Assembling the Geekcreit® 8x8x8 LED Cube 3D Light Square Blue LED Electronic DIY Kit

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Introduction: Assembling the Geekcreit® 8x8x8 LED Cube 3D Light Square Blue LED Electronic DIY Kit

About: Fullstack Dev. Maker. Interested in electronics, C/++, microcontrollers, 3D printing, etc.

I've been meaning to build an LED cube for a while, and I've wavered between sizes, single color VS RGB, kit VS from scratch, etc, but when I happened on this one Geekcreit® 8x8x8 LED Cube 3D Light Square Blue LED Electronic DIY Kit from Banggood for only US$14.29 (on sale) I jumped. Why? Frankly, it's just cheap. And no SMDs! For other kits and DIY cubes, check out this collection of 8x8x8 LED cubes.

Plus, it has commonly used parts:

  • 8x SN74HC573AN Latches
  • 1x ULN2803 Darlington Array
  • 1x STC12 Series Microcontroller

My kit has a STC12C5A60S2, which according to the data sheet: voltage 5.5-3.5V, 60KB flash, 1280B SRAM, 4 timers, 2-3 UART, and 1KB EEPROM.

Not surprisingly, there's no build instructions shipped with the product, but there's instructions/info available for download buried here. That zip includes:

  • "3D8 light cube modulo software" - Windows app which I haven't even tried (I use a Mac)
  • "74HC573" - data sheet for the chip - why just that well known chip? Dunno.
  • "Program HEX and C file" - C Language source and hex dump
  • "Schematic" - which includes am (apparently) Altium Protel .ddb file (I didn't attempt to open), and a PDF
  • "Steps of soldering.pdf" - which is pretty poor. Don't worry, you've got this Instructable.

Don't take any of it as 100% reliable though, as the PDF Schematic includes:

  • A "MAX232" Dual Transceiver that doesn't exist in the parts and there's no obvious place on the PCB for it to go
  • A "80C52" Microcontroller which isn't correct - my kit has the STC as above
  • It shows the latches as 74ALS573

... and the Steps of Soldering shows:

  • SMDs
  • A different PCB
  • Various components not in the kit
  • Different standoffs (metal vs plastic in the kit)

... etc.

... so who knows how accurate the whole thing is!

Step 1: Equipment and Supplies

The downside of any 8x8x8 LED kit is that there's 512 LEDs that need soldering! So make sure you have an iron that works well and you're comfortable using - you'll be spending a lot of time with it.

Equipment:

  • Soldering iron
  • Flush-cut wire cutters (or your preference)
  • Wire strippers
  • Desoldering wick/braid and/or desoldering vacuum pump (optional, if/when you make mistakes)
  • Awl, or pencil, or equivalent thing for punching holes in cardboard
  • Two alligator clip leads (optional)

Supplies:

  • Solder!
  • A piece of corrugated cardboard - at least 5" x 5" x 0.25"
  • Electrical tape - used to hold parts in place
  • An extra soldering iron tip (optional, I ended up burning through a tip - see image)
  • Two AA batteries (optional)

Step 2: Prepare and Solder the Pin Headers

The "top" of the PCB is the side that has the "X" and "Y" axis indicator arrows in one corner.

Each vertical "sheet" of LEDs is held in place by the metal portion of a 8 regular pin headers.

Prepare:

  1. Cut apart the provided 40-pin header into individual pin headers - you'll need 72 of them
  2. Using the flush cutters, cut each one off center - with any luck the plastic will crack and fall off, without ruining the metal pin
  3. Remove the metal pin

Place the pointy end of each one into a white circular hole on the top of the PCB. I found if you heated each pin right at the base of the PCB it would suck the solder right in and stay upright. Along one side there's two pin holes quite close to each other; one is for the vertical LEDs, the other for the common connection.

Make sure each pin is as vertical as possible - it'll make assembly later on easier. Adjust any that are out of plumb - do better than I did ;)

Note: From the pics you can see I soldered the chip sockets first, which was not a good idea.

Step 3: Solder the DIP Sockets

They are not all the same height, so pick the shortest and do those first, then progress the next larger, etc.

Make sure you observe proper orientation by aligning the divots on the ends.

One of my sockets had a busted pin so I had to do a little surgery - see pics.

Step 4: Solder the Other Components

On the top:

  • J2 : Power connector socket
  • S1 : Push Switch
  • D1 : Red LED
  • R1, R2 : 4.7K Ohm resistors
  • C1, C4 : Electrolytic 10uf Cap, make sure to get the polarity correct

On the bottom:

  • R3 - R10 : 470 Ohm resistors
  • C2, C3 : 22pf ceramic caps (unpolarized)
  • Y1 : 12Mhz crystal

Unused/optional:

  • J3 (VCC, GND, P30, P31): put a 3-pin (included, skip VCC) or 4-pin pin-header here for programming
  • S2, S3: for momentary push-buttons (not inclued), which can be used with custom code

Finally, there's J1, the 10K Resister Array, and that'll be addressed in the next step.

