Decoder output voltages

Post all your DCC only problems, solutions and discoverys here.
johnco
Posts: 500
Joined: Sun Aug 28, 2011 9:30 pm

Decoder output voltages

Postby johnco » Mon Apr 02, 2018 12:59 pm

I will shortly be fitting DCC decoders to some older diesel locos, to which I will also be fitting headlights with leds.
What is the voltage output from the decoder on the yellow, white, green and purple wires so that I can fit white light leds with the correct resistors?
I will not be fitting red rear lights as the trains will be fixed formation goods trains.
Thanking you in anticipation for your answers.

User avatar
Ironduke
Posts: 608
Joined: Mon Sep 26, 2005 12:04 am
Location: Ballarat Victoria Australia
Contact:

Re: Decoder output voltages

Postby Ironduke » Mon Apr 02, 2018 1:32 pm

The blue wire is positive and never more than the supply voltage on your rails (so could be from 12V up to 18V on some systems). Just say 12V.
For a bright white LED at full brightness the recommended resistor value at 12V is 560R generally, but I usually use a 1K resistor. Use an even higher value if that is still too bright.
Regards
Rob

Suzie
Posts: 255
Joined: Tue Dec 17, 2013 11:46 pm

Re: Decoder output voltages

Postby Suzie » Mon Apr 02, 2018 3:03 pm

Hi Johnco

Absolute maximum voltage should be below 27V at extreme, and 24V in normal operation, but typically expect to see around 19V down to about 14V on most systems.

You will probably want to experiment a bit with resistor values as many modern LEDs - especially white ones and others derived from blue, will be very bright indeed when run at full power.

Suzie x

User avatar
Peterm
Posts: 1420
Joined: Fri Nov 09, 2007 1:26 pm
Location: Bribie Island. Australia

Re: Decoder output voltages

Postby Peterm » Tue Apr 03, 2018 12:01 am

To give an example with a job I recently did on lights for one of my diesels, I used between 20K and 50k resistors depending on colour to get the lights dimmed down to realistic levels.
Pete.

Bigmet
Posts: 6207
Joined: Tue Aug 14, 2007 2:19 pm

Re: Decoder output voltages

Postby Bigmet » Thu Apr 05, 2018 11:04 am

There should be a recommended resistor value to use with the LED for nominal 12V operation. Most (all?) decoders offer output trimming for the auxiliaries, and it is usually possible to dim LED's satisfactorily in this way. (It can be worth trying '0' even if it is not specified as part of the operating range, all electronics leak.) Typically the value for a 'dim' light will be somewhere between 0 and 5 on a decoder offering 255 step output range. I also make a lot of use of 'Pentel' permanent markers to tint LED outputs in addition, simple to get the colour of warm incandescent filament lights, as used on BR's early diesels.

User avatar
Peterm
Posts: 1420
Joined: Fri Nov 09, 2007 1:26 pm
Location: Bribie Island. Australia

Re: Decoder output voltages

Postby Peterm » Thu Apr 05, 2018 11:27 pm

As Bigmet knows, Zimo decoders and maybe others can dim every lighting FO individually, but I took RJ's advice and used resistors of suitable values on each output so that if I ever have to reset the decoder for any reason I don't have to go through resetting all the dimming values.

I must have a look for those Pentel markers to see if I can buy them out here. Thanks Bigmet.
Pete.

User avatar
Peterm
Posts: 1420
Joined: Fri Nov 09, 2007 1:26 pm
Location: Bribie Island. Australia

Re: Decoder output voltages

Postby Peterm » Thu Apr 05, 2018 11:29 pm

Peterm wrote:As Bigmet knows, Zimo decoders and maybe others can dim every lighting FO individually, but I took RJ's advice and used resistors of suitable values on each output so that if I ever have to reset the decoder for any reason I don't have to go through resetting all the dimming values.

I must have a look for those Pentel markers to see if I can buy them out here. Thanks Bigmet.

Edit: I see I can get them here, I think they're worth a look.
Pete.


Return to “DCC Forum”

Who is online

Users browsing this forum: No registered users and 2 guests