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Smooth signal lamp transitions Patch

#11 User is offline   Railcat 

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Posted 27 April 2020 - 05:13 PM

Like this topic I sent:
http://www.elvastowe...__fromsearch__1

I suggest to divide this parameter into two parts. One is ORTSOnTime, another is ORTSOffTime. If the light is a flashing one, time will be the sum.

#12 User is offline   YoRyan 

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Posted 27 April 2020 - 06:50 PM

Are there signals with asymmetric fade-in and fade-out times?

#13 User is offline   ebnertra000 

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Posted 28 April 2020 - 06:17 AM

I'm going to check thursday, but it seemed to me that fading out took longer than fading in

#14 User is offline   YoRyan 

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Posted 04 May 2020 - 12:20 PM

I've reviewed some videos of flashing signals and I have yet to see a signal that fades out slower or quicker than it fades in. I don't believe this is a scenario we have to worry about.

If there are no further concerns, I will submit a Trello card:

  • All signals will fade on/off by default.
  • The default fade time will be 0.5 seconds 0.2 seconds (be conservative with the new effect).
  • The ORTSOnOffTime property in the SignalType block will control the fade time.


#15 User is offline   markus_GE 

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Posted 04 May 2020 - 03:24 PM

View PostYoRyan, on 04 May 2020 - 12:20 PM, said:

I've reviewed some videos of flashing signals and I have yet to see a signal that fades out slower or quicker than it fades in. I don't believe this is a scenario we have to worry about.
[...]


I have only now stumbled upon this thread (well, I have done so earlier, but ignored it http://www.elvastower.com/forums/public/style_emoticons/default/whistling.gif ), otherwise, I would have replied to that issue a little earlier ;)

By coincidence, I'm currently in the process of studying for an exam in electrical engineering on May-18 (just part of my degree program, even though it's the last exam before I can finally start my BSc thesis). And in doing so, I also learned a lot about electromagnetic coils, which are the usual form the filament in a traditional light bulb takes.

WRT real signal lights, we are usually talking traditional light bulbs, I guess, but not LEDs, since LEDs usually switch on and off instantaneously. Only traditional bulbs (and maybe - I cannot say that for sure - halogen bulbs etc.) CAN exhibit the fading behavior upon switching them on and off, but that depends on the type of current you use them in. In a typical household electrical installation, everything is run on AC, which will prevent the fading effect from occurring (but that's a different story). In signal installations, much of the time the lights run on DC - at least according to what little I have read about signals in the US which often run from batteries that always yield DC.

When a DC current is switched on in a circuit containing a light bulb (IE a coil), the coil will build a magnetic field around itself, which gobbles up a lot of the energy supplied by the current. The magnetic field will slowly stabilize at a certain intensity and while getting there, its formation will take ever less energy, thus increasing the current available for heating the filament, which will make it glow and consequently radiate energy - mostly as heat and to some minor degree as light, too (that's why bulbs are so inefficient - about 96% of the input energy is radiated as heat!). Since the current keeps increasing only slowly, though, so will the amount of light emitted and you get a fading effect.

When the current is shut off again, the energy stored in the magnetic field will start to "bleed off" again by inducting a current in the coil. Said current starts at the same value of the DC run through the coil before and diminishes ever further until the magnetic field is depleted. However, this diminishing current still is a current, thus providing energy to keep the filament glowing. Of course, as the intensity of the current decreases, so will the light and there you have the fading effect again.

Now, what does this have to do with the time it takes for the fading effect to complete in each direction? - The increase and decrease of the current can be described using specific forms of a natural exponential function, which take a constant as the exponent to indicate the half-life period (IE the time in which the current has reached half of its maximum value). That constant is the dependent on the inductance of the coil, which is a constant as well. Actually, the increasing current's function is defined as 1-dec, where dec is the decreasing current's function. Thus, both the increasing and decreasing currents' functions take the same half-life constant which means the fade in and fade out time must be the same.

http://www.elvastower.com/forums/public/style_emoticons/default/sign_sorry.gif for the lengthy post, but I just found it cool to be able to put my newly acquired knowledge to good use, aside from writing another silly exam http://www.elvastower.com/forums/public/style_emoticons/default/pleasantry.gif

I just hope this is not too hard to understand, while still trying to be scientifically correct. It took me more than two days to wrap my head around the processes when switching on and off a current through a coil. http://www.elvastower.com/forums/public/style_emoticons/default/curiousPC.gif

Cheers, Markus

#16 User is offline   ebnertra000 

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Posted 04 May 2020 - 03:42 PM

Science!

