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Interfacing the WSC-200B Controller
for Illuminated Laser Warning Signs

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The WSC-200B controller provides power to indicator lamps in one, two or three WS-100B, WS-1O1A, WS-102A, or WS-103A illuminated warning signs. These warning signs serve to indicate to persons outside a hazardous area the status of activities inside. Additionally, the controller provides for either manual or automatic operation of the signs; the latter mode relying on signals from the hazard-creating equipment, for example, an x-ray machine or a laser. This technical note will offer some examples and suggestions to those responsible for connecting the WSC-200B to other equipment.

Manual Operation

The WSC-200B produces 24-volts DC (rectified sine-wave), both for the sign lamps and for its internal use. In the manual mode of operation, this power is simply switched to the appropriate warning sign lamps (i.e. red, amber or green to indicate "danger," "caution" or "safe"). For operation of the sign system in the manual mode, the sign(s) must be connected to the controller and the controller plugged in to a 115 volt 50-60 Hz outlet. No other connection is necessary for manual operation. The sign system may be installed and operated in the manual mode until necessary connections for automatic operation are made.

Automatic Operation

When operated in the automatic mode, the WSC-200B normally provides power to the "safe" condition indicator lamps in the warning signs. Two 2-contact connectors provide for two independent remote controls that switch controller power from the "safe" lamps to the "caution" or to the "danger" lamps. Within the WSC-200B, priority logic dictates that "caution" overrides "safe" and that "danger" overrides "caution." In the case, for example, of a laser laboratory where application of power to the laser was used to activate the ''caution'' lamps and the laser ''beam-on signal was used to activate the "danger" lamps, only the "danger" lamps would light during "beam-on" operation, even though both the "caution" and the "danger" signals were present.

Automatic operation is possible from single or multiple signal sources, that is, more than one laser, power supply, switch, or what-have-you can be paralleled such that any of them will activate the desired warning.

The signal required by the WSC-200B is a normally open contact closure. If appropriate, a transistor or SCR pulldown may also be used, particularly if the opto-isolated version thereof is necessary or advisable for isolation of signal sources. In nearly all cases, a simple low-power relay will suffice as a means of providing both the contact closure and isolation required. See interface circuits, below.

CV-1A Converter

Provided as a convenient means of generating the contact closure associated with "power-on" (usually used to activate the "caution" lamps), the CV-1A is simply a low power relay in a box. It is provided with a line cord so that it can be plugged into the same rack, bench, outlet, etc. that the laser or x-ray machine uses for line power.

"Beam-on" Contact Closure

A means of generating a contact closure during the "beam-on" condition may be more involved, however, it is usually straightforward and can be easily fabricated and installed by a competent electronics technician. The need here is to find, preferably in the power circuitry, an electrical signal that is present only during "beam-on." In most equipment there is some switch or relay that is activated to supply power, control a shutter, etc. to enable the beam, turn on the high voltage, etc.

An important point - any connection between the WSC-200B and other equipment should provide electrical isolation, for example, a separate set of contacts, a relay, an opto-isolator, etc.

In the case of a switch, a spare set of contacts may be found, or the switch replaced with an equivalent type having one more set of contacts. Alternatively, the switched power may be used to power a relay of low enough power requirement that neither the switch nor power source is overloaded. Such small relays are generally available in ac or dc versions with coil voltages of 6, 12, 24, 48, 115 and 220 volts. The minimum contact rating for any relay used to provide a contact closure for the WSC-200B should be 1/2 ampere, inductive. In the case of a relay, it is likely that a low power relay of the same coil voltage and frequency can be connected across it. Again, make certain that the additional load of the added relay does not overload the switch, transistor driver, power source, etc., that supplies the original relay.

Interface Circuits

The provision of a wall-outlet receptacle that allows use of a CV-1 converter is shown in Figure 1. An alternative "built in" contact closure is shown in Figure 2. In the event that it is necessary or desirable to interface directly from some equipment's control logic, the circuits of Figures 3 and 4, below are given as examples.

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Installation Instructions For Illuminated Warning Sign System

Two-wire cables are wired contact #1 to contact #1, and Contact #2 to contact #2. Four-wire cables are wired with Each wire connecting a numbered contact on a connector to its counterpart of the same number on the other connector. (numbers can be seen inside connectors) if the installer Would like to standardize on color coding (not necessary, but helpful) the following is recommended (applies to Belden 8444):

4-Pin Connector
(Viewing Wire-Attachment Surface of Male Plug)

Signs with concealed mounting plates are installed by removing the mounting plate, securing it to the wall, then attaching the sign to it. Caution: be certain that the mounting hardware for the mounting plate does not come in contact with the lamp-holder terminals.

Option LL-1A (Long-Life Lamps)

Long life lamps, #1822. Are actually 36-volt lamps that operate on 24 volts with an expected life of five times that of the #1820 Lamps, and with a just-noticeable decrease in brightness.

Option PT-1A (Pigtail Lead)

4-conductor lead, 8 inches long, exits warning sign through center of mounting plate into wall. (Replaces standard 4-conductor plug on bottom of sign.)

NOTE: Installation

WS-100B and WS-103A signs with pigtail leads exiting from the center of the mounting plate are installed as follows: bring control cable (Belden 8444 or equivalent) from controller to hole in the wall, flush box, or other mounting surface. A hole pattern for a four-square box mounted horizontally or vertically is provided in the mounting plate in addition to the normal hole pattern.

Cut pigtail lead to appropriate length, connect each of the 4 leads, matching colors. Color assignment for the pigtail is as follows: Black - common; Green - Green Lamps; White - Amber Lamps; and Red - Red Lamps. A convenient connector for #22 gauge stranded wipe is the white crimp connector commonly used for telephone installation. However, any reliable butt or side-splice connector that completely insulates the connections is ok.

After connecting the pigtail and testing the sign for proper operation, remove the four 6-32 Phillip head screws on the sides of the sign, and attach the mounting plate to the wall and/or the four-square box. Reattach the sign to its mounting plate.

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