Document: LED electronic display common troubleshooting troubleshooting
Author:Gu Ying Time:2021-09-14 16:53 Browse(446)
1. The whole board is not on: the board is not connected to the power supply; The input cable is inserted reversely; The input and output are reversed; The positive and negative poles of the power supply are connected reversely. 2. The board does not light up and the transmission is normal. The protection circuit is damaged. The solution can short circuit the fourth and fifth pins of 74HC138.

Document: LED electronic display common troubleshooting troubleshooting

3. One line in every three lines does not light up. 4953 is damaged (one of them is damaged).
4. One line in every other line lights up: a signal problem.
please check whether 74hc245 and 74HC138 have false soldering; You can use a multimeter to measure whether the voltage of the first pin of 74HC138 is equal to about 2.5V. If so, replace 74HC138; Carefully measure the ICA signal pathway of gold needle belt.
5. Light up two lines every two lines: B signal problem.
please check whether 74hc245 and 74HC138 have false soldering; You can use a multimeter to measure whether the voltage of the second pin of 74HC138 is equal to about 2.5V. If so, replace 74HC138; Carefully measure the channel condition of ICA signal of gold needle belt.
6. The upper half board is normal, and the lower half board is all on or not on: if the t08a interface has this condition.
this is to check whether the Dr data signal of the next 8 lines is on the channel, if it is normal, first replace 74hc245, if it is not good, then replace the first 74HC595, The data is separated (if it is T12 interface data, it is also one).
if the t08a board is the upper and lower half board, it should be checked separately.
8. If there is one lamp on the board that doesn't work: check whether there is false soldering and replace the lamp tube.
9. If there are four lamps standing vertically that don't work: first, check whether there is false soldering on 74HC595; Second, replace 74HC595; Thirdly, replace the lamp tube.
10. Among the four vertical lamps, three are not working and one is normal: replace the normal lamp tube.
1011. If the display of the board from the middle or other position is abnormal: check the data signal path; Replace the 74HC595 of the last normal display control lamp; If it is not ruled out to replace the 74HC595 controlled by the first lamp with abnormal display.
each 74HC595 controls eight light tubes wide and four light tubes high.
74HC595 is connected in series with Dr data signal, that is, the Dr signal is connected from the 14th pin of 74HC595 to the 9th pin of 74HC595, from the 14th pin of the next 74HC595 to the last 74HC595. For example, the Dr data of this board is amplified from gold needle to 74hc345 to ur1 to UR2 to UR3 Until the output of the gold needle after ur8.
12. Sometimes in the process of debugging the whole screen, the display from the front module to the back module is abnormal.
the general fault is that the cable is not plugged in or damaged; You can also use a slightly longer cable to plug the module under investigation into the abnormal module above to see how it is displayed. You can also connect the output of the normal module in front of the abnormal part above to the next row of modules to see how it is displayed, In the end, it's the wrong module.
how to make the LED display screen
teach you how to assemble the LED bar screen.
1. Overview of the LED bar screen
LED screen.
as a new media, the moving light-emitting pictures and texts are more likely to attract people's attention, have a large amount of information, update at any time, and have a very good advertising and announcement effect.
LED screen is simpler than neon light.
it's easy to install and use, LED screen is a kind of high-tech electronic products.
the price is relatively high, and it used to be used in the government and units.
technology is constantly improving.
LED screen is a kind of high-tech electronic productsWith the price decreasing, it is easier to assemble and maintain the small LED strip screen.
because of the low price, simple installation and use, it has been accepted by the public for a long time, and gradually entered the stores, the application is more popular, and gradually began to be popularized.

2. Strip screen application:
2.1. Advertising application new media.
new effect, new business
as a new media, LED strip screen is also a new decorative material, It can be embedded in many interior decorations to make the decoration more dynamic. The constantly updated subtitles can be used as new notice boards, It has a good visual effect.
because the installation and use of LED bar screen has a certain technical content.
it restricts the development of advertising industry.
mastering LED technology can improve the technical content of interior decoration, Expand business.

2.2. System integration - secondary development
LED bar screen.
because of simple control, it is embedded into all kinds of public oriented devices.
large font.
dynamic, large amount of information, suitable for long-distance viewing, timely broadcast the latest news to the public, attract public attention.
it is widely used in queuing system.
station reporting system, Water dispenser, etc.
LED strip screen control card.
with simple and stable functions, it can be easily embedded into the system, which saves developers the tedious work of developing LED display, and focuses more on the function and innovation of the system.
LED strip screen control card development kit.
provides a detailed development example, which provides a good environment for your system integration and secondary development.

