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AT2424L: Microprocessor Based Remote I/O Board with RS232 / RS485 Interface


"Let me spin a very large
RS485 network for you!"

  • This unit interfaces 24 opto-isolated inputs and 24 NPN open collector outputs to a host computer through a bidirectional serial port at jumper selectable data rates up to 115.2 Kbps.

  • The addressable bi-directional RS485(2 wire) port provides multi-drop capability at the device count and distance limitations of the EIA/TIA specification. Typically: 32 standard loads at 4000 ft.

  • The addressable bi-directional RS232 port provides point to point communications at the distance limitations of the RS232 EIA/TIA specification.

  • The 24 non-isolated inputs are activated low true using a contact closure, or by a current sinking device.

  • The 24 non-isolated 50VDC 500 mA NPN Darlington outputs pull low to the shared common terminals. The outputs are protected by free-wheeling snubber diodes allowing the outputs to drive inductive relays.

  • The onboard firmware accomodates a wide variety of operational modes. A new, compact, fast command structure enhances the user interface. The classic command structure has been preserved for compatibility with older systems.

  • The extensive flexible command structure is fully explained on the RS485.com web site

  • When factory configured in "Stand Alone" mode, two units serve as a I/O extension pair through the serial link. The inputs on one board energize the corresponding outputs on the other board.

  • LEDs provide visual indication of input , output, data activity, and power level.

  • A polarity protected efficient switching power regulator accepts supply voltages from 9 to 35 VDC (2 Watts max.)

  • User connections are spring loaded "Wago" style terminal strips for I/O, the RS485 interface, and supply power. An RJ11/12 telephone style connector is used for the RS232 interface

  • Broad environmental range. Temperature: -40C to +85C(-40F to +185F). Humidity: 10 to 90% RH(non-condensing)

  • Six(6) easy mount through hole standoffs, which accept #6 hardware, are provided on the circuit board

  • Accessories available are a 12VDC Switching Power Supply(Wall Wart), and a 7ft DB9F-7 to RJ11/12 RS232 cable.

  • We strongly recommend that a first time user of this product purchase the optional DB9F-7 to RJ11/12 RS232 cable.

  • The limitations of the RS232 communications method can be solved by the wide variety of R E Smith devices. Our converters, buffers, isolated converters, and addressable converters mitigate the distance limitations and electrical noise problems that contribute to unreliable communications and product failure.

  • Conformal Coating, other cables, and other connectors are factory options. If what you see here is not exactly what you need, don't hesitate in calling us at (513) 874-4796.

General Description:

This board is used worldwide for gathering digital input data and controlling external devices through the 24 isolated inputs and the 24 form C independent relays. In addition to the commands for reading and writing the I/O points, there are a set of commands, which enable the user to check the I/O status, unit type, unit address, configuration, software version, and jumper settings.

The new command structure maximizes the data flow to and from the board. The classic command structure has been preserved to maintain compatibility with our earlier installed base of units. The choice of command structures is selected by a single jumper, J19. When the configuration jumpers are changed, the power to the board must be cycled to make the changes effective.

The AT2424L Remote I/O Board has 24 opto-isolated inputs and 24-Relay (Form C) outputs. The unit can be controlled by our simple/efficient command structure from a host computer (computer mode), such as a PC. The unit can communicate using RS485 or RS232, at data rates up to 115.2K bits/second. Up to 256 units (in computer mode & with repeaters) can be connected on a single pair of wires to form a large (12288 I/O points) RS485 multi-drop network. The AT2424L has an onboard switching regulator for 9-32VDC operation, LED indicators for all inputs and outputs, 28 jumpers for communications address, Baud rate, mode control, etc. Wago terminal connectors (spring loaded) are provided for ease of installation/removal. The RS485 serial port has built in transient protection and jumper selectable termination. LED indicators monitor the data flow of the serial port. "Less is more" when using our command structure to control the AT2424L. Only short ASCII commands are needed for full control: 1) The "LXX" command addresses the unit and returns the unit address and the input status of IL7 thru IL0; 2) The "K?DD" command can be used to time control any one of the first eight individual relays (K1 - K8), plus the on/off status of the 24 relays, can be updated in groups of 8 with the execution of single commands. Other commands are available to check current I/O status, jumper settings (J8-J24), unit type, and software version. A terminal emulator and a few minutes are all that is necessary to learn our command structure. Quick basic software with source code is also provided to monitor/control the unit. The simplicity of the command structure allows for fast control in large multi-drop networks (less than 20mSec/unit at 9600,n,8,1 and only about 2mSec/unit at 115.2K,n,8,1). Delays are NOT required and bandwidth utilization is at a maximum. All commands and hex data are in capital letters. The range 0-9 and A-F are reserved for data. The letters G through Z are available for commands. Command strings are generally 1 to 4 characters in length. Return strings from the AT2424L are generally 4 characters long; however, larger strings (up to 21+ characters) are also sent for fast monitoring of the I/O status. In addition the

Need something special? Please contact us. We have additional isolated and non-isolated converters, repeaters, and repeater hubs. Units are generally stock to 2-3 business days for shipment. We design and manufacturer our entire product line, and offer technical support for our units, and can offer system recommendations for your application. Please give us a call: 513-874-4796

Related Files:

pdf icon AT2424L.pdf Schematic - CPU
pdf icon AT2424IO.pdf Schematic - Digital I/O
pdf icon AT2424LSS.pdf Physical Characteristics  

Physical Properties and Features:

Additional information coming soon!


Additional information coming soon!

Options and Ordering Information:

Additional information coming soon!

Need a different configuration or more information? Give Ron a Call at 513-874-4796 or 513-638-0228(Cell)


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