Re: Using LEDs to light model train layouts

wkaiser@[EMAIL PROTECTED]
 wrote:
> 
> I can never remember which lead is + or -.  I connect the LED to a 1.5V 
> source.  If it lights, I have it right.  If it doesn't I reverse the 
> leads.  If it doesn't light then, it's no good.  

    I recommend that everyone that is building a layout have a 
multimeter. The usefulness of one of these for electrical work and 
troubleshooting can't be ignored. You can get a rudimentary one in the 
$20-30 that will probably have all of the functions you'll need for most 
hobbyist work, including a diode check function.
    The easy way to visually identify anode and cathode on a normal LED 
is to hold it sideways. If you look through the lens the cathode is 
normally the lead attached to the little "cup" in the center, and the 
anode is attached to the wire that comes out of the "cup" to the other 
lead. Anode is + and cathode is -. SMD or other packaged LEDs are harder 
to determine without a meter with a diode check, though many will have 
some type of marking that a manufacturer's data sheet will help you 
identify. A good source of data sheets if you know the part number of an 
electronic component is www.alldatasheet.com. I use it nearly every day 
at work trying to find information on components in equipment I'm
repairing.

-- 

                      Rick Jones
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"Traditionally, most of Australia's im****ts come from overseas."
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