Colonel Bogie
I decided to put in led indicator lights for my Cobalt ss point. Before starting I checked to see what voltage was on the led circuit, but there is no indication in the comprehensive instructions. I assumed a normal led would be OK. I wired in two and tried them. One worked, one didn't. Put in another one and that went phut too. Tried a third and that lasted only a few seconds.
OK, check the voltage. 
The Cobalt SS led voltage was 5 volts, so my 3v leds were not  much use.
I am not into electronics, but I thought the average led was 3v, without resistor.
I then went to the DCC concepts page for led's, and none of them state a voltage! 

So I have a query. If I buy new indicator leds from DCC concepts, will they work with my Cobalt SS, - and for that matter, why 5 volts? I already have led's , but they are now no use.
Anyone else had this one?
CB
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Ron Solly Sol
If the output from terminals for Panel LEDs is 5v, then put a 200 ohm resistor in the common LED wire ( the green one based on the instruction sheet).
Ron
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newbryford
I think the markings on a CBSS control board next to the LED terminals say "5v".

LEDs are different voltages, so the exact resistor value will vary.
Typically - I will use 1k 0hm and then if it doesn't work, reduce to 470 ohm and in rare cases - lower.
If it is too bright, then add resistors in series.

No need for lots of resistors to be kept in stock.

Formula for parallel resistors is: 1/R = 1/R1 + 1/R2 + 1/R3 etc, where R is the total resistance and R1 etc are the individual resistors.
But a simple thing to remember is: Total resistance for a pair of resistors in parallel will be half the value of each resistor.

i.e a pair of 470s in parallel will be 235 ohm)

Cheers,
Mick
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Ron Solly Sol
based on this https://www.hobby-hour.com/electronics/ledcalc.php

approx 150 - 200 ohm resistor based on current requirement data of the LED
https://www.kitronik.co.uk/blog/led-datasheet/
Ron
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Jack Wong
The voltage required for different LED is also different, and the voltage of LED lights with different colors is also different. When most of the LED lights with this indication function are in the proper brightness, the current should be within 10mA, so when the input voltage is 5V, the series resistance should be between 470r-1000r. Personal opinions are for reference only.
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Colonel Bogie
Thanks for all the resistor advice, I can see I will have to get a resistor for the led's. I think I have a few somewhere when I had some station lamps that came with them for 12v use. The link to Kitroniks from Ron Solly is very useful, a business I was not aware of.
I think I was just getting a little frustrated that a standard led did not work, and there was no indication of voltage in the very comprehensive instructions. My other larger layout has a 3v led bus, so I did not expect a 5v system..
I see DCC Concepts sell leds with resistors, but don't state the voltage. Newbryford is correct, the only reference to voltage is on the CBSS board, one that I did not spot.
Oh well, no plug and play for me, - out with the soldering iron! 
Thanks again,
CB
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Ron Solly Sol
CB, still use resistors with LEDs even on the 3v bus. Use the calculator.
Ron
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AHJAY
LEDs do NOT have a voltage. They have a current draw specification. Even that is laregely irrelevant in this discussion as we are using LED as indicators, not as part of a specific circuit that has critical specs. "Use a 1K resistor as minimum on model railway use" is the most useful advice.

* The same LED can be used on 3v or 240 volt as long as you understand how to calculate the resistance. Be wary of using simple calculators unless you are certain of voltage.

* We will never recommend a simple resistance calculation ad LED efficiencies vary which means that brightness can vary too. ALSO modellers often think they have one supply voltage which is in fact not reality - for example on any DC conctroller the output marked 12v will almost ALWYA be 15/16v. Use minimum resistance on that and there may be problems

* Resistance on an LED does NOT have a linear effect. On the same LED and same voltage - I may use 1k or more than 30k. One will be close to max level of illumination, the other a weak light like a loco lamp.

* We supply 1k as standard with ALL LEDs because it is a safe start point for DC and DCC users..

* Data voltage levels are generally 3 to 5 volts. The variance does not matter as long as you are using LEDS.

* The same LED is used irrespective of voltages. Use a 1K to start with and vary ONLY if you need to.

If you do not understand LEDS then use this document to learn a little more. It is written to halpe those who are using LEDS for all sorts of purposes and has clear informnation. https://www.dccconcepts.com/manual/leds-and-how-to-get-the-best-from-them/

regards, Ahjay
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Colonel Bogie
I think I have reached information overload, but thanks to all, including Ahjay's 7 page article on LED's. All of which leaves me wondering how I managed before, although I did make a point of checking any transformer voltage, as I have been down this one before. Cheap transformers are not always good ones.
Armed with all this information, all I have to do now is fix the bloody light!
Hey Ho
CB
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