I'm working on picking up a dual motor DD40, as well as eventually buying or building a dual motor Big Boy. Also looking at eventually going to DCC. Question, should I install two decoders (one for each motor), or one decoder for both motors? AND, which decoder can handle both motors? Mark in Utah
I'd vote one decoder; as the penalty for two decoders ever getting "confused" would be.. spectacular... (Imagine if one got a "reverse" command which the other missed somehow... And if it can happen, it will happen. Murphy guarantees it.) As for the decoder, the only advice I can offer is to work out the "stall current" - the most current the loco can draw - and pick a decoder that can handle at least that much current. If it fits in the shell, so much the better. To measure stall current, wire an ammeter into the circuit (in series between controller and rail works) on DC, wind up the power supply, and prevent the motor from spinning. Pushing down on the loco works well. Looking for the largest reading the meter gives. Try not to stall the engine for longer than necessary, you can damage things Depending on scale and decoders available, you should allow for a bit of "wiggle room" - so if the meter reads 1.25A max, consider a 1.5A decoder, or maybe even 2A, if you're in one of them "larger" scales.
HO scale. Given that Athearn HO motors tend to draw 3/4 amp under full load, it'll need to be at least a 2 amp decoder. I'm not a DCC expert, but just looking down the road. I'm guessing that a decoder for O or G should be used? One decoder would definately save the "Murphy" problem for sure. Just hoping somebody has the experience and can give a quick answer out there... Mark in Utah
Hi Mark, I'm not really an expert, but I can make a few observations. The amp rating on some decoders, I've found, might be optimistic, if anything. Someone like Tony's Train Exchange would probably be glad to make you a recommendation--they always have for me. Programming in small amounts (like "3") in the acceleration and deceleration tables will save you from a blowout when you go from full speed forward to full speed reverse. There seems to be a surge there that fries decoders--my direction button is directly above my "increase speed" button, so I've done it a few times. It's these surges that blow decoders, in my case. Two motors running normally, or even stalled (and they will stall), should be within a decoder's output range--nope, not in my experience! I considered wiring A-B units with one decoder, as have others in N scale. But, in my case, the work involved in stringing wires from engine to engine wasn't worth the effort beyond a $25 decoder in each. I'd definitely give it a try, with a high output HO decoder. I've got a twin-motored custom beast in N scale--but putting a decoder in is a far-away project.
I know what you mean about the optimistic ratings on equipment. A standard rule of thumb for electronics is to not load resistors beyond 10% of their load rating, and electronics beyond 25% of its rating for reliable operation. Given the frequency of failure in decoders, I'd say people are regularly overloading them and not even realizing it until it's too late. Does anyone make a 4 amp decoder that'll fit under an HO shell?? Mark in Utah
Mark, if this is HO you can use one ZIMO MX64H that handles up tp 2 amps. All ZIMO decoders are thermally protected so even if power consumption is exceeded it won't destroy the decoder. Regards, Art Zimo Agency of North America http://www.mrsonline.net/
Thanks for the information. The DD40 is in the mail. Now I just have to complete the layout! Mark in Utah
