Fibre optic signal lamps

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Bob Ellis
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Fibre optic signal lamps

Postby Bob Ellis » Sat Jun 05, 2010 9:58 am

Does anyone have any experience of using fibre optic cable attached to an LED for lighting signal lamps?

You might ask why I don't use an LED in the signal lamp itself instead of having the LED below the baseboard and a fibre optic cable leading up the inside of the signal post to the lamp. The reason is that I am building lattice post signals and I think that fibre optic cable would be less visible inside the lattice posts than wires from an LED.

The problem I am finding with the fibre optic cable is that the light shines out of the end. The cable feeds into the signal lamp from the bottom, which means that the end points vertically inside the lamp, whereas the light needs to shine horizontally forwards through the lens and backwards through the back light. I have tried abraiding the side of the cable with a file and taking a sliver off the side with a scalpel blade, but both only succeeded in providing a very feeble light. Any other suggestions or any advice from someone who has made this system work would be most welcome.

I have also copied this question to the MERG webgroup.
Bob Ellis

Modelling Hawes (NER/MR) c.1905

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Jol Wilkinson
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Re: Fibre optic signal lamps

Postby Jol Wilkinson » Sat Jun 05, 2010 10:43 am

Bob,

if you use the signal structure for the return, then you would need only one feed wire. Fine enamelled copper wire (as used in transformer windings) would be adequate and not very visible.

Jol

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Bob Ellis
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Re: Fibre optic signal lamps

Postby Bob Ellis » Sat Jun 05, 2010 1:13 pm

Thanks for the suggestion, Jol. I had thought of that and may go down that route if I can't make the fibre optic idea work, but I would like to persevere with it for the moment. I believe there are people who have used fibre optic cable successfully and I would be interested to hear how they did so.
Bob Ellis

Modelling Hawes (NER/MR) c.1905

johnp
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Re: Fibre optic signal lamps

Postby johnp » Sat Jun 05, 2010 3:56 pm

Would cutting the end of the fibre at 45 degrees and then polishing work?
Regards,

John

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Bob Ellis
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Re: Fibre optic signal lamps

Postby Bob Ellis » Sat Jun 05, 2010 4:16 pm

johnp wrote:Would cutting the end of the fibre at 45 degrees and then polishing work?


It's worth a try. What would you recommend to polish the cut end?
Bob Ellis

Modelling Hawes (NER/MR) c.1905

ClikC

Re: Fibre optic signal lamps

Postby ClikC » Sat Jun 05, 2010 7:41 pm

Personally, i'd look as reflecting the light feed from the fiber-optic cable through 45 degrees using a highly polished metal surface, or similar.

Other options would be to purchase something that does the job already.

http://www.studiospares.com/Adaptors/Optical-Toslink-Mini-Jack-Adaptor/invt/586070

http://www.studiospares.com/Adaptors/Optical-Adaptor-RATos-Tos/invt/586060

These are right angled connectors for TOSlink (S/PDif or ADat) connections, I dare say with a bit of looking you could find something similar and cheaper to strip and use to fulfill the role.

Regards

Matt

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Tim V
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Re: Fibre optic signal lamps

Postby Tim V » Sat Jun 05, 2010 9:46 pm

My opinion is why bother?

The signal lamps can only be seen when it's dark, and I personally don't play trains after dark.
Tim V

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Bob Ellis
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Re: Fibre optic signal lamps

Postby Bob Ellis » Tue Jun 08, 2010 9:58 am

You have set me thinking now, Tim. I wonder whether the lamps woud be visible during the day. Hmmm!
Bob Ellis

Modelling Hawes (NER/MR) c.1905

martin goodall
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Re: Fibre optic signal lamps

Postby martin goodall » Tue Jun 08, 2010 10:38 am

Taking up Tim's point, and Bob's earlier reference to his original method of illumination producing only a 'weak and feeble light' , that is a very reasonable description of the light actually provided by the prototype lamps themselves. The signal lamps burned all day and night (lasting about a week between refills of the oil) and were completely invisible by day. By night they could only properly be seen head on by loco crews. An oblique view from the trackside at night would have given only a very limited impression of any light. So, if Bob can see his signal lamps in daylight, they are already too bright, but if they only give a 'weak and feeble light' by night, then it sounds as though he has got it about right.

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Bob Ellis
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Re: Fibre optic signal lamps

Postby Bob Ellis » Tue Jun 08, 2010 2:38 pm

The signals I am building are for a friend's layout. I have just had a detailed discussion with him of the pros and cons of fibre optic cable, grain of rice bulbs or no lighting at all. His decision is that he wants lighting, but we have decided to abandon the fibre optics because of the problems I have encountered and to use grain of rice bulbs, but with a fairly dim light. I plan to follow Jol's advice (now, there's a first, Jol! :o ) and use fine enamelled copper wire for the feed and the signal post for the return.

Thanks to all who have offered advice.
Bob Ellis

Modelling Hawes (NER/MR) c.1905

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stephenfreeman
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Re: Fibre optic signal lamps

Postby stephenfreeman » Mon Jul 05, 2010 10:38 am

Hi,

I personally prefer the grain o'rice bulbs where possible, sometimes it isn't and I have to use fibre-optic.

For Grain O'Rice, where possible, use the post for one path and the ladder (suitably insulated from the post etc of course) for the other.

If I have to use Fibre-Optic, I use Crofon .025". It's a plastic Fibre-Optic cable and suitable bends (quite sharp ones too) can be induced by holding a hot soldering iron tip close to where you want the bend. Cut the surplus off. You then have to thread it into the lamp housing and down the post. To do this you need an oversize hole in the lamp. To make everything fit nicely, thread some insulation tube over the cable and trim using a sharp scalpel at 90 degrees. Repeat for backlight. All covered in Railway Modeller in the early 80's- 'Light your lamp'.

Main problems are

1) Doesn't like solvents or paints - so leave it to last
2) getting it down a post - we used to use a slot and cover with tape but there will shortly be a better solution, of which more elsewhere in due course.

These days I prefer smd led warm white of suitably diminutive size.
Last edited by stephenfreeman on Sun Oct 22, 2017 9:13 am, edited 1 time in total.
Stephen Freeman
Bespoke Finescale Trackwork and Semaphore Signals 7mm to 4mm scales
https://www.tracknsignals.co.uk

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grovenor-2685
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Re: Fibre optic signal lamps

Postby grovenor-2685 » Mon Jul 05, 2010 11:04 am


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steamraiser
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Re: Fibre optic signal lamps

Postby steamraiser » Fri Jul 09, 2010 9:32 pm

Stephen Freeman is right about bending plastic fiber optic through 90 degrees. I found that the heat from the shaft of a soldering iron was enough to get a sharp 90 degree bend, without having the optic optic touch the iron. Also if you heated the lamp end in a similar manner, you got a rounded bulls eye effect which gives a larger area of light emission through the spectacle plate.

My experiments were on ready assembled Ratio signals quite a few years ago.

Gordon A
Bristol


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