Using phone charger for LED's

Should be no problem, depending on how bright you want the led's, each one would require something like 10mA so you should be able to run at least 50 and may be 100 if the voltage does not droop too much under load. Each led will need a series resistor to limit the current through it. somewhere in the region of 500 ohms to 1kohm should do depending on the brightness. If you need to run at lot of diodes, with a 5V supply, you should be able to put 2 diodes in series with one resistor, effectively using the same current to power 2 diodes.

Regards Jeff

, West Sussex, England

"Jeff" wrote

Those little "wall wart" chargers are great for little plug'n'play applications. However I'd advise against loading them too heavily as they not only emit unhappy buzzing noises (as the coils reach current saturation) near full load but also get worryingly hot. They're only intended for light intermittent use. That said, one rated as yours ought to run a reasonable array of LEDs such signalling or a station building's lights. Maplin's can be good for supplying the requisite sockets to wire in if you want to make plug-in buildings that can be removed from the layout.

The suggestion about running them in series can be neat but it won't work with 6V with white LEDs, as these have a forward voltage (Vf, the minimum required to pass lighting current) of about 4V so two in series won't light unless there's at least 8V across them Reds are fine as they light on 1.8V and yellows and greens are typically 2.2V.

I just wish there was a colour in between yellow and white for modelling purposes, as yellow LEDs are really yucky old oil lamps and look wrong inside buildings (though great for sodium street lamps), while the whites are very cold so look best for fluorescent tube light - to resemble ordinary lightbulbs they really need to be tamed with a dip in yellowy varnish or a piece of straw-coloured lighting gel across LED or as glazing.

Tony Clarke