
With the fan drawing 90 mA, how long will the charge last? It would last only an instant.
While we are not able to drive the fan continuously, we are getting closer.
Figure 5-13 RC Network Discharge
√
Set the PWM Value control to 255 (100% duty cycle) and adjust the samples to
measure the full time it requires the charge to dissipate to 0 V. It may be
beneficial to log the data and read the times from the file for better accuracy, or
the StampPlot Values window may be used to read the times under the mouse
pointer (Menu View → Values).