Wednesday, January 28, 2015

Lighting Signals with Surface Mount LEDs

Sorry, but here is another signal related post although it is also related to progress on Bylong.

The instructions on the Signals Branch blog for my 3D printed signals discuss using 0.8mm SMD LEDs to light the signal aspects so here are a few photos showing how I did a bracket signal.

Firstly it is best to buy the SMD LEDs pre-wired, they can be bought without wires but they are so small that soldering very fine wire is difficult.

The lamps on the signals have a slot in front and back. The rear slot is to allow the wires to come out and the front is a slot as the minimum wall thicknesses make it difficult to have a lens or hole.

The 0.8mm SMD LED will be a slight push fit into the hole in the top of the lamp and the square LED sticking out of the front of the tiny circuit board will fit into the front slot.

The 0.8mm SMD LEDs are to be gently pushed vertically into the body of the lamp. I found that I had to use my finger nail to push it in but a toothpick would also work. Don't use a metal object to push the LED home as damage may be done to the fine wire on the top end. The other wire is at the bottom of the LED. Ensure that the wires align with the slot at the rear of the signal as it is pushed into place.

The wires from the small outrigger dolly post of the bracket signal were threaded under the landing and then through the angled bracket supports under the rear of the landing and then down the main post.

The wires from the lamp on the main post were run down the back of the post around the end of the landing and then down the back of the post.

Glue the wires to the signal with Super Glue progressively stopping at each change of direction.

A small circuit board can be made from a printed circuit board (PCB) sleeper or with a piece of PCB cut to size (4mm x 15mm). The copper on the PCB is cut down the middle of its length with a fine stone in a hand motor tool (Dremel, etc.) and then one side of the copper is cut at the half way point. A 1K Ohm resistor is soldered across the half way gap, this is the +ve side of the circuit. The other copper strip is the -ve side of the circuit.

A small 2 pin plug and socket is made by cutting up an integrated circuit socket. solder the long pins of one half to each side of the circuit board as shown on the diagram and photo below. Solder the wire from the LED to the two connections at the other end of the circuit board. The longer wire of the LED goes to the +ve terminal and the shorter wire of course goes to the -ve terminal. I have used a 1K Ohm 1/2 Watt resistor so that the light shows through the spectacle plate of the arm during daylight but any value from 1K Ohm to 10K Ohms could be used, your choice. 10K Ohm will probably not show during 'daylight' (room lights on).

Glue the circuit board to the signal where shown in the photo below and tuck the excess wires of the LEDs out of the way up in between the two halves of the mechanism.

The wires on the male plug are soldered across the two holes rather than into the holes, this is needed from clearance from the main operating crank of the signal (see photo).

Signal Circuit Board Diagram
Please note that the plug and socket doesn't have to be on the circuit board or even used for that matter. This method is presented in case the modeller wants to disconnect the wiring from the signal.

Signal showing small homemade circuit board
Lit LEDs during 'daylight'
LEDs lit during 'night' - No signal arms.
Once it has been confirmed that the LEDs work then the wires can be painted over or even smoothed over with a filler. It has been found that Selleys Spakfilla can be applied and once dried the signal can be flexed without it falling off. Spakfilla is an interesting material, it has no real weight and must be pushed onto the surface then carefully smoothed with a metal spatula or similar tool.

One thing I found while doing this is that posts glowed internally from the LED so I had to paint the posts black from the top of the counterweight brackets to the cap on the post. Of course I then had to paint the post white again.

Glowing bracket posts

Lit signal arms during 'night'
The light showing on the posts in the photo above is reflecting back off the rear of the signal arm lenses, perhaps some matt clear might reduce this.

I found that the LED was not yellow enough to give a green glow through the Tamiya X23 Clear Blue so I give the blue lens a coat of Tamiya X25 Clear Green.

Now it looks like I will have to light the Brakes Landmark, what have I started....

Installing lights though is a long term project for Bylong as I would like to operate eventually at 'night'.

Wednesday, January 21, 2015

Painting the Clearance Post and Lamp

Well, I painted two posts again, the first with two coats of black and then white and the second with silver, black and then white.

It seems that either is sufficient to hide the glowing light from the LED so I think I will recommend two coats of flat black and then the final flat white coat. There did not seem to be any difference in light between the silver and the black painted posts.

