# help needed developing new concept.. looking for a smart EE!



## SD90WLMT (Feb 16, 2010)

If I was writing an add... I'd say I wanted a dynamically functionally fluid EE, smarter than myself - a mechanic with a broad base electrical understanding...able to tackle certain challenges.... yet at this juncture...have a developing concept in my head which I find beyond my pay grade!

I have done some research... some reading...I need most likely a small class A amp, for the purpose of signal boosting...keeping an amplified signal in it's original context... just stronger in such a way as to allow broader use of said signal.

My idea I'm pursuing is a basic "Master/Slave" set-up for a multiple loco consist. I want to have a Master loco - with full functions using a G-wire & QSI decoder...no biggy here!
Where it gets interesting tho is my desire to use the one single G-wire as the shared source feed to each slave decoder...sending the signal down the line for 5 more locos...these need motor control, engine sound, air compressor sound.. no controled lites needed.

I have tried to understand the G-wire, its 5 conductor ffc cable to the decoder. At one end of the pcb are add on solder points for the receiver.. but only 4 lines are present. Two are for power, marked plus n minus. The other two say signal. Yet when looking at the installed ffc plug on the pcb itself... only three traces flow to it... with a possible two other oblique traces disappearing under the ffc plug....in conclusive at best. 

This has lead my thoughts to form the base idea that I need the two signal lines further fed on to each slave decoder.... not sending their power back to the reciever... allready getting power from the master decoder. I feel a common ground through out the system is note worthy.

This then leads to the need for a small signal amp at the rear of the master loco.... grabbing signal after its use in the master.... boosting it such that the following 5 locos get a matched input..
The question arises though... how many slaves would be effectively handled.. or would a 2nd signal booster be required say in the 3rd slave loco..feeding the last few.

I see using a shielded 2 conductor - 22-24 ga wire to run the length of each slaved loco. I fore see the master having a rear plug .. under the anti climber only... all slave locos would have plugs at both ends...

The ability to have slaves face in any direction ... behind the master is a plus... should be no biggy tho.

I'm reasonably assured this can be developed into a successful and well running combination.... yet is slightly beyond my 'sperience therein....

So .. at this point I'd like to open my idea to the larger forum for further ideas...

Dirk
DMS Ry.


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## East Broad Top (Dec 29, 2007)

Are you looking at a dedicated power source (battery) for each locomotive? 

Here's my thoughts:

The two pads labeled "TX" on the G-wire receiver are the DCC signals that go to the decoder. The other two pads are (as you noted) +5v and ground. If I recall correctly, the +5v feed is carried on two of the 5 wires on the ribbon cable between the G-wire and QSI. 

What you'd need is something that takes that DCC signal from the G-wire and integrates it with power coming from the on-board batteries to feed the "slave" decoders in each of the individual locomotives. 

If I recall correctly, I saw an installation where someone had the G-wire attached to the QSI board, then also used the solder pads to connect a secondary lighting function decoder. (Google "G-wire QSI" and look for images; you'll see some wiring diagrams which show how to hook up generic decoders to the G-wire receiver.) If I'm understanding those diagrams correctly, the "TX" output is technically all you'd need in terms of sending DCC instructions to the decoders. The other connections provide power for the lights and such that the decoder is controlling. Here's a wiring diagram showing how to use the G-wire to power a generic lighting function decoder:










The 7805 is a 5-volt voltage regulator that is providing power for the G-wire receiver and the LEDs (lights 1 and 2). The battery + is providing full battery power for the incandescent lights (lights 3 and 4).

In your installation, you'd not need to provide the +5v and ground to the G-wire via the solder pads since it's drawing it from the QSI board via the ribbon wire. The only thing you'd need (if I'm reading things correctly) is the two wires coming from the "TX" pads. 

One option might be to run that DCC signal output between each locomotive, then use an on-board booster on each loco to combine that signal with power from the traction batteries to run the decoder. Tam Valley Depot makes a 3-amp (5-amp peak) booster that can be used for such applications. I don't know what circuitry goes into a booster; you may be able to build one yourself. You can then hook whatever DCC decoder you want to the output of this booster. 

Unknowns (at least by me):

1) Whether the "TX" output of the G-wire is truly a valid DCC signal that can be boosted externally as I describe. 

