Photoelectric Sensors

More Information about Photoelectric Sensors

In most photoelectric sensors, the transmitter and the receiver are either housed separately (through-beam configuration) or in the same housing (retro-reflective or diffuse).

In a through-beam configuration, the transmitter and the receiver are placed opposite each other. When an object interrupts the light beam, the sensor is triggered. These sensors have long sensing distances and are extremely reliable, even for detecting very small objects.

Retro-reflective sensors work by emitting a light beam from the sensor transmitter which is reflected back to the receiver by a reflector. When an object breaks this beam, the sensor registers this change and generates a response. This is useful for reliable detection over large distances.

In diffuse sensors, both the transmitter and receiver are located in the same housing. The light emitted by the transmitter is reflected by the object itself back to the receiver in the sensor. These sensors are ideal for detecting irregularly shaped, or transparent objects and for applications where reflectors are not practical.

In certain instances, photoelectric sensors use plastic fiber optic cables or glass fiber optic cables to guide the light beam. Fiber optic cables allow the sensor to operate in tight spaces or harsh environments as they can withstand various surface conditions and wet environments.

The sensor's ability to detect objects can depend on several factors such as the object's size, shape, color, and material, as well as the intensity and type of light being used. Some sensors also use background suppression or foreground suppression to prevent the sensor from being triggered by irrelevant objects.

Once the sensor detects an object, it converts this detection into an electrical signal. This signal can be used to control various aspects of an automated process, such as starting/stopping machinery, opening/closing doors, or triggering safety measures.

FAQs

Which type of photoelectric sensor provides the most reliable object detection?

For applications where reliability is paramount, through-beam sensors are often the first choice. However, other factors such as installation constraints, cost, and the need for regular maintenance and alignment can influence the decision. As with most technology, the "best" choice depends heavily on the specific requirements of the application.

Limit Switch Basics 

What are limit switches?

Limit switches are electromechanical switches that operate based on the movement or presence of an object. They are designed to detect the presence of an object using an actuator connected to a series of contacts to detect the presence and proximity or absence of a material or object. When the switch's actuator is moved by an object it will change the state of an electronic contact set. This movement signals that some preset limit has been reached. There are many different ways a switch can be actuated depending on the type of switch that is being used. Some use a roller and lever, some use a button or plunger, while others might use a rotating arm and rod attached to the main body of a switch. The type of switch that is used will largely be dictated by the specific application.

Where are limit switches used? 

Limit switches can be used to tally or count items, so that when a limit is reached, the switch will open or close. This open and closing action can be counted by a controller allowing the action to be totalized. Limit switches can be used as safety interlocks to prevent machine parts from moving any further when specific point is reached. Limit switches are also commonly used in larger control systems. For example, when a certain limit is reached, the actuator can deactivate or activate a device to prevent it from malfunctioning.