Timeline for "Sharp" transistor switching / minimizing fading effect
Current License: CC BY-SA 4.0
13 events
| when toggle format | what | by | license | comment | |
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| Dec 24, 2021 at 7:10 | comment | added | Autistic | Your circuit is simple and will work .I have used a constant current source for R1 and sometimes used a diac for the zener to make things snappy , | |
| Dec 23, 2021 at 13:21 | vote | accept | theerrormagnet | ||
| Dec 23, 2021 at 12:42 | comment | added | Andy aka | I've never been good at reading peoples minds. | |
| Dec 23, 2021 at 12:35 | comment | added | theerrormagnet | Another reason why I did not do it like in your first schematic is because I used three different diodes - green, blue, and red, and they all have different forward voltages, so the calculation of zener diode values and resistor values was complicated. And I think with transistors it is at least not as sloppy, as the brightness of the LEDs is more equal. | |
| Dec 23, 2021 at 12:10 | comment | added | Andy aka | No, forget it. Take my word for it. If you are using a zener as a voltage detector then it will be sloppy. Of course you could use two BJTs wired as a differential pair with a zener voltage reference on one input and the voltage sensing on the other input but, then you are half way to a comparator and, it still won't be as good as just buying a comparator because you'd probably need to add at least two more BJTs to get the interface to the LED working. | |
| Dec 23, 2021 at 11:47 | comment | added | theerrormagnet | The idea with the LM311 is good. I will look into this IC. But I usually like to work with analog discrete components. It should be possible to do this somehow, you probably would need some form of transistor logic, but I have no clue how to do it at the moment. | |
| Dec 23, 2021 at 11:32 | history | edited | Andy aka | CC BY-SA 4.0 |
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| Dec 23, 2021 at 11:25 | history | undeleted | Andy aka | ||
| Dec 23, 2021 at 11:25 | history | edited | Andy aka | CC BY-SA 4.0 |
deleted 13 characters in body
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| Dec 23, 2021 at 11:23 | history | deleted | Andy aka | via Vote | |
| Dec 23, 2021 at 11:23 | comment | added | Andy aka | @theerrormagnet true so I shall reduce the zener voltage. | |
| Dec 23, 2021 at 11:22 | comment | added | theerrormagnet | Your circuit will not work as the Z-diode has a voltage drop of 9.1V and there will be not enough voltage for the LED. I tried similar circuits, but the problem is that in the end I will be using 3 LEDs and it is much cleaner with a BJT as a switch as the LEDs will have a more equal power. | |
| Dec 23, 2021 at 11:12 | history | answered | Andy aka | CC BY-SA 4.0 |