Headcode Lights for an EMU
Tim Stubbs
Pictures by the author
2-HAL EMU 2699 approaches the terminus at Peacehaven, with the numerals lit, showing headcode 28
I AM a self-confessed hoarder. There is so much useful stuff around, and I cannot bring myself to chuck things away! This applies to coffee stirrers, of course, and consider those lovely small plastic boxes which come with Slater’s wheelsets, containing and protecting the axle-end bearing brasses. The boxes look so useful and it must be possible to put them to use. Ah! Just the job headcode lights on the Peacehaven EMU fleet.
The headcode displays themselves are made up of a sandwich comprising a piece of thin white plastic card, then stencil or computer printed digits to suit the route to be displayed and finally a piece of clear plastic card at the back. The displays require illumination to make them effective as, with no light showing through, the appearance is of a white blank, which needs to be shown only at the rear of a train. To display the headcode number, illumination is required. Using an LED, this can be fed from the traction circuit in the train so that the light comes on when the unit is moving forwards.
The headcode numerals themselves are set out on the computer in a Word document and printed white on black. The font can be selected to suit, and I have found that ‘Tw Cen MT Condensed Extra Bold’ in 24pt size gives a reasonably proportioned display for a 7mm scale EMU. Alternatively, stencil numerals for Gauge O are available and are supplied in some EMU kits.
Ingredients
- Plastic box 21 x 21 x 8mm, from a Slater’s wheelset
- 3mm diameter white LED
- 0.5W resistor (suitable for the LED e.g. 680 ohm)
- Miniature plug and socket
- A dab of paint (not black)
Tools
- A drill or pin chuck with 1mm bit
- Soldering iron, solder and flux
- Wire snips and small crocodile clip
- Glue such as UHU
- Coffee stirrer stick for applying paint (saves using a paint brush)
Components used to provide the headcode illumination
Drill two 1mm diameter holes in the back of one flange of the plastic box, offset a little to one side.
Bend up the legs of the LED and resistor as shown in the photograph. At this stage, the polarity of the LED is not important, as this is decided later, when the plug and socket are installed.
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Solder one leg of the resistor to one leg of the LED, as shown in the photograph. The LED is best protected by a heat-sink during soldering, for example by using a small crocodile clip across its leads. Snip off the surplus wire from the LED.
Thread the legs of the LED and resistor through the holes previously made in the plastic box.
Solder the miniature plug to the two wires emerging from the box.
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Solder the miniature socket to a feed from the traction wiring of the train, positioned to the rear of the cab.
Conduct a trial run to determine the correct polarity of the light circuit, reversing the plug if needed.
Once the polarity is correct (light illuminates with
the vehicle moving forwards) mark one side of the plug and socket with a dab of paint to show the correct position.
Install the completed box into the cab of the EMU by gluing it inside the body, behind the headcode display. Leave for glue to set.
