The sample LCD unit that I am using in this article was housed in a larger module which was sourced from a digital
satellite receiver. There are a total of 6 screws and a couple of clips are all that hold the LCD captive. Once
freed, the LCD is much smaller than my first impression had suggested.
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Click image for larger view
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Click image for larger view
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Click image for larger view
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Click image for larger view
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The printed circuit board of the larger module connects to the LCD using a 16-pin socket. Using a soldering iron, I removed
the socket from the circuit board. We will make all of our connections to this socket so the LCD will be easier to remove
in the future, especially if you plan to mount the LCD in a removable panel.
Click image for larger view
The build is broken into three parts:
- Connecting the printer cable to the LCD socket
- Building the circuit board for contrast and backlight control
- Connecting the circuit board to the LCD socket and printer cable
Connecting the LCD and Printer Cable:
The first step is to cut off the Centronics connector (printer end) from the printer cable. The next step is to strip the
covering back to expose the wires inside. Use a voltmeter set to impedance or continuity in order to find the correct wire
for pin #1. This step is accomplished by holding one lead to pin #1 and then touching the other lead to the cut end of
each wire until the meter changes from 1 to 0 or some small resistance reading. Record the wire color and repeat for the
other 24 pins. On my cable pins 18 though 25 where tied together into one black/white strip wire.
| Parallel Port Pin # |
Wire Color |
|
1
|
Brown
|
|
2
|
Red
|
|
3
|
Orange
|
|
4
|
Pink
|
|
5
|
Yellow
|
|
6
|
Green
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7
|
Mint Green
|
|
8
|
Blue
|
|
9
|
Purple
|
|
10
|
Grey
|
|
11
|
White
|
|
12
|
Black
|
|
13
|
Brown/White Strip
|
|
14
|
Red/White Strip
|
|
15
|
Orange/White Strip
|
|
16
|
Green/White Strip
|
|
17
|
Blue/White Strip
|
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18-25
|
Purple/White Strip
|
NOTE: The wire colors above are for reference only, your cable may be different.
Verify the pin layout of the LCD socket next to the LCD. I have arranged the diagram where the socket would be plugged
into the back of the LCD and the solder leads would be sticking up with the LCD face down. Now using the color coding
you just created attach the following parallel port pins to the designated LCD pins. Use a small piece of heat shrink
to insulate each connection, just remember to put it on before you solder the connection.
|
LCD Pin
|
Parallel Port Pin
|
|
4
|
16
|
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5
|
14
|
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6
|
1
|
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7
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2
|
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8
|
3
|
|
9
|
4
|
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10
|
5
|
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11
|
6
|
|
12
|
7
|
|
13
|
8
|
|
14
|
9
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Click image for larger view
I removed the pins from the socket to make soldering easier.