2) Whether the G-wire receiver is "upstream" of the decoder address of the master decoder; in other words, can the master decoder have one address and the "slaves" potentially have others. I think in the case you're describing, you'd want all the slaves to have the same address anyway, so this is probably a moot point. 


Another option might be to forgo the G-wire receiver and use either Tam Valley Depot's "DRS1" receiver or Airwire's "Convertr" receiver. These _do _output valid DCC command packets that can be put through a booster as I described above. The Tam Valley unit is limited to operating on Airwire's Channel 16 only, while the Convertr can use all of Airwire's available frequencies. In these installations, you wouldn't use the ribbon wire at all, nor would you have to enable Airwire on the QSI decoder's CV settings. 

Later,

K


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## SD90WLMT (Feb 16, 2010)

Thank you for your comments Kevin,

Each loco is treated like a stand alone R/C battery loco, minus the receiver.

I felt there was no need for 5-6 traffic cops in the same intersection!

I have been discussing a similar M/S concept with a friend, my set-up limited to a pair of power units...yet with one decoder and batteries and sound in both...left me with 8 wires crossing the end plates....
I became less interested in chasing down that road...

Then it hit me that I may run as many as I'd like.. yet using one receiver... a 6 or 10 A decoder/battery set in each loco, lacking a signal to gain control of the consist.

Now ... I'm here..

Under your plan of using just the two TX lines for signal to each Slave loco, do you forsee the actual need of a common ground between all locos? I ask as this affects connector plug choices across the end plates. 2 or 3 wire.

Each could have its own signal booster... drawing from the common shared main path thru all the locos...

More pondering as JJ says.... ;-)


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## East Broad Top (Dec 29, 2007)

I think just the two DCC command wires would work. With each unit having its own dedicated power supply and booster, I'm thinking you can just hook each booster to the DCC command line in parallel. Looking at the Tam Valley Depot booster, it's got a port for DC power (battery or power supply), DCC in, and DCC out. There's no place for a common ground connection anyway. 

*Tam Valley Booster*

You may want to contact Duncan McCree over at Tam Valley Depot. He talked me through the Convertr/Booster set-up that I'll be using for a loco project later this summer. He may be able to shed some light on the DCC output of the G-wire receiver. 

Later,

K


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## SD90WLMT (Feb 16, 2010)

I contacted Duncan, including a link to this thread for info..

;-)


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## Greg Elmassian (Jan 3, 2008)

I don't believe you can parallel the "DCC" data lines, besides the conflict on reading back, I don't think the signal will handle the load and distances of the cables (more load).

Sure is a lot of work to save the money on the receivers.

Also, you would not necessarily have to have all the addresses the same, in fact it would be better to use advanced consisting.

You need basically a repeater for the transmit signal, and then perhaps only take the first decoder's receive signal.. I thought the TX and RX lines were separate, Kevin's picture shows both labelled as TX.. 

Greg


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## SD90WLMT (Feb 16, 2010)

The 1 gwire I have indicates the two inner traces as both - RX+...

Not every one has open budgets fer toys....
Some are can dos..
Why I find myself "scratch building locos", to have that which is not for sale...not because its easy... but because I can..
My world is not main stream ... nor are my layout needs.. or desires!


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## SD90WLMT (Feb 16, 2010)

Or... you could sit at your bench Greg..
... do a bread board mock up... prove it does or does not function!

Fun & Educational....

D


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## Greg Elmassian (Jan 3, 2008)

Sorry, my personal projects themselves are out of control.

Gots no extra time, still have an unopened USAT Hudson in the garage if that gives you any calibration.

Greg


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## SD90WLMT (Feb 16, 2010)

That's. .. "precisely", why its called a "Hobby"....!!

Good Luck...


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## krs (Feb 29, 2008)

There is a bit of info on connecting a G-Wire receiver to a DCC decoder in this thread:
http://forums.mylargescale.com/39-dcc-large-scale/28182-connecting-zimo-mx645-gwire-receiver.html

The three main issues seem to be:
1.Output of the G-Wire DCC signal is only 5 volts which not all DCC decoders will accept as a valid DCC signal
2. DCC normally combines signal and power while the G-Wire output does not,so one needs to supply power to the decoder separately
3. The G-Wire DCC signal does not fully conform to the DCC spec so again some decoders may not recognize the DCC signal from the G-Wire receiver as valid.

