We assume that you want to use a standard (CAT5/6 EIA/TIA-568B) Ethernet patch cable to connect to the RJ45 pass-through connector on the side of the SeaI/O module, due to their low cost, wide availability and various lengths.

If you are connecting a SeaI/O module to another RS-485 device, plug one end of the patch cable into the RJ45 pass-through connector on the side of the SeaI/O module. Cut off the RJ45 connector on the other end of the cable and connect the following wires to your RS-485 device:

• Blue is RS-485 Data + (Data B)
• White/Blue is RS-485 Data - (Data A)
• Both Brown and White/Brown are Common (Signal Ground)

Note: If you are connecting two SeaI/O modules together, you can simply connect them together using a standard Ethernet patch cable. Do not use an Ethernet crossover cable, else you will short the power and ground wires.

TTL I/O devices are commonly used to control solid-state relay modules that interface a variety of input and output devices.  An important consideration in these applications is to make sure that the solid-state outputs are properly configured before being energized. 

Solid-state relays operate using negative logic, where the off state (logic 0) is 5V. Sealevel TTL devices adhere to the Opto22 standard for solid-state relays and are designed to power up in the off state by having 5V present on all I/O pins at start-up. This prevents unintended activation of connected negative logic devices.

Sealevel TTL I/O adapters follow a specific start-up sequence to provide safe operation by guaranteeing a single transition from no state to either 0V (logic 1) or 5V (logic 0).

• As soon as power is applied to the TTL adapter, the I/O pins are pulled to 5V through a 10K Ohm resistor. At this point all I/O pins are inputs and power up in a known state.
• Next, the device driver or firmware applies the preset values from the device configuration to all pins. All TTL I/O pins are still configured as inputs and the preset values have no affect on input pins. Therefore, this step does not change the state of any I/O pins. 
• Finally, the device driver or firmware switches ports that are configured as outputs to an output state. Since the presets were applied before this step, only output pins that are preset to negative logic 1 (0V) change their value. All outputs that are preset to negative logic 0 remain at 5V and do not change state.

All I/O pins remain in this state until the user’s application takes control of the adapter.

"When a circuit requires logic 1 to operate, engineers may refer to this condition as positive logic. Thus, the more positive voltage causes the action to take place. On the other hand, if a circuit requires a logic 0 to cause action, this type circuit is referred to as negative logic.

There is nothing negative or positive about these various circuits. The notation simply provides a shorthand that tells engineers and users whether a logic 1 or a logic 0 causes an action." The Digital I/O Handbook, Chapter 1 Logic Principles, Tom O'Hanlan and Jon Titus

Sealevel digital I/O adapters that use the SeaIO driver support configuring them for positive or negative logic. The relay outputs are configured for positive logic by default, meaning that the relays are in the open or reset position and logic 1 must be written to close or set the relays. If the relays are configured for negative logic (through Windows Device Manager), then logic 0 would be written to close or set the relays.

Optically isolated inputs are also configured for positive logic by default, meaning that the inputs report logic 1 when a voltage is applied across the contacts. If the inputs are configured for negative logic (through Windows Device Manager), then logic 0 would be reported when a voltage is applied across the contacts.

The SeaI/O data acquisition modules use the SeaMAX driver and support positive logic.

All Sealevel TTL Digital I/O products are configured to power up in input mode by default. This ensures that no outputs are inadvertently activated.

Open-collector outputs with circuit protection are the best choice for controlling power to devices with highly inductive loads such as DC motors, solenoids, and high-current relays.

Switching off inductive loads can induce a voltage spike capable of causing damage to relays, digital outputs, or the DC motor itself.

Both SeaI/O-530 and SeaI/O-540 modules have isolated open-collector outputs with integrated flyback diodes. The flyback diode provides a high level of circuit protection against the voltage spike damage caused by switching highly inductive loads.

Non-polarized means that the input trigger condition measures the voltage magnitude across the input, or alternatively the current magnitude through the input, regardless of the actual direction of the voltage polarity or current direction. This distinguishes these optically isolated inputs from polarized inputs because the optical isolator uses a back-to-back arrangement of light emitting diodes. Inexpensive optical isolators will only trigger when the voltage across the input has a specific polarity or the current through the input is in a specific direction.

All Sealevel I/O products with isolated inputs use non-polarized optical isolators for trouble-free field wiring and improved reliability.

Sealevel SeaI/O devices offer flexible I/O expansion to APC Netbotz remote environmental monitoring equipment. All APC NetBotz appliances that have a USB port support SeaI/O 450U and 462U modules to expand the amount of digital I/O. SeaI/O 450U modules provide 16 Form C relay outputs useful for locking doors, turning lights on or off, and other relay controlled actions. SeaI/O 462U modules provide 96 channels of TTL digital I/O useful for monitoring a large number of dry contact sensors. APC has developed a useful application note (download link below) with more information on using SeaI/O modules with your APC NetBotz appliance.

For guidance covering the initial steps of compiling and running individual example projects using Microsoft Visual Studio, please refer to the SeaMAX API Documentation.

