LED Nanolights: wiring re. resistor

[philsandy]

A while ago I used DCC Concepts Nanolights to light some working semaphore signals and they work very well. They are connected to a 9 volt DC supply, with a 10k resistor soldered to the positive wire.

I have just built a junction signal with 3 semaphore arms and want to fit LED lights to this.

 

So 3 LED's needed. The plan is:  join the 3 negative wires together and connect as one to the 9V negative supply,  join the 3 positive wires together, solder in a 10k resistor and connect as one to the 9V + supply,

 

My question is will this work, ie.  one 10k resistor for all 3 LED's, or will each LED require it's own resistor?

Also, can they be wired to a DCC supply, and if so will it require a higher value resistor?

[richard brown]

For me it has worked but you should always have one resistor per led

 

Richard

[Gordon H]

It might work, but you are relying on the forward voltage of each LED being the same.

This is quite likely to be the case if the LEDs are from the same manufactured batch, but cannot be guaranteed.

Better to connect them in series and use a lower value resistor. Less power wasted too.

[dhjgreen]

DCC would be a better bet as if these are white LEDs there will not be enough voltage for series operation. Bridge rectifier on the DCC and a smoothing capacitor. Yes a higher value resistor is needed. BTW someone may suggest no resistor on 9V, do not be tempted.

[jdp298]

In your plan, the LEDs are in parallel, so the total current through the resistor should be higher, but the voltage required will be the same a single LED (or lower than if they were in series). Using a 10k like you have with single LEDs will work, but they will be a bit dimmer. It might be what you're after; many are the examples of a correctly weighted resistor giving me an aircraft searchlight on the layout rather than a reasonable streetlight glow.

[Junctionmad]

In your plan, the LEDs are in parallel, so the total current through the resistor should be higher, but the voltage required will be the same a single LED (or lower than if they were in series). Using a 10k like you have with single LEDs will work, but they will be a bit dimmer. It might be what you're after; many are the examples of a correctly weighted resistor giving me an aircraft searchlight on the layout rather than a reasonable streetlight glow.

One of the issues is that people are still using 20mA in their calculations when many modern leds will illiminate quite brightly on 2mA