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More Details about Digital Input Modules

Input/output Modules form an important part of control systems used by industries to automate processes. They are used in conjunction with other equipment like programmable logic and automation controllers as well as distributed control systems. A digital input module’s primary function is to gather and measure information in the form of input signals from a variety of sources like limit and proximity switches and push button switches as well. USB Digital Input Modules are usually found in 0-24V with built in tolerances of up to 30V.

Simply put, input ports work like gates and let information pass from external devices to a computer’s data center at specific times. To avoid conflicts, input ports are connected to the data bus only when they receive the proper signals. At other times they have to disconnect from the data center. For all of this to work as intended, modules have to be programmed before they can be used.


How the signals work

Signals sent from DC sensors in PLC input modules tend to be of a higher voltage and have to be isolated before they can be serialized. Digital input serializers are used to channel a larger number of inputs to PLC I/O modules. Isolation is then limited to specific SPI interfaces by using a daisy chain method. This provides the benefit of sensing higher voltages, programmable debounce time and adjustable current limits.

USB Digital Input Module

A large number of control applications used by industries need to use low cost PLCs combined with a number of USB digital IO modules with built in functions like timers, numerous SPI Ports, low power, UARTS and so on.

Current USB Digital Input modules available on the market can be connected to any computer and offer a variety of choices like optically isolated inputs, Form C and Reed relays, TTL interface and solid state relay racks as well. Well designed software drivers make using these modules as well as troubleshooting for problems extremely easy. Digital input modules can be used with any OS and reassembled in different configurations.


Types of USB Digital IO Modules

  • Ethernet digital IO modules allow for remote monitoring from anywhere in the world. Modules are powered by 9-30VDC sources or one can use the RJ45 connector.
  • PCI Express digital inputs are designed to work with computers which have an X1 PCI slot.
  • Optically isolated inputs are designed to protect the computer from surges in voltage which can be quite common to different industries. Reed Relay outputs are designed for reliable and long life switch closures which are best suited for applications with low current.

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