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Serial to Fiber Optic Converter

Technical Guide

TABLE OF CONTENTS

Serial to Fiber Optic Converter2

Form: WM-FBROPTICS-TGD-01B Copyright 2017 WattMaster Controls, Inc. WattMaster Controls, Inc. assumes no responsibility for errors, or omissions.This document is subject to change without notice.

WattMaster Controls, Inc.8500 NW River Park Drive · Parkville, MO 64152Toll Free PH: (866) 918-1100PH: (816) 505-1100 · FAX: (816) 505-1101 · E-mail: [email protected] our web site at www.wcc-controls.com

OVERVIEW ................................................................................................................................... 3

Introduction to Fiber Optics ..................................................................................................................... 3Fiber Optic System Overview .................................................................................................................. 4

INSTALLATION & WIRING ..................................................................................... 5Serial to Fiber Optic Converter ................................................................................................................ 5Setting the Dip-Switches ......................................................................................................................... 6Fiber Optic Adapter Board ....................................................................................................................... 7Fiber Optic Adapter Board Wiring ............................................................................................................ 8Technical Details ...................................................................................................................................... 9

WCC III SYSTEM OVERVIEW ............................................................................... 10

OVERVIEW

Serial to Fiber Optic Converter 3

Introduction to Fiber Optics

Introduction to Fiber OpticsIn recent years it has become apparent that fi ber-optics are steadily replacing copper wire as an appropriate means of communication signal transmission. They span the long distances between local phone systems as well as providing the backbone for many network systems. WattMaster Controls, Inc. has designed an RS-485 to Fiber Optic device to work with the WCC III communication network as well as with WattMaster’s other product lines—Orion and Auto-Zone.

Figure 1: WattMaster Controls, Inc. Serial to Fiber Optic Converter for the WCC III System

OVERVIEW


Fiber Optic System Overview

The Fiber Optic System A fi ber-optic system is similar to the copper wire system that fi ber optics is replacing. The difference is that fi ber optics use light pulses to transmit information down fi ber lines instead of using electronic pulses to transmit information down copper lines. Looking at the components in a fi ber-optic chain will give a better understanding of how the system works in conjunction with wire based systems.

At one end of the system is an optical transmitter. This is the place of origin for information coming on to fi ber-optic lines. The optical transmitter accepts coded electronic pulse information coming from copper wire. The RS-485 to Fiber Optic board (PL102335) then processes and translates that information into equivalently coded light pulses. An injection-laser diode (ILD) is used for generating the light pulses. Using a lens, the light pulses are funneled into the fi ber-optic medium where they then travel down the cable. The light (near infrared) that is used within the PL102335 device is 850nm and is generally used for shorter distances up to 2.5 miles long.

Think of a fi ber cable in terms of very long cardboard roll (from the inside roll of paper towel) that is coated with a mirror on the inside of the tube. If you shine a fl ashlight in one end, you can see light come out at the far end - even if it’s been bent around a corner.

Light pulses move easily down the fi ber-optic line because of a principle known as total internal refl ection. This principle of total internal refl ection states that when the angle of incidence exceeds a critical value, light cannot get out of the glass; instead, the light bounces back in. When this principle is applied to the construction of the fi ber-optic strand, it is possible to transmit information down fi ber lines in the form of light pulses. The core must be a very clear and pure material for the light or in most cases near infrared light (850nm, 1300nm, and 1500nm). The core can be plastic (used for very short distances) but most are made from glass. Glass optical fi bers are almost always made from pure silica.

There are three types of fi ber optic cable commonly used: single mode, multimode, and plastic optical fi ber (POF). The RS-485 to Fiber Optic board (PL102335) uses single mode cable.

Single Mode cable is a single strand (the RS-485 to Fiber Optic module (PL102335) application requires the use of 2 fi bers) of glass fi ber with a diameter of 8.3 to 10 microns that has one mode of transmission (RX or TX). Single Mode Fiber with a relatively narrow diameter through which only one mode will propagate carries higher bandwidth than multimode fi ber but requires a light source with a narrow spectral width.

Single mode fi ber gives you a higher transmission rate and up to 50 times more distance than multimode, but it also costs more. Single mode fi ber has a much smaller core than multimode. The small core and single light-wave virtually eliminate any distortion that could result from overlapping light pulses, providing the least signal attenuation and the highest transmission speeds of any fi ber cable type.

