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ESU Lokpilot V4 auxiliary functions


kbriffa

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Hi,

 

I have an SMD LED which I installed as a cab light in my loco. It was very bright so to dim down to the brightness I wanted it, I soldered a 100K resistor to the LED.

 

I am now changing the decoder to the ESU Lokpilot V4. Reading the instructions manual it says that LEDs attached to the auxiliary functions should have a resistor with a value between 470 and 2.2K. Why should there be an upper limit? I know you should have an lower limit to protect the LED but why an upper limit? Will I be able to use the current (no pun intended!) LED with a 100K resistor?

 

Thanks

Kenneth

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Try it and see - you'll certainly not damage the decoder or LED with a large value resistor.

 

I'm not up to speed with v4's as I only possess two so far, but can the output of the auxiliary functions be limited (dimmed) by CV's?

 

 

 

EDIt - yes you can - CV 278/CV 286 for Aux 1 and Aux 2 brightness

 

Cheers,

Mick

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Reading the instructions manual it says that LEDs attached to the auxiliary functions should have a resistor with a value between 470 and 2.2K. Why should there be an upper limit? I know you should have an lower limit to protect the LED but why an upper limit? Will I be able to use the current (no pun intended!) LED with a 100K resistor?

There is no upper limit. The resistance range quoted is based merely on typical LED currents.

Instruction manuals like this almost always assume the user has no idea about electonic matters, so err on the side of caution giving only numbers that will definitely work.

In this instance a series resistance spec of '>=470R' might be more accurate, but fewer people would understand that kind of terminology.

I doubt whether you will see much light at all with a 100k resistor. 10k might be a more reasonable value to start with if you want lots of dimming.

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Sorry Gordon, but there is an upper limit as there needs to be a sufficient potential difference (voltage) across the anode and cathode of the LED to get current to flow and therefore produce any light at all. The resistor limits current,; there is (was) a school of thought that says LED's should be run at their design current to maximise their life and that doing otherwise reduces the life, perversely even when running at a lower current.

 

I agree with all the other things though :-)

 

Editted to correct spelling

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Thanks for the replies. When I asked about why their should be an upper limit I was thinking of possible damage to the decoder since it is something mentioned by the ESU decoder's instruction manual. I think from the comments above that you all agree that no damage will be done to the decoder with higher values than those recommended by the manual. Obviously a too high resistor value will not produce light from the LED.

 

BTW, yes I did get light from a 100K resistor. I think I chose an LED which is inherently too bright - that's why it needs such a big resistor.

 

@Mick Yes you hit on my plan B. In fact I chose this decoder because of the interesting lighting effects especially dimmable light and intelligent firebox flicker.

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Hi Kenneth

 

I use ESU V4 decoders for all my locos, and I add LED cab lights too! Normally I use 560Ohm resistors for SMD LEDs. If you find them too bring, don't forget to change the brightness (value 0-31) in CVs 278 and 286 (for AUX1 and AUX2 respectively).

 

Chris

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  • 5 months later...

id love to know how the decoder "knows" it now has some extra lights added (assuming these are totally separate from any existing lighting features which is easy to just splice into).  I can understand you telling it so via CV changes but for extra stand alone lights how does the decoder learn that "this is my new LED and when I press XYZ function key that will switch this LED on or off".  Where does one run the feed and returns for new standalone lights?

 

Cheers

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id love to know how the decoder "knows" it now has some extra lights added (assuming these are totally separate from any existing lighting features which is easy to just splice into).  I can understand you telling it so via CV changes but for extra stand alone lights how does the decoder learn that "this is my new LED and when I press XYZ function key that will switch this LED on or off".  Where does one run the feed and returns for new standalone lights?

 

Cheers

 

The decoder doesn't "know". You'll have to look at the decoder manuals to find out the default function key setting, but AUX1 and AUX 2 are often set to F1/F2 on a four function decoder (two outputs are usually used for the directional headlights via F0) They are often reconfigured for sound decoders - I normally use F7/F8 or F11/F12, by altering CV values.

 

The manual will also tell you the feed and return, but the NMRA standard is green wire for Aux1, purple wire for Aux 2 and blue for common positive for 8 pin/4 function decoders (the purple wire will be a flying lead). I can't remember the pin outs for Aux 1/aux 2 on a 21pin decoder (somewhere about pin 12/13 or 13/14 from memory).

 

If in doubt, refer to the decoder manual

 

Cheers,

Mick

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