Introduction: .56inch LEDs Display With MAX7219
Such modules are available on the market at a very low price, but of smaller dimensions (.36 inches).
A larger module costs more, so it is advantageous but also instructive to build a .56 inch module driven by MAX7219.
By buying the component parts, ordering the PCB at the factory and adding a little work, we can build and test such a module. It will cost about half of one bought ready assembled.
This is the idea of building some modules. You will find here all the details necessary for construction and testing, which can be done in two variants: THT and SMD.
Electronic components can be purchased from AliExpress at low prices. PCBs are ordered from one of the profile factories.
Step 1: Gathering Components and Tools
These are not many.
Electronic components (per modul):
U1 MAX7219-1pc. THT or SMD
R1 10K/0.125W THT-1pc.
C1 47...100uF/6V THT-1pc.
J1 Male pin header 6 pins-1pc.
U2,U3 4 digits LED display .56inch : KYX-5461AB (Blue) or KYX-5461AS (Red) - 2pcs.
Soldering tool with tin.
For testing we will need:
Power supply 5V / 1A and 12V / 0.2A
Step 2: Schematic Diagram
Schematic Diagram does not present anything new compared to the application scheme in the datasheet.
Due to PCB design considerations, J1 plugs are different from SMD to THT and therefore two different Schematics Diagrams appear.
Otherwise they are identical.
The diagram shows two common cathode displays of CC-56-12SYKWA type, 4 yellow digits, with multiplexing. In fact I used identical displays as the configuration, but more modern:
- KYX-5461 AB - 4 blue digits
- KYX-5461 AS - 4 red digits
They are cheaper and easier to find.
Resistor R1 has the role of limiting (analog) the maximum current through LEDs and has practically the value of 10K (9k51 value is hard to find).
In the THT variant, R1= 10k, Rv1= 0 (shortcut).
The power supply is 5V / 500mA, preferably from a separate source from the one that supplies the microcontroller(Arduino).
The control signals are applied to the module at the Load, Din, Clk pins.
Step 3: Making PCBs
At the address:
are the files necessary to make the PCB using KiCad program, a program that can be found freely on the Internet. Here you can also find other details of the project.
It is a more difficult PCB to make at home due to the long and thin routes. That is why the factory order of the PCB is recommended.
The project contains all the necessary data to order at the factory and the dimensions of the PCB place it in a reduced price category.
The first two photos show the PCB coming from the factory (SMD version) and the next two screenshots of the PCBs projects in KiCad.
On the PCBs are inscribed the electronic components and the J1 plug pins. This helps to plant the parts and connect the module to the Arduino.
Step 4: Assembling
Assembly is easy using cutting pliers and soldering tool with tin.
The placement of the components on the PCB is done according to the KiCad project or the photo from this step.
In the photo, for the THT version, MAX7219 is mounted on IC socket, which allows a test of other MAX7219. Of course, whoever wants can give up the IC socket. .
We will have to plant the two LED displays in the end, in order to be able to solder the components on the opposite side.
Step 5: Testing. Wiring and Software
Wiring for test.
See photo from this step.
For the test I used an Arduino UNO module, wires and a source like the one in the photo. But you can use any source of 12V / 200mA and 5V / 1A and even two separate sources with common ground.
The 12V source supplies Arduino and the 5V supplies the display module with MAX7219 .
Wired connections are made according to the table:
Arduino UNO--------------MAX7219 module
The two modules must have a common ground wire.
Software for test.
Allows a quick, visual test of the module's operation. This can be seen in the attached video.
The program is made around the LedControl.h library which can be found at:
The library is very well documented at:
For start it will download and install the library, if it is not already installed in your Arduino IDE.
At the beginning, the library is included in the program, the object is defined at pins 5,4,3 of the Arduino UNO and there is only one MAX7219.
The character matrix called CHR is defined, in which all the ASCII characters that can be displayed are entered, according to the LedControl.h documentation.
In the "setup", the brightness of the display is set to maximum (15). Tests will be performed at this brightness, but in normal, long operation it is recommended to use an average value (8).
In "loop" the following tests are performed successively:
Shut down/wakeup test.
All LEDs on the display turn on and off twice.
All LEDs on the display simultaneously change their brightness from 0 (minimum) to 15 (maximum). Note that at brightness 0 the display is not off.
Decimal Points Test
The decimal points light up from right to left successively (scroll).
LED segments test.
All the characters that can be displayed light up successively from right to left (scroll).
The end of the test
Is marked by the appearance of eight "-" characters on the display.
After this the test is repeated in a loop.
We'll upload the program to the Arduino UNO (or Nano) board and that's it.
Step 6: Final Conclusion
Once the module is completed and tested, it will give not only financial satisfaction (it is an economy compared to a purchased one), but also the satisfaction of the personal achievement of a thing.
It can be instructive for beginners.
Thank you for reading the article and for any questions do not hesitate to contact me.