LUDLUM MODEL 2241-2 Technical Manual page 26

Model 2241-2
Refer to the Switch
Board schematic for
the following:
Refer to Display
Board schematic
for the following:
Ludlum Measurements, Inc.
Technical Manual
S1 (FUNCTION)
S1 is a 16-position binary rotary switch, which selects the programmable
parameters for the Model 2241-2. The switch selects the parameters using
the hexadecimal numbering system via buss lines
S2-S4
S2-S4 are pushbutton switches that enter/change the variables for each of
the 16 parameters.
U1
U1 is a +5 V powered RS-232 driver/receiver used to interface the Model
2241-2 to a computer.
LCD Drive
U111 and U211 are serial input 32-bit LCD drivers. The data is loaded
serially into the 32-bit shift registers (internal) via the "D" IN input. The
input instructs the shift register to receive data while the
LOAD
shifts the data through the 32-bit registers. After all the data is loaded, the
line is pulsed by the µP, instructing the registers to transfer the data to
LOAD
the LCD drivers. The backplane (BP) signal from U211 provides the
reference signal (approximately 125 Hz at 5 Vdc) to the LCD (DSP1) BP
connection. When a segment is illuminated, the signal to that segment will
be out-of-phase with the BP signal. If the segment is
in-phase with the BP signal.
Backlight Drive
Depressing the
LIGHT
31 on µP, "low" for the predetermined backlight
board schematic for details.) A "low" condition on pin 31 causes Q212 to
conduct sending +3 V to P8-3 on the display board with +3 V at P8-3
(refer to display board schematic). Backlight oscillator Q011, T011, and
related components start to oscillate, producing a 2.5 kHz, sine wave signal.
The signal is amplified by T011 to 150 volts peak-to-peak to drive the LCD
backlight.
button instructs the µP to set the
Page 7-3
Section 7
1- 4.
SW SW
input
CLOCK
, the signal will be
OFF
line, pin
BACKLIGHT
time. (Refer to main
ON
January 2016