Page 23 - March April 2017

To wire the signals I found that it was easiest to cut the enamelled wire to length and running them up the tube before soldering to the LEDs. I used the thinnest enamelled wire I could find, it comes in 1⁄2 kilo coils, enough for a life time of signals, loco lights etc. The type I use has insulation that melts off at around 400oC, this is far easier than trying to scrape the insulation off. I normally solder (lead free) at 320oC, To do this I use a temperature controlled soldering iron, It has several preset temperatures which makes it easy to change temperature.
The six wires required for the double headed signals are hard to pass through the tube (presumably why 3mm tube is often used). I put in five first, don't twist them, try to keep them parallel not crossing over, then I pushed the sixth in while pulling the rest at the same time, this pulled the sixth trough the tube, I could then pull the individual wires back as required.
Once pulled through I tinned both ends of each wire by heating until the insulation melted in a small bubble of solder on the iron tip. I then soldered the wires to the LEDs at this point I was not concerned which wire ran to which LED.
With the wires connected carefully pull each one back down the mast so they look like photo 10.
I test the LEDs again using the wires to check all connections are good. I then painted the LEDs (not the lenses!), mast and wires with thick black acrylic craft paint. This is partly to hide the wires a bit and to stop light from coming out of the back of the LEDs.
I also glue the base in place, lining it up with the LEDs, see photo 11.
On my second set of signals I made a bottom mast clamp by winding some thin paper strip around the bottom of the mast, securing it with cyano and leaving a small bit sticking out as in photo 12. I made sure the cyano was soaked into the paper. It adds a nice touch and is simple to do.
While all this is drying I painted the signal heads matt black, photo 13. Cover all sides and inside the holes as the plastic is translucent and the light will shine through it. Once dry glue the heads over the LEDs, I used Deluxe Glue 'n' Glaze, but any of the very clear glazing glues, such Krystal Klear should be ok. Using these glues allows you let the glue really fill around the LEDs with out affecting the light from the LEDs.
I then left the signal to fully dry before doing the detailing.
I cut out some maintenance platforms, I filed a curve at one end to fit around the mast and notched the other end to fit in between the ladder sides, photo 14.
I glued a length of plastic strip to the base to act as mounting point for the ladder and glued the platform below the signal head, top one in the case of a double headed one with cyano. I cut the ladder to length removing rungs above the platform, see photo 15. For double headed signals I cut another platform to fit between the ladder and mast below the lower head.
Guard rails for the platforms were made with plastic strip, I used the thinnest I had, thinner would look better or brass wire (which I will probably use next time). The rails were wrapped around the mast and passed between the ladder sides and glued, spreading the top of the ladder out, see photos 16 and 17. An additional stay was installed about half way between the base and lowest platform, this is shown in prototype photos.
Once dry I cut the rails and stay flush with the ladder, see photo 18.
The signal was then painted with silver craft paint, leaving just the front of the heads black. Finished signals are shown in photos 19, 20 and the heading photo.
Mounting on the layout just means drilling a hole for 1 the mast. They are normally set about 12' from the track. If you don't want to see the base cover it with ballast or other ground cover. If you want a more modern and
removable mounting check out the Jan 2017 NMRA Magazine.
The signals require current limiting to avoid burning out the LEDs, your decoder may do this, but most don't, the same if controlling them off 12v through switches. I limited the current to 10mA, well within the LED's rating, running on 12v that worked out to be a 1K0 (1000 ohms) resistor.
With a single head you only need one resistor as only one LED is on at a time, this is fitted in series with the mast common connection. These LEDs light to fairly similar brightness, but some makes are quite different, usually the red brighter. Then you can fit resistors for each LED with a lower value for the dimmer ones. Then the common feed goes straight to the mast.
With the double headed signals two LEDs are on at the same time and a single resistor would feed both, a red one will be bright while yellow or green would be very dim. To stop this happening all six LEDs need a resistor in series. The mast is connected with the common feed.
I use Digikeijs decoders to operate the signals, they can flash the signals and make them go dark. They are controlled by JMRI, a free program that works with most DCC systems on the most common computer operating systems.
LED current limiting resistor values can be worked out from a simple formula:
Resistor (ohms) = [Supply voltage (Vs) – LED forward voltage (Vf)] / LED current (Af).
orR=(Vs-LEDVf)/LEDAf. Thefstandsforforward.
An example a 12v supply with a 2v 10mA LED:
(12v - 2v) / 0.01A = 1000 ohms.
If the value does not match a standard resistor value, go for the next largest.
List of materials:
Shapeways signal heads (pack of 8) http://www.shapeways.com/product/K28PGLKWW/proto-ho-scale-1- 87-grs-type-d-3-light-signal?optionId=59390862
Red 1.8mm LEDs - Rapid Electronics 72-8350
Yellow 1.8mm LEDs - Rapid Electronics 72-8365
Green 1.8mm LEDs - Rapid Electronics 72-8360
Enamelled wire - Rapid Electronics 05-0200
1K0 (1000 ohm) 0.25w resistors (for these LEDs on 12 volts)
2mm brass tube
Ratio signal ladder 451
Deluxe Glue N Glaze (or any clear drying glue)
Cyano glue and activator (without activator it takes much longer to dry).
Plastic card and strip.
Silver and black paint.
Solder and non-corrosive flux.
ROUNDHOUSE
April 2017 23