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| LED signals on Network Rail 04/09/2020 at 17:46 #131294 | |
indian_railways_fan
72 posts |
Hello, I recently came across this image on Twitter and had a discussion with fellow railfans as to how these LED signals work. The main point of contention is whether these are multi-colored LEDs or are the LED arrays seperate for each color displayed by the signal.  My personal understanding is that all colors are displayed by the same LED but friends are differing! Khalid. Log in to reply |
| LED signals on Network Rail 04/09/2020 at 18:37 #131296 | |
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Stephen Fulcher
2080 posts |
The technical information for the signals as pictured (Dorman Classic) can be found here: https://www.unipartdorman.co.uk/technical---trackside-signals.html Log in to reply |
| LED signals on Network Rail 04/09/2020 at 19:25 #131301 | |
Steamer
3985 posts |
Stephen Fulcher in post 131296 said:The technical information for the signals as pictured (Dorman Classic) can be found here:I've had a look through a selection of the documents, but can't see anything that explicitly states if there's an array per colour or if they're tri-colour LEDs? "Don't stress/ relax/ let life roll off your backs./ Except for death and paying taxes/ everything in life.../ is only for now." (Avenue Q) Log in to reply |
| LED signals on Network Rail 04/09/2020 at 19:56 #131306 | |
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clive
2789 posts |
The ones I've looked at carefully (which might not have been Dormans) had separate LEDs for each colour. The requirements for colours of railway signals are quite specific and it's probably not possible to get a tri-colour LED to generate accurate-enough colours. Log in to reply |
| LED signals on Network Rail 04/09/2020 at 20:11 #131307 | |
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Stephen Fulcher
2080 posts |
I’m fairly sure you’re right Clive, couldn’t remember for sure but I think I’ve heard it mentioned that there are twice as many yellows as red and green too.
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| LED signals on Network Rail 04/09/2020 at 21:36 #131314 | |
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bill_gensheet
1413 posts |
The head has an array of 'bright spots' which are optical lenses / apertures. Any one spot can be lit as either (red / yellow) or (green / yellow). So there are twice as many yellow 'bright spots' as there are reds or greens, making yellow twice as bright. I stood at Colchester and checked it one day. In the image you can see that red is only showing on every other row. the intervening rows are where green is shown. Now, whether each optic spot has a true bi-colour or dual colour LED, two single colour attached to one optic, and/or filtered, is a different question and may well depend on how they detect correct operation. I'd suspect two singles myself, only the very low power seem to come in twin packs. Higher power tend to be one huge emitting diode as most of the heat comes from one terminal so that has to be the heatsink one. Bill Log in to reply |
| LED signals on Network Rail 04/09/2020 at 23:07 #131316 | |
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bill_gensheet
1413 posts |
Photo montage of the same signal head. Bill  Post has attachments. Log in to view them. Log in to reply The following users said thank you: pebbens, 9pN1SEAp |
| LED signals on Network Rail 05/09/2020 at 13:40 #131331 | |
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bill_gensheet
1413 posts |
Looking a lot closer it is an array of single LED Odd numbers of Y in each row with even numbers of R or G between G G Y Y Y Y Y R R R R R R Y Y Y Y Y Y Y G G G G G G G G Y Y Y Y Y Y Y Y Y R R R R R R R R Y Y Y Y Y Y Y Y Y G G G G G G G G G G Y Y Y Y Y Y Y Y Y < Centre line R R R R R R R R R R Y Y Y Y Y Y Y Y Y G G G G G G G G Y Y Y Y Y Y Y Y Y R R R R R R R R Y Y Y Y Y Y Y G G G G G G Y Y Y Y Y R R Total of 34R, 69Y and 34G (needs fixed width font) Bill Last edited: 05/09/2020 at 13:41 by bill_gensheet Reason: font comment Log in to reply |
| LED signals on Network Rail 05/09/2020 at 19:01 #131341 | |
Hap
1039 posts 
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Does the upper aperture only have Y LEDs, since that's all it would ever display?
