4-Digit 7-Segment Display From Trash




Introduction: 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:

Lenovo tab

ASUS phone

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

s3 pin10

s4 pin11

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!

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    2 years ago

    this instructable revived one of my dying ideas!!! I wanted to make a custom SMD LED, 10 segment display. this project laid dormant for a while because I didn't know what I could use to shine the light in a bar-like fashion... and I see you use hot glue on yours and it works beautifully. THANKS A MILLION!

    I'll show you and everyone else what I have made when it's finished ;)


    3 years ago

    Wow, very nice project, I love how this was done using mainly discarded materials!


    Reply 3 years ago

    Also the transistors and resistors were from trash


    Reply 3 years ago

    Cool, is it common that such components are still intact in broken electronical devices? We still have an old tv with a broken LCD screen, do you think I would be able to salvage anything from that? (and is there any danger?)

    I'm a beginner at electronics, so I don't know much about this stuff, but the idea of recycling electronic components is appealing to me.


    Reply 3 years ago

    I took the transistors from a small led solar light, which is about 15 year old! It,s battery leaked and the pcb was destroyed and the solar cell was not working.

    In an LCD TV you cannot get LEDs for this display(old LCD TV have CCFL backlights).

    But you can take the speakers, some connectors, and there is a big piece of transparent plastic for spreading the backlight.

    Maby I will create an instructable to salvage the polarising filters without damage


    Reply 3 years ago

    Thanks for your reply


    3 years ago

    I was probably thinking what to do with my junk display? Thank you for helping me. Love this one for sure....


    3 years ago

    I like how absolutely no money was spent on this!