_ 3. Assembly significance
the LED industry chain has been very perfect.
1All the accessories can be easily bought online. The technical parameters of LED are becoming more and more unified, and the industry standard has been basically formed. All the spare parts have been modularized.
it lays the foundation for self assembling LED screen.
LED strip screen.
due to the low cost of materials and high retail price, when purchasing from LED screen suppliers in batches, the price of LED strip screen is low, The cost and price are not easy to control.
end users are not familiar with LED screens.
they need the installation and maintenance services provided by suppliers, so they assemble LED screens and sell them locally, You can get the maximum profit.

for example, assemble a 128x16 point single red indoor LED screen.
update the content of the screen by connecting the PC serial port
3.1. Screen composition
let's first understand the composition of LED bar screen, unit board, power supply, control card, wiring

back of unit board

front of unit board

switching power supply and LED strip screen control card
(picture of each accessory) 3.1.1. Unit board
unit board is one of the core components of LED display, The unit board, which directly affects the display effect, is composed of LED module, driver chip and PCB.
LED module is actually composed of a lot of LED light-emitting points encapsulated in resin or plastic.

the driver chip is mainly 74HC595, 74hc245 / 244, 74HC138 4953.

the commonly used unit board specifications of indoor strip screen are:
parameter: D=3.75; 75 mm, 64 points wide x 16 points high.
1 / 16 scan indoor brightness.
1 / 16 scan indoor brightnessSingle red / red green two color
parameter explanation:
luminous diameter: refers to the diameter of the luminous point d=3.75mm
luminous point distance 4.75mm --- selected according to the distance of the viewer.
indoor general selection 4.75
unit board size: 64x16 --- the most commonly used unit board, the most easily available, The price is also the cheapest.

1 / 16 scan: control mode of unit board.

indoor brightness: refers to the brightness of LED lighting points.
indoor brightness is suitable for the environment that needs fluorescent lighting in the daytime.

Color: single red.
most commonly used, The price is also the cheapest.
two color generally refers to red and green.
the price is high.

if you want to make a 128x16 point screen.
you only need to connect two unit boards in series.

the price is high_ 3.1.2. Power supply
generally uses switching power supply.
220 V input and 5 V DC output.
it should be pointed out.
because LED display screen belongs to precision electronic equipment, switching power supply should be used instead of transformer.
for a single red indoor 64x16 unit board,
when it is fully on, the current is 2A.

when 128x16 dual color screen is fully on, The current is 8A.
switching power supply of 5v10a should be selected.

3.1.3. Control card
we recommend using low-cost strip screen control card.
it can control 1 / 16 scan 256x16 dot dual color screen, and can assemble LED screen with the most cost advantage.
the control card belongs to asynchronous card.
that is to say, it can control 1 / 16 scan 256x16 dot dual color screen,The card can save the information without connecting to PC.

please refer to the user's Manual of the control card for details.
the card can save the information without connecting to PC
When purchasing unit boards.
please ask for clear parameters. The 100% compatible unit boards are:
08 interface 4.75mm point distance 64 point width x16 point height, 1 / 16 scan indoor brightness.
single red / red green dual color
08 interface 7.62mm distance 64 points wide x 16 points high.
1 / 16 scan indoor brightness.
single red / red green dual color
08 interface 7.62mm distance 64 points wide x 16 points high.
1 / 16 scan semi outdoor brightness.
single red / red green dual color
because there are many manufacturers of unit board and control card.
so there are many interface styles of unit board. When assembling LED screen, the consistency of interface must be determined first, The most commonly used LED interface is introduced here: LED industry number: 16pin 08 interface: the interface sequence is as follows:
2abcdg1g2stclk161nnnenr1r2nn15 explanation:
ABCD is line selection signal.
STB (LT) is latch signal, CLK (CK) is clock signal, R1, R2, G1, G2 are display data, en is display enable, N is GND.
confirm that the interface between the unit board and the control card is consistent.
then it can be directly connected.
if it is not consistent.
the interface between the unit board and the control card is consistentYou need to make your own conversion line (the order of converting to offline)
3.1.5. The connection line is divided into data line, transmission line and power line.
the data line is used to connect the control card and the LED unit board.
the transmission line is used to connect the control card and the computer.
the power line.
is used to connect the power and the control card, Power supply and LED unit board.
the copper core diameter of the power cord connecting the unit board is not less than 1 mm (mm)
3.2. Accessories manufacturing
3.2.1. Cable (data line) manufacturing
the cable is similar to the data line in the computer chassis.
only the width of the cable is a little different.
you can buy relevant materials in the computer city.
a tool is needed to make the cable.
it is special pliers (picture), It can greatly improve the work efficiency and yield.
the materials used to make the braid are: braid.
braid head, braid cap.
pay attention here.
if you make the 16pin braid, you need to buy the 16pin braid and the corresponding size of braid head and cap.
production steps.
cut the braid head flat with scissors, and then put the braid head (pay attention to the balance between the thread and the head), Then put it in the center of the crimper, press it hard, then wind the wire around, and install the cable cap.
the cable cap is very important.
it can effectively protect the cable, make the cable more solid, and do not save.

