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Author Topic: A three digit seven segment display  (Read 865 times)
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Beijing
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Hi all I just got a couple of three digit seven segment displays, I was planning to make a device that displays temperture readings on a three digit seven segment display, but I just noticed that each three digit SSD has twelve pins, the seller said there were three common grounds, and one pin that does not connect to anything. How do I controll each segment seperatly? eg. display three different numbers on each digit?
Thanks
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Your device will be something like this.
Write a loop that drives an anode, and sinks a cathode.
Continue for all 7 or 8 anodes.
Repeat for the next cathode.


* 3x7segment-common-cathode.jpg (53.27 KB, 960x720 - viewed 26 times.)
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Beijing
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You mean display one digit, then the other, ect, and the Arduino is so fast that you can't tell?
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It's the same principle behind led dimming with pwm: you turn a (fast) light source on and off so fast it looks continuously lit to the human eye. The higher the ratio between on and off time, the brighter the light will look.
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Beijing
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I see. Thank you very much!
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Its called Persistence Of Vision. It works because you can turn them on and off many times within a second, It happens so fast that you can not tell that its flashing.

https://en.wikipedia.org/wiki/Persistence_of_vision
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Thanks!
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