# some dumb DCC questions



## lownote (Jan 3, 2008)

DCC is very confusing. It's clear enough how it works in principle, but every manufacturer seems to give its products different fancy names, and the HO stuff isn't appropriate for large scale, and it's hard to know which is which. . 





I'm currently using track power with remote control. I have some locos running Aristo's 75 mhz. train engineer, and some running QSI/airwire. I can see the advantages/appeal of DCC with what the QSI airwire system can do, and I've been thinking about going to full-on DCC. 



So first, can I convert to DCC and continue to use the Airwire throttle? It wasn't cheap. Airwire makes, it seems, all the components needed for DCC. If I want to keep the Airwire throttle do I have to use airwire's command station/boosters etc.? Are they any good? 



Second, the real advantage of converting to full DCC, for me, would be the ability to easily do reversing loops and switches. I've been thinking about making a wye or a loop for a while now, but want it to be automatic and to be honest I don't really entirely understand how to wire/control a reversing loop for automatic operation. We invite a lot of neighbor kids to ruin on our layout and I'd want something that was basically invisible. Controlling switches with a wireless throttle would be cool too.


Third, we have a lot of buildings and cars lit with leds via track power. Would going to DCC interfere with that? I don't think so but I want to make sure. 

Thanks!


----------



## StanleyAmes (Jan 3, 2008)

Posted By lownote on 01/03/2009 5:14 AM
DCC is very confusing. It's clear enough how it works in principle, but every manufacturer seems to give its products different fancy names, and the HO stuff isn't appropriate for large scale, and it's hard to know which is which. . 





I'm currently using track power with remote control. I have some locos running Aristo's 75 mhz. train engineer, and some running QSI/airwire. I can see the advantages/appeal of