Intro: 4-Digit 7-Segment Display From Trash
It has been a long time since I uploaded an instructable, very long time.
So today I am going to show you how to convert some junk into a nice display!
This display can be used for a clock, that i will publish in my future instructable.
Let's dig in!
UPDATE!!!!!! I have made a clock using this display.Check out this link:
Step 1: Gathering the Trash
I have many broken LCD displays lying around in my collection of e-trash. So i thought why couldn't I make something useful out of it?
LCD displays have some kind of backlight. Smartphones are backlit by LEDs.
Since the displays are broken we cannot use it for anything, but we can recycle the LEDs.
These are the displays I have got:
very old samsung keypad phones(Every LED counts!)
WARNING! : All broken glass are very sharp and it can injure you
wear saftey goggles and gloves before handling them.(Unfortunately I didn't have any of these,so i did everything bare-handed)
Step 2: Getting the LEDs Form the Display
Let's start off by separating the LCD from the back light.
Carefully cut the tape from side of the display and sepsrste it from the metal back plate.
you will now see thick clear plastic on it.
remove it and locate the led strip.
Almost all displays are the same.
For cellphones it is really simple.
Step 3: Preparing the Display
I used an old keyboard's back panel for the display frame.
Is started off by drawing the design on a plain paper and traced them on the plastic back.
Then cut the led strip into individual pieces.
Desoldering the LEDs could damage them.
Test each LEDs using multimeter to see if it is shorted or working.
Glue the LEDs to the board as shown. Each segment contains 2 LEDs at each end.
Step 4: Connections
It is time to connect the segments.
The LED pairs in each segments are connected in parellel indivudally.
Then fix seven long copper wires on the back of the display.
connect all the anode of a's togeather
then the b's on the next wire
do this to all segments
After all the anodes are connected correctly
Run individual wires from each digit
After all the wiring jobs are done it is time to glue the display
pour hot glue on the segments so that the segments will lit up evenly.
Step 5: The Circuit
The circuit is build using 4511 bcd to 7segment decoder ic
we can drive the display without this ic but it would atke 7+4=11pins. That means it would use up almost all digital pins of arduino uno.So if we use this ic it will only take 8 pins
You can use any 7-segment decoders but look for the datasheet before wiring them up.
I used a piece of prototyping pcb
parts list for circuit
ic - 4511 x1
transistor - 2n3904 (npn) x4
resistor -1k x4
Step 6: Testing
The code for this display is written in arduino.
Download the code and upload it to arduino.
Connect the wires in the following order:
d0 pin 2
d1 pin 3
d2 pin 4
d3 pin 5
s1 pin 8
s2 pin 9
Step 7: Final Thoughts
I know that this takes time to build, but we have managed to reuse some e-waste.
This is a green display! (Even if it's white :-))
That's all for this instructable.
I'm sorry that I couldn't capture the video.
If you have any doubts about this leave a comment.
In my future instructable I am going to make an alarm clock using this diaplay.
See you soon!