PCB introduction video: PCB right-angle routing is really beautiful, LED dot matrix design sharing_bilibili_bilibili
Physical display video: 48X32LED dot matrix module production_bilibili_bilibili Open
Special note, the pin and female headers in the schematic diagram are bent female headers, and the pin headers are called reverse bent pin headers.
Component purchase link: [Tencent Document] Electronic Studio shared table https://docs.qq.com/sheet/DYm1tTUFlRWhkQVJt
PCB proofing, select PCB4 to make (PCB4 made by myself), this is the largest dot matrix (one PCB), the sizes of these PCBs are all greater than 10cm, so you can only go to JP to make them for free.
I will talk about the code later.
LED luminous character board
video link:
https://www.bilibili.com/video/BV1LT4y167RS/My
homepage link: https://oshwhub.com/woshi6666444444?tab=project&page=1Recommended
link for component purchase: [Tencent Document] Electronic Studio Component Purchase Reference https://docs.qq.com/sheet/DYm1tTUFlRWhkQVJtPreface
I
have been playing with lights for a long time and have designed many light strips and dot matrix modules. However, the name of my account has not been displayed yet, so I made this light board that can display fixed Chinese characters. Of course, this fixation is completed during welding. In reality, many situations are still fixed, such as the name of a store.
Fixed has the advantage of fixed, no controller is required, the circuit is simpler, and the reliability of the circuit is increased.
1-Design scheme introduction
This design uses 0603 packaged LEDs, which is a common package I use, and this package is acceptable for hand welding. Each Chinese character is displayed with a 16*16 dot matrix. This is a common operation. Generally, this size is used when playing with LCD screens. This size can display more Chinese characters. Of course, 11*11 can also display a lot, but I don’t really want to use this size.
After we have selected the number of LEDs, we can then distribute the array in the PCB and roughly determine the size of the board. Because I found that one dot matrix did not take up the full 10*10cm size, so I made two. At this time, the adjustment of the LED spacing is to control the length of the board.
When the number of LEDs is determined, the front of the board has actually been determined. The rest of the circuit is also very simple. For the current limiting resistor of the LED, I used the method of distinguishing the left and right half screens, so that which Chinese character can be controlled separately. At the same time, the number of LEDs for each Chinese character is different, and the current limiting resistors they need are also different. (In order to ensure uniform brightness).
As for the power supply of the board, the commonly used TYPE-C package is used, using 16PIN. The two boards can be directly connected and powered through the connection unit. One TYPE-C port can power all boards.
2-Circuit
diagram The circuit diagram is very simple. The LED, resistor, and capacitor are all in 0603 package. The resistor welding will be described in the subsequent chapters. A switch is left for each Chinese character. We can toggle the switch to determine whether the Chinese character is lit. TYPE-C-16PIN is a conventional structure, and only the power supply pin is retained. The connection unit on the right side of the circuit diagram is used more for double-board connection, so it is placed as a backup.
3-PCB physical welding process
After receiving the PCB, the connection unit under the board should be cut off. Then it is the welding of the PCB. A TYPE-C is welded on the back (only one board needs to be welded), and then a switch is welded to the part that needs to be displayed (if a switch is not needed, a flying wire can be short-circuited). The capacitor can be left unwelded, and the resistor welding is referred to below.
The welding of the LED is the most time-consuming part. Use the Chinese character modeling software to generate a 16*16 dot matrix pattern of the LED, and then weld the LED according to this pattern. Pay special attention to the position and do not weld the wrong row. If the welding is wrong, it can be removed. The soldering of LED can only be done one by one with a soldering iron. First, tin a point on the LED to be soldered, then use tweezers to clamp the LED, melt the solder, put the LED on, and finally solder the other end of the LED. Pay special attention to the spatial order of soldering to avoid accidentally removing the LED next to it because of soldering the LED.
Finally, the double boards are spliced. The screws used here are M3*6 specifications (M3*5 is just right), and nylon materials can be used, or metal can also be used. Put the connection unit under the double board and tighten the screws. In most cases, a good connection can be obtained. If the connection is not good, it is recommended to add tin to the connection unit (a small amount, do not affect the flatness and holes).
