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Step 13: Choose your LEDs

There are many things to consider when choosing LEDs.

1)
You want the LED cube to be equally visible from all sides. Therefore we strongly recommend using diffused LEDs. A clear LED will shoot the majority of it's light out the top of the LED. A diffused LED will be more or less equally bright from all sides. Clear LEDs also create another problem. If your cube is made up of clear LEDs. The LEDs will also partially illuminate the LEDs above them, since most of the light is directed upwards. This creates some unwanted ghosting effects.

We actually ordered diffused LEDs from eBay, but got 1000 clear LEDs instead. Shipping them back to China to receive a replacement would have taken too much time, so we decided to used the clear LEDs instead. It works fine, but the cube is a lot brighter when viewed from the top as opposed to the sides.

The LEDs we ordered from eBay were actually described as "Defused LEDs". Maybe we should have taken the hint ;) Defusing is something you do to a bomb when you want to prevent it from blowing up, hehe.

2)
Larger LEDs gives you a bigger and brighter pixel, but since since the cube is 8 layers deep, you want enough room to see all the way through to the furthest level. We went with 3mm LEDs because we wanted the cube to be as "transparent" as possible. Our recommendation is to use 3mm diffused LEDs.

3)
You can buy very cheap lots of 1000 LEDs on eBay. But keep in mind that the quality of the product may be reflected in it's price. We think that there is less chance of LED malfunction if you buy better quality/more expensive LEDs.

4)
Square LEDs would probably look cool to, but then you need to make a soldering template that can accommodate square LEDs. With 3mm round LEDs, all you need is a 3mm drill bit.

5)
Since the cube relies on multiplexing and persistence of vision to create images, each layer is only turned on for 1/8 of the time. This is called a 1/8 duty cycle. To compensate for this, the LEDs have to be bright enough to produce the wanted brightness level at 1/8 duty cycle.

