Coach lighting using LEDs

Lighting adds a special something to coaches running in the evening. LEDs (light emitting diodes) are an easy, cheap and everlasting (since they won't burn out) way to do this. On my son's GWR coach built from an IP Engineering kit, I ran two lengths of single strand cable through the floor, up the back, and across the top of the compartments. I stripped the sleeving in the middle of each compartment, and glued the wires in place with superglue.
At the centre of each compartment I soldered a small yellow LED and 18 Ohm resistor in series. The resistor is to limit the current to around 20mA per LED when running from 2.4V (two 1.2V rechargable batteries). Since LEDs are diodes, it is essential to solder all of them in the same orientation in each compartment. LEDs, resistors and a huge variety of other electronic components are available from Maplin Electronics.
I screwed a small AAA battery holder under the floor, and soldered the wires to this, making sure that they were the right way round for the LEDs to light.
Two 750mA rechargable AAA cells will light two LEDs for up to 18 hours. Similarly they will light say 6 LEDs in a larger coach for 6 hours. I did not fit an on/off switch. I just remove the batteries to turn the lights out. The glow from 20mA LEDs is very low, and only really visible after dark which is fine for me. If you want a brighter glow, either add two LEDs per compartment, or fit brighter, higher current LEDs. Total cost for two LEDs, resistors and battery holder for my son's coach was around 40 pence!