SMD LEDs to light up n-scale signals?

[krt]

G'day,

 

I have a pack of GreenMAX 2186 signals ~ http://www.1999.co.jp/eng/10169342

 

I was planning on LED illuminating these with some 1005/0402 (metric/imperial) sized SMD LEDs with appropriate resistors.

 

The 1005 components are approximately 1mm by 0.5mm, and I *guess* this is small enough to put one behind each lamp socket, which look to be approximately 1mm in diameter.  I figured on wiring them with some coil-winding enamelled wire (~0.2mm).

 

While I wait for the components to arrive from China, I wondered - has anyone done this sort of thing before?  Any Hints?

 

Some of the problems I foresee are:

• Light leaking through the plastic (fix with foil?)
• Too many cables to return down the back of the post (twist together tightly, paint black)
• Afixing the LEDs to the plastic model.

 

I would also like a model of a rotation-type obstruction indicator - are these available similar to the GreenMax 2186 ?

 

cheers,

-krt

[cteno4]

Krt,

 

I've not yet mounted smd LEDs in signals, was planning to do them on some traffic signals and street lights and have been experimenting some.

 

One thing to look at is called gallery glass here. It's basically acrylic stained glass. It's in a very thick paint constancy and drys clear to translucent (depending on the kind you get). What it works well for is making a lens of sorts.

 

For the light leakage I would look at using like a pot so you can experiment on the brightness. I don't think the led has to be super bright to be seen well as a signal.

 

you can use very fine magnet wire like 40g as you are only doing 60mA per led. You can also use a single wire for ground for all of them as well. I would run them in parallel rather than winding them as they tend to get a little lumpy when twisted. Maybe run them down the back of the pole like conduits.

 

Keep us posted on your efforts, it will be interesting what you find.

 

Cheers

 

Jeff

Edited January 6, 2016 by cteno4

[mrp]

I would also like a model of a rotation-type obstruction indicator - are these available similar to the GreenMax 2186 ?

 

 

There’s this one from TGW (althought the quality is not that great).

 

 

 

For my own work on signals (see this thread), I wanted some way to individually control the light output from each LED to match the different intensities (the green LEDs were crazy bright) and to allow dimming during night running.  Currently I’m using the WS2811 Constant Current LED Drive IC which then also allows the control circuit to be easily daisy-chained from one signal to the next.

[kvp]

Just two tips:

-ca glue holds a led by the lens or side but only apply it after soldering as it burns easily

-acrilyc paint is good for masking and non conductive after drying (also easier to apply than foil)

[mrp]

I would also like a model of a rotation-type obstruction indicator - are these available similar to the GreenMax 2186 ?

 

I just spotted that GreenMAX themselves also released the obstruction indicator last month - the 2806.

 

 

[JR 500系]

I just spotted that GreenMAX themselves also released the obstruction indicator last month - the 2806.

 

 

 

Yap, along with 2 others:

 

 

 

Painted Repeating Signal Set

 

and

 

 

 

Painted Shunting Signal Set (9 Pieces)

 

I too, got myself the 2805 Painted Repeating Signal Set  as it is a great set for putting up markers on the tracks for these 'proceed' lights. They also come with speed markers and position stoppers for stations in the set.

 

 

[krt]

Just a quick update on this ~

 

I have the surface-mount LEDs and resistors.  Geeze they're so tiny, I'm not sure my eyes will be up to the task of soldering.

 

A 1mm drill is the perfect size for drilling out the existing model. 

The drill-bits arrived, so I bored out the first of the signals.  It looks OK from the front, but at the back one of the holes is slightly out of alignment.  Not sure how that happened.

 

I designed a surface-mount "PCB" board to fit behind the lights - it's 6mm x 2.6mm.  The LEDs will be on the front-size, the resistors on the back.

After I'd sent the design away to be manufactured, I thought to myself that perhaps the resistors could be placed on a separate board anyway (that goes under the layout).

But it was my first-ever design, and to be honest I was a bit out of my depth.

 

I'm starting to wish I got out the callipers to measure the distance between the bulbs separately though.

I did measure it to be very close to 1mm a few times, but only with a ruler.

 

I'll post some photos once the boards arrive.  I've not done any SMD work before, so it will probably be a spectacular failure ;)

[cteno4]

Krt,

 

No be bold and give it a whack or two! Hey if you get this figured out you can sell the pcb!

 

Smd soldering takes practice, but you usually have a peck of them extra Ina 100 pack so just practice away! The first smd led I did worked great then I fried about 6 in a row, then I got better! You can use the paste flux and just put a tiny dab on the pcb contacts and then it helps hold the smd in place. I solder wire leads onto them by putting them on masking tape sticky side up taped down to the bench and then laying the wore in next to them. This holds it all in place well. I've used a toothpick in a third hand clamp to hold an smd in place during soldering as well. The 402s do require the magnifiers!

 

So are you going to run 6 strands of magnet wire down the pole?

 

Also just picked up a new paint to fiddle with light leaking. It's tulip fabric paint. It's used to make raised markings on fabric. Apparently it's exceptional to get into cracks and such to limit light leaks and is very opaque.

 

Do you have a 5 light chase circuit yet? One of our club members was fiddling with one to make a large static display of this type of signal. I can ask him for it if you wish. I also have one I have been meaning to try.

 

Cheers

 

Jeff

[kvp]

The common solution i've seen on some small series N scale lights was to mount the leds facing towards the circuit board and looking through holes. This solves the masking problem as the entire front (before soldering) and back (after soldering) can be painted black and the front can have a full metal plating to make it easy to solder the light houses onto the surface. (short metal tubes cut off at an angle). This gives a self contained signal head with pcb connection points on the back. Sadly those leds are just too tiny for me to position reliably. So please keep us up to date on your progress!

 

For driving the lights i would say a small arduino and a 7 output low active ULN2003 driver chip would work and easy to wire and program. It would be possible to use a 50 cent microcontroller too instead of the arduino, but that's harder to set up as extra circuits and chip programming is needed.

 

ps: By using led pairs connected back to back and driving with a square wave or an ac signal, it's possible to use 3 wires and 2 resistors for 4 leds. Turning off each led in a pair with a polarity matched series diode, no diodes for both lights and disconnect for both off, easy to set up on a rotary switch, even for multiple pairs like a 2 circuit 6 position one for 6 different aspects on 4 lights. For blinking, a common relay based blinking power source can be used for all lights, of course going all digital is possible and even easier as long as the accessory decoder supports bipolar outputs.

 

slightly off topic: My favourite chase circuit i built as a little kid was a drum with bent metal sheet contact plates nailed onto it and brass wipers taking off the signals and it could be driven with a geared down motor. It was driving some 4.5V small bulb traffic lights on a board. (you could just cut out the sheet metal with scissors according to the printed pattern you had and then wrap it around the wooden drum) It's called a fixed program, but i didn't know that back in elementary.

Edited February 2, 2016 by kvp

[cteno4]

lots of simple ic circuits for chase leds with 4017 and 555 chips no programming needed. this was the one i made a long time back (cant find the actual one i had done) and was thinking of doing again. you can actually get a whole kit for it on ebay for $1.59 for a 10 led but you can reduce to 5 by just knocking out a trace and moving the 6th output to the reset if you dont want to hand wire the circuit.

 

love the simple drum mech! when i was a kid is had some track power presets i did with a huge 14 position, 10 contact rotary switch i salvaged from some old naval electronics that were being scrapped. similar idea of simple program as you turned the knob, but no motor to keep it going! could really do a lot with old player piano concept and some momentary switches to do traffic lights!

 

cheers

 

jeff