6)
Leg length. The cube design in this instructable uses the legs of the LEDs themselves as the skeleton for the cube. The leg length of the LEDs must be equal to or greater than the distance you want between each LED.
<p>hello all of you, I have an idea to replace 16 BJT by ULN2803, it would save up for your area, and it works very tot.Toi did 2 cube leds and it all works fine however, I did not design the RS232 connection on my circuit. and here are some pictures about it:</p>
<p>You can use even less space using SMT 2N2222 type transistors. My board will take either.</p>
<p>Can you please kindly send me the circuit and diagram.</p><p>MAy mail add<br>isurutharanga019@gmail.com</p>
Can you please kindly send me the circuit and diagram.
<p>The circuit diagrams for this project are in this instructable.</p>
My email address is sisirroy777@gmail.com
<p>Hi DongP1, I am so like the Cube and I want to make it and give to my girl friend as a big surprise. Can you send all schematics ,programs and other files to me . Thans so much.</p><p>My e-mail address: dongliang.ma@matrixopto.com </p>
https://drive.google.com/file/d/0BzXbfPpoHKV5eWQxU1VQODZhTTA/view?usp=sharing
<p>Hey guy, if i use STK500 device to set up for atmega32 then plug it to the board , so, can i remove RS232 and AVR Isp?</p>
<p>sir, i have successfully made my cube, now the problem is with the code... im using arduino uno and the code given in this article i.e for arduino user is working fine for me... but other codes which are used for AVR is not compatible with aduino ? does coding for both arduino uno and AVR are different ?</p><p>i got a error as &quot;compilation terminated </p><p> exist status 1</p><p> error compiling &quot;</p><p>if there is solution for this plz post . </p><p>and the code in the link which u gave is compatible with arduino uno ? </p><p> Thanks :)</p>
<p>You likely need an older, or possibly a newer copy of the IDE.</p>
<p>sir presently im using latest version of IDE i.e 1.6.7</p><p>can i know the the exact version of IDE ??</p><p>and sir how can i make others codes compatible with IDE?</p><p>Thanks :)</p>
mail me.. 233himanshu@gmail.com
This is here. https://drive.google.com/file/d/0BzXbfPpoHKV5eWQxU1VQODZhTTA/view?usp=sharing and don't need chager in program .
<p>Hi Phamd4 , thank you so much. I have another question, I can not open the CUBE schematic and pcb files with Protues Desing Suite 8.0 , my computer is Win 7 system. whether the version of the Protues is not matching? Can you help me .</p>
<p>Hello DongP1, <br>Can you share a more clear schematic how did you used the ULN2803 and explain what changes have you done to the code ?</p><p>Thanks</p>
You don't need changes in code
<p>OK you, I'm very fun when help you. You can use Proteus to open file schematic and PCB, and i did fixed code. all in here:<br>https://drive.google.com/file/d/0BzXbfPpoHKV5eWQxU1VQODZhTTA/view?usp=sharing<br>when you use atmega32 you must set fuse for it. <br></p><p>and when you solder PCB solder you should note carefully and did not miss any legs, as this is the second circuit face, you can also book for someone trained to do it to ensure circuit reliability. And my final non-electric circuits become restricts motherboard area, it absolutely does not affect the led. And can not forget that it is a 5V supply. Wish success. I look forward to seeing your circuit here.</p><p></p><p>Inside the downloaded folder: principle diagram, schematic print, inside a simulated 3d opened by Proteus, the revised code with external hex file, inside the code can edit custom and standard you, use WINAVR (recommended recommended). and images to set the fuse for ATmega32.</p>
<p>Hi!!<br>Do you know hoe to flash the EEPROM of Arduino just like we do in normal non-arduino boards..<br>i.e. we flash .eep file directly into the micro controller.. do you know any similar or equivalant thing in Arduino...?</p>
<p>I sorry you, because I do not use Arduino, so I did not go through the difficulties you face, but you can read more online material on its use. I can only help you in terms of hardware. Good luck. I believe you will succeed! : D</p>
<p>Thnx for replying!<br>I got a solution for it already!</p>
<p>Hello, </p><p>Now I got it. The idea to use the ULN2803 is to avoid using transistors correct ?<br>What do you mean that I need to set the fuse for the ATMEGA32 ?<br>I will be using arduino board, either Nano or mega. </p><p>Thanks for your reply </p><p>Jose </p>
<p>is this, if you use it you must chip atmega fuse set inside the IC, the fuse is to control a number of functions such as: using the calibrated internal or external crystal, and and some rather different features, please reference IC data sheet. so that it operates according to your desired this function. I use the load circuit to the load burn-e program for my IC, please find out more about it, or you can use the load circuit which you are available. <br>ULN2803 help replace the transistor 16 in the layer. you read this ic data sheet to learn more. I had to diagram inside folders principle schematic. you see that in order to better understand how it works. wish success! : D</p>