Flat or matt paint should be used for coverage as the matt effect is caused by the pigment protruding through the surface of the paint and diverting the light rays in all directions. A gloss paint just has a nice smooth surface and as such does not have as much pigment.

While the paint was drying I went to Jaycar and bought a selection of 1/2 Watt resistors in 2K Ohms, 3K Ohms, 5.1K Ohms and 10K Ohms. I made up a 10K Ohm resistor by putting several in series.

The end result of swapping the resistors around gave the following effects.

1K Ohm resistor - Light flare from lens
1K Ohm resistor - Light shows in 'daylight'
10K Ohm resistor - No light flare from lens
10K Ohm resistor - Lamp appears to be off in 'daylight'

I will recommend that the modeller chooses which resistor to use depending on the preferred effect.

I prefer the 10K resistor as the lamp appears to be off although it is actually on. So back to Jaycar to buy some of the 10K Ohm resistors that I didn't get today, oh well, that's how it goes.

Tuesday, January 20, 2015

Lighting a Clearance Post Lamp

I have had a chance to try lighting a clearance post lamp as discussed in the last post.

I may need to amend the installation painting instructions on the Signals Branch blog as the light from the LED is much brighter than expected and as can be seen in the photo below the light is showing through the paint.

Here is the clearance post lamp lit by a warm white LED. As this was a temporary mounting I added loose ballast around the base for the photo.

This post was painted in black first then white.

Another post painted in silver and then white was actually worse so the silver has less covering power than black.

At the moment the instructions state to use silver then black and finally white but I don't think that the silver adds anything and isn't needed for light transmission either.

I am currently painting another clearance post and lamp with two coats of black and then a white top coat. I will report on this in a day or two as each coat needs to dry thoroughly before the next coat is applied.

The LED is powered from a bridge rectifier running off the DCC track bus. I used a PO4 6A 400V Bridge Rectifier (Jaycar Cat. No. ZR1314) to convert the DCC power to a nominal 12 volts DC. This bridge rectifier has the AC and the + and - terminals clearly marked on it. Also it has a hole through the centre which allows it to be screwed to the layout frame near where the lighting is needed.

I bent the legs out at right angles and screwed them into two terminal blocks at each side as shown in this photo.

The resistance I used for the LED was 2K Ohms which was made by using two 1K Ohm 1/4 Watt resistors in series. I will rewire the LED and resistors and use shrink wrap tubing once I have decided about the resistor value.

The light level could still be a bit lower which could also help to reduce light leakage through the paint. I will have to get a few 5K Ohm 1/4 Watt resistors and see how the light level looks.

I will post the results and amend the instructions accordingly.

Monday, January 19, 2015

NSWGR Clearance Posts with Lamps

I have just added some instructions for clearance posts with lamps to my Signals Branch blog.

Clearance posts with lamps were placed at fouling points of sidings and loops and were painted white for visibility. The lamps were lit at night usually by the Station Assistant and spares would have been kept along with kerosene in the lamp room attached to the men’s toilet.

I have made these in two material types, the White Strong and Flexible for those who may be worried about the posts breaking if hit while cleaning track with a track rubber and Frosted Detail and Frosted Ultra Detail for those who want more detail and who also may wish to have the lamp lit.

If printed in Frosted Detail or Frosted Ultra Detail material they may break if knocked hard (I don't know yet as I have only just installed one), if so then just pull them out and replace with a new one.

These clearance posts with lamps are to be mounted in a 3mm hole drilled through the baseboard at the clearance location of a set of points (turnouts).

The Frosted Detail and Frosted Ultra Detail are an acrylic material which can transmit the light from a 3mm golden white LED placed into their mounting hole from below the baseboard.

Clearance post and lamp in Frosted Ultra Detail - Not lit yet.
Just a quick photo, ballast not yet reinstated around post, being white the detail doesn't show well but the black dot is the hinge of the lamp top and the catch is on the other side.

I have tested it with a torch from below and it gives a small circle of light that would only be seen with the room lights off as you would expect, this is no glaring headlight.

Further details can be found on the Signals Branch blog.

Wednesday, January 7, 2015

Signal Assembly Instructions Update

I have just updated the assembly instructions on the Signals Branch blog.

I did this as a result of currently assembling 16 signals (single posts and brackets).

