The LED digital tube is a common electronic component for easy display of the device. The following describes its performance characteristics, simple detection methods and application notes.
1. Performance characteristics
The main features of LED digital tube are as follows:
(1) It can drive light at low voltage and low current, and is compatible with CMOS and ITL circuits.
(2) The illuminance response time is extremely short (<0.1μs), the high frequency characteristics are good, the monochromaticity is good, and the brightness is high.
(3) Small size, light weight and good impact resistance.
(4) Long life, service life of more than 100,000 hours, and even up to 1 million hours. low cost.
Therefore, it is widely used as a digital display device for digital instrumentation, numerical control devices, and computers.
2. Simple performance test
LED digital tube appearance requires uniform Color, no local discoloration and no air bubbles, etc. Under the amateur conditions, dry batteries can be used for further inspection. Now take the common Yin digital tube as an example to introduce the inspection method.
The negative electrode lead wire of the 3 volt dry battery is fixedly contacted on the common negative terminal of the LED digital tube, and the positive electrode lead wire of the battery is sequentially moved to contact the positive end of the stroke. When the lead wire touches the positive end of a stroke, the stroke should be displayed. In this simple way, you can check whether the digital tube has a broken pen (a stroke can't be displayed), even a pen (some strokes are connected together), and can compare the strength and weakness of different strokes. If you check the common anode digital tube, just reverse the positive and negative lead wires of the battery, the same method as above.
LED digital tube work current ILED is about 5-10mA. If the current is too large, it will damage the digital tube. Therefore, the current limiting resistor must be added. The resistance can be calculated as follows:
R value = (U - ULED) / ILED
U is the voltage applied across the LED, ULED is the voltage drop of each stroke of the LED digital tube (about 2 volts).
The LED multimeter's hFE jack makes it easy to check the LED digital tube's illumination. When the NPN block is selected, the C hole is positively charged and the moon hole is negatively charged. For example, when checking the LTS547R type common cathode LED digital tube, insert a single-strand thin wire from the E hole, and the wire lead-out terminal is 9 poles (the third leg and the eighth pin are connected internally, and one can be selected as the Ó¨); The C hole leads a wire to sequentially contact each of the segment electrodes, and the corresponding pen segments can be respectively displayed.
3. Precautions for use
(1) If the light is dim during inspection, the device is aging and the luminous efficiency is too low. If the displayed pen segment is incomplete, the digital tube has been partially damaged.
(2) For the LED digital tube with unknown model and no pin arrangement diagram, use the digital multimeter's h-range gear to complete the following test work: 1 Determine the structure of the digital tube (common or common); 2 Identification tube Feet; 3 check the full bright pen segment. It is presupposed that an electrode is a common pole and then verified based on whether the pen segment is illuminated or not. When the pen electrode is reversed or the common pole is judged to be wrong, the pen segment cannot emit light. (Edit: Technology)
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