Timeline for Interfacing unusual 4 digits 7 segments display
Current License: CC BY-SA 4.0
11 events
| when toggle format | what | by | license | comment | |
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| Dec 11, 2020 at 17:05 | comment | added | Allen Chak | You answered my last question, and give me an idea for the resistor, but I have no idea how to implement your code. | |
| Dec 8, 2020 at 13:05 | comment | added | Peter Paul Kiefer | @EdgarBonnet That's a good point. I did not expect the LED to dim much because of the duty cycle, but now I'm not sure anymore. I'll have to get such a LED Display and try it. Thank you for the comment. | |
| Dec 7, 2020 at 19:30 | comment | added | Edgar Bonet | You are right, of course, the display will be dim. But that's not my point. My point is that it will also be dim if you handle the segments one by one. Think duty cycle, and average the brightness over a full scan cycle. | |
| Dec 7, 2020 at 18:12 | history | edited | Peter Paul Kiefer | CC BY-SA 4.0 |
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| Dec 7, 2020 at 18:07 | comment | added | Peter Paul Kiefer | @EdgarBonnet As multiple LEDs with a common cathode or a common anode have a single source or drain with a resistor. The current through all LEDs together is the same as the current through that single resistor. So each LED sees only a part of the current. Say you have 5 LEDs with a common cathode then the current through the common resistor is 5V / (100Ohm+20Ohm) ~~ 41mA. The current through each LED is 1/5 of this ~ 8,3 mA. I think you would see the difference. Using high impedance state for unused pins is one of the better solutions I mentioned. | |
| Dec 7, 2020 at 17:23 | comment | added | Edgar Bonet |
Re "show all Segments with a common cathode [...] could dim the LEDs remarkably": no more than showing the segments one by one. If you want a brighter display, you have to drive the cathodes with transistors. Re "If the cathode of S2 is connected to GND there is a very small chance, that the segment lights up": that's why that cathode should not be pulled LOW (connected to GND): it should be left floating (INPUT mode, a.k.a. "high impedance").
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| Dec 7, 2020 at 16:50 | history | edited | Peter Paul Kiefer | CC BY-SA 4.0 |
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| Dec 7, 2020 at 16:45 | comment | added | Peter Paul Kiefer | @EdgarBonet Showing Digit one by one is meant in addition to show each segment one by one. It seams that I did not express myself clearly. I'll edit the answer. | |
| Dec 7, 2020 at 16:44 | history | edited | Peter Paul Kiefer | CC BY-SA 4.0 |
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| Dec 7, 2020 at 15:44 | comment | added | Edgar Bonet | Re "You must schow all four digits one by one in a fast loop": That won't work. At any given time, you can only light segments that all share either the same anode or the same cathode. So, instead of looping over the digits, you will have to loop over the anodes (or over the cathodes). | |
| Dec 7, 2020 at 15:25 | history | answered | Peter Paul Kiefer | CC BY-SA 4.0 |