Decoder question

[graphitehemi]

  I'm just finishing up one of my LL P2K SW1200's, and decided I would wire the decoder in since I already have the shell off.

  So I have a Digitraxx DZ125 all wired correctly, when I test it on DC track I do not get any lights. Very seldom there is a faint flicker from one or both of the LED's. I checked my wiring all over and then tested the outputs on the decoder with a meter. I found that the decoder is not even sending voltage out to the LED's. So my question, are the lighting outputs on the DZ125 disabled in DC by defualt or do I have a bad decoder.

  I do not have access to a DCC system at the moment. My only access is to bring it down to the hobby shop and put it on their tracks (I don't know when I will be able to do that).

  Thanks in advance!

[cacole]

 Are you absolutely certain you have the polarity of the LEDs correct?  The blue wire is positive output to the lights and the white and yellow wires are the negative.  As near as I know, the lights should come on by default on DC power, but if you have them wired backwards they won't come on even with DCC.

[CSX Robert]

I have not used the DZ125, but other Digtrax decoders that I have used remember the state of their functions the last time they were run on DCC. If the headlight was on the last time it was run on DCC, it will be on when run on DC, and if the headlight was off the last time it was run on DCC, it will be off when run on DC. I'm guessing if it was never run on DCC, then the headlight would default to being off.

[rrinker]

 CSX Robert has it right. The FX3 decoders from Digitrax use the 'memory' method of controllign which functions are on under DC. Their prior decoders used CV13 to control which functions where active in DC - see the Digitrax Decoder Manual for this information. CV13 has no effect witht he FX3 decoders, which the DZ125 is one of.

                              --Randy

[graphitehemi]

So once I get it on DCC track and turn the lights on, they should be on when I put it back on my DC. Thanks!

[rrinker]

 Assuming you have the LEDs wired correctly. Take a look here, you can see how to dtermine the polarity of the LED just looking at the bits inside. http://en.wikipedia.org/wiki/Electrical_polarity_of_LEDs

 The larger chunk of metal is the + side. This should be connected to the BLUE wire on the decoder. The other side goes to function wire, either white or yellow. You also need a resistor - if you used white LEDs, use a 1K resistor. There shoudl be 1 resistor for each LED, and it can go on either side of the LED:  blue----resistor------LED------white OR blue-----LED-----resistor----white. Either way works equally well. Force of habit, mine are usually with the function lead.

 Turn them on in DCC, and then they should stay on when used on DC.

                                   --Randy

 

[graphitehemi]

CSX Robert

I have not used the DZ125, but other Digtrax decoders that I have used remember the state of their functions the last time they were run on DCC. If the headlight was on the last time it was run on DCC, it will be on when run on DC, and if the headlight was off the last time it was run on DCC, it will be off when run on DC. I'm guessing if it was never run on DCC, then the headlight would default to being off.

That was it! I brought it to the LHS today and threw it on their DCC track and turned the lights on. Now they work on DC. Thanks!!

[selector]

Dang!  You learn something every day...or at least I do.  Nice catch, Robert!

[CSX Robert]

I'm glad you got them working. For the most part, I am satisfied with the Digitrax Decoder manual, but this is one thing they apparently left out. While it does say that FX3 deocders do not support CV13 to set the state of the function outputs when operating on DC, I could not find anywhere that explained about the decoder remembering the last DCC state of the functions. I just happened to notice it while playing around.