I'm about to do my first DCC conversion. The directions recommend a 1/4 watt 1K resistor. The next paragraph says there is a built in resistor and a trace that should be cut if you wish to use LED's.
Am I supposed to use one or the other or both?
It's an HO Atlas RS1 if that makes a difference.
Henry
COB Potomac & Northern
Shenandoah Valley
Henry,
It's your choice which to use. I like custom resistance levels higher than typically found with the recommended 1k ohm value, because that's usually too birght for my tastes.
But using a LED with the specified output is easy, you cut the trace that otherwise bypasses the built-in resistors. try it and see, you can always add more resistance if too bright.
Mike Lehman
Urbana, IL
Ouch, and people complain about Digitrax's web site? If you go to the manuals section on the NCE page and find the DA-SR, you get the old manual from 2003 which says nothing about built in resistors, the version from 2003 didn't have them. But if you go to the product page and click the link that says "DA-SR solder pads" you get the 2006 version of the manual, in which the decoder now has built in resistor.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
You can use your own resistor or cut the trace and use the built-in resistor, but don't do both. It is meant to be one or the other, not both.
Rich
Alton Junction
Thanks guys, other manufacturers directions that I have read make it clear it is an either or, NCE was not clear, at least to me. The manual page on the website, does say it's for old and achived manuals. The don't bother to alphabetize the list and there seem to be 3 links to DA-SR manuals, one of which is the 2003 version.
BigDaddy Thanks guys, other manufacturers directions that I have read make it clear it is an either or, NCE was not clear, at least to me. The manual page on the website, does say it's for old and achived manuals. The don't bother to alphabetize the list and there seem to be 3 links to DA-SR manuals, one of which is the 2003 version.
I have several of the older DA-SR decoders, and those older ones were problematic. I had a few that fried for no apparent reason and a couple where the function outputs burned out. Hopefully, the new version is more reliable.
Don't a set of instructions come with the decoder??
Yep, they do. You don't always have the manual with the decoder later. The internet pulls up old and newer documentation. Sometimes you need to do a little investigative work to nail down what version of a decoder you have. All in a day's work in DCC land.
mlehman Yep, they do. You don't always have the manual with the decoder later. The internet pulls up old and newer documentation. Sometimes you need to do a little investigative work to nail down what version of a decoder you have. All in a day's work in DCC land.
Here is a link to the NCE site. The manual is a PDF, linked at the bottom of the page for those who are curious.
https://ncedcc.zendesk.com/hc/en-us/articles/201382145-DA-SR
A word to the wise: If you decide to cut the trace instead of using an external resistor, make sure you really cut the trace!
I bought a four-pack of DA-SR's a while back. Put one in and cut the trace per the instructions. Headlight LED exploded when I first turned it on.
Hmm, apparently I didn't cut the trace well enough. Grab the Exacto and make a few more passes over my previous cut. Replace the headlight LED, which then proceeds to explode when I turn it on.
Now I'm ticked. Grab the Dremel with a fine burr. Remove the trace entirely. Repeat for the rear light. Now there are grooves in the PCB where the traces used to be. Replace the LED yet again, which (thankfully) doesn't explode this time.
Threw the other three DA-SR's in the drawer, where they remain to this day. Used TCS A6X's with built-in regulated 1.5v power for my next conversions.
Want to be sure, use a meter with some good quality small pointy probes (some of the cheap ones MIGHT break your skin if you jammed them in really hard, others, like most Fluke probes, are almost as sharp as a hobby knife) set on ohms, and measure across the resistor whose jumper you are cutting. If you get 0 ohms or close to it, the trace isn't cut enough. You should get somethign near the value marked on the resistor. Based on the picture in the instruction sheet, they are 1K (102). For once this is actually a decent value, many others with built in resistors use 560 or 680 ohms, which usually makes for a very bright LED.
Since resistors are pennies a piece, it may make sense to just leave the trace and use an external resistor on each LED.