Led display screen

LED display common fault handling methods

A, circuit basis and common element USES

1, resistance: plays in circuit current limit points pressure role. Use R said ?), the unit ohms (. In the pixel products used in the current size limit resistance.

2, capacitance: the role of circulation exchanges between straight in pixels products, used for filtering. Use C says, the unit (F) method.
Example: common 0805 encapsulates the 104PF capacitance, is used to filter out the circuit of the higher frequency voltage ripple 470UF / 16V, electrolytic capacitor, used to filter out the lower frequency voltage ripple. Are all play filtered jamming signal, improve circuit, the circuit anti-interference ability stable job.
Three, IC integrated circuit function:
Example: our 74HC595, MBI5026 etc, are IC.

74HC245 role: to signal power amplifier.

Article 1 foot DIR, input and output port conversion for use, DIR = "1" high levels by "A" signal at the input "B" output, DIR = "0" low levels by the "B" side signal input "A" end output.
Article 2 ~ 9 feet "A" signal input output terminal, A1 = B1,,,,,, A8 = B8, A1 and B1 is A group, if DIR = "1" G = "0", A1 input B1 output, other similar. If DIR = "0" G = "0", B1 input A1 output, other similar.
Article 11 ~ 18 feet "B" signal input output terminal, function and "A", not the same description.
Article 19 feet G, make can end, if the feet for "1" A/B the signal will not conduction, only for "0" A/B end to be enabled, this feet also is the role of play switch.

Article 10 feet GND, power.
Article 20 feet VCC, power positive.
74HC04 role: six inverter.
Article 7 feet GND, power.
Article 14 feet VCC, power positive.
The input signal by A reverse phase output, the Y Y1 for A group with A1, other analogy. Example: A1 = "1" then Y1 = "0", A1 = "0" is Y1 = "1", other groups function the same.

74HC138 role: 8 binary translation of decimal decoder.
Article 8 feet GND, power.
Article 16 feet VCC, power positive
Article 1 ~ 3 feet A, B and C, binary input feet.
Article 4 ~ 6 JiaoPian choose signal control, only in four, five feet six feet for "0" for "1", will be elected by the general, output A, B and C signal control. Any other combinations will not be selected, and the Y0 ~ Y7 output for the entire "1".
Through controlling the foot to choose cascade, make expanded to 16.
Example: G2A = 0, G2B = 0, G1 = 1, A = 1, B = 0, C = 0, then as "0" Y0 Y1 ~ Y7 for "1", details see true value table.

The role of 74HC595 drive chip: LED, eight shift latches.
Article 8 feet GND, power.
Article 16 feet VCC, power positive
Article 14 feet DATA, serial DATA input port, display DATA thus enter, must have the clock signal coordination can move.
Article 13 feet EN, make can mouth, when this pin for "1" on QH mouth all for QA ~ "1", "0" QA ~ QH output by the input data control.
Article 12 feet STB, latch mouth, when the input data transmitted into registers, the only to supply a latch signals will will move into the data sent QA ~ QH mouth output.
Article 11 feet, clock CLK mouth, each clock signal will move into a data to register.
Article 10 feet SCLR, reset, as long as there are reset signal mouth, registers the data will move within feet without the empty,led screen, general pick VCC.
Article 9 feet DOUT, serial data output terminal, the data to the next.
Article 15, 1 ~ 7 feet, parallel output is also drive the jammer, and drive leds.

4953 role: to do the drive tube, power tube.
The interior was two CMOS tube, 1, 3 feet VCC, 2, 4 feet, 2 feet control feet control 7, 8 feet output, 4 feet control 5, 6 foot output, only when 2, 4 feet for "0", 7, 8, 5, and 6 will output, or output to high impedance condition.
MBI5024 role: LED drive chip, 16 shift latches.
Article 1 foot GND, power.
Article 24 feet VCC, power positive
Article 2 feet, serial DATA input DATA
Article 3 feet, clock CLK input
Article 4 feet STB, latch input
Article 23 feet output current adjust end, connect resistor adjustment
Article 22 feet DOUT, serial data output
Article 21 feet, make can input EN
Other functions and 74HC595 similar, just MBI5024 is 16 shift latches, and take the output current adjustment function, but in parallel output will not appear on the high level, only high impedance condition and low level. 74HC595 parallel output have high level and low level output.