Practical Tips and Techniques
Wiring outputs to the plc like relays and motors.
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
We apply the five steps of PLC development to a plc shift register example. This PLC programming example will use a shift register to reject a product on a conveyor. When programming a PLC, you need to track what has previously happened. Shift registers allow you to do just that. We will look at a … Read more
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 outputs, Discrete and analog. Discrete outputs are either ‘ON’ or ‘OFF’; 1 or 0. You can think of them as a single light bulb. Analog outputs have a range … Read more
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
The term I/O means Input/Output. I/O can come in two different types; Discrete or Analog. Most people starting out learning about programmable logic controls (PLC) are taught all about discrete inputs and outputs. Data is received from devices such as push-buttons, limit-switches, etc., and devices are turned on such as motor contactors, lights, etc. Discrete … Read more