<p>Sorry for answers will tell you now, when using ULN2803 then your program absolutely nothing changes, we simply optimized hardware only. Good luck! soon see your results here. : D</p>
<p><iframe allowfullscreen="" frameborder="0" height="400" src="https://www.youtube.com/embed/4gNiDprbUPc" width="600"></iframe></p>
<p>hello everyone, I have an idea to replace 16 BJT layers by ULN2803, it will save your area, and it works very well I did 2 LED cube and all activities well however, I did not design the RS232 connection on my circuit.</p>
<p>look the video led not working and bord file in pdf can u people help me fix my problem</p>
<p>look my video led was not working on 2 row actually working but working different way I don what mistake I have done I attached board file in pdf please anybody can help I am really appreciate. I put full effort for this project but finally animation make me upset </p>
<p>hai I have problem in cube I done well but some animation not coming properly 1 and 2 row I mean 1and 2 ic I checked very well circuit is correct can u help me I upload pdf of my schematic and pics</p>
<p>Hello,</p><p>I read these sentences in this post:</p><p>With a cpu frequency of 14745600 Hz, 128 prescaler and output compare of 10, the interrupt routine is called every 1408th CPU cycle (128*11) or 10472.7 times per second.</p><p>Can anybody help me to explain how to calculate to 10472.7 times per second. I am new to AVR timer.</p><p>Thanks,</p>
Thanks for sharing the awesome project.? . The instructibles are very elaborative. Atfirst i was sceptical if i could make this project. But atlast after backbraking hours of soldering and debugging , it was a succes. And the credit goes to chr. Thanks chr . U rock☺.<br>I used arduino uno as the controller. But the code is not complete. I mean many effects are missing. I dont know anything about programming. I request u to please mail me the code with every effect. It will be a great help. Thank u.<br>dbnjnds@gmail.com
<p>Is there some other way other than gray coding in software to avoid 74HC138 glitches </p>
<p>If the latch order is incorrect from the 138, usually it's the binary inputs are either miswired (wrong order, or a line not connected) or 2 inputs are shorted together.</p><p>Another issue you may run into is switching the data too fast, not latching long enough etc. which has to be fixed in the code.</p>
<p>hey can you please help me.</p><p>IC 74hc138 is misbehaving. I suspect it to be race hazard.</p><p>Wrong latches are being selected by the address selecter.</p><p>the following sequence seems to fix the proplem.</p><p>void draw(char *buffer)</p><p>{</p><p> PORTB=0b00001000;</p><p> PORTA=buffer[0]; </p><p> PORTB=0b00001001;</p><p> PORTA=buffer[1];</p><p> PORTB=0b00001101;</p><p> PORTA=buffer[5];</p><p> PORTB=0b00001100;</p><p> PORTA=buffer[4];</p><p> PORTB=0b00001110;</p><p> PORTA=buffer[6];</p><p> PORTB=0b00001010;</p><p> PORTA=buffer[2];</p><p> PORTB=0b00001011;</p><p> PORTA=buffer[3];</p><p> PORTB=0b00001111;</p><p> PORTA=buffer[7];</p><p> PORTB=0b00001000;</p><p> PORTB=0b00000000;</p><p>}</p><p>What I did was to change one logical state in the input to decoder at a time.</p><p>some sites recommend temporary disabling of output to prevent race hazards.</p><p>how did you deal with this issue&gt;</p><p>pls help </p>
<p>WOW - 5 million views.</p><p>I think it's some kind of record! LOL!</p>
Hi, Where do i buy all that stuff for 69 dlls? Thanks
<p>thats projects its great! Im looking for all the stuff and making time for doing! please continue doing amazing thing. :)</p>
<p>hi, really great instructable, kind that inspires people.</p><p>This code, cube[5][3] |= (0x01 &lt;&lt; 4);</p><p>Hex01 bit wise move 4, or with a 2d array, I can't get my head around it.</p><p>Plz, a more detailed description will save me from more tablets, cheers</p>
<p>Made it!!</p><p>Thank you for the great instruction!!</p>
<p>Your print looks very neat. Mine is very messy.</p>
<p>Wow, how do you get your trace wires so straight and the perfect length?</p>
<p>I measured 1, and cut them all to the same length at once...</p><p>And alcohol-free-february also did the trick ;-)</p>
<p>Hahaha nice work!</p>
<p>Nice job. Many never get their hand wired boards working! Nice and tidy job too.</p>
<p>Do you have a list of components that that board required?</p>
<p>Thank you for your guidance chr..</p>
<p>i am selling most of the components needed from Futurlec. I decided to do the Tindie kit instead. You can find my list of parts (less 512 LEDS) and further info in the classified sale section here: </p><p><a href="http://www.instructables.com/community/Major-Parts-KIT-for-8X8-CUBE-LED-from-Furturlec/">http://www.instructables.com/community/Major-Parts...</a></p><p>I am offering this at a discount and Priority mail within the US. </p><p>thank you</p>

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Bio: I like microcontrollers and LEDs :D
More by chr:Reverse Engineering: RGB LED Bulb with IR remote Reverse engineering: USB controlled home automation hack LED Cube 8x8x8 
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