Tag Archives: plc input output wiring

Capacitive Pushbutton Sensor Switch and Indicator

Normal pushbuttons on a panel are usually a mechanical device. They can become “sticky” when too much dirt or oil is present. Capacitive push buttons do not have moving parts to stick, so the life expectancy is increased. Disinfectant sprays can be applied directly to a capacitive pushbutton and left to dry so it can be more effective for the safety of your operators.

Captron pushbutton sensor switches use capacitive sensing to detect when a hand or body part nears the device surface; built-in or stand-alone indicators provide multi-color signaling options. The robust IP69K design provides wear-free operation, plus resistance to water, oil, and harsh environments. These PNP NO DC-operated devices are available in 22mm, 50mm, and 60mm mounting diameters. Construction materials include plastic and stainless steel, aluminum, or polycarbonate. The corresponding 22mm LED signal indicator lights are also IP69K rated and have a 20mm diameter illuminated area; green, red, yellow, white, orange, and magenta signal colors are available.

We will be wiring a 22mm captron pushbutton to a click plc. Upon activating the sensor for half a second output on the click plc will turn on. The green LED on the captron will turn solid green. When the sensor is selected again, the output will turn off. The Green LED will then blink indicating that the output is off.
Let’s get started! Continue Reading!

Wiring 3 Wire DC NPN and PNP Sensors

I recently received a question on PNP and NPN sensors. They wanted an explanation of what a sink is and how to wire one. Confusion over the Normally Open and Normally Closed function of the sensor is also a common question. Several diagrams will show a resistor attached to the blue wire and a load across the others, what does it all mean?

It is quite confusing sometimes the language we use for these devices. Sometimes it is the way we talk about the sensor and sometimes about the device we are connecting. (PLC)
We will break it down and go over the wiring to a PLC input. Let’s get started. Continue Reading!

Universal Signal Conditioner and Isolator

Signal conditioners are used with analog current and voltage signals. They have the ability to change your input analog signal to another output analog signal. As an example, we can have 4-20mA analog input and change it to a 0-10VDC output signal so we can wire this into our PLC. Typically signal conditioners will also electrically isolate the input and output signals. This is either done by magnetic or optical isolation. You would usually specify the input and output signals that are required in your circuit to choose the signal conditioner required. Using a universal signal conditioner will take a variety of signals and is a great product to use in troubleshooting analog circuits.

We will be using a universal signal conditioner to convert a thermocouple temperature input into a 0-10VDC linear output. This will be wired into the analog card of the Click PLC.
Let’s get started. Continue Reading!

Wiring an Ultrasonic Proximity Sensor to the Click PLC

An ultrasonic sensor (switch) is able to detect object presence without physical contact (limit switch). No physical contact means that the switch has no parts that will wear out. The life span of the sensor is increased with less maintenance.
An ultrasonic sensor will use sound waves to detect objects. These sound waves are at a level that we cannot hear. Distance is measured by the time it takes to send and receive the ultrasonic wave. Objects can be measured the same no matter what the colour, transparency, shininess, or lighting conditions of the application.

We will be wiring an ultrasonic sensor into the input of our Click PLC. This will include a discrete and analog input signal. The UK1F-E7-0A is an 18mm diameter sensor that has a PNP N.O./N.C. selectable output with analog output of 0 -10 VDC. The sensing distance is 200mm to 2200mm and has a one-hertz switching capacity. A 4-pin M12 quick disconnect is available but we will be wiring in our 2m wired version. Let’s get started. Continue Reading!

Wiring Push Buttons and Selector Switch to Click PLC

A push button (pushbutton) is a simple human interface for controlling some aspect of a machine or process. The push button requires a force to push the button to change the electrical operation from off to on or vice versa. The condition of the output is usually momentarily. Some common everyday pushbuttons we use are keyboards keys.

A selector switch is also a mechanical device that will require a force to turn the electrical operation from off to on or vice versa. The selector switch usually locks into a position.

We will be wiring two illuminated pushbutton switches into our Click PLC. A selector switch will also be wired in. Let’s get started. Continue Reading!

