# dumb question--does sierra sound work with DCC?



## lownote (Jan 3, 2008)

I just bought a USAT F3 that came with a sierra soundcard in it. I would like to put a DCC decoder in the loco and oerate the siarra card via DCC

I've got no experience at all with sierra--none, zero, zip. George Schreyer's page suggests tat you have to do a fairly elaborate workaround to get the Sierra card to work properly on DCC. 

Can anyone point me towards more info? MAybe a sierra manual?


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## East Broad Top (Dec 29, 2007)

You need an accessory control board to trigger the sounds with DCC. My dad uses the Digitrax TF4 board with his, though others make similar boards. If I recall how he has his wired, there are two wires (red and black) that go to the rails/DCC output, and four wires for each of the 4 triggers. It's designed primarily as a lighting board, but since all you're doing is opening and closing switches, it works to trigger the sounds. 

Good luck! 

Later, 

K


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## Cougar Rock Rail (Jan 2, 2008)

With the cost of a sound decoder being not that much of a premium over a non-sound decoder, I would strongly suggest you get a good sound decoder and sell the Sierra or reprogram it and use it in something else. That way you get properly coordinated sound with the speed/load of the motor etc. I would start by listening to the sound samples on the various websites---Zimo, Massoth, ESU.... 

Keith


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## lownote (Jan 3, 2008)

I have plenty of sound decoders, and I'm very aware of what's out there. I have a QSI titan on the way that I might just put in there. I was just wondering how well the sierra would work on DCC. since it's one brand I have no familiarity with. 


Thanks Kevin, I'll look into that. What I'm wondering about is how the Sierra senses the motor current. If anyone has a sierra manual, I'd love to take a look


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## Cougar Rock Rail (Jan 2, 2008)

Sorry about that-- after I posted I realized who actually made the post...I know you are aware of all the options. 

Keith


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## East Broad Top (Dec 29, 2007)

To my knowledge, it doesn't sense current at all, just voltage. You'd simply run wires from the motor output of the DCC decoder to pins 7 and 8 of the Sierra board. I believe Stan Cedarleaf has Sierra manuals in PDF format. The programming for the diesel board is different than the steam, so make sure you get a copy of the right one. The one thing that I can't say for certain would be whether you'd need an opto-isolator board between the DCC decoder output and the Sierra's motor inputs. You do with RCS and Revolution controls. Stan may know. With the diesel, you'll need to accurately sense the motor voltage to get the motor to rev up along with the speed of the train. My suggestion would be to try it without, then if it doesn't work, get one from Tony (RCS) and try again with it. I'm sure Soundtraxx could probably tell you if one's needed as well. 

Later, 

K


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## lownote (Jan 3, 2008)

Well I took it apart this afternoon and I'm going to have to rewire it altogether,as some of the wiring had deteriorated. One of the track power leads had either overheated or decayed or both. I'll probably tear the whole Sierra business out and just install a sound and motor decoder


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## TonyWalsham (Jan 2, 2008)

The Sierra pcb creates a sneak path for the PWM motor output voltage to get back to ground. Depending on the actual output design most PWM output ESC's always have one line high so when a pwm voltage is applied to pins 7 & 8 the motor will rev up to full speed and stay there. So, actually you will need the opto isolator pcb to *stop* the sound board from revving up. The Sierra can then be powered via pins 2 & 4 and the Sierra battery discarded. You will need to provide a regulated 12 volts (and no more) or the Sierra will not rev up to notch 8.


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## Greg Elmassian (Jan 3, 2008)

The Sierra does not sense motor current. It could only do that by being inline (electrically) with the motor somehow. 

It, like the Phoenix, senses motor VOLTAGE, which tells you very little about actual speed and nothing about actual load. It tells you how much voltage is applied to the motor. If there was no load, no grades, no friction, then voltage would relate well to locomotive speed. 

As usual, the Sierra can be "fooled" by PWM outputs, and you may need the isolator EBT has described, and also maybe the filter like the one Aristo sells. 

I agree, try it and see.


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