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How do you test a seven segment display?
Each segment is a diode that when forward conducting
(bias) illuminates its segment. The segment illumination is seen because of
electrons moving from and into the outer shell of its atom with such intensity
photons of light energy are released. The photo energy visibility is
enhanced by the plastic colored coating.
Seven Segments displays are either common cathode or common anode. Which
means all the segment diodes are connected together either by their anodes (+)
or cathodes (-) . Therefore one of the legs off the seven segment displays
is either the cathode or anode of all the segments. But which one? If you have
no data sheet for identifying it then you have to determine it for yourself.
1. Use an Analog meter with sufficient current capabilities to illuminate
a segment enough to be seen. X1 scale.
Or use a Digital Multi-Meter on its diode setting.
2. Use a power source (5V in series with 150 ohm resistor) for your
positive lead and return side is the common side of the supply.
...try to determine if the 7 - segment display you
have is a common cathode or a common anode type display. Test
all segments for proper operation.
All decimal numbers can be achieved by illuminating the right segments.
The common cathode seven segment display is wired as follows:
Try following the letters back to the segments.
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