4-Chinese character design
uses the software "PCtoLCD2002". After opening the software, enter the Chinese characters below without modifying any parameters. After we get the pixel layout of the Chinese characters, we open EXCEL, reproduce the same layout in the table, and adjust it to the Chinese character format we want. EXCEL is used to calculate the number of LEDs required, and it can also display the row and column positions of the points for easy soldering.
Some formulas have been entered in the table. Enter 1 in the 16*16 area and the table will change color (conditional format). Delete 1 and it will fade, so it is easier to observe the font. For example, the number 65 in the word "electricity" is the number of LEDs, and the same applies to other words. The 274 on the far right is the number of LEDs used by the five Chinese characters. There are many formula operations in this table, all of which are relatively simple summation operations. We can look at the rows and columns in the table and solder the LEDs.
5-LED resistance calculation
LED resistance calculation is actually a relatively simple thing. In this circuit, we connect multiple resistors in parallel to share power. We need to calculate the power output ourselves to avoid excessive current and burn out the resistors. We calculate the resistance to keep the brightness of all LEDs basically consistent.
Our power supply is 5V, and the resistor voltage + LED voltage is 5V. I use a white light LED + 10K resistor, and the LED voltage is 2.57V to light up (I can accept the brightness at this voltage). At this time, the resistor voltage is 2.43, so the current through the LED is 0.243mA (resistor voltage divided by circuit current). We want to display the word "electricity". There are 65 LEDs in parallel, and the total current is 65*0.243=15.8mA.
Then the current limiting resistor value of the word "electricity" is 2.43V/15.8mA=153 ohms. We can get 153 ohms by connecting multiple resistors in parallel.
However, in the actual welding process, the resistor I used is 470 ohms, and 5 are welded in parallel. At this time, the resistance value is 94 ohms.
The selected line in the figure is the result of dividing the number of LEDs by 13. The result can be rounded off, so the corresponding number is the number of welded resistors (the resistance values of the resistors I use here are all equal). If the resistance values are different, you can calculate it yourself.
Another question is whether the resistor can withstand this power. I didn't consider this because the current in my circuit is very small. If the current in your circuit is large, you must consider it to avoid burning the resistor. Theoretically, the power of 0603 resistor is 1/10W, and the power of 10 resistors with the same resistance value in parallel should be 1W.
6-Problems and improvements
This PCB is my first splicing PCB work. The stability of this splicing structure is OK, but it is a little big. I will consider designing a smaller one in the future.
Problem 1, CC line cannot supply power.
Solution, change AC line
Problem 2, so many LEDs in parallel will have different conduction voltages and uneven light emission due to different LED physiques.
Solution, remove the darkest one and replace it with a new one.
Problem 3, the LEDs are not bright after soldering.
Solution, some LEDs may be short-circuited, burn the short-circuited LEDs, and then remove them. Demonstration video: https://www.bilibili.com/video/BV1Y54y1f7Jy/
Improvement 1, TYPE power supply position is not very good, you can consider placing it sideways for better
Improvement 2, the constant lighting of Chinese characters is too rigid. Although a switch is added to manually control whether it is lit, it is better to add MOS control and a single-chip microcomputer to produce a breathing effect. It is specially noted here that most of the brightness adjustments are PWM, and there are high-frequency flickers. The light board I made does not have this, which is relatively good. The brightness is consistent no matter how the mobile phone shoots.
7-End
Today's open source sharing is a light board that can display Chinese characters and can be spliced. There are no complex devices such as single-chip microcomputers, which is convenient for novices to use. There is no refresh flicker like a dot matrix. It is relatively good for shooting videos and daily observations.
This PCB is the first splicing structure work I designed. With the splicing structure, our PCB design will have more space, and we don’t have to be limited to 10*10. The current active splicing method also enhances the reusability of the circuit board. Later, I will design more splicing PCB works to share with you.
Attachment content
1 "PCtoLCD2002"
2 EXCEL Chinese character table
京公网安备 11010802033920号
Burning and debugging are completed. 
Dog leg 
lithium battery power supply (two 18650 in series). 
The shell is made. There is no acrylic board, so a box is used instead. 
The burner is used as a dog tail. Hahaha. 
The final product is that the legs fall off when walking. It is still being improved. Due to time constraints, it is made into a shape. It will be improved.
HDSP-303G-KL000
