Dual Decoder Synchronization

[chuff_n_puff]

I am putting dual decoders in a Spectrum DDA40X dual motor unit, at the recommendations of several "experts" and have got 1 question, due to "they" say 2 motors would overload 1 decoder. How do I check the synchronization? It has always been an issue in a consist, but this was easy to check in that situation. This unit will have a straight no-sound decoder and the other is a sound decoder and will probably be a major mis-match!

[Hunt]

It depends on the decoders you installed -- you did not state the decoders you are using or the make and model your DCC command station. Even so, you will need to disable the Power Source Conversion on both decoders (CV 29, bit 2 -- set to 0)

[chuff_n_puff]

I am using a Digitrax DH123 for the straight decoder and a MRC #1632 Sheer Brilliance for the sound decoder. I have the DH123 installed on the rear motor and working and waiting on the MRC. I am using a Prodigy Advance Squared, 2 of them. I have a MRC Power Station 8 booster, but I always keep it set on it's lowest setting. I have nearly 250 feet of track and 18 trains, so far. You say I need to call up bit 2 on CV29 and set both decoders to 0? Thanks for your help.

[Hunt]

Disabling analog operation is just the first of other CV settings that are needed.  Some examples, you need to change the controlling CV (not talking about CV 2) so no voltage is supplied to the motors when on Speed Step 1. Must turn off BMF. etc., etc.

However, I feel you are wasting your time trying to synchronize the motor speed using a MRC and Digitrax decoder in same locomotive.  Who knows you may get lucky. You may have better chance if you change from MRC  to LokSound or Digitrax sound. But no guarantee. 

Conventional Rule of thumb  ---  don’t try to consist a sound and non-sound decoder. 

Run this test â€"
Place only the MRC sound decoder in a different locomotive.
Set CV 29, bit 2 to 0. This will disable analog operation for a DCC compliant decoder, which MRC is not.
Now place the locomotive on track powered by a standard DC power pack. Likely the locomotive will run as the few  MRC sound decoders I tested automatically overrides the bit 2 setting in CV 29. MRC states their decoder is designed to work this way. MRC may have changed this in the decoder you get.

[r0bert]

My HO dual motored DD's have been running on a single DH163 for several years, and my N scale ones (also dual motored) have a single DZ143.
No power or load issues have developed with either.
motors wired in parallel. headlights, numberboard lights, and roof beacon each on sererate function circuits, 0,1, and 2 respectivly.
when they get updated to sound,  the HO models will get a sound only decoder added, while the N ones will probally get new sound/motor decoders.

[chuff_n_puff]

Robert, thanks for your reply and your comment makes sense! I was told the DD40AX was same as the DD40, but when I got my Spectrum DD40AX, it measured 1.25" longer than the Athearn DD40. As a matter of fact, I have been running my Athearn dual motor on a single decoder for a year and have had no problems. But these motors are about twice the size and I thought they needed more power. I am still waiting on my MRC decoder and was wondering how you wired your light board in to the decoder. I've isolated the motors from the frame and removed the 2 spring power pick up clips from the light board. Do I isolate the circuits on the board with my hobby knife, then use my correct wires from the decoder? Do I run the decoder wires through the capacitors or by-pass them? Can I use the firebox wire for the beacon light power? Does the decoder have it's own built in resistors, or do I have to add them? Do you know a link depicting this, or maybe a picture of your wiring? I am taking my time with this one to get a near perfect factory looking upgrade as possible. Your help will be greatly appreciated.  Thanks, Roger.

[r0bert]

give me a couple of hours, and I will put up some pics.

[chuff_n_puff]

Thanks Robert,will be waiting!

[r0bert]

OK, here goes;
after the motor tab were removed I ran a pair of jumper wires between them along the chassis, and connected the decoder motor leads to the front motor

view of other side



lights to follow

[Hunt]

Current draw does not need to be a guess and hope it works affair. Do a Stall Test. Without any decoders installed, remove the shell, hold the flywheel of each motor at the same time, turn power of a DC power pack to 12 to 16 volts and measure the amp draw. Because there are two motors involved get someone to help you do the Stall Testing.

