How to quickly test whether a seven-segment digital tube is good or bad using a multimeter?
Did you know that testing a seven-segment digital tube can be done simply with a multimeter ? Follow the test steps below to easily complete the test of a 7-segment digital tube.
1. Take out the seven-segment digital tube and identify pin 1 first.
2. Next, set up the multimeter (when using, the red test lead should be inserted into the jack marked with a "+" sign and the black test lead should be inserted into the jack marked with a "-" sign.) - Set the multimeter to the continuity range.
3. Set the multimeter to the buzzer mode and test it (when in the buzzer mode, the red and black test leads are short-circuited and a sound will be heard). When the multimeter battery is low, it will not display the correct data and you need to replace the battery with a new one.
4. Place the black probe of the multimeter on pin 3 or pin 8. Generally, these two pins are internally connected.
5. Then place the red probe of the multimeter on any other pin, such as pin 1 or 5.
6. If any segment lights up, it means that the seven-segment digital tube is a common cathode.
7. If no segment lights up, swap the test leads to test the positive and negative poles.
8. Place the red probe of the multimeter on pin 3 or 8.
9. Now put the black probe of the multimeter on the remaining pins. If any segment lights up, it means that the seven-segment digital tube is a common anode.
10. Please check whether all pins of the seven-segment digital tube are common cathode or common anode to ensure that the display works normally.
11. If some segments are not lit, then the seven-segment display is bad.
Below we share a specific seven-segment digital tube test example.
Take the following digital tube LDD-A814RI as an example. Some people think that there is a problem with the A and F segments in the digital tube number 1. I have two purposes for doing this test - first, to confirm whether the digital tube is common cathode or common anode; second, I want to confirm which two pins activate the A and F segments.
According to the data sheet , both pins are at the bottom right. This is a common anode digital tube, the anode pin of the digital tube number 1 is 14, the cathode pin of the A segment is 16, and the cathode pin of the F segment is 18.
Knowing the structure of the digital tube, you can adjust the multimeter to the diode mode for testing, put the red test lead on pin 14, and the black test lead on pins 16 and 18 respectively. You can see that both sections can work normally. With this knowledge, you can confirm the problem in the circuit.
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