122-28176 Parallax Inc, 122-28176 Datasheet - Page 65

• 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

Figure 3-7 is a sample plot of the results.
When the pushbutton is pressed, current passes through the switch to register a solid
HIGH value. The input is now committed and no longer floating.
When the normally-open (N.O.) pushbutton is not pressed, the input to P8 is floating and
not committed to any voltage level. By touching the lead, the static electricity on your
body is creating voltage spikes on the input above the threshold voltage. This noise
causes the digital input to switch states. During process control, the uncommitted input
may cause erratic and undesirable conditions. Again, the monitored analog voltage and
digital input are not measured simultaneously and may not match HIGH and LOW values
exactly.
√
√
Place a 10 kΩ resistor from the P8 side of the pushbutton to Vss as shown in
Figure 3-8.
Test the circuit again. Are the results more stable?
Figure 3-7
Plot of
Uncommitted
Input