What is the purpose of this whole exercise?
Trying to save money?
Or just seeing if it can be done?

Knut


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## SD90WLMT (Feb 16, 2010)

Knut.. thanks for your thoughts...
As this is a straight gwire to titan configuration...all three observations from your reference really are not applicable...

That said...I want to do this!! Why be restricted to the samo convention. I wish to run longer loco consists than most do or have room or need for. Why have not have many locos tied into a single unit...all acting as one..
Why spend more money than is really needed...just because!?

The thread is about grasping the signal used and sent to a Titan... such that it can be understood ... thus tweaked as needed to control more than the typical single decoder per receiver.. a very inefficient process....


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## Greg Elmassian (Jan 3, 2008)

It's not just because, the function of consisting in DCC is there to do this function.

It allows individual "tuning" of speeds between locos, i.e. matching, and it allows smart functions like only the horn sound from the lead unit, no matter what the direction.

Your idea can work I think, but you need something designed, as you have asked.

Do not forget that while you want to distribute the received signal to all locos, you cannot have multiple locos sending information back at the same time. This will take some trickery. Also, you will not be able to do service level programming on the rest of the locos. This means you won't be able to read back settings.

All in all a lot of work for reduced functionality. Don't know what the receivers cost now, but it was around $100 a loco. 

Greg


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## SD90WLMT (Feb 16, 2010)

Individual functionality is not neccessarily lost with multiple locos tied as a single unit..
Only the lead power really has to function.. for options beyond motor control.
Matching cloned locos should not be required.

Moving forward... what info does the decoder send back to gwire..and why?
& why.. is not this signal attenuation retained on the decoder in the first place..

This is more than an issue of cost... esp. since gwire are not selling at the Big Box stores or the local grocery store..oh thats right... they aren't for sale!

Kind of a moot point..with no lite in the tunnel..


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## Greg Elmassian (Jan 3, 2008)

Service mode is the programming track, when you set CV's, it responds.

The more things connected in parallel to the radio receiver the more load on the receiver data lines.

It will need experimentation to see what the situation is, or someone getting specs on the input requirements of the QSI decoders (which I doubt exists)

Greg


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## Michael Glavin (Jan 2, 2009)

Greg,

Perhaps a DCC 'booster' as proposed will solve the current syncing needs of the decoders. 

Knowledge of the how, what and when of the bipolar DC data stream is in question. Will a decoder respond without a handshake or not? Lots of questions, but where does one find the answers?

Michael


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## Greg Elmassian (Jan 3, 2008)

Unfortunately, the booster is not bidirectional, which will work to a degree, although not all will work with a unipolar DCC signal, it should be bipolar.

Also trying to find one that works at 5 volts, which is the output level from the receiver.

So, it will take some engineering work, to even work without readback, which knocks out service mode. Now you cannot program certain CVs, and cannot read back current settings.

I see that it saves money, but it sure adds limitations. I know it could be designed, but who would do it.

Greg


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## Bill Swindell (Jan 2, 2008)

I have a different idea. Use a CVP Converter to receive the signal from your transmitter. Install a Tam Valley transmitter in the loco and drive it with the output from the Converter. Put a Tam Valley receiver in each locomotive and have it driven by the Tam Valley transmitter. That way, you transmit to the train on any channel but #16. The Tam Valley transmitter and receivers are all on #16. This way, there are no wires between the engines.


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## East Broad Top (Dec 29, 2007)

Bill, you'd still have the expense of an individual receiver in each locomotive, which is what Dirk is trying to avoid. With a receiver in each loco, you wouldn't need the Convertr. You'd just hook the Tam Valley Depot receiver to each QSI decoder and group them all as a consist. What we're trying to accomplish is building a "permanent" consist of locomotives with only one receiver sending signals to all of them. You can do this with the Tam Valley Depot booster in each loco, but even that's $50 worth of extra electronics in each loco--still cheaper than $120 for the Tam Valley Depot receiver or $135 for the G-wire receiver if/when it is ever put back into production, but an extra expense nonetheless.

(Incidentally, I've been testing the Tam Valley Depot/QSI combination in an installation I'm doing for my dad. So far, so good.) 

Later,

K


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