Illumination Control

controlled by the DISPLAY potentiometer are shown in

Illumination Control

figure 4-50.

Two circuits control the level of illumination of the

control-indicator's panel lighting and indicators. These

Power Supplies

circuits are illustrated in block diagrams in figures 4-49

and 4-50.

There are two power supplies to the AN/WSN-2

gyrocompass. These are the backup power supply and

PANEL LIGHTING.-- The control indicator

the normal power supply.

panel lighting is controlled by a potentiometer marked

PANEL. The PANEL potentiometer is excited by 15

BACKUP POWER.-- The backup power supply

volts dc. The potentiometer adjusts a biasing level

consists of the inverter and the inverter module, located

applied to the illumination sensing circuit in the

in the synchro signal amplifier, for backup during loss

dimming control circuit card. The output of the sensing

of single-phase power, and the battery set and relays

circuit drives the dimming control amplifier. The output

located on the transformer-rectifier assembly, for

of the dimming control amplifier is an aboveground

backup during loss of 3-phase power.

variable voltage determined by the position of the

NORMAL POWER.-- The normal power supply

PANEL potentiometer. Figure 4-49 identifies the lights

consists of the control monitor, battery charger, 5-volt

controlled by the PANEL potentiometer.

regulator, 13-volt regulator, DC/DC module, and

STATUS INDICATOR AND DISPLAY

transformer rectifier. These are all located in the control

LIGHTING.-- The control indicator's status indicators

power supply. Three-phase, 115-volt ac ship's power is

and the digital display are controlled by the DISPLAY

routed through an EMI filter and power circuit breaker

potentiometer. The potentiometer provides a triggering

to the transformer rectifier for normal power. The

level input (0 volts to +5 volts) to a controlled-width

transformer rectifier converts the 115 volts ac to 35 volts

blanking pulse circuit, located on the dimming control

dc and unregulated 28 volts dc. The 35 volts dc goes to

circuit card. The blanking pulse is applied to the

the battery charger and the unregulated 28 volts dc is

indicator enabling logic, also on the dimming control

sent to the 5-volt and 13-volt regulators.

circuit card. When the input to any indicator, controlled

The battery charger receives high- and low-voltage

by the DISPLAY potentiometer, is determined to be

sensing signals and a temperature-sensing signal from

correct by the display logic, the indicator is energized.

the battery set. The battery charger uses the

The period of the blanking pulse, established by the

temperature-sensing signal to regulate the 35 volts dc to

DISPLAY potentiometer, determines the illumination

provide a charging voltage to the battery set. The

level. Indicators on the control indicator that are

Figure 4-49.--Panel Iighting dimming block diagram.

4-54