Wiring Stack Light to Click PLC

Stack lights are usually modular stackable components that provide a visually illuminated and audible indication for machines, systems, and processes. They are usually located on top of equipment to provide this notification to personnel in the area.

Stack lights are also known as signal tower lights, indicator lights, warning lights, industrial signal lights, tower lights, and light towers.
We will be connecting a Patlite NPS-402-RYGB Super Slim stack light to our Click PLC.

These stack lights come in preassembled units in the most popular combinations of colours with ABS resin main bodies that offer superior impact and heat resistance; double-insulated construction enhances durability and safety. Interchangeable light modules require no rewiring. Let’s get started. Continue Reading!

Create an Analog Voltage Input Tester for a PLC

We will create a simple and inexpensive analog voltage tester for a PLC using a potentiometer and a 9VDC battery. The potentiometer will be 5K ohms. This should be enough impedance for most analog inputs of the programmable logic controller. (PLC) Voltage impedance for analog voltage inputs are in the mega ohm range where current input is typically 250 ohms. Our tester will be for analog voltage inputs (0-10 VDC). Check your input specifications before wiring anything to your PLC. I have used this tester for other voltage inputs along with a meter to ensure that the voltage levels do not get out of range for the input signal.
Analog inputs to the PLC are continuous and can come in a variety of signals. These signals can come from temperature, flow rate, pressure, distance, etc. Continue Reading!

Wiring Interposing Relays

Interposing relay means a device that will separate two different circuits. The isolation can be for current consumption, voltage differences, voltage references or a combination of both current and voltage. We can use these relays to help connect our inputs and outputs on our programmable logic controller. (PLC) Continue Reading!

Here’s a Quick Way to Wire NPN and PNP devices

Here’s a Quick Way to Wire NPN and PNP devices

I get asked often on how to wire NPN and PNP devices to the programmable logic controller. This can be confusing at first when looking at the wiring diagrams. I have managed to destroy a few sensors in the process….. so let’s get started and I will share my experiences.

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NPN and PNP refer to the transistor in the output device.
NPN – Negative Positive Negative Switching. Sometimes referred to as ‘Sinking’ the load.  People have told me that when the NPN sensor blows it has a tendency to blow in an open state. (No Signal)
PNP – Positive Negative Positive Switching. Sometimes referred to as ‘Sourcing’ the load. People have told me that when the PNP sensor blows it has a tendency to blow in a closed state. (Signal On)

When the sensor blows, (malfunctions) it usually will also take out the power supply. (Fuse) It generally does not matter if you use NPN or PNP sensors provided they are all connected to the PLC using isolated commons.

You cannot mix PNP and NPN sensors on the same common point for inputs to the PLC. If you do mix the sensors, then the different common points on the PLC must be isolated from each other. This means that the commons are not connected internally to each other. Not ensuring this takes place will provide a short across the power supply and blow your sensors and supply. In general, machines tend to use all NPN or all PNP only.

Colour coding of the wires vary. Do not always rely on the colour code of the wires for connection. Refer to the wire diagrams in the documentation.

The following is a wiring diagram of an open collector PNP sensor. You will notice that the load appears between the 0V (Blue)  and Switching wire (Black). When connecting to the PLC, the PLC input acts as the load. The 0V (Blue) will be attached to the common input and the Switching wire (Black) will be attached to the input number.PNP1

The following is a wiring diagram of an open collector NPN sensor. You will notice that the load appears between the +V (Brown)  and Switching wire (Black). When connecting to the PLC, the PLC input acts as the load. The +V (Brown) will be attached to the common input and the Switching wire (Black) will be attached to the input number.NPN1

As you can see a direct short will be created if NPN and PNP sensors are wired into the PLC on the same common. The following shows an example of wiring of the 3 wire sensors into a PLC with isolated commons.


Watch on YouTube : Wiring NPN Sensor to PLC

Watch on YouTube : Wiring PNP Sensor to PLC

Watch on YouTube : Wiring Contact (Discrete) PLC Inputs

Wiring Interposing Relays
Watch on YouTube
: Wiring NPN and PNP Sensors into the PLC with an Interposing Relay
If you have any questions or need further information please contact me.
Thank you,

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