Step 3: Schematics

The only thing I didn't specified in the schematics is the value of the current limiting resistors because they change from each type of LEDs, so you will need to calculate them by your self.

Now to calculate the value of the 24 resistors you can use this site :
You should first get some specs on your LEDs, you should know their forward voltage and forward current, you can get this info from the seller. The circuit operates on 5V so your Source voltage is 5V.

Download the original file to see the schematics better.(press the "i" icon in the top left corner of the picture)

I have added a PCB layout of the control board, and i want to thanks Willard2.0 who made this layout and let me use it so thanks a lot mate!
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QuincyC5 months ago

Would the Arduino Micro be usable with this?

can you e mail me the eagle cad board for this

Anybody have the code to display the digital clock on this led matrix??
umfan1102 years ago
on the decade counter if i added more rows on q6-9 could i add more rows and aslo how could i get to 26 rows im kina new but your schematics are awsome could i just add like 2 more decade counters would that work or would i have to get a bigger decade counter
The_Tom2 years ago
anybody know how long those 2 perf board should be?
ElsaCastro2 years ago
can you give me information on how to solder the diodes, a diagram if you can the connection between them, I am beginner in this
pleeease... if you can , and you have an diagram please send it to my mail
yours31f2 years ago
Can you email me the PCB? There is a tag on the [i] in the pic so I cannot download it. I could use the file if you have it available.

I think if I have the PCB I can eliminate wiring as my issue.

My LEDs barely light up and when they do it is completely random in position. I am running from a 24x6 led board and the rest is on bread boards. Any idea why (besides wiring since I have retried it about 5 times) that it would not work? My LEDs are soldered perfectly and the wires should be right but still a no go.
Also, I have the correct resistors on the way but do you think having too high of resistors would cause this?
jamesxL2 years ago
In the wiring schematic it says 2N4401, but in the material list it says 2N3904; is that just a software limitation that you put that in the drawing?

Also in the PCB drawing if I'm not mistaken, it has 8 rows instead of the 6 rows(that are attached to the transistors), am I correct?

When calculating the resistor value, is it correct if I calculate for 1 LED for the entire row? Example if I want an LED to operate @ 10mA , Vf 2.9 and 5V would 220Ohm 1/8w be the correct resistor? (I'm new to electronics) Is it because of the transistor that sort of acts as a amplifier (in case multiple or all LEDs are lit up in a row/column)?

P.S. thanks for the awesome project!
meny942 years ago
Hello! Im planning on building your project, but i was wondering what would i need so i could change what it displays wirelessly. Preferably through wfi..
kks_19792 years ago
pl send me full description how 2 oprerate with usb .my i d is
mkunst2 years ago
this is only for wan led
gsellers32 years ago
In the materials pin headers are listed. Would these be fine?
And is that was is in the PCB schematic in the bottom left, the symbols with the semicircles that have a B in them? If not, what are those? I'm new to electronics but want to get a few projects worth of supplies for Christmas, including these, but I'm not sure about the pin headers. Thanks
Syst3mX (author)  gsellers32 years ago
yeah those will be good.
The things with the B in them are the transistors.
The pin headers are the connection in the right(11,10,13,+v and so on)
dharmik2 years ago
heyy ..what is arduino discussed so far above ,,, cant be i use at89c51 or ds89c4x0 to do the same ? i have only knowledge of this controllers,,,,,,,,
Syst3mX (author)  dharmik2 years ago
yeah sure you can do the same but you will need to put extra work in the communication between the controller and the PC.
dharmik2 years ago
can any body who is pro member can please send me the pdf for this above project i really want to make this please ........ thanks
email id is