Optical fi bers are connected to terminal equipment by optical fi ber connectors. These connectors are usually of a standard type such as FC, SC, ST, LC, or MTRJ. The FOSTC uses the “ST” connectors.

INSTALLATION & WIRING


Serial to Fiber Optic Converter

Serial to Fiber Optic ConverterThe WattMaster Controls, Inc. Serial to Fiber Optic Converter for the WCC III system consists of two parts. The FOSTC Serial to Fiber Optic Converter and the FOSTC Serial to Fiber Optic adaptor board.

With the cover off of the FOSTC Fiber Optic to Serial Converter, Figure 2 shows the Switch detail of the FOSTC Serial to Fiber Optic Converter (shown set for WCC III SAT III communications.)

Figure 2: Serial to Fiber Optic Converter Switch Detail for the WCC III System

In order for the FOSTC Fiber Optic to Serial Converter to work with the WCC III communication, the internal Dip-switch as shown in Figure 2 must be properly set. Please remove the cover and verify the dipswitch setting. The WCC III SAT communications is 19.2K, RS-485 / 2-Wire Mode.

WattMaster Controls modifi es/replaces the standard RS-485 driver in the standard FOSTC Serial to Fiber Optic Converter. This newer driver chip that is installed can handle +/- 60 Volts of differential voltages on the RS-485 “R” and “T” connections with respect to ground. The standard RS-485 driver chips can only handle -7 to +12 Volt of differential voltages on the RS-485 “R” and “T” connections with respect to ground.



Setting the Dip-Switches

Dip-Switch SetupThe Dip-Switch (SW1) on the FOSTC defi nes the mode of operation when being used for RS-422 or RS-485. Positions 1 through 5 on the switch determine the timeout of the RS-485 driver. Because the driver is controlled by hardware, a specifi c time must be set to tell the hardware how long to wait for data on the fi ber side before turning off the RS-422/485 driver. If this time is set too short, the driver could be disabled before transmission is complete, resulting in data corruption. If the time is set too long, the RS-485 device may respond before the RS-422/485 driver in the FOSTC is disabled, thus corrupting this response.

We recommend that the timeout be set for approximately one character time or longer. The character times for several different baud rates are selectable on switch positions 1 through 5. If you need a different timeout than what is provided, R10 can be removed and replaced with a different value R9. Table 1 shows different timeout values for the switch positions as well as typical R9 replacement values.

RS-485 Timeout SelectionBaud Rate

R9 Time(ms)Pos. 1 Pos. 2 Pos. 3 Pos. 4 Pos. 5

1200820 K8.20

ON OFF OFF OFF OFF

2400430 K4.30

ON OFF OFF OFF OFF

4800Not Used 2.20

OFF OFF OFF OFF ON

9600 Not Used 1.30

OFF OFF OFF ON OFF

19.2KNot Used 0.56

OFF OFF ON OFF OFF

38.4KNot Used 0.27

OFF ON OFF OFF OFF

57.6K Not Used 0.22

ON OFF OFF OFF OFF

76.8K Not Used 0.14

ON OFF ON ON OFF

115.2K Not Used 0.10

ON ON ON OFF OFF

153.6K 6.2 K0.06

ON OFF OFF OFF OFF

230.4K 4.3 K0.04

ON OFF OFF OFF OFF

460.8K2.2 K0.02

ON OFF OFF OFF OFF

Table 1: RS-485 Timeout Selection

Position 6 of SW1 sets the unit in a “Multidrop” mode or a “Point-to-Point” mode. When the FOSTC is set in a “Multidrop” mode, data arriving on the Fiber Optic receiver is repeated back out the transmitter. When set in a “Point-to-Point” mode, data arriving at the Fiber Optic receiver is not sent back out the Fiber Optic transmitter. Position 6 must be turned “On” when the FOSTC is to be used in a multi-drop ring confi guration and must be turned “Off” when the FOSTC is to be used as either end of a point-to-point communication line. See Figure 3 for typical system setups using the FOSTC in its different modes.

Positions 7 and 8 of SW1 determine when the RS-422/485 driver and receiver are enabled. Position 7 controls the driver and Position 8 controls the receiver. For RS-422 operation, set both switches to the “Off” position. For multi-drop RS-485 four-wire systems, position 7 should be “On” and position 8 should be “Off.” This allows the receiver to be enabled all of the time and eliminates some possible timing problems. For RS-485 two-wire systems, both switches should be in the “On” position. This disables the RS-422/485 receiver whenever the driver is enabled, preventing data from being echoed back to the fi ber side of the FOSTC.

