Ampro Corporation LITTLE BOARD P5X - Manual (Page 61)

Little Board/P5x Technical Manual
2–43
Table 2– 34. LCD Bias Supply Option Connector (J4)
J4 Pin J3 Pin Description
1 Ground
2 +5V to the Vee Supply Option board
4 Ground
6 38 Enable Vee — TTL control signal, driven by the VGA
controller chip
8 Ground
11 46 Vee Output, to panel
12 47 Contrast adjustment — analog control signal
Selecting Vee Polarity
Most LCD displays require a Vee supply of between 15V and 35V. Some panels need a negative
supply, and some a positive supply. The LCD Bias Supply Option provides a jumper for selecting
the Vee output polarity. To select the polarity for the panel you will be using, set the jumper on W1
(on the LCD Bias Supply board, not on the Little Board/P5x) as follows:
! Negative Vee W1-1/2
! Positive Vee W1-2/3
Note
Incorrect Vee polarity or voltage can damage an LCD panel. Set the
polarity and voltage on the Vee supply before connecting the LCD
panel.
Attaching an External Contrast Control
Vee controls the contrast of the LCD display. (Do not confuse this with a backlight, which
illuminates the screen using one or more fluorescent tubes. Backlights generally require a high
voltage AC supply.)
An on-board control (R1) on the LCD Bias Supply board allows you to set the precise Vee voltage for
the contrast you require. However, you may want to provide a more accessible Vee control so that a
user can set the display contrast to accommodate various ambient lighting conditions. The board
provides a jumper and control signal to allow the attachment of a remote potentiometer.
To use the contrast potentiometer on the LCD Bias Supply board, install a jumper on W2 on the
LCD Bias Supply board.