How to report an issue: www.SimSig.co.uk/Wiki/Show?page=usertrack:reportanissue Log in to reply |
| LED signals on Network Rail 06/09/2020 at 01:34 #131348 | |
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Airvan00
129 posts |
For ease of manufacture there is probably only one type, also I read somewhere that, in case of failure of a lower signal, a Upper can also display a G or R
Last edited: 06/09/2020 at 02:01 by Airvan00 Reason: Clarity Log in to reply |
| LED signals on Network Rail 06/09/2020 at 09:06 #131353 | |
headshot119
4869 posts |
Airvan00 in post 131348 said:For ease of manufacture there is probably only one type, also I read somewhere that, in case of failure of a lower signal, a Upper can also display a G or RIt's unusual to have the feature where the upper aperture, can compensate for a failure of a certain aspect on the lower aperture. The only place I know if it being in use is Manchester South SCC "Passengers for New Lane, should be seated in the rear coach of the train " - Opinions are my own and not those of my employer Log in to reply |
| LED signals on Network Rail 06/09/2020 at 10:26 #131356 | |
Splodge
720 posts
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headshot119 in post 131353 said:Airvan00 in post 131348 said:I was going to say - we had a special brief when training on the Manchester South signals because they can do this and are apparently unique in this ability. They also show the green aspect from the top aperture, wheras four aspect LEDs elsewhere will show it from the same as the R and lower Y.For ease of manufacture there is probably only one type, also I read somewhere that, in case of failure of a lower signal, a Upper can also display a G or RIt's unusual to have the feature where the upper aperture, can compensate for a failure of a certain aspect on the lower aperture. The only place I know if it being in use is Manchester South SCC Notably, they can also mitigate for an aspect failure - so if the G aspect fails, the signal will automatically show YY as its least restrictive aspect. If one of the Y aspects fails the signals automatically sequence so that the failed aspect will not be called and the signaller doesn't have to use replacement switches to avoid displaying a failed aspect. There's the right way, the wrong way and the railway. Log in to reply |
| LED signals on Network Rail 06/09/2020 at 15:16 #131368 | |
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bill_gensheet
1413 posts |
Splodge in post 131356 said:Does that mean the R and G look less 'threadbare' than the Colchester ones posted above as this should allow better fill ? Bill Log in to reply |
| LED signals on Network Rail 06/09/2020 at 16:36 #131371 | |
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Splodge
720 posts
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Both apertures can show all three colours so you don't really see a difference between the top and bottom. I believe they are LED signals but seem to be based on an earlier technology. However I actually find them poor light wise, especially on a bright day when it can be really difficult to pick the aspect up (green in particular) compared to the Dorman LEDs. There's the right way, the wrong way and the railway. Log in to reply |
| LED signals on Network Rail 06/09/2020 at 17:03 #131372 | |
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Steamer
3985 posts |
bill_gensheet in post 131368 said:Splodge in post 131356 said:I think the heads are fibre-optic- they might well be LED at source, but not in the head itself.Does that mean the R and G look less 'threadbare' than the Colchester ones posted above as this should allow better fill ?  airvan00 said: For ease of manufacture there is probably only one type, also I read somewhere that, in case of failure of a lower signal, a Upper can also display a G or RLooking at the manufacturer's info linked to above, Y only modules are available. Post has attachments. Log in to view them. "Don't stress/ relax/ let life roll off your backs./ Except for death and paying taxes/ everything in life.../ is only for now." (Avenue Q) Last edited: 06/09/2020 at 17:04 by Steamer Reason: None given Log in to reply |
| LED signals on Network Rail 06/09/2020 at 18:38 #131375 | |
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Stephen Fulcher
2080 posts |
These are different signals to the ones I linked Rick.
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| LED signals on Network Rail 06/09/2020 at 19:56 #131379 | |
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Steamer
3985 posts |
Stephen Fulcher in post 131375 said:These are different signals to the ones I linked Rick.Ah, sorry, I could've made that clearer. Dorman produce Y only LED modules, and their kit can't show G or R in the upper head. The kit used on Manchester South is Ansaldo, and (if memory serves) is fibre-optic. As others have said, they can show R/G in both heads. "Don't stress/ relax/ let life roll off your backs./ Except for death and paying taxes/ everything in life.../ is only for now." (Avenue Q) Last edited: 06/09/2020 at 19:56 by Steamer Reason: None given Log in to reply |