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Step 14: Choose your resistors

There are three things to consider when choosing the value of your resistors, the LEDs, the 74HC574 that drive the LEDs, and the transistors used to switch the layers on and off.

1)
If your LEDs came with a data sheet, there should be some ampere ratings in there. Usually, there are two ratings, one mA for continuous load, and mA for burst loads. The LEDs will be running at 1/8 duty cycle, so you can refer to the burst rating.

2)
The 74HC574 also has some maximum ratings. If all the LEDs on one anode column are on, this chip will supply current 8/8 of the time. You have to keep within the specified maximum mA rating for the output pins. If you look in the data sheet, You will find this line: DC Output Source or Sink Current per Output Pin, IO: 25 mA. Also there is a VCC or GND current maximum rating of 50mA. In order not to exceed this, your LEDs can only run at 50/8 mA since the 74HC574 has 8 outputs. This gives you 6.25 mA to work with.

3)
The transistors have to switch on and off 64 x the mA of your LEDs. If your LEDs draw 20mA each, that would mean that you have to switch on and off 1.28 Ampere.
The only transistors we had available had a maximum rating of 400mA.

We ended up using resistors of 100 ohms.

While you are waiting for your LED cube parts to arrive in the mail, you can build the guy in the picture below: http://www.instructables.com/id/Resistor-man/
<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>Neat.</p>
<p>You can use even less space using SMT 2N2222 type transistors. My board will take either.</p>
<p>Great idea!</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><iframe allowfullscreen="" frameborder="0" height="400" src="https://www.youtube.com/embed/4gNiDprbUPc" width="600"></iframe></p>
Circuit diagrams<br>Or kits details me <br>Also thes programmes code
<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>hi , can you send me the circuit and diagram.</p><p>my mail suynghj@gmail.com</p>
<p>I still haven't got round to making this, can't wait to start!</p>
<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>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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awesome
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Hi I want to buy these components, any body guide me
<p>This is the best kit that I have come across for the LED's</p>
<p>.</p>
<p>can you please kindly send the code for programming </p><p>my emai id chiranjitkarmakar838@gmail.com</p>
<p>can you please kindly send the code for programming</p>
<p>look the video led not working and bord file in pdf can u people help me fix my problem</p>

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Bio: I like microcontrollers and LEDs :D
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