atlas commander : LUSENET : Wiring for DCC : One Thread

I have a atlas commander installed on my layout qand am now considering installing sound in a Bachman shay loco.So Atlas says the voltage has to be reduced for soundtrax to work properly.I installed 4 FR 301 diodes from Digikey,2 in each wire, as they recomend. however the voltage when mesured with a digital V M does not seem to drop as far as it is supposed to do i need to 1: install more diodes 2: modify my V M to get a proper reading or should i assume that everything will work OK? I dont want to let the smoke out Help H L M

-- Hank Meyer (, July 08, 2002


A drawing of the circuit that Bert described is on my website at:

-- Allan Gartner (, December 21, 2004.

Hey Hank: Its never a good idea to let the smoke out. Those things run on smoke and when you let it out, they don't work any more. I am not an electrical engineer but I think diodes block voltage going in one direction. This is how you can get DC from AC. Perhaps you need some resisters to lower the voltage. I would NOT hook it up as you have it. Sorry I can't help more. Bryan

-- Bryan Hinkle (, July 18, 2002.

A silicon diode will not only block the voltage in the reverse direction but will also produce a drop of about 0.7 volts in the forward direction. Therefore if you take two of them and wire them anti-parallel with their oposite leads together each will pass the current in one direction only and an AC or DCC signal will be reduced by 0.7 volts in both directions. chaining two pairs would result in a 1.4 v drop. Putting two pair in the other lead would result in a total of 2.8 volt drop and keep things balanced as well when the wires are reversed to match the phase coming out of a reversing loop.

-- Bert Holmes (, December 21, 2004.

I appreciate getting an answer to my question finally i'ts only 2 1/2 years late. I have since gone to a Lenz 01 and discarted my commander since it did not want to operate more than one Engine at a time so my original problem disapeared thanks Hank

-- hank meyer (, December 21, 2004.

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