Hacked SCSI Hard Drive Cable for 128x64 Screens Using Microcontrollers

Introduction: Hacked SCSI Hard Drive Cable for 128x64 Screens Using Microcontrollers

About: My favorite distraction is Learning and Tinkering.

Long time listener, First time caller to Instructables!  
Welcome to my first Instructable!

This hack is a reuse of the old 40 pin SCSI cables.
I was tired of using breadboard space for loading up a bunch of resistors for driving a 128x64 display on microcontroller projects.

It turns out you can use a SCSI hard drive cable for conditioning signals from your device before it gets to the breadboard.
SCSI cables have 2 rows of 20 wire lines running from one of Female Headers to a middle Set of female headers to the other end of female headers.  Both rows are accessible at any of the headers.

The 128x64 LCD  I am using has 20 lines to attach to my breadboard.  I soak up alot of breadboard space conditioning these signal lines with resistors, potenetiometers or capacitors.  I decided to use the middle headers of the SCSI cable to add these components in.
Row 1 of one end of the SCSI cable attaches to the breadboard with header pins.  Row 2 of the other end attaches to my device, the 128x64 LCD.

I believe this has more potential to make projects more modular, perhaps by adding a small perfboard to the middle header for more conditioning of your data lines.

Step 1: Equipment

I wont go into detail about the microcontrollers, because I am using here a propeller, but this works well for Arduino or any other microcontroller project you are using.
Just note what voltage the reset pin of the LCD need to not constantly reset.  Some microcontroller pin outputs are only 3.3v
This oversight soaked up time in my troubleshooting, I eventually tied the reset pin (17 of the LCD) to 5 V.

For Equipment:
Your microcontroller of choice.
a Schematic of your connections(this came from the propeller obex.)
14  470 ohm resistors
20k single turn Potentiometer( I used a 10 K and seems to work fine)
40 Pin SCSI cable with a middle female header.
                             (prep the cable by taping the same side of each header with electrical tape, see the cable picture for more details.)
128x64 LCD display, I already soldered header pins to the LCD
Something to cut wire and excess leads,  and you might have to strip a wire.   These needle noise pliers with a cutting tool worked great.

Step 2: Prepping the Resistors.

The resistors run across both row for pins 4 through 17.  Below I have step by step pictures for seeing up resistors.   You wasn't three leads short so that three resistors don't short themselves.   Use the leftover leads for jumpers on pins1,2,19, and 20.
Note on jumper 2, you need a jumper thinner than normal because you will need to fit two wires there,  one for the jumper and one for this he potentiometer.   

This first picture is the end result for your 14 resistors.
The pictures are self explanatory.

When you finally cuyt the ends off, use the well of the cutting tool as a guide for how deep to snip the wires.

Step 3: Prepping the Pot.

It was easy for me to get confused on how the potentiometer should be arranged, but looking at the schematic was helpful in keeping me striaght.

Keep in mind what side or row your device is on and what side or row your controller is on.
For me, the blue taped side is  where the microcontroller is located.
The Black side is the side my LCD is located.

Step 4: Assembly

Again for reference:
For me, the blue taped side is  where the microcontroller is located.
The Black side is the side my LCD is located.
Also note that there is a thin red wire tat runs the entire length or the ribbon cable.  This is a reference.
For me, this is a reference for where pin 20 is located. (The first picture will show what I am talkkng about.)

Pin 1, 19, 20 should have jumper pins made from the leftover resistor leads.
Pin 2 has a thinner jumper from a thinner piece of wire.  (I took mine from a smaller resister with thin leads)

Pins 3 and 18 should be left empty for now.

Pins 4 - 17 should have resistors across both rows.

The potentiometer should be added last.  the last image shows how it should fit with the resistors removed for clarity.
The potentiometer is faced inwards.  Thats the only way I could get its middle pin, or the swing arm of the pot, on pin 3.
     Make sure its on the black side, the side with the LCD.
One end of the potentiometer will share the hole of pin 2 on the blue side(the side connected to your controller) with the thin jumper wire.

With the Resistors and Potentiometer with the connecting wire hooked up, it is now ready to try.
After some trial and error on my end, I report the final design here and it is functional.

I can now drop this LCD screen and cable to my Arduino, Basic Stamp or Propeller Chip.

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    6 years ago on Introduction

    i took sort of your idea, i have an old sound blaster card with a 2x20 pin array, connected one of these cables, and can now use other features on the card, it is a ct4830 card