I amended the drill bit sizes for the fine holes in the White Strong and Flexible (WSF) material and the Fine Ultra Detail (FUD) material. The  drill bit sizes were amended because the WSF expands slightly when drilled so you end up with a smaller hole than the drill bit. As a result the next drill bit size larger than for the FUD is used.

I also added something that I forgot to mention which is that the signal lamps have been designed to take a 0.8mm golden white LED (the ones with 150mm/6 inch leads). Some thoughts are included on wiring.

I haven't installed any 0.8mm LEDs in the signals as I am using Tam Valley Singlet Servos which have Green and RED bi-colour LEDs on the small control board.  The control boards are all under the layout near the servos. I won't be using the push buttons on the control boards to change the signals they will be run from a layout panel on JMRI using some logic. I will probably extend one of the bi-colour LEDs from each control board out to the fascia opposite the signal to show the status.

One problem with semaphore signals on a model railway is that we view the signals from some unusual angles and can't always see the actual arm position. The bi-colour LED will show the arm position for the driver.

If I ever get into night time operations then I will probably install the 0.8mm LEDs in those signals that can be viewed from the front.

Lastly, there are instructions on making clear lenses for the signals and colouring them with Tamiya Clear Red and Clear Blue.

The prototype signals had blue lenses so that the yellow light from the kerosene lamp would show green. This is why a golden white LED should be used, probably at a low light level which will depend on the value of the resistor used.

A statement and an amended date is at the top of the instructions and if there are any further amendments the date will change and I will list the amendments.

Saturday, January 3, 2015

3D Printed Signal Pictures

I  have received a comment about the difficulty of seeing the signals on the very light coloured computer rendition of the signals on my Shapeways shop. Unfortunately I have no control over this as it is part of the Shapeways system. Also there is no zoom which is annoying.

Here are a couple of photos of a distant signal in its raw as received state. Sorry but this is the best I have been able to do, it is very hard to photograph a white object.

Distant Signal Side View

Distant Signal Front View
The 'T' shaped part at the bottom is the main operating crank that is to be cut off the short sprue at the top, placed on the small post behind it and held in place with a small screw (see assembly instructions on the Signals Branch blog).

There is a spare counterweight lever(s) printed on the base of all signals, I left them there from my pilot model just in case the Frosted Ultra Detail ones were fragile but so far they seem to work fine.

Here is a picture of the details parts without the handling protection enclosing framework. The material shows as being clear but it has yet to be rinsed in some acetone to remove a light oil that is used by Shapeways to remove some waxy supporting material from the printing process. Once rinsed in acetone the material goes whitish.

Signal Detail Parts
Here is a view of a completed bracket signal (an early version) showing the operating mechanism below. As you can see from the pictures the main structure of the operating mechanism is printed as part of the signal. The mechanism is designed to fit in a 20mm (single arm posts) or a 22mm (multiple arm post) hole in the baseboard. The mechanism has also been designed to be within the depth of a baseboard construction of 13mm board plus 2" x 1" (what is that in mm?) frame.

Early Version Bracket Signal
The silver screws adjust the throw of the signal arms and the large operating crank absorbs the mechanical throw protecting the delicate signal arms and rods above. Please note that the heads of the two silver screws interfere with each other so I suggest the use of 8BA or 2-56 screws (see the assembly instructions for more detail). I have used some of those black acetal plastic Kadee screws with success (and I have a heap collected won the years).

Here is a picture showing a two arm outer home and distant signal and two Tam Valley servo motors mounted underneath the baseboard. I like the Tam Valley Singlet servos as they are relatively cheap, include a DCC accessory decoder on the control board, have an auto adjusting feature for the throw and are easy to install.

Two Servo Motors Driving Two Signal Arms
Here is a video just to show that it works.

And another video showing the down loop starter at Wollar, yes I know some like to call it an inner home or some such.... ;-)

Til next time.

Friday, January 2, 2015

Signals Branch

As promised I have just opened my Shapeways shop online and it is known as Signals Branch. I have added it to a list of links on the right side of this blog.

I hope that you get some value from the design work I have done over the last six months.

Be aware that the prices quoted on the Shapeways site are in US$ and that any order you place will be converted to AU$.

Please read the welcome post which can be accessed on the right hand side of the Signals Branch blog. It would be nice if it could remain at the top of the posts but there doesn't seem to be facility for this.