Bending Light/Prisms

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DafyddElvy
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Bending Light/Prisms

Post by DafyddElvy » Mon Jun 14, 2021 9:53 am

Their are some clever folk on here that do lots of clever things and the www has let me down.

What I want to do is put an LED under the floor of a tram and reflect the light from the LED through the dash lamp holder, basically make a periscope for the front and rear light.

First idea was file the end of a 2 pieces of fibre optic and glue them together, then glue the LED to the end under the floor, light goes up above floor level through 90deg and out the lamp holder.

Second idea which I don't think would work out too cheap is to use a 2-3mm prism behind the lamp holder.

Questions:
Has anyone done this before?
What have others done to project light with an LED out of sight?
Does anyone have a better idea that keeps the LED under the floor?

Thanks, David

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Re: Bending Light/Prisms

Post by Andrew » Mon Jun 14, 2021 11:12 am

Sorry Dafydd, don't know the answer, but I'm interested to find out!

I've got an RH "Hercules" that's scheduled to have its body replaced with something Kerr Stuart-ish, but I'd like to retain the the headlight, maybe in the style of an oil lamp. I haven't played with it yet, but if the LED's not amenable to being moved easily I'd also wondered about the possibility of doing something with fibre-optics...

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Re: Bending Light/Prisms

Post by philipy » Mon Jun 14, 2021 11:20 am

Not sure why you are considering a complicated technical solution? If I'm understanding what you want to achieve correctly, then I would use micro LED's. At about 0.8mm square they will go pretty much anywhere that a fibre optic or prism would fit.
These are bright white but they also come in various colours and warm white which might be better for your application. Just search micro LEd with wires ( you really don't want to be soldering to these!)
s-l1600 (2).jpg
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https://www.ebay.co.uk/itm/393246966883 ... SwaldgeAJw

Rik pointed me to them some while ago and they are brilliant ( in both senses!).
Philip

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Re: Bending Light/Prisms

Post by DafyddElvy » Mon Jun 14, 2021 11:42 am

My engineering lecturer always said I made life too difficult for myself sometimes with my solutions to problems.

A bit annoyed I didn't think of that, I have some of those LED's for the interior, two different colours together would do just the trick, thanks.

All I need to do now is put a non-conductive sleeve in the lamp holder, simples.


David

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Re: Bending Light/Prisms

Post by DafyddElvy » Mon Jun 14, 2021 11:43 am

My engineering lecturer always said I made life too difficult for myself sometimes with my solutions to problems.

A bit annoyed I didn't think of that, I have some of those LED's for the interior, two different colours together would do just the trick, thanks.

All I need to do now is put a non-conductive sleeve in the lamp holder, simples.


David

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Re: Bending Light/Prisms

Post by GTB » Mon Jun 14, 2021 2:39 pm

This is the arrangement that I used on my old Motor Mule when I converted it to r/c control. I don't make a habit of running at night, but the headlight reminds me to turn the power off when putting it away. At night it will light up a couple of metres of track, even though the 'reflector' is just silver paint. With a polished aluminium reflector it would probably throw an even longer beam.

The LED is a warm white 0.8mm SMD package. The leads on these are magnet wire, for use in HO models, but basically they are invisible under a coat of paint in large scale. These came from a local supplier here in Oz, but I've no idea if they are still available.

If you look carefully at the loco headlight you can just see the leads running vertically down into the motor cover, simulating the conduit on a real loco. The holes for the leads are 1mm dia. and the leads support the SMD LED at about the focus point of the 'reflector' in the headlight. A small drop of canopy glue keeps them there.

Fowler-rc5.jpg
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I grew up when there were still tram systems in the Victorian provincial cities. The ones we had were built before WW1 and the headlights were about as effective as a VW beetle with a 6V electrical system and a flat battery. The inside lightbulbs were even dimmer. You might want to consider using yellow LEDs and fitting a resistor that just gives a wan glow in the dark.

Regards,
Graeme

ps. This post would be better moved the 'Garden Railway Technical Help & Advice' section, as this section is meant to be for help with deciphering the intricacies of the forum software.

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Re: Bending Light/Prisms

Post by philipy » Wed Jun 16, 2021 1:07 pm

GTB wrote: Mon Jun 14, 2021 2:39 pm
ps. This post would be better moved the 'Garden Railway Technical Help & Advice' section, as this section is meant to be for help with deciphering the intricacies of the forum software.
Excellent suggestion Graeme - now done ( of course!)
Philip

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