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Step 33: Build the Controller: Power Terminal and Filtering Capacitors

The cube is complete, now all that remains is a monster circuit to control the thing.

Let's start with the easiest part, the "power supply".

The power supply consists of a screw terminal where you connect the GND and VCC wires, some filtering capacitors, a switch and a an LED to indicate power on.

Initially, we had designed an on-board power supply using an LM7805 step down voltage regulator. However, this turned out to be a big fail.

We used this with a 12V wall wart. But as you may already know, most wall warts output higher voltages than the ones specified on the label. Ours outputted something like 14 volts. The LM7805 isn't a very sophisticated voltage regulator, it just uses resistance to step down the voltage. To get 5 volts output from 14 volts input means that the LM7805 has to drop 9 volts. The excess energy is dispersed as heat. Even with the heat sink that you see in the picture, it became very very hot. Way to hot to touch! In addition to that, the performance wasn't great either. It wasn't able to supply the necessary current to run the cube at full brightness.

The LM7805 was later removed, and a wire was soldered between the input and output pins. Instead we used an external 5V power source, as covered in a previous step.

Why so many capacitors?

The LED cube is going to be switching about 500mA on and off several hundred times per second. The moment the 500mA load is switched on, the voltage is going to drop across the entire circuit. Many things contribute to this. Resistance in the wires leading to the power supply, slowness in the power supply to compensate for the increase in load, and probably some other things that we didn't know about ;)

By adding capacitors, you create a buffer between the circuit and the power supply. When the 500mA load is switched on, the required current can be drawn from the capacitors during the time it takes the power supply to compensate for the increase in load.

Large capacitors can supply larger currents for longer periods of time, whereas smaller capacitors can supply small but quick bursts of energy.

We placed a 1000uF capacitor just after the main power switch. This works as our main power buffer. After that, there is a 100uF capacitor. It is common practice to have a large capacitor at the input pin of an LM7805 and a smaller capacitor at it's output pin. The 100uF capacitor probably isn't necessary, but we think capacitors make your circuit look cooler!

The LED is connected to VCC just after the main power switch, via a resistor.
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<p><iframe allowfullscreen="" frameborder="0" height="281" src="//www.youtube.com/embed/7XtjsIys6w0" width="500"></iframe></p><p>RGB CUBE </p><p> <iframe allowfullscreen="" frameborder="0" height="281" src="//www.youtube.com/embed/Pe7EmXuinjQ" width="500"></iframe></p>
<p>Beautiful PCs. Could you share the PCB files for etching?</p>
<p>PCB</p>
<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>Nice homebrew PCB, can you share PCB files?</p>
<p><iframe allowfullscreen="" frameborder="0" height="400" src="https://www.youtube.com/embed/4gNiDprbUPc" width="600"></iframe></p>
<p>can u help me to make the cube<br>can u send me some photos<br>and the list of things used to make the cube</p>
<p>Hi I see you got the cube working.</p><p>I have everything soldered together meaning all parts are on the PCB board, and all LEDs are connected in a 8x8 MATRIX and inserted into the PCB. I am not sure how to proceed with the final steps. Which side goes into the PCB board and which gets soldered to the RED wires in the diagram. </p><p>One version of the Welding guide contradicts the other. One shows the MATRIX going along the X-Axis (PICTURE #4, which is what I have), and the other shows the each MATRIX going along the Y axis (PICTURE #5).</p><p>Here are some images of what I have so far.</p><p>Now I have two options</p><p>1. Bend the NEGATIVE on the right side of each 8x8 MATRIX, and solder them together, then connect each ROW with the board.</p><p>2. or, follow the fourth image and switch all MATRICES to follow the Y-AXIS on the PCB</p>
<p>And in case it matters I have THIS cube kit from GikFun3D 8x8x8 CUBE with the blue PCB #11129F71578</p>
<p>đẹp lắm thanh ni&ecirc;n. m&agrave; cậu c&oacute; t&agrave;i liệu về led xoay n&agrave;o c&oacute; thể l&agrave;m được kh&ocirc;ng vậy. m&igrave;nh đang l&agrave;m m&agrave; n&oacute; kh&ocirc;ng chạy mới khổ. đang l&agrave;m đồ &aacute;n :D</p>
<p>send me pls PCB documentery sunayyildiz1989@gmail.com</p>
Circuit diagrams<br>Or kits details me <br>Also thes programmes code
<p>cho mình sin file hex của bạn với</p>
<p>You can use even less space using SMT 2N2222 type transistors. My board will take either.</p>
<p>Great idea!</p>
<p>Thanks. Most components on the board allow for SMT or through-hole.</p>
<p>hi sir, can you send me the circuit and diagram.</p><p>my mail qdat1202@gmail.com</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>Neat.</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>
<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>
Your led cube <br>Whitch kits using<br>
<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>
You don't need changes in code
<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>Cho e xin sơ đồ mạch in đc ko ạ</p>
<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 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>My last 8x8x8 cube</p><p>animations is in *.dat format and it played from microSD card</p>
Hi,<br>Please can you guide me to make the rgb cube? i have 12 weeks from now to end it<br>Email me: rahimabdenasser@gmail.com
<p><br>Hi. I have saved the .SCH files and downloaded several programs which are supposed to open these files - both failed. </p><p><br>Can someone please let me know of a program that will open the .SCH files?<br><br>As I am hoping to expand my electronic work, I don't even mind buying a decent piece of well-programmed software as opposed to freeware - but I would appreciate some advice on a program that actually WORKS?<br><br>If you have some good advice, can you check your software works to open the above files?<br><br>Thanks guys. </p>
<p>Hi,</p><p>The .sch files are made with Eagle. They have a free version for non-commercial use. Eagle may seem a bit complicated at first, but you can find tons of guides online, as this is one of the most popular schematics/pcb cad programs for makers..</p><p><a href="https://cadsoft.io/">https://cadsoft.io/</a></p><p>/Chr</p>
<p>Please guide me about LED Cube and the Hex Files <br><br>email me <br>ilyass_7@yahoo.com</p>
<p>Great thanks for that. I've been able to view the schematics now. Is there a function where you can convert the schematic to the layout on the actual circuit board? Thanks again for your help. I am enjoying building this. </p>

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Bio: I like microcontrollers and LEDs :D
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