5.0 ROBOT SENSORS

5.0 ROBOT SENSORS

Sensor - A device that responds to physical stimuli (such as heat, light, sound, pressure, magnetism, motion, etc.) and transmits the resulting signal or data for providing a measurement, operating a control, or both.

5.1 Understand the characteristics of contact and non contact sensors.




5.1.1 Explain the Photoelectric sensors

•       A photoelectric sensor, or photoeye, is a device used to detect the distance, absence, or presence of an object by using a light transmitter, often infrared, and a photoelectric receiver.

•       They are used extensively in industrial manufacturing. There are three different functional types: opposed (through beam), retroreflective, and proximity-sensing (diffused).

(source: http://en.wikipedia.org/wiki/Photoelectric_sensor )

 

• Separate or through beam type: The sensor system includes two devices: a light source to produce a beam of light and a receiving device to sense the presence of the light beam. 

   •       Through Beam:

                 – Long range (20m)

                 – Alignment is critical !

  

 • lRetroreflective type: The sensor system includes two separate devices: a sensor with both a light source and receiver in the same case, and a retroreflective target, which is a highly reflective surface. The light beam leaves the sensor, bounces off the target, then returns to the receiver. The sensor is triggered when a part breaks either the outbound or returning beam. 

   •       Retro-reflective

            – Range 1-3m

            – Popular and cheap

 •  Diffuse reflective type: The sensor has a light source and receiver built into the same case. Stable operation assumes that the part to be detected will return sufficient diffused light to trigger the receiver when the part is in range, and that the background equipment will not return enough light to trigger the receiver when the part is out of range. The light beam is diffused back to the receiver by using the natural reflective characte-ristics of the part’s surface. 

•       Diffuse-reflective

               – Range 12-300mm

               – Cheap and easy to use

 

•Definite reflective type: This sensor works like a combination 

ADVANTAGES OF PHOTOELECTRIC SENSORS

– Non-contact, no moving parts, small.

– Fast switching, no switch bounce.

– Insensitive to vibration and shock

– Many configurations available

DISADVANTAGES OF PHOTOELECTRIC SENSORS

– Alignment always required

– Can be blinded by ambient light conditions

–      (welding for example)

– Requires clean, dust and water free, environment

APPLICATION OF PHOTOELECTRIC SENSORS

•       Stack height control/box counting

•       Fluid level control (filling and clarity)

•        Breakage and jam detection

•        And many others…

http://ee.sharif.edu/~industrialcontrol/Summary_Automation_Sensors_tutorial.pdf

VIDEO: WHAT TYPE OF PHOTOELECTRIC SENSOR IS  THIS????