In PLC application and implementation, the terms of digital input, digital output, and also analog input is often heard. Nowadays, people are free to use the digital input and output or the analog input. But before choosing which input is the best, they need to have deeper and further understanding of the term because each method is different from one another and the application is naturally different in traits. So, what is meant by digital input, anyhow?
Digital Input: What Is It?
Most people always associate the digital input as the new and modern ways in operating the PLC program and mechanism. Well, it certainly seems simpler and more efficient than the analog signal, but each of them has their own special characteristic and use. In digital input, the system is using a discrete signals that function as binary switch that will activate the ON and OFF application. The binary system is using basic 1 and 0 or true or false methods. These types of signals are often used to operate switches limits, push buttons, and photoelectric sensors. The signals are available whether in current or voltage form, with specific point is marked as the ON and the other one as the OFF switch. For instance, when a PLC program is using 24V digital signals for the I/O (input and output), the arrangement may be that ON will be represented by values more than 22V while any value under 2V will be considered as OFF signal. Any other intermediate values will be considered undefined. That’s how the discreet signal of digital input works.
Now that people know how the digital input works, they only need to adjust their needs and specifications of the program. In operating the PLC program and system, users interface is still needed because it will act as intermediate between the processor and the process. The interface will interpret the address device that is resulted from the processor because the interface has the ‘logic’ or the program that has been initially designed for such purpose. That’s why in order to make the digital input works, users interface, the required logic, and the suitable program are all needed to work together so the required output can be reached. It’s not easy to understand the overall concept of the PLC program, but PLC experts should know what they must do if they’re about to work with the right digital input and implementation.