<3.2.2. Power cord production
the power supply is divided into 220V power cord and 5V power cord.
the 220V power cord is used to connect the switching power supply to the commercial power supply.
it is better to use the 3-pin plug, which can be bought in the hardware store.
here we focus on the 5V DC power cord.
As the current of 5V is relatively large, it is better to use red and black pair wire with copper core diameter of more than 1mm (red and black must be used).
if possible.
it is better to install metal parts on both ends of the wire<(as shown in the figure) 3.2.3. RS232 cable is used to connect the computer and control card and update the screen data.
DB9 head and network cable (which can be bought in the computer city) are needed.
carefully observe DB9 head.
if there are numbers on it, connect 5 to brown and connect 3 to brown white.
clamp the network cable.
install it on DB9 head.
(it's very important here.
be sure to clamp it and pull it yourself a few times, Then use a multimeter to measure whether the two terminals are connected.
it should be pointed out here.
the head of DB9 is divided into male and female.
the one at the back of the computer belongs to female.
so you need to buy a male plug corresponding to it.
if you don't understand, please carefully observe your PC.
there is no serial port in current notebook.
please buy a USB to RS232 serial port cable.
please buy a USB to RS232 serial port cable_
(DB9 accessories picture) 3.3. Wiring guide
for the first installation, please strictly follow the steps to reduce errors.

Step 1: check the power supply voltage.
find out the DC positive and negative connection switch power supply, and connect the 220 V power line to the switch power supply, Connect to AC or NL terminal) and plug it in.
you will find that a light of the power supply will be on.
then measure the voltage between V + and V - with a multimeter and dc gear to ensure that the voltage is between 4.8v-5.1v, and there is a knob beside it,You can adjust the voltage with a cross screwdriver.
in order to reduce the screen heating and prolong the service life.
when the brightness requirement is not high, you can adjust the voltage to 4.5v-4.8.
after confirming that the voltage is OK.
disconnect the power supply and continue to assemble other parts.

Step 2: turn off the power supply first.
connect the V + to the red line.
connect the V - to the black line, Connect to the control card and LED unit board respectively, and connect the black line to the GND of the control card and the power supply.
connect the red line to the + 5V of the control card and the VCC of the unit board.
after each unit board is completed.
please check whether the connection is correct.

power connection diagram step 3: connect the control card and the unit board.
use the prepared cable, Connect.
pay attention to the direction.
it can't be connected reversely.
Please note.
the unit board has two 16pin interfaces, one is input, one is output, and the one close to 74hc245 / 244 is input, which connects the control card to the input.
the output is connected to the input of the next unit board.

the control card is connected to the input_ Step 4: connect the RS232 data cable.
connect one end of the data cable to the DB9 serial port of the computer and the other end to the control card, and connect the 5-pin (brown) of DB9 to the GND of the control card, Connect the 3-pin (brown white) of DB9 to the rs232-rx of the control card.
if your PC does not have a serial port,
you can buy a USB to RS232 serial conversion cable at the computer city.

Step 5: check the connection again.
the black line is connected to - V and GND.
the red line is connected to + V and VCC + 5V.
the connection is correct
Step 6: turn on 220 v.
under normal conditions, the power light is on, the control card is on, and the screen is displayed.
if it is not normal.
please check the connection.
or check the troubleshooting.

step 7: open the downloaded software.
set the parameters of the screen, Send subtitles.
refer to the software instructions for details.

If two unit boards appear on the screen to display the same content.
please set the screen size to 8 Chinese characters.

4. Software instructions - led-update
to Download

figure 2-14.1. Simple steps:
1 select the PC serial port connected to the control card
2 Click .
the status bar displays "send OK"
3 the screen immediately displays "input display information here"
4.2. Led-update details:
4.2.1. Set screen parameters
click "set screen parameters>,
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