122-28176 Parallax Inc, 122-28176 Datasheet - Page 84

• 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

The proximity switches shown in Figure 3-20 are commonly used in industry to detect
the presence of an object and operate on one of three principles:
Table 3-2:
•
•
•
Normally
Normally
Closed
Open
Inductive proximity switches sense a change in an oscillator’s performance when
metal objects are brought near. Most often, the metal objects absorb energy via
eddy currents from the oscillator, causing it to stop.
Capacitive proximity switches sense an increase in capacitance when any type of
material is brought near. When the increase becomes enough, it causes the
switch’s internal oscillator to start oscillating. Circuitry is then triggered, and the
output state is switched.
Optical switches detect the presence or absence of a narrow light beam, often in
the infrared range. In retro-reflective optical switches, an object moving into the
switch's range may reflect the light beam back to the sensor. Through-beam
optical switches are set up such that the object blocks the light beam going
between the light source and the receiver.
Schematic Symbols for Various Industrial Switches
Pushbutton
Mechanical
Limit
Proximity
Switch
Contacts
Relay