That is a pretty cool explanation on how filaments work (I'd given it some thought in the past, but never bothered to read into it). Based on observations in the field, I can also confirm that the on/off fade rate is equal. Once it's in, I will definitely retrofit any of my signals to better use this feature.

Also, Markus, you're right about US signals being DC powered, 12V being the most common form. AC is very rare, ecept maybe in some transit or electrified systems

#17 User is offline   markus_GE 

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Posted 04 May 2020 - 03:49 PM

View Postebnertra000, on 04 May 2020 - 03:42 PM, said:

Science!

That is a pretty cool explanation on how filaments work (I'd given it some thought in the past, but never bothered to read into it). Based on observations in the field, I can also confirm that the on/off fade rate is equal. Once it's in, I will definitely retrofit any of my signals to better use this feature.

Also, Markus, you're right about US signals being DC powered, 12V being the most common form. AC is very rare, ecept maybe in some transit or electrified systems


Science CAN be cool (when you finally got your head around it, of course) http://www.elvastower.com/forums/public/style_emoticons/default/wallbash.gif

http://www.elvastower.com/forums/public/style_emoticons/default/sign_thank_you.gif for the compliment and your additional info, Travis!

BTW, I've added some more clarifications to my above post just a minute ago.
Cheers, Markus

#18 User is offline   markus_GE 

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Posted 04 May 2020 - 04:40 PM

View Postmarkus_GE, on 04 May 2020 - 03:24 PM, said:

[...]
Now, what does this have to do with the time it takes for the fading effect to complete in each direction? - The increase and decrease of the current can be described using specific forms of a natural exponential function, which take a constant as the exponent to indicate the half-life period (IE the time in which the current has reached half of its maximum value). That constant is the dependent on the inductance of the coil, which is a constant as well. Actually, the increasing current's function is defined as 1-dec, where dec is the decreasing current's function. Thus, both the increasing and decreasing currents' functions take the same half-life constant which means the fade in and fade out time must be the same.
[...]


On a (late) side note that occurred to me qhile doing some more studying, the above goes only for a circuit consisting of one or multiple switch(es) (like in a relay), a power source (battery) and the light bulb. If any other elements are contained in the signal light's circuit (which I doubt, though, as it wouldn't make much sense to my understanding of US signals, at least), the behavior might be different.

Cheers, Markus

#19 User is offline   YoRyan 

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Posted 04 May 2020 - 04:53 PM

I also appreciate your science, Markus. :sign_thanks:

I have submitted the Trello card and pull request.

#20 User is offline   R H Steele 

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Posted 04 May 2020 - 05:33 PM

View Postmarkus_GE, on 04 May 2020 - 03:24 PM, said:

I have only now stumbled upon this thread (well, I have done so earlier, but ignored it http://www.elvastower.com/forums/public/style_emoticons/default/whistling.gif ), otherwise, I would have replied to that issue a little earlier ;)

By coincidence, I'm currently in the process of studying for an exam in electrical engineering on May-18 (just part of my degree program, even though it's the last exam before I can finally start my BSc thesis). And in doing so, I also learned a lot about electromagnetic coils, which are the usual form the filament in a traditional light bulb takes.

WRT real signal lights, ...

Cheers, Markus

Ahh memories, takes me back to my electronics training at Lowry AFB, Co. in the mid 1960's --- it was run by the Navy for the USAF...rigorous and hard...had to pass NASA soldering tests. To admit...I've not used it in years.


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