I picked up a new Atlas RS3 and an NCE DA-SR decoder the other day. I got home and with soldering iron in ha nd (ok Randy - stop laughing) installed the decoder. I forgot to test the engine on address 00 - but it runs fine with the decoder even slow speed but no lights in either direction.[?] I tested with a multi-meter and all connections look ok, motor, track pickup, light common etc. The engine has LED’s with resistors and I have them going to the F0 front/back connections on the resistor lead - Reading long hood front. It configures just fine with my Digitrax Zepher and JMRI 1.7.5. Any suggestions folks?
Probably just have the LEDs backwards. I forget which of the two center tabs is the blue wire and which is the white or yellow, but since neither seem to work you probably just have them backwards. Decoders use a positive common, each funtion output is a current sink, so the blue wire is always +, has to be conencted to the triangle side (anode) of the LED. The flat (cathode) side goes to whichever function wire you connecting (with a resistor in there somewhere, fo course - doesn’t matter which side of the LED the resistor is on).
Don’t worry, I’ve been doing this (electronics, not necessarily decoders) for how long now? And I STILL either touch the wires or use clip leads to verify they work before I solder them in. Didn’t stop me from doing the exact same thing when I put a decoder in my Walthers FA. Ran fine, no light. DOH! LED was backwards. Luckily I only had to unsolder and change one. Actually, I think I got your E8 backwards the first time too. If the white wire fromt he decoder connects to the blue wire from the LED and vice-versa under the cab interior insert - that’s why [:D]
–Randy
Oh, I was gonna ask, how does it run, thinking you said Athearn not Atlas. I guess it’s a green and yellow then. I need to pick up some of the new Athearn ones - after all I was oe of the ones that told the guy at the Athearn booth in Philly to make the darn things, in the as-delivered scheme. Still need to finish the MDC kit and Atlas undec I have, too. I ditched the impossible to assemble plastic horn and picked up a pair of DW brass ones, and also found an old article in MR that gave me a sure-fire way to make the bracket to mount them on, now I just have to glue it all together and start painting.
–Randy
The “positive” common threw me for a loop too. I’ve been in electronics for 20 years, and the common in all of my schematics was always ground. They should really change that on the diagram or explain it better. The function is actually being switched on and off at the ground potential. It makes sense after you think about it. Oh, and 9 times out of 10, the motor plus and minus terminals don’t seem to match either. I check them and resolder if needed.
Now I don’t have first hand experience with the new NCE DA-SR decoders only the older ones, but it is my understanding that the new ones have tabs with built in resistors so you don’t have to replace the 1.5 bulbs that come in so many of the newer engines. So if there are resistors in the engine and built into the board this may be a cause of the problem. Just a thought, keep us updated. Joe [sigh]
I’m pretty sure the NCE decoder manual shows the orientation for using an LED, I know the Digitrax and TCS ones do.
That’s why they call it ‘common’ and not ‘ground’ or ‘common ground’ because it’s not ‘ground’ in any way, shape for form. The Brits are one up on us, they have ground and earth. WAY more accurate then just calling it all ‘ground’. You can have a circuit with a common ground that is not in any way tied to an earth ground (stake, water pipe, ground lug on a 3-pin outlet) so sometimes it comes in handy having two different terms. More circuits than not use current sinks as the controlling device - it’s more efficient, meaning a smaller device can be used to switch the same current vs a current source design, or the same size device can switch a larger current.
As for the motor leads - at least one of the ‘atlas’ type decoders is designed to be mounted with the solder side up and the component side down, pretty much NOT the obvious way to install it, and the directions only vaguely mention this. Put it in the way it looks right, with the component side up, and the motor wires will be backwards.
–Randy
Thanks Randy and Drilline - that was it - I had the LED wiring backwards.[#oops] I had to flip the decoder to match the long hood forward for Reading and the old brain didn’t adjust - oh well.
Randy - the Atlas RS3 - Reading 445 is indeed green and yellow. It runs smoothly but I have to pop the case again - I have something rubbing and making a buzzing noise at higher speed. It runs quiet at slow speed and after a slight bit of extra juice to get going I can back down the throttle to a crawl. I only have the 3’ section of flex track on the bench to do testing so that is not a real good workout.