[r0bert]

Now for the lights, I removed the light board, stripped everything from it except the front and rear bulbs, and cut the entire center section out of the board in between the rear and front screws

yellow and blue light wires to the rear lamp, black tape to cover light leaks
so the whole shell doesn't glow

the tape covers up all the wiring, but here it is,
I used the remaining board traces to run the blue wire for the front lights, and all three are connected to it.
I added a LED (white and blue wires with 560 ohm resistor) in the nose for the headlight, again sealing light leaks with the black tape.
the original headlight bulb on the board now only lights the number boards, and is wired to function 2, but remapped to function 3 because on the Digitraxx command systems function 2 is not locking, and will only stay on if button held down.
for the roof beacon, I used a 1.5V grain of sand bulb with a 820 ohm resistor, and wired to function1.
the bulb slides up into the hole I drilled in the new beacon and housing I added to the shell, it's more to scale


the full album can be viewed here
http://s46.photobucket.com/albums/f123/river_eagle/HO-Scale/install/
hope this helps you along
action vid/clip at
http://www.youtube.com/view_play_list?p=5573D5793FAE11F6

[chuff_n_puff]

Robert, That helped me a whole lot. That is basically what I have got and have the motors wired like yours and awaiting my sound decoder. But I have a couple of questions. Do I leave the in-line capacitors on the front and rear bulb circuits, or cut them out and just go blue/yellow and blue/white? But on the other hand, what if I used my hobby knife and sever one of the circuits between the front and rear lights, at the original DC clips location. Then I could connect the yellow and white to each leg and the blue common to the other clip location. That would not only put the lighting in DCC mode, but will leave the beacon light in tact. Or do I need to seperate that too and maybe run it off another one of the accessory light wires. I think the MRC has a special beacon light wire on it, as it is a 19 function decoder. Thank you for all your help. It's people like you that makes this hobby worth while!

[r0bert]

Current draw does not need to be a guess and hope it works affair. Do a Stall Test. Without any decoders installed, remove the shell, hold the flywheel of each motor at the same time, turn power of a DC power pack to 12 to 16 volts and measure the amp draw. Because there are two motors involved get someone to help you do the Stall Testing.

in normal operation the glue in the flywheels for the drivshaft sockets will give long before there is enough load to stall the motors, and a DH163 is rated for 1.5 amp constant load with a 2 amp peak.
the average modern motor in HO locos will draw around.45-.50 amp when slipping under load, and around .90 amps when stalled.
assuming a worst case event, something causing BOTH motors to lock up at the same time, and stay that way, then yes poof! out comes the magic smoke, no more decoder, in such an event, the damaged decoder would be the least of my concerns, because something went very VERY wrong some where else.
In the real world if one motor stalled the other could absorb enough of the load long enough to get it shut down.
I have cooked more than my share of decoders over the years, don't claim to be an "expert", and have learned a bit along the way.
Use two decoders if you want, I'm not going to stop you. IMHO it's overkill, and wasted $$$$, but I'm just some guy on the internet.
Using one decoder has not, in my experience, with six such locos, over years of use, caused any load issues with the decoder.
Trying to get two decoders to operate in perfect unison would be a far more difficult, and greater issue, it's not the same as A-B set of F units, there is no play, coupler slack action or minor towing at various speeds, it's one solid unit.     

[r0bert]

Robert, That helped me a whole lot. That is basically what I have got and have the motors wired like yours and awaiting my sound decoder. But I have a couple of questions. Do I leave the in-line capacitors on the front and rear bulb circuits, or cut them out and just go blue/yellow and blue/white? But on the other hand, what if I used my hobby knife and sever one of the circuits between the front and rear lights, at the original DC clips location. Then I could connect the yellow and white to each leg and the blue common to the other clip location. That would not only put the lighting in DCC mode, but will leave the beacon light in tact. Or do I need to seperate that too and maybe run it off another one of the accessory light wires. I think the MRC has a special beacon light wire on it, as it is a 19 function decoder. Thank you for all your help. It's people like you that makes this hobby worth while!

I removed all the electronics except the actual bulbs from the light board, and wired them directly using many of the existing traces on the board, and made jumper wires across the traces where the directional diodes were,
for the beacon, if reusing the LED, again I would directly wire it to the decoder, with the proper resistor, and not use the original flasher, you'll get a better effect.
http://www.youtube.com/watch?v=6-1VeD-oXbU

[chuff_n_puff]

Hey Robert, I got a little 'Diddy" of info for you! Do you remember what I told you the "experts" were saying at the start? Well, "Mr. Decoder"(Frank Verrico of MRC) emailed me and stated it was impossible to convert these type units to DCC, 1 or 2 motors, due to this type motor draw too much current. He is head of the technical department at MRC! See what I mean? By the way, I completed the light board like you said, but used the entire board. Using my hobby knife, I isolated the 3 circuits, soldered in 1K resistors like required and jumped the common legs together for the blue wire hook up. Now all I need to do is connect my blue, yellow and white decoder wires, when my decoder arrives.