In industrial automation we put our products through a lot. Extreme temperatures, harsh environments, and the demands of high performance can put a strain on the components of any machine. This led me to wonder, if our products could talk, what would they say?
Cordset: Cables have certain limpness which makes installing the cordset in automation easier to fit in tight spaces. Most cable installers prefer to have the least amount of slack in cable to prevent the cable being snagged or pulled during operations. Cables need to have a bend radius to prevent kinking of the conductors and a continuous flow of power. The bend radius is “the smallest radius of curvature into which a material can be bent without damage” (McGraw-Hill Dictionary of Architecture and Construction). Typically in a fixed (stationary) application, an unshielded sensor cable has a minimum bending radius of 8 times the outer diameter of the cable.
Power Supply: Everyone wants a friend. When a load is too much for one power supply, adding another power supply helps increase the voltage or current output. “The simplest method to create higher current is to connect the power supplies in parallel and leave only one supply in constant voltage mode. Some power supplies are equipped with analog control signals that allow auto-parallel or auto-tracking, a more elegant way to control multiple power supplies. Auto-parallel supplies can be controlled with a single master supply; a second advantage is that all of the master power supplies features can be used.” (Keysight Technologies) By stringing together power supplies, it allows more voltage or current but also keeps operations up and running.
From The Free dictionary by Farlex, a receptacle is defined as “A fitting connected to a power supply and equipped to receive a plug.” I like this definition it describes both halves of the receptacle. In the automotive industry, the back half of a receptacle has threading on the nut with leads that could possibly connect a power supply. The front half describes which kind of cordset is needed. Typically, receptacles are used in a control cabinet, where there is easy access and out of the movement of machinery. Inside a control cabinet is a power source and/or programmable logic controller (PLC) which a receptacle would be wired to in the configuration of the controller. Receptacles used on a control box normally have a tight seal to keep out moisture and dust.
When looking at a receptacle there are two ends with different kinds of threading. In the front of the receptacle has a connection for a cable to connect to the outside environment, cells, and machinery, to the control box. The different cables could have diameter widths of M8, M12, 7/8”, 1” and more. From the picture, we see the front side of the receptacle calls for the M12x1 which would use a M12 cable. The first number is always the diameter of the outer threads. The other end of the receptacle, ½”-14NPT, where the leads come out, has another diameter referred as to the mounting type. There are many different kinds of mounting: Metric, PG, NPT, front mount, back mount, panel mount, etc. The two mounts types being explained here are Metric and NPT.
Three-wire sensors are used in various applications from detecting parts to locating position of the actual machine. They can come in all different technologies such as inductive sensors, photoelectric sensors and capacitive sensors, just to list a few. Although the sensor technology may differ, all 3-wire sensors are wired the same way.
A three-wire sensor has 3 wires present: two power wires and one load wire. The power wires will connect to a power supply and the remaining wire to some type of load. The load is a device that is being controlled by the sensor. The most common type of load would be a PLC (programmable logic controller) DC input. Other examples of a load could be a relay or machine alarm. Just make sure the load rating of the sensor is not exceeded. A typical 3-wire DC sensor’s output has a rating of 100mA to 200mA.
As an example, let’s reference an inductive proximity sensor. When a target (the object that a sensor is detecting) comes within sensing range of the sensor, the sensor output turns on and current flows. A 3-wire sensor typically is color coded with one brown wire, one blue wire and one black wire. The brown wire is the +VDC wire that connects to the positive (+) side of the power supply and the blue wire is connected to the common terminal of the power supply — this is the negative (-) terminal that is present on the power supply. The black wire is the output (load) wire of the sensor. 3-wire DC sensors can have a PNP (sourcing) or NPN (sinking) output. Just make sure the correct sensor part number is selected for the correct transistor circuit.
There you have it! As you can see wiring a 3-wire sensor is not too difficult.