Switches & Sensors

Automation processes require rigorous safety equipment to ensure that personnel are protected against hazards. Switches and sensors form an integral part of a safe automation system by controlling the power within automation processes as well as sensing and collecting particularly helpful data. Here at Cromwell, we have a wide range of switches and sensors from leading brands such as Omron, Schneider Electric and ABB.

Why switches and sensors?

Most commonly used in automation systems, switches and sensors are an easy way of controlling the flow and current of electricity to potentially hazardous equipment, in order to keep your personnel safe when working in conjunction with automated machinery. Switches and sensors are cost effective in most cases, need little maintenance and can be adapted to suit your required applications with ease.

Switches and sensor types

Whilst there are numerous types of switches and sensors, below, we've outlined the most commonly used types and explained their uses to help you make an informed and confident purchasing decision.

Proximity sensors   -   As they sound, proximity sensors are a non-contact component that is specifically designed to detect the presence or absence of an object without requiring physical touch to trigger it. There are three main types - capacitive, inductive and ultrasonic- all of which vary slightly in the way they operate, but all fulfil the same purpose of sensing the absence or presence of an object within their range.

Proximity switches   -   Commonly used interchangeably as a term with proximity sensors, proximity switches are a more precise component as opposed to the more general term of proximity sensors. Proximity switches work by opening or closing the electrical circuit that it is attached to when the sensor successfully senses the absence or presence of an object within its range.

Photoelectric sensors   -   The three main types of photoelectric sensor are through-beam (opposed), retroreflective and proximity sensing (diffused). All three types of photoelectric sensor work to sense the presence, absence or distance of an object via a light transmitter of some description and a photoelectric receiver.

Through-beam - or opposed - photelectric sensors work by having a receiver and a transmitter at different locations to each other, but in the line of sight of one another. Detection occurs when the beam of light passing between the two is blocked.

In retroflective photoelectric sensor types, the transmitter and receiver are in the same position, with the beam of light inverted back to hit the receiver. Again, detection occurs when the beam of light is interrupted as an object passes through it.

Diffused - or proximity sensing - type photoelectric sensors have the emitter and the receiver in the same casing and work by sensing when there is an object as opposed to when there isn't one. In this case, an emitter sends out a beam of light which is then deflected back to the receiver when an object enters the detection sensing zone.

Switches   -   Designed to control whether the circuit is open or closed and thus providing power, switches are an invaluable component for controlling the flow of electricity. They come in all shapes and sizes and can possess multiple positions depending on your needs and the circuit you have in place.

Switch accessories   -   This encompasses products such as cabling and actuators which can be used to enhance your switches and sensors and help to convert energy in a circuit.

Disconnect switches   -   Designed for completely de-energising a circuit prior to maintenance work, disconnect switches are a simple way of ensuring maximum safety from electrical hazards and injuries when working on a circuit. They are most often used on permanently wired equipment that cannot be safely switched off by other means.

Light curtains   -   Also referred to as safety light curtains, safety light screens, safety light barriers or optical guards, light curtains create a barrier that protects personnel against danger from hazardous machinery. A light curtain is formed of one receiver and one transmitter head, between which an LED barrier is created. When the light curtain senses that it is disturbed or broken, this then triggers the machinery to stop. Machinery can then be restarted via a button that lies outside of the detection zone to ensure maximum safety.

Sensor connectors   -   Sensor connectors form part of the larger sensor technological system that is commonly found in automation applications. They can be largely broken down into four categories: O2 sensor connectors, temperature sensor connectors, speed sensor connectors and pressure sensor connectors.

O2 sensor connectors are designed to monitor the levels of O2 in a particular surrounding. This type of sensor and sensor connector is most frequently used in the automotive industry to keep track of emissions emitted through the exhaust of the vehicle. The sensor connector helps to connect components to one another and does not sense the O2 in and of itself; it must be paired with an O2 sensor.

Temperature sensor connectors are utilised in conjunction with either a contact or non-contact temperature sensor to monitor and record the temperature of a set, defined area.

Speed sensor connectors are used to form part of an intricate sensor system that measures and documents the speed of something. Most commonly, they form part of a system that is designed for measuring the speed of a wheel's rotation or similar applications.

Lastly, pressure sensor connectors are designed to attach and help pressure sensors to function. These are often used to measure and record the pressure in either liquid or gas systems. Pressure sensor connectors form part of this system but do not directly sense pressure, the same as the other main types of sensor connectors.


What is a proximity sensor on a phone?

Almost all recent smart phone models will be equipped with some form of proximity sensor. Most often, this will be in the form of an infrared proximity sensor which has the primary function of ensuring accidental tapping, swiping or contact with your phone is kept to a minimum. A good working example of this in action is thinking about when you are taking a call and thus have your phone close to your ear. The proximity sensor will detect the presence of your ear nearby and will turn off the touchscreen display to avoid accidental taps.

Likewise, if your phone is in your pocket, your proximity sensor will send a message to the phone's internal processor and tell it to disable the screen to save power.