Table 2 illustrates the switch settings for typical setups.

422/485 Switch Settings Position 7

TX EnablePosition 8RX Enable

RS-4852-Wire Mode(Half Duplex)

ON ON

RS-4854-Wire Mode(Full Duplex)

ON OFF

RS-422 Mode(Full Duplex)

OFF OFF

Table 2: 422/485 Switch Settings



Fiber Optic Adapter Board

Fiber Optic Adapter BoardThe PL102334 FOSTC Fiber Optic Adapter Board provides for a two-wire, RS-485 interface to the FOSTC Fiber Optic converter for the WCC III / SAT III communications loop. It is also the power supply for the FOSTC Serial to Fiber Optic Board.

RS-485 BIAS Jumpers

The RS-485 BIAS jumpers for the terminating resistors need to be ON only when there is no WCC III - MCD connected to the FOSTC fi ber optic adapter board’s SAT RS-485 communication loop.

The RS-485 BIAS jumpers for the terminating resistors need to be OFF only when there is a WCC III –MCD connected to the FOSTC fi ber optic adaptor board’s SAT RS-485 communication loop.

It is recommended that this circuit board has its own 24 VAC transformer for optimal isolation on the RS-485 side.

The LED D3 “POWER” will light when the PL102334 circuit bard has power (24VAC) applied to it.

The LED D4 “COMM” will blink with the fl ow of data to and from the RS-485 communications loop.

Figure 3: The PL102334 FOSTC Fiber Optic Adapter Board



Figure 4: The PL102334 FOSTC Fiber Optic Adapter Board Coupled to the FOSTC Serial to Fiber Optic Converter

Figure 5: The PL102334 FOSTC Fiber Optic Adapter Board Shown in a Typical Application

Fiber Optic Adapter Board



Technical DetailsFiber optic cabling has inherent resistance to EMI/RFI and transient immunity, making it ideal for industrial and utility data communication applications.

The FOSTC was designed to provide the most versatile connection possible between any two-wire, RS-485 equipment using Fiber Optic cable. The FOSTC can be used for point-to-point communications between serial devices or in a multi-drop fi ber ring confi guration, allowing multiple serial devices to communicate with each other.

The FOSTC allows any two pieces of asynchronous serial equipment to communicate full or half-duplex over two fi bers at typical distances up to 2.5 miles (4 km). To extend the distance of the fi ber link beyond 2.5 miles, use B&B model FOSTDRP Fiber Optic Repeater.

The FOSTC uses a separate LED emitter and photo-detector operating at 820 nm wavelength. Connections to the emitter and detector are on ST type connectors. Almost any multimode glass fi ber size can be used including 50/125 � m, 62.5/125 �m, 100/140 �m, and 200 �m. One fi ber is required for each connection between a transmitter and receiver. In a point-to-point confi guration, two fi bers are required between the two modems, one for data in each direction. A multi-drop ring confi guration requires one fi ber between TX and RX around the loop. See Figure 2, page 5 for typical point-to-point and multi-drop confi gurations.

The most important consideration in planning the fi ber optic link is the “power budget” of the fi ber modem. This value represents the amount of loss in dB that can be present in the link between the two modems before the units fail to perform properly. This value includes line attenuation as well as connector loss. For the FOSTC the typical connector-to-connector power budget is 12.1 dB. Because 62.5/125 �m cable typically has a line attenuation of 3 dB per Km at 820 nm, the 12.1 dB power budget translates into 2.5 miles. This assumes no extra connectors or splices in the link.

Each extra connection would typically add 0.5 dB of loss, reducing the possible distance by 166 m (547 ft.). The actual loss should be measured before assuming distances.

Technical Details



WCC III ARCHITECTURE WCC III SYSTEM OVERVIEW

Figure 6: Typical WCC III System Overview with the FOSTC Used to Connect a Second Building to the WCC III System

WCC III Architecture


NOTES

Form: WM-FBROPTICS-TGD-01B Printed in the USA June 2017 All rights reserved. Copyright 2017 WattMaster Controls, Inc. 8500 NW River Park Dr. Parkville, MO 64152 Phone (816) 505-1100 www.wcc-controls.com Fax (816) 505-1101

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