Step 5: J1 - the Resistor Array

Although "J1" is on the bottom, it's close to a socket, so I found it easier on solder it on top. I used some tape to hold it in place while soldering. You'll need to find the common pin first.

Determining the array common pin and resistance:

Lacking any markings you need to identify the common pin.

In general, pick two adjacent "inner" pins and measure the resistance - it'll be twice the per-pin resistance (in the pic it's 19.99).

Then try an end pin and an adjacent one. If it's half the above measured value (in the pic it's 9.96), that end pin is the common pin.

Step 6: Seat the Chips

Make sure you observe proper orientation by aligning the divots on the ends.

You'll probably have to bend the pins of the chips inward. Make sure you do this slightly, slowly and evenly - and ground yourself so you don't have any static.

Sorry, no pics.

Step 7: Prepare to Solder the LED "Sheets"

Polarity and "The Bend":

LEDs are polarized. The positive or anode side has the longer lead. The negative or cathode has the shorter lead and also the rim on the LED on that side is "flat".

The LEDs have to be bent at different points to ensure that the positive and negative portions of the grid don't touch.

The +/positive/anode/longer-lead side gets bent right where it goes into the clear plastic of the LED. It's also bent "down" or perpendicular (to the line between both LED pins).

The other lead, the -/negative/cathode/shorter-lead, gets bent right at the point where there's a flat point in the lead - you should be able to see it or feel it. It gets bent perpendicular to the other lead (so in-line with the line between both LED pins).

The Layer Jig:

Using the cardboard, mark out an 8x8 grid - spaced at 1.5cm.

Get the corners correct and "square", then fill in the edges, then inside. If yours looks better than mine you'll be better off.

Use the awl (or whatever tool) to make appropriate sized holes that will fit the LEDs snugly.

LED Jig:

With another piece of cardboard I made another LED hole and marked off where to trim the leads - after you bend them. Trim them so they'll overlap by ~0.5cm. Increase this if your grid isn't very accurate or you find your bending isn't accurate.

But don't trim them all that way; the ones on the right and bottom edges need one long lead each (see next page's image), and the one LED on the bottom/right needs two long leads.

LED Tester:

I built a tester out of two AA batteries and two alligator clip leads, held together with electrical tape. When the batteries are new it's ~3.2V which is perfect for the LEDs.

Step 8: Soldering the LED Sheets

The +/positive/anode/longer-lead (well, before you cut them)/bent-at-the-base lead points "down" (or towards you in the pic).

The -/negative/cathode/shorter-lead (well, before you cut them)/bent-offset lead points "right".

When the LEDs are loose and have nothing fixed to brace against it's toughest to solder them. So, I soldered the right side, then the bottom. Then placed and soldered each line at a time.

Once complete the whole grid should pop out easily and without bending (see last image).

Step 9: Test Each LED of Each Row As You Complete Them.

Connect the positive side of your 3ish volt power source to the bottom of each column, then drag the negative side along the right side rows of the "sheet". You should see each light up.

If you find a one that doesn't light, check your solder. I had one (shown) that was bad.

Once I finished all of the "sheets" I re-tested them all - you don't want to have to unsolder the completed cube once it's done!

Step 10: Getting the "sheets" on the PCB

Getting all 8 leads seated into the pin headers can be a bit of a trick. Each lead should sink solidly into the pin headers. Make sure the row "end" leads are all facing the correct way.

If you've soldered the pin headers in straight it'll be easier.

Once you've verified it's seated correctly and completely, solder it.

Step 11: Soldering the Sheets Together

You'll want to ensure the space between sheets is 1.5cm.

Bend each "end" about 1cm from the LED, and trim so as keep the overlap just enough to solder.

For each sheet, I soldered a top and middle-ish "end" lead so as to give it some rigidity.

Once you have all the sheets connected by a couple leads, solder up the remaining.

Step 12: Add the Cathode (negative) Wires

My kit came with black wire, but I used 22 gauge solid hook-up wire. I think white "disappears" better against the silver leads.

You can see I started on the left and worked my way to the right, getting sloppier. Try to cut it to size better than I did. ;)

Step 13: Left Overs. No, Literally "Left-over" Parts.

Left over parts include:

  • 58 LEDs
  • DIP socket
  • the black wire (where I used white)
  • 3-pin 90 degree M-M pin header ... although this has a use....
  • 3 loose cut pin headers
  • 74HC573 chip!
  • 22pf ceramic cap

Step 14: The Grand Finale!

The video shows the built-in demo code.

I'm working on some new code, but that'll be a different Instructable.

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    26 Discussions

    0
    BarryD58
    BarryD58

    5 months ago

    I'm halfway finished building my led cube and I noticed the "I 💙 U" is inverted, or upside down. My cathode leads are oriented accurately, c1 on level 1, as in the instructions. Any advice?

    0
    SeanAlexander
    SeanAlexander

    Reply 27 days ago

    Try reversing your negative wires. I noticed the same thing on mine and inverting the cathode connections worked for me.

    0
    BarryD58
    BarryD58

    Reply 27 days ago

    Thanks man. I actually did exactly that about two months ago and it's been working ever since. I put it together right; I guess a few we're inverted accidentally.

