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Old 15th May 2010, 05:07   #1
hpept
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Default Railway crossing lights

Hello,
here is my new scratchbuilt project: A railway crossing light, brazilian style, like this one below:


Iīll present a step by step process so that itīs easy to replicate for those who want to try it.

Materials needed:
n.2 3mm red LEDS
n.2 3mm metallic washers
brass tube, 3mm dia.
shrink wrap tube 2mm dia.
wire, AWG 26 or smaller
Cyanoacrylate glue

Tools of the trade:
Soldering iron
Third hand
Dremel with cutting disc (0.5mm) , 1 mm drill bit and a 2mm spherical burr
Files (cylindrical and triangular)

Letīs start with the lights.
Take the LED and gently but sharply bend the legs so that the bend is as close as possible to the LED head. Take the washer and put it on the LED.
To make the sunshade, take the 3mm brass tube and cut with a cutting disc (0.5mm thickess) a piece of 6mm length, then file one side at an angle of approx. 30 degrees, and finally, cut it lengthwise in the lower part, so that it can open and fit the led snugly.



Do the same with the other led, but bend the legs so that the anode of the left LED faces the cathode of the right one, and viceversa. In this way, when the LEDS are powered, depending on the current polarity, one will light and the other will not.

To prepare the pole, cut a 70mm piece of brass tube, either with triangular file or cutting disk. Drill a 1mm hole at 15mm from one edge of the tube, and right below, 3mm under, drill another hole and the open it up with the burr. This second hole will be the passthrough for the wiring of the LEDS.
Cut a lenght of approximately 20cm of wire and feed through the lower hole to check if it exits easily.


Bend the LEDs legs at right angle exactly where there is a small squared notch, and cut one leg exactly where thhey meet. The photo below is wrong, showing the cut legs as being the upper legs, where it should be the lower legs. I simply rotated the sun shades after i took the photo.

Align the two sub-assemblies and solder the upper legs together, and trim them at 5-6mm from the bend.

Letīs prepare the wiring. There will be only one wire fed through the pole. The other wire will be the pole itself.
Cut the wire at a distance of approx 2cm from the edge, and solder a 1kohm resistor. Please check that it will slide through the tube hole. To avoid problems of shorting, use a small length of heat shrink tube on both terminals of the resistor.


Solder the lights to the pole. Consider that the tube will draw alot of heat from the soldering iron, so be sure to heat the parts well before soldering. Itīs good to use the third hand to keep everything in place and avoid melting the previously tinned parts.


Finally, feed the wire through the bottom of the pole and make it exit from the lower hole, then solder it to the cut legs of the legs, making sure that the wire maintains electrical contact with both LEDS.

The crossing light is basically done. Check if the lights are working with a 9V battery by inverting the polarity to see if both LEDS work. Touch one end of the battery with the wire, and the other with the pole body. If everything works well, glue with a small drop of cyanocarylate glue the washer to the sun shade.

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Old 15th May 2010, 05:22   #2
hpept
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Default Re: Railway crossing lights

Next phase is the drawing of the cross and warning plates.
I used Corel Draw to make the plates. Size is shown below.
.
Iīve not decided yet if the plates will be printed on regular paper and glued on 0.5mm styrene sheet, or if i will print them on inkjet waterslide decal paper.
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Old 15th May 2010, 14:21   #3
GWRman
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Default Re: Railway crossing lights

Very inventive and a good result. Thank's for bringing us this "how to".

Doug.
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Old 15th May 2010, 17:36   #4
mysterd429
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Default Re: Railway crossing lights

Bom dia! Brasil's a wonderful country! Thanks for the very detailed information! That looks really excellent so far. Will you include the light on the top? Will you be fabricating the electronics, as well?
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Old 16th May 2010, 02:01   #5
hpept
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Default Re: Railway crossing lights

Hello Don.
I will not include the light on top because of scale factor. A 3mm led would look huge on top of the pole, so I will discard it.
About the elctronics, yes, I will make the flashing circuit also. I need to find a little of time to go downtown to buy the components. Itīs a very simple circuit that I found online some time ago, based on a LM555 oscillator. Later I will publish the schematics too. Iīve started painting the signal. As soon as I finish I will update the thread.
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Old 16th May 2010, 08:35   #6
Howqua
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Default Re: Railway crossing lights

Great work.
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Old 6th June 2010, 23:12   #7
hpept
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Default Re: Railway crossing lights

After a long hiatus I finally finished the signal. Here is the result, inserted in the final road scene.



Next step will be the electronics.
I bought from eBay an IR detector which will be positioned on both sides of the railroad crossing. I decided to go this way because in this point I have 5 lines crossing the road, so oter types of individual track activation would be too complicate or expensive. When a train crosses the IR beam the circuit is activated and the signal goes on. When the trais has passed, a delay (which is programmable via trimpot) makes the circuit stay on for some additional seconds.
About the flashing circuit, Iīm waiting for a colleague to lay down a circuit that allows to invert current polarity alternatively, based on a LM 555 oscillator.
More to come...
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Old 8th June 2010, 00:26   #8
mysterd429
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Default Re: Railway crossing lights

Quote:
Originally Posted by hpept View Post
After a long hiatus I finally finished the signal. Here is the result, inserted in the final road scene.
That looks awesome. Do you have the ability to post a video when it's fully functional? I'm looking forward to those schematics, too. Thanks for posting!
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Old 8th June 2010, 03:29   #9
hpept
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Default Re: Railway crossing lights

Hi Don,
yes, that's what I was planning to do. As soon as my colleague wakes up and lay down the circuit for me, I will build it and test it and then post a short video on Youtube showing how it works.
Glad you liked it.

Roberto
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Old 8th June 2010, 03:52   #10
Roy Buchanan
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Default Re: Railway crossing lights

That is fantastic, Roberto. Can't wait to see it in operation.
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