PHOTOELECTRONIC SENSORS Diffuse Sensors proximity mode Transmitted beam

PHOTOELECTRONIC SENSORS Diffuse Sensors (proximity mode) Transmitted beam (through beam) Retro-reflective

DIFFUSE SENSOR Rely on sensing light reflected off a target object Standard, Sharp Cutoff, Background Suppression, Fixed Focus, and Wide Angle

TRANSMITTER-RECEIVER (THROUGH) Comprised of a light source and a sensor to detect its beam. Both parts require a power source, can come from different supplies. When a part passes between the transmitter and receiver, the beam is broken and the sensor sends a signal to the automation controller Ø IR, laser, LED Dark and Light Applications http: //www. baumerelectric. com/be 130. html? L=1&country=US

RETROREFLECTIVE The transmitter and receiver are incorporated into a single housing. A reflector is mounted opposite to the sensor and returns transmitted light back to the receiver. The effective beam describes the area that must be completely interrupted in order to reliably sense a target and it increases as the distance between the sensor and reflector increases. When the target is directly in front of the reflector, it must be at least as large as the reflector. Smaller objects can be detected if they are located closer to the sensor and they are at least as large as the optics. Dark and Light Applications

SUMMARY Transmitter-Receiver is not valid because of mounting limitations. Diffuse requires background suppression – expensive Retro-reflective is picky and hard to mount, but might prove to be most reliable. Sensitivity is issue. http: //sensor. baumerelectric. com http: //www. ab. com/catalogs/sensors/index_prodtype. html All require an A/D converter Different power supplies Reliability has been questioned (due to errors in mounting)

WEBSITES http: //machinedesign. com/article/a-background-check-for-photoelectric-sensors-0519 http: //everything 2. com/title/Photoelectric%2520 sensor http: //www. ab. com/sensorstoday/nov 01/techtalk/index. html http: //ugpro 143. blogspot. com/2008/06/basics-of-ir-transmitter-and-receiver. html http: //www. solarbotics. net/library/circuits/sensors_prox. html http: //www. ifmefector. com/ifmus/web/pinfo 1_40_10_40_20. htm

COMPARISON Sensor Type Difference Advantages Disadvantages Reliability, tough to precisely control the sensing range, triggers on shiny objects Sensative to reflective, shape, etc. Access to other Different sensing distances and sensitivity side of obj is not required settings are required for different objects (colors) Diffuse (general) Sharp sends light to a smaller, objects close to reflective background fixed area Background Suppression Ignores the background Can detect object and background Wide Angle sends light to a wide area ignore imperfections in target, not sensitive to angle of view, metal reflects well, does not need a background http: //www. acroname. com/robotics/parts/R 146 -GP 2 D 120. html More complex, expensive

THROUGH COMPARISON Advantages Disadvantage only receiver needs to be connected to smart device Crosstalk (alter sides to fix) Commercially available in a wide range of distances 2 x components of diffuse Can be reasonably priced 2 power supplies (or lines) Sense both sides of device The transmitter must be aligned directly at the receiver and will fail if either part is bumped or moved out of position. dirty environments, where dust and particles in the air might impede light

RETROREFLECTIVE COMPARISON Advantages Disadvantages Large sensing range must compelely break beam to count Matte finished objects are recognized independent of their surface properties. target cannot be highly reflective Can fixed to a moving target