    0
    doormat_1
    doormat_1

    6 months ago

    Hi,
    I've built this and want to recode the animations. I have managed to do this when it is tethered to my PC. Anyone got an idea how to bake these in so it will run off any powersource?

    0
    Linkersinho
    Linkersinho

    9 months ago

    Hi, what do you think about C4 capacitor change for bigger one, is it good idea? Maybe it will be better for LEDs ,because power supply filtration will be better?

    1
    kazuhiko.mikuni
    kazuhiko.mikuni

    1 year ago

    I made same kit. But my LEDcube was so dark.
    I carefully observed the schematic and found a mistake in the location of the current limiting resistors.

    In the original circuit, the limiting resistors are connected to the cathode common, and as the number of lit LEDs increases, the current flowing to each LED decreases. If the resistance connected to the sink driver (ULN 2803) is set to 0 Ω and 64 pieces are connected in parallel to the LED anode side, the current flowing to each LED is stabilized.

    My LED cube with the above improvements lighted up brightly. For your information.

    improvement.pngDSC_1067.JPGDSC_1069.JPG
    0
    ToddZebert
    ToddZebert

    Reply 1 year ago

    Thanks - that seems like a great hack! How did you come up with 570ohm value?

    0
    kazuhiko.mikuni
    kazuhiko.mikuni

    Reply 1 year ago

    My kit incuded red LEDs(almost Vf=1.9V) and 510ohm resistors.
    I decided the current value to 7mA by LED brightness.
    If If=7mA then R=(V-Vf)/If=(5-1.9)/0.007=442.9ohm(=470ohm).
    If using BlueLEDs(Vf=3.2~3.7V), so R is 200~240ohm, I think.

    0
    ToddZebert
    ToddZebert

    Reply 1 year ago

    Sounds good, thanks!

    2
    LedMick
    LedMick

    2 years ago

    Thanks for showing this so clearly. I have just ministering and like TonyM60 mine is going very fast. I'm new to electronics so not sure which component causes the circuit to go fast or slow. In my kit R1 & R2 are 47k ohm in your article yours are 4.7k ohm could this be my problem.

    I also use flat ice lolly sticks to keep the gaps at to top of the 8 rows of LED's tapped properly, I made 8 marks 15mm apart and using a 12" hacksaw blade I cut slots halfway through the stick. I put one front and back, this kept them downloaded while bending and soldering the legs together.

    I also marked out the 64 hole jig on an old piece of flooring laminate, I drilled the holes with a 3.2mm drill, the extra 0.2 made it possible to remove the frame.

    0
    ToddZebert
    ToddZebert

    Reply 1 year ago

    I should verify my resistor as I can't recall if I measured it, read the codes, or just took the value from the instructions.

    0
    RitchieW
    RitchieW

    Question 1 year ago on Introduction

    So I have extensive experience building boards and kits. I'm quite certain I assembled the board correctly. I stuck an LED in one of the first row cathode/anode sockets as I've seen on youtube as a sanity check. Unfortunately it just glows at about 30% duty cycle. It definately AC because I can shake the board an see a trail of blue dots. I checked VCC and GND on all the chips, verified pin 9 reset was low, and inspected all the solder joints. When I applied power, there was a short delay then the blue LEDs come on dimly, but no activity whatsoever. Should I try and reload the uC? I have the 4-pin header and serial driver kit. Any hints/clues? Thanks, Ritchie

    20190108_215123.jpg
    0
    ToddZebert
    ToddZebert

    Answer 1 year ago

    Ritchie, I haven't seen that. I suspect kazuhiko's answer is probably correct and there's either no or incorrect firmware.

    1
    joscthomas
    joscthomas

    1 year ago

    Todd, I appreciate you taking the time to post this! I don't think I could've figure it out otherwise! Thanks, Joe

    0
    n7rgw
    n7rgw

    Question 2 years ago on Step 10

    Still not certain which end of the diode actually plugs into the PC board? I can rotate the diode banks at this time if I am wrong.

    0
    ToddZebert
    ToddZebert

    Answer 2 years ago

    Sorry, but I reviewed my write up and still don't understand your question.

    0
    n7rgw
    n7rgw

    Answer 2 years ago

    Solved the problem. I did not see anywhere in the description that you place the positive or anode side of the LED bank into the pins on the PCB. I reviewed what you had written and on Step 12 you said to attach the Cathode wires, so I interpreted that the solution was to put the anode side in the individual bank pins while the cathode wires went into the extra pin bank. The schematic doesn't show the orientation of the LED's either.
    Sorry that my original question was not clear, but it is working great now.
    Thanks for your great article. I would not have been as successful without it.

    0
    ToddZebert
    ToddZebert

    Answer 2 years ago

    So glad it worked out! I'm re-reading my Step 12 ... any suggestions on how I can make it clearer?

    0
    TonyM60
    TonyM60

    3 years ago

    Thanks for this. It cleared up the array solder connections for me. Mine runs a lot quicker than yours and probably a different demo program. Anyone else experience the same outcome? In my demo, if you can avoid blinking, you can just see a "Good Luck!" message and a beating heart.