Although many colours can be had, white LED’s come in several variations. They are specified by colour temperature, expressed as degrees kelvin (K), the higher the number, the whiter the light. Also sometimes quoted as a description:- warm, natural, day or cool.
Warm White - 2700-3500 Kelvin - typical incandescent light bulb
Natural White - 4000-4500 Kelvin - typical retail space "white" fluorescent lighting
Day / Daylight - White 5000-6000 Kelvin - used for high colour definition - typical noon day sun in many parts of the world
Cool / Commercial - White 6000-7000 Kelvin - used in many industrial and commercial applications like hospitals
I use Warm White , for my houses
I might go up to Natural white for offices/shop window etc
3mm Daylight for Mercury (inside engine shed) and 3mm yellow For sodium bulbs (street lights)
LED’s come in two main packages, “through hole” and “SMD” (Surface mount device). Each type has many sizes. Most can be had in the full set of colours. Some come in various angles of illumination (spread of light). Some clear lens give out coloured light.
If your rolling stock is too light, potentially long trains can derail on tight corners. The NMRA has a recommended practice that defines a practical weight for rolling stock. It is by no means a definitive standard, but is very useful as a guide, to getting more reliable running by weighting your rolling stock. It interprets in OO to about 30g for the initial weight plus 15g for each 25mm of the wagon/carriage.
Wagon example = 115mm long (roughly 4x25 + 12.5)
So 30g + 67g (4.5 x 15g) = 97g (100G)
Carriage example = 280mm long (roughly 11x25)
So 30g + 165g (11 x 15g) = 195g
Wagon length should be taken from the end of the couplings, weights should be distributed evenly and be the same either side of the middle point.
Use a small digital weigh scale to determine the weight of the wagon, then subtract from the calculated weight, the remainder is the weight that needs to be added.
SMD type can be had in strips up to 5 meters long, driven by 12V, these are handy for work area lighting and come in two types of SMD size (and in waterproof versions) with either 150, 300 or 600 lights per 5 meter.
Steer clear of superbright and 40mA and higher types as these will be too bright to be realistic on a layout (OK for task lighting)
Having glued together a filter and airbrush holder tube into a jar lid, to act as my homemade airbrush cleaner, it worked well, but several days later has started to fall apart!This means that I have discovered an interesting nugget of information! I use white spirit to clear the airbrush, and the mist coats the whole of the inside and the remainder does not evaporate. Thus the vapour has been attacking the hot melt glue I used to glue everything together.The glue goes very gooey and releases its bond on the substrate. I am not sure if the constant vapour is the trick, but I guess that a repeated application onto hot melt (that is not contained by a jar) may do the same over a period of time.Knowing that you can "undo" hot melt glue with heat, I thought it may also be useful to know that White Spirits is a solvent that can soften hot melt glue and allow its removal from a surface.
This chart is only a guide, cable calculations take a number of factors into account, not shown here. Generally use 7/0.2mm for short droppers and led’s and 16/.02 and larger for everything else.
See TIP202 for more info
This site has a good chart too