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LED strobe with fading effect possible with a NE555 ?

Phil00787

Feb 27, 2023
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Hello,
This is my first post here !
Trying to make a LED blink the same way as the "beacon lights" (?) on some airplanes, like this :
This circuit, using a transistor, works fine but is very sensitive to voltage fluctuations. I can't use it as I'll draw the power from a N-gauge model train circuit (pretty dirty 8-12V).
I built some NE555 blink circuits, that work fine with the fluctuating voltage, but I can't find any which have the same look as this one, not just a square waveform, but the fading/flashing effect.

Thanks for any hints !
 

Harald Kapp

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Could possibly be done with a 555 plus some additional circuitry for the strobing.
Possibly easier to use the transistor circuit "as is" and an additional linear voltage regulator (e.g. 78L05) to provide a clean power supply to the transistor circuit. Also very low componnet count and small size.
 

Phil00787

Feb 27, 2023
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Thanks. It will be connected to a shared rail system, so I have to limit current consumption to the lowest possible. I thought about using a 7805 but was assuming (wrongly ?) that a 7805 would "waste" quite a lot of power.
 

bertus

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Nov 8, 2019
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Hello,

Have a look at this post on AllAboutCircuits:

Bertus
 

Phil00787

Feb 27, 2023
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Hello,

Have a look at this post on AllAboutCircuits:

Bertus

Thank you ! Loads of useful information there.
 

AnalogKid

Jun 10, 2015
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Thanks. It will be connected to a shared rail system, so I have to limit current consumption to the lowest possible. I thought about using a 7805 but was assuming (wrongly ?) that a 7805 would "waste" quite a lot of power.

I like this circuit because it gets double-duty out of the timing current; storing it up in the timing capacitor for the delay, and then dumping it through the LED. A standard 555 circuit wastes its timing current. There is a way around that, but the flash profile will not have the same look. Two things.

First, your circuit usually requires an operating voltage of at least 9 V, so a 7805 is not the right part. If you have at least 14-15 V available, a 7812 should work.

Second, the 78xx series has around 5-10 mA of current through its GND pin. That would be the additional "waste". If you can tolerate 2 additional resistors, an LM317 has a much (~100x) lower operating current. There is an "L" version in a TO-92 package for low power applications, plus various surface mount options.

ak
 
Last edited:

Delta Prime

Jul 29, 2020
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Trying to make a LED blink the same way as the "beacon lights" (?) on some airplanes
.This gives the effect of a rotating beacon OR just like the lights on an aircraft tail.
1677536189316.png

 
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