To access the documentation from the Start Menu, click All Programs and locate the Sealevel Systems folder. In the SeaMAX subfolder, click on Documentation, and then click on the SeaMAX API Documentation link, which will open in your default browser.

Click on "Example Code & Instructions" under the Getting Started heading. Be sure to also read the "Integrating SeaMAX into Your Project" for a complete list of integration steps.

The SeaMAX Software package automatically installs several application samples with source code in the Example Projects subfolder.

To access the samples from the Start Menu, click All Programs and locate the Sealevel Systems folder. In the SeaMAX subfolder, click on Documentation, and then click on the Example Projects Folder shortcut. Select your development platform from the available choices. Sample applications are supplied for Microsoft .Net C#, native C++, and Microsoft Visual Basic 6.

The sample applications are designed to let you walk through the same integration steps that are required to integrate SeaMAX with your own project.

A Quadrature counter, also known as a Quadrature decoder, shaft decoder, or rotary decoder, is a type of digital input that uses a two-bit Gray code input to increase or decrease a value. The Quadrature counter works in combination with an optical or mechanical encoder, also known as a rotary or shaft encoder, to monitor the exact position, speed, and direction of a DC motor shaft.

The Quadrature counter works by reading the angular position of a shaft and converting it to high resolution digital data. This data is used for synchronizing moving parts for reliable, trouble-free operation. Optical encoders are commonly found in motors installed in industrial control applications, precision robotics, drive shafts, and rotating radar platforms.

Sealevel includes Quadrature counters in certain models of our R9 family of embedded RISC computers.

Sealevel SeaI/O and SeaDAC devices are fully compatible with other Modbus compliant devices, PLCs and applications.  Many third party software applications and PLCs support interfacing digital I/O devices via the Modbus protocol. Sealevel devices with USB, RS-232, or RS-485 interfaces use the Modbus RTU protocol.  Sealevel devices with Ethernet or Wireless interfaces use the Modbus TCP protocol. Detailed information is included in the documentation installed with the Sealevel SeaMAX software.

Modbus information is available at www.modbus.org.

Depending on your application, Sealevel digital I/O products with either optically isolated inputs or TTL level signaling can be used.

Sealevel products with TTL inputs require tight coupling and will work for simple applications where there is a short distance between the input and output modules. TTL signals require voltages of 5 VDC.

Sealevel digital I/O devices with optically isolated inputs offer increased flexibly over TTL level inputs. The optically isolated inputs can interface over greater distances than possible with TTL signals. Optically isolated inputs are compatible with higher voltages (typically 5-30 VDC) and offer protection from ground loops. Each optically isolated input has an inline current limiting resistor and is non-polarized, so they can be wired without regard to the polarity.

Many third-party software packages (and PLCs) include support for the open and well-documented Modbus protocol. Sealevel SeaI/O modules use the Modbus protocol for communication and control. SeaI/O modules with USB, RS-232, or RS-485 interfaces use the Modbus RTU protocol. Ethernet and wireless SeaI/O modules use the Modbus TCP protocol. More information is included in Sealevel SeaMAX library documentation.

The Modbus protocol is documented at www.modbus.org.

SeaIO is the classic software driver that supports our PCI Express, PCI, PC/104, ISA, and classic USB digital I/O devices. SeaMAX is the driver for our latest digital I/O data acquisition products, including SeaI/O modules, SeaDAC modules, and SeaDAC Lite modules.

This is located in the API Documentation file when SeaMAX is installed. From the Start menu, locate the Sealevel SeaMAX folder and choose Documentation and then SeaMAX API Documentation. For Function call descriptions and examples, select the link titled SeaMAX API. This will explain the Usage and API references that fully document the SeaMAX API, including function calls and enumerations.

You can download the SeaMAX manual in PDF format at the link below.

The SeaIO software package automatically installs several application samples with source code in the Samples subdirectory.

To access to the samples, navigate to: [main drive]:\Program Files\SeaIO\Samples. For a listing and description of the samples, refer to the help file located at: Start > All Programs > SeaIO.

This is located in the help file when SeaIO software is installed. From the Start menu, locate the SeaIO folder and choose SeaIO Help. In the contents you will find a section titled Programmers Interface. This will explain the Usage and API references that fully document the SeaI/O API, including samples and descriptions of all calls.

Sealevel Digital I/O products with reed relays are not designed to switch inductive loads such as the coil on another relay. If you need to switch an inductive load, Sealevel recommends using a Digital I/O product with Form C relays instead. You should remember to place a diode parallel to the coil to suppress the inductive kickback voltage. Failing to install a diode will shorten the life of the relay contacts.

Yes. Supporting documentation is located in the help file when SeaIO software is installed. From the Start menu, locate the SeaIO folder and choose SeaIO Help. In the contents you will find a section titled "Active X Controls" that explains the Properties, Methods and Events for Active X I/O control.

Sealevel offers Digital I/O TTL products that interface to industry standard relay racks and solid state relay modules that are designed to sense and switch AC voltages. Relay racks with solid state relay modules are also ideal for switching other relays and inductive loads.