Inputs

Wiring inputs to the plc like switches and proximity sensors. This also includes analog input signals.

Wiring Interposing Relays – NPN PNP Isolation

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Wiring Interposing Relays - NPN PNP Isolation

We will now look at wiring interposing relays to connect an NPN and PNP sensors into the PLC. 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 … Read more

How PLC Inputs Work – Discrete and Analog

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This post is a further follow-up from my original ‘Here’s a Quick Way to Understand PLC Inputs and Outputs.’ There are two different kinds of PLC inputs, Discrete and analog. Discrete inputs are either ‘ON’ or ‘OFF’; 1 or 0. You can think of them as a single switch. Analog inputs have a range to … Read more

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

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Here’s a Quick Way to Wire NPN and PNP devices I often get asked how to wire NPN and PNP devices to the programmable logic controller. This can be unclear 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 … Read more

Here is a Method That can Help You with Difficult Level Sensing

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Turn a capacitive proximity sensor into a level sensor. This is ideal for tanks and vessels you cannot drill through the side for mounting. Wrap the bare wire around the sensing head and extend it to the length you need to detect. Insulate the wire using electrical tape, but leave the end exposed. This acts … Read more

Get Rid Of Surges That Are Destroying Your PLC Outputs

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DC Solenoids are the worse culprits for electrical surges in your system. When the electrically generated field collapses, an opposite polarity voltage is generated. This voltage spike can be high enough to weld the contacts on a PLC output relay. To protect your PLC output relay, use a diode to ensure that the voltage spike … Read more

The Secret Of Getting Rid Of Noise On Your Analog Signal

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In industrial environments, we often get noise on the analog signal input to PLCs or other controllers. Motors, lousy wiring, etc., can generate noise. Placing a 1- 100 uF capacitor on the input signal and ground (common to the cabinet)  will reduce the noise the input receives. If you have any questions or need further … Read more