axeman9112 years ago
In the picture above when you say colums 1-8, colums 9-16, colums 17-24 are you counting them from left to right or right to left?
hanchapola3 years ago
Could you please tell me what is the microprocessor which used in above project, thanks!
Syst3mX (author)  hanchapola3 years ago
ATmega328 wit arduinno bootloader
cox1814 years ago
I don't really understand some parts on your schematic..... Does the 4017 decade counter connect in any way to the shift registers?.....If the line coming off of a pin on one of the chips has a square on the end...does that mean it is actually connected to the other chip pin with that same number and a square???
Syst3mX (author)  cox1814 years ago
The square with the pin number means that you need to connect this pins to the arduino. So the 4017 CLK goes to pin 9, and the RST goes to pin 8 of the arduino.
cox181 Syst3mX4 years ago
I'm actually talking about the tiny squares...for example...on the 4017 in the bottom right corner there are 5 lines with little squares at the end of them...and they all have a I attach these pins to the corresponding numbers on the shift registers??? Or are those pins not used on the 4017??? And one more question...on the side of the 4017 and the shift registers....some connections show a diamond and some show a square...and some don't touch the side of the chip and some are inside the outline of the chip....are these different connections?
Syst3mX (author)  cox1814 years ago
These pin are not used(with the little squares) except the 6 transistors that are connected to the 4017, they go to the LED rows. If there are 2 or more lines that cross each other and there is no red point where they cross, there is no connection. And when there is a red dot they do.
Could you please tell me what is the microprocessor which used in above project, thanks!
cox181 Syst3mX4 years ago
OK. I think I have everything, but I just have couple more questiosn... On on shift registers..does the wire labeled Vcc run and connect to pin 10 on the shift register like it is illustrated in the picture? And then that wire continues onto the 5v supply on the arduino correct? And the same with pin 13 labeled "G" on the shift register...does that connection connection with the ground connection of the shift register? And on the 4017, does pin 13 labeled "ENA" on the 4017 connect to the ground of the 4017 as shown in your schematic?
Syst3mX (author)  cox1814 years ago
Thats right
cox181 Syst3mX4 years ago
And on the 4017 chip ....does pin 16 go to the 5V pin on the arduino?....I am asking because there is a square on the end of pin sixteen on your schematic...which would imply that it doesn't connect to anything,,,,, but the 4017 has to get power somehow right?
Syst3mX (author)  cox1814 years ago
ohh right, I missed that connection. yes it connects to 5V.
Xombee3 years ago
On the PCB layout, why are there 8 transistors, if there are only 6 in the whole project? I assume 2 of them have to go, which would be 4 and 5 since the first 6 pins down match up to the schematic and would go to one of the 1k resistors. What does this do the the number sequence on the bottom of the PCB view (6,2,1,3,7,8,4,5)? Does the 7 and 8 become the 4 and 5?

I'm sorry if I made this sound totally confusing. Am I right in assuming that 2 of the 1K resistors and 2 transistors don't belong in the PCB view?
Syst3mX (author)  Xombee3 years ago
The guy who did the PCB made it for a 26X8 matrix thus you 8 transistors.
The numbers on the PCB are the order at which you need to connect your rows.
So if you want to use only 6 rows you take out transistors 7 and 8(and there 1K resistor)

micko123 years ago
The led I have chosen gives a single led resistor value of 150ohms and with two led's in series the calculator gives a value of 56ohms for a 2x72 array.This project uses 6x24 but the calculator doesn't let me change the number of leds in series to 6.
Would the resistor value of the 6x24 array be the same as the 2x72 array?
If not, how can I calculate it?

Thanks for your help
Syst3mX (author)  micko123 years ago
If you are doing a matrix of 2X72 and plan on scanning the 2 rows, there will never be 2 LEDs ON in series. So you would need to use the 150Ohm resistors and not the 56 ones
AndrewGarza3 years ago
Just wanted a confirmation of a very brief psudeo code description, let me know if this is right/wrong:

1.)ONE ROW at any given moment is grounded via transitor and 4017. The entire display appears to be lit all at once but in fact only 1 row at a time is being grounded allowing the LEDs in that row to become lit if there input from the SIPO (serial in parallel out, 74HC595) is high.

2.) Before you change from a row to next row new information needs to be serially uploaded to SIPO chips.
Syst3mX (author)  AndrewGarza3 years ago
yes thats about right
tomolobla4 years ago
How is the ground of the transisters connected and how are the 3 shift resistors powered? Could you please make a plan with metric symbols ?
Syst3mX (author)  tomolobla4 years ago
Well the the shift registers all powered from the arduino 5V and the ground is also from the arduino. The emitter of all the transistors connect to the same ground of the arduino.
auquocphong4 years ago
very nice cool.thanks
pdrpatnaik4 years ago
Hey, GOOD JOB !!!! Can I use the same one to display a digital clock? What modifications do I need to make? I want to use ATmega 16 MC.
pg894 years ago
i want to use avr microcontroller ATmega8 in place of Arduino what modification is required?