Practical Tips and Techniques
A collection of random thoughts on PLC programming and doing more than just basic logic and making your program intuitive. PLC programs usually control the logic between the inputs and outputs. If this turns on and that is not on, then this output is on, blah blah blah. Programmable logic controller programs can go far … Read more
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
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
In part 1, we looked at writing PLC programs to control a traffic light using discrete bits and timed sequencing using indirect addressing. We will now look at how we can use indirect addressing for inputs and output to control the sequence in the program. Let’s look at an example of controlling pneumatic (air) cylinders. … Read more
What is the best way to program a PLC? My answer is simple. The best way is one in which someone can look at your program and understand it. I cannot stress the need for good documentation of your program enough. The best programs are ones that I can return to after several years and … Read more
Programmable Logic Controllers (PLC) will scan very quickly. This can be anywhere from 1 to 20 ms, translating into 1000 to 500 times each second. But what exactly is a scan? A scan is when the PLC will complete the following: Read Inputs: Look at all of the inputs to the programmable controller. Digital, Analog, … Read more