Author Topic: Position light signal project  (Read 909 times)

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unittrain

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Position light signal project
« on: December 24, 2016, 08:35:08 PM »
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I've ordered a couple bags of the Pennsy position light targets by Jim Hale, I want to add LEDs to light them but before I order them what brightness should I get 150 mcd or less? Also was wondering do I need 4 resistors per mast (one for each aspect plus one for the center led). I'm using my Traincat kit for the rest of the signal. I've never done electronics this small  :scared: I'll be using the wiring diagram that is on the original thread, so should I use insulated magnet wire? If so what gauge? And do I just need to find the wire and not the led?

peteski

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Re: Position light signal project
« Reply #1 on: December 25, 2016, 09:26:16 PM »
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So you just have the 3D printed targets?  I have to say that I think that for someone not familiar with electronic or precision soldering, this might be quite a challenge.  The wiring details are covered in that thread you alluded to. After several iterations we arrived in a wiring circuit which only needs a single resistor and 4 wires for each target. Or only 3 wires if you use a brass post and use it for a common positive.

As far as the magnet wire goes, the 38 AWG wire sold by Ngineering will work nicely. http://www.ngineering.com/accessories.htm

I would still recommend you practicing your precision soldering skills before tackling this project.  See this thread for some more info on precision soldering. Also a good temperature-controller soldering iron with very small tips will be needed.

150mcd is plenty bright for LEDs (you can always dim them using a higher value resistor).  I'm not sure what you mean by "And do I just need to find the wire and not the led? ".
« Last Edit: December 25, 2016, 09:30:38 PM by peteski »
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unittrain

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Re: Position light signal project
« Reply #2 on: December 25, 2016, 10:15:34 PM »
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My spell check changed the wording I meant to say do I just need to tin the wire or the LED too? Thanks for the help. I'll definitely be practicing first as these are extremely small targets,

peteski

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Re: Position light signal project
« Reply #3 on: December 25, 2016, 10:24:03 PM »
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My spell check changed the wording I meant to say do I just need to tin the wire or the LED too? Thanks for the help. I'll definitely be practicing first as these are extremely small targets,

Yes, you need to strip the enamel from the wire (which also tins the exposed wire). The LED solder pads are usually gold-plated so no tinning is needed.  But you have to use some flux to insure a fast and good solder joint.

Check out some of these videos (not mine): https://www.youtube.com/results?search_query=soldering+wire+to+smd+leds
--- Peteski de Snarkski

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jdcolombo

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Re: Position light signal project
« Reply #4 on: December 26, 2016, 11:56:53 AM »
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Just a note on soldering tools for this.

Soldering leads to a 603 or 804-sized surface-mount component is nearly impossible with any kind of "standard" soldering iron.  On Peteski's advice, I invested in a Pace ST50 digitally-controlled soldering station with a TD100 iron.  The TD100 is nearly as small as a real pencil (well, actually, more like a good hefty fountain pen, like a Montblanc President, which I'll never own, but have touched on occasion); the tips are interchangeable (and the tips contain the actual heat cartridge), but I've found that the 1/64" conical tip is perfect for 603/804 sized components (and they are pretty cheap - about $12 each).  The key here is that you can set the temperature of the ST50 precisely; the tip is tiny enough to work with the pads on SMT components, and the iron itself is small enough that you can actually manipulate it like a pen or pencil - meaning you can be VERY precise).   The ST50 is about $350 (with the TD100 iron; the tips you'll have to order separately).  That's a significant investment, I know, but if you're going to do any kind of precision soldering (including things like re-soldering wires to DCC decoders when they break off), then it is definitely worth it.  Like every other task, having the right tool is 90% of the battle, and the wrong tool makes the process impossible.

I do note that Ngineering sells a small 12w iron with a tiny tip for this kind of work.  I haven't tried that, but I can tell you that if you try to do this with a Weller or Radio Shack iron - even their smallest ones - you'll end up disgusted and throwing nearby objects.  I just got through soldering some 32-gauge magnet wire leads to two 603 LED's with the Pace, and the whole process took about three minutes (literally - I put a piece of double-sided tape down on my desk, laid out the LEDs upside down pressed to the tape, cut 4 pieces of magnet wire, turned on the Pace - which takes about 15 seconds to reach operating temperature BTW - tinned the magnet wire ends with a blob of solder on the Pace tip, cleaned the tip and then soldered the leads to the LEDs).  There is no way on earth I could have done this with my 20w Weller, even with its smallest conical tip.

John C.
« Last Edit: December 26, 2016, 11:59:02 AM by jdcolombo »

Lemosteam

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Re: Position light signal project
« Reply #5 on: December 26, 2016, 03:38:33 PM »
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On the more practical side of things, I was given a used temp controlled soldering iron that the owner used for RC electronics.  I was able to find tips to fit the handle for all types of applications.  I have been quite successful using the smallest chisel  point tip I could find, able to make an 0402 LED into an N Scale lantern.



I found that the pencil point style did not carry the heat to the joint as effectively as the chisel point (as @mmagliaro told me once- "It's all about surface area.").

These types of irons can be had for around $80.  I was also fortunate to find replacement handles (the original on mine was pretty abused) for $20.

I think the brand name is now Trak Power TK-950:

https://www.amazon.com/Trakpower-TKPR0950-TK950-Soldering-Station/dp/B0051VD82U



Other tips are readily available.

« Last Edit: December 26, 2016, 03:45:44 PM by Lemosteam »

Wutter

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Re: Position light signal project
« Reply #6 on: December 26, 2016, 09:18:43 PM »
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Similar to what everyone has already said, small tips and temperature control are key for soldering SMD components. My soldering setup is a Hakko FX-888 which can be had for around $95 on ebay. I actually liked it so much I have two, one with the analog knob and one with the digital display so I don't have to keep moving my soldering setup around.

The contact area of the tip is definitely important but I've been able to get away with a flat application of the conical tip. That said, theres also a lot of different replaceable tips available for the FX-888. The replaceable tips and temp control are so flexible that I can use it for SMD components all the way up to soldering track and bus feeders. I don't think I could ever go back to the old Weller 40W pencil iron I used before this.
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