ROB-8A Relay Accessory

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  • Eight SPDT, Form C Relays (DPDT Optional)
  • Fully compatable with any ACCES digital I/O card (except for IOD-64)
  • Contacts rated to 2A
  • Can mount in ACCES T-BOX
  • As many as four cards (providing 32 relays) can be controlled by a single 24-bit digital I/O port
  • Designed, made, supported, and manufactured in the USA
Last updated on November 2, 2023, 6:28 pm


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This accessory card mounts outside the host computer and contains eight Form C electromechanical relays. (Note: Dual Form C relays are available as an extra-cost option, specify model number ROB-8A-S02.) This card is provided with stand-offs and can be mounted on your panel or you can use ACCES’ optional T-Box. ROB-8A receives outputs from Port A of any 24-bit group of any ACCES digital I/O card and Readback is provided at Port B pins. Interconnection is provided by CAB50F-xx ribbon cable.

For Remote (RS-485) control of relays, you can also connect the ROB-8A to our RDG-24.

A “Polarity Select” switch on the card provides means to select relay actuation from either high or low logic levels. An LED associated with each relay illuminates when the adjacent relay is energized. Also, Port C (high nibble) bits are coupled to screw terminals on the ROB-8A card for general digital I/O use. The lower nibble Port C bit PC2 is used for read/write select. Lower nibble Port C bits PC1 and PC0 are used for address decoding if more than one ROB-8A card is used on the same I/O port. As many as four ROB-8A’s can be connected to one 24-bit I/O port. If only one relay card is used, +5 VDC from the I/O card can power the card. If more than one ROB-8A is to be used, then there is a jumper that should be removed and external +5 VDC can be applied at screw terminals on the card(s).

If your application requires that the relays be in a known state at power-up, you may optionally specify additional 2.2 kilohm pull-up or pull-down resistors on the card. If, for example, you wish all relays to be de-activated at power-up and you will have the polarity switch set for actuation on logic HIGH inputs, then you will want pull-down resistors installed. You may specify this with model number ROB-8A-S04. Conversely, if you intend to set the switch for actuation on logic LOW inputs, then you will want pull-up resistors installed and you may specify this with model number ROB-8A-S03.

Relay outputs are brought out to eight sets of labeled screw terminals. The relays used are UL-recognized, non-latching, polarized units designed to FCC Part 68 isolation requirements. These relays can switch up to two amperes DC current with a resistive load or 1.25 amperes AC. Relays in sockets for easy replacement are available as an extra-cost option, specify model number ROB-8A-S01.




Drivers and Downloads

Full list of available Downloads: Software Packages, Drivers, Manuals, and other documents

Information about our Free Software packages:

ACCES is proud to provide a full suite of software support with every Data Acquisition product. We are committed to supporting the most popular operating systems and platforms for our customers. Currently we are actively supporting XP -> 10, both 32 & 64 bit, including “Server 2008,” “Embedded,” and “Compact” flavors for all plug-and-play products including PCI, PCI Express, USB, and more. Many products continue to ship with support for additional operating systems such as DOS, Windows 95, 98, Me, NT4, and 2000.


Among the software we deliver with our products are sample programs in a wide variety of programming languages. These samples are used to demonstrate the software interfaces to our products — and many can be used as-is in your production environments, or to test functionality of the devices out-of-the-box. We’re currently actively supporting sample programs in Microsoft Visual C#, Visual Basic, Delphi, and Visual C/C++, with many devices including samples in Borland C/C++ 3.1 for DOS. Additionally we provide National Instruments LabVIEW compatible DLLs and many demonstration VIs for our devices.


Drivers for various operating systems are also provided, including active support for Windows XP -> 10 — all in both 32-bit and 64-bit flavors, and including consumer, server, and embedded varieties — as well as the 2.6 and newer Linux kernels and recent OSX / macOS versions. Many products continue to ship with driver support for Windows 95, 98, Me, NT4, and Windows 2000, but support for these operating systems is considered deprecated.

Setup Programs and Utilites

Our Data Acquisition devices also include a graphical setup utility that walks you through the process of configuring any option jumpers or switches on the device, as well as explaining a little about the various connectors present.

Many devices also include utility programs – little tools to make your use of the device easier, such as EWriter, a program that allows you to read and write data in the user-accessible EEPROM locations on all our USB data acquisitition products; or WinRISC, a “Really Incredibly Simple Communications” terminal program that lets you get started instantly with serial devices.

“Register Level” Documentation

Besides all this software in all these languages and operating systems ACCES has a policy of open and transparent development: none of our lowest-level “register” interfaces are hidden from you — we document every register in every bus card, every command in every serial board, and every usb control transfer in every USB Data Acquisition board. These lowest-level interfaces allow you to develop for our products in ANY operating system or language, regardless of our actively supporting it or having a driver for it. We have customers actively developing in ADA, Android, Python, Java, MATLAB, Solaris, and more, just by referring to our complete low-level interface documentation! And we provide the full source code to all of our drivers, regardless of operating system, to give you an even bigger head start in your own development tasks.

No Fees or Royalties

All of this software is provided at no additional charge, and is licensed under any of a variety of flexible — and royalty free — options. Check out our software license explanation if you’d like more information.

Custom Software

ACCES also offers Custom Software Services for our products. Our prices are unbelievably low, often as inexpensive as free! If you need something tweaked to support your needs, or an entire enterprise application developed from scratch, it is definitely worth your time to inquire with us, first.

Further information about available ACCES Software:

Redistributing Windows Drivers
A list of ACCES drivers and the files that compose them under different versions of Windows, so you can easily redistribute ACCES cards and drivers.


  • Contacts: Form C, SPDT, non-latching (DPDT optional)
  • Contact Material: Gold overlay silver
  • Max. Switched Current: 2A DC, 1.25A AC
  • Max. Carry Current: 2A, AC or DC
  • Max. Switched Voltage: 125 V DC or AC RMS
  • Max. Switched Power: 30W (DC), 60VA (AC)
  • Operate Time @ nominal voltage: 6 millisecond max (including bounce)
  • Release Time @ nominal voltage: 8 milliseconds max (including bounce)
  • Mechanical Life Expectancy: 20 million operations min.


  • Operating temperature Range: 0o to 50oC.
  • Storage Temperature Range: -30o to +105oC.
  • Humidity: 45 to 85% RH, non-condensing.
ModelDescriptionPrice (USD)

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