Thanks for all your informative inputs.
Measured with 12.2 VDC supply using 20 ma max current LED's. Values will vary some depending on actual DC supply value.
Resistor Current
1000 ohm 9.0ma
750 ohm 12.45ma
680 ohm 13.12ma
510 ohm 16.25ma
Probably will not apply to the OP. If the LED is too bright, just start increasing the resistance until you get the brightness you like. Super bright LED's are available now.
Rich
If you ever fall over in public, pick yourself up and say “sorry it’s been a while since I inhabited a body.” And just walk away.
I just use 1K ohm 1/4 resistors for all my light function leads with LED's regardless of the brand of decoder. Never once having had an issue. Google Resistor color codes, there are hundreds of web sites with them listed. I purchased a large number of 1K resistors from eBay, they were cheap. If you really want to get technical use a resistor calculator. http://led.linear1.org/1led.wiz
Simon Modelling CB&Q and Wabash See my slowly evolving layout on my picturetrail site http://www.picturetrail.com/simontrains and our videos at http://www.youtube.com/user/MrCrispybake?feature=mhum
alloboard,
Generally, a 1K (1000) ohm, 1/4 W[att] resistor is all you'll need for an LED. However, it depends on the which decoder (whatever brand) you are using. Some boards already have the resistors built-in; others don't. That information can usually be found in the decoder manual that comes with the decoder. It has a lot of useful information in it to glean what you need.
Resistors can be purchased from any electronics store like Radio Shack or even your LHS. Sometimes LED packets will come with resistors already included.
You don't necessarily need to know the color-coding for the resistors. The resistance value is usually printed on the packet. There a sites online that have that information. Just google "resistors+color-coding" and you should be able to find a color-coding chart.
A multimeter would be a good investment, if you don't already have one. I got a decent digital one at Sears for $20. It's handy for double-checking resistor values.
Lastly, resistors are bi-directional. Like incandescent bulbs, current can travel through them in either direction. Diodes (e.g. LEDs) are the only ones that you need to be concerned about their orientation. If you wire it it backwards, it won't light up.
Tom
https://tstage9.wixsite.com/nyc-modeling
Time...It marches on...without ever turning around to see if anyone is even keeping in step.
1. Normally, the resistor value will depend on the track voltage as well as what voltage and amperage requirement is needed for what you're trying to do. Usually anywhere from 680 to 1000 ohms and 1/4 watt for most LEDs on a normal HO layout. It also depends on how bright you want your light--assuming that's what you want since you mentioned anode. BTW, you don't have to have the resistor on the anode side. Use one resistor per LED as a general rule.
2. It doesn't matter which way you put the resistor. It's not like a diode.
3. Here's a link to color bands
wiki.lvl1.org/images/9/93/ResistorQV.pdf
Richard
What type of resistors should I get when wiring lighting functions to Digitrax decoders? Where should I purchase these resistors. When wiring a resistor to the Anode (+) how many colors and what should be the color of their bands, and which orientation should the resistor face?