I/O-Modules
Fox Series
Lightbus - Coupler

The TRS Fiber Optic Industrial Input/Output System, which is referred to as the FO-II/O system to save space, consists of an intelligent central module and an optical waveguide-based field bus. The TR-Fieldbus Systems Industrial Input/Output System is a universal input/output system for industrial control technology. 

Depending on the system (PC/AT, SMP, AMS, AT96, VME, SIMATIC, Mitsubishi etc.), the link between the FO-II/O system and the host is implemented by means of a Logic Cell Array. This guarantees fast, convenient communications. Various FO-II/O peripheral modules are available for processing the process image. These modules are connected together in a ring structure. 

By contrast with other types of communication, which are based on handshaking, in a fiber optic ring only the central unit is active and the other input and output modules that are connected in the ring are passive. This makes possible rapid data communication with these modules. 

Data transfer on the optical waveguide is specified by a communications protocol that is optimized for speed and simplicity. This type of communication means that the message that the central unit transmits is received by each module, which interprets it and passes it on with a delay of approximately 1.5 µs. With a wavelength of 660 nm, the fiber optic-bus achieves a maximum transfer rate of 6 Mbps. The system that TRS Fieldbus Systems uses has a transfer rate of 2.5 Mbps; in this connection, the entire transfer time of 25 µs is needed for one 32-bit message. This means that with a central unit connected to ten modules, the system triggers and updates all the modules in approximately 300 µs. The central module detects any faults that may occur in the fiber optic ring and reports them to the host system. The implemented ring diagnostics functions then make possible rapid troubleshooting and removal of faults. 

The central module controls communication in the fiber optic ring. It transmits messages that run through the individual modules in the fiber optic ring and finally receives them again and checks them. 

The use of optical waveguides provides significant advantages compared with conventional copper cabling:

• High transfer capacity

• Low signal attenuation

• No electromagnetic disturbances

• Potential freedom

• Low weight

Fox-10

          

Fox-10 Base Module fitted with three Input and one Output Submodules

The Fox-10 is a cost effective input/output module. It fits only digital input / output submodule. This is most times used if you need 32 or less I/O points.

Fox-20 Base Module  with one analog input, one analog output, 
 one digital input and one digital output submodule 

The Fox-20 base module is used if you have a high density of digital I/O points (up to 64), any analog, any position or pulse with modulation submodules.

Power Supply

You connect the power supply for the control logic via the four pin connector terminal X10 on the upper left side of the module.

Connector X10:

Connector X90 / X91:

Pin	Signal	Description
X90	FO-OUT	Fiber optic ring OUTPUT
X91	FO-IN	Fiber optic ring INPUT

Three LEDs provide information about the status of the module:

Power LED Base Module (+5V only Fox-20)

Error LED (Error (Fox-10) or (PAE) Fox-20)

Cycle LED (CYC)

Watchdog

You mount the DeviceNet base module off-center of the machine or in control cabinet by simply fastening it to a device mounting DIN rail.

Setting the Transmission Power

In the LED connection cap, there is a rotary switch that you can turn from outside using a small screwdriver. A green LED shows the switch setting: if the LED is lit up, the transmission power is set to 10 m .. 45 m with plastic cable or 60 ..300m with glass fiber cble; otherwise, the system runs at a power reduced by 4 dB with fiber optic cable lengths of 0.2 m .. 15 m.

Technical Data

Two base types of fiber optic cable are available, i.e. all plastic fiber, APF and plastic cladding silica fiber, PCS. You can lay both types on a trailing cable chain, since the varying load meets the requirements. The fiber optic cable transmission and reception chips are designed for APF as well as PCS cables. APF cables guarantee safe data transmission up to 45 meters; with PCS cables, this distance is 300 meters. Using special transmission chips with PCS cables, you can achieve distances of up to 1000 meters. 

PCS cables need different connectors from APF cables, however the II/O modules are identical (up to 300 meters). In addition, you need special tools for PCS cables.

You can use a measuring instrument to measure the attenuation of the cable or of the connector.

The II/O modules are connected to the bus link via fiber optic plug-in connectors X90 and X91 as shown in figure 2.

Preparing the Fiber Optic Connector

It is quite easy to prepare the fiber optic connector on the APF cable. First of all, you strip about 25 mm of the 6-mm polyurethane jacket and cut off the Kevlar strain relief appropriately without damaging the black internal sheath. After this, strip 7 mm of the black internal sheath using a cable stripper or a special cable-stripping tool. Under no circumstances must you damage the transparent fiber while doing this. Ensure that the cut surface of the fiber does not split. By feeding in red light at the other end of the fiber, you can check the end of the fiber. You then push the fiber from the back all the way in to the connector and then push in the clamping fixture in to the connector using a screwdriver or similar tool. After this, sand the end of the fiber that is sticking out of the connector at right angles to the connector; to do this, first use 600 grain and then 1000 grain emery paper. You must not sand the connector itself. Do not use any chemical-based polishing pastes, as they harden the fiber. It is sensible to use a magnifying glass to check the results.

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Copyright © 2000 TRS Fieldbus Systems, Inc. All rights reserved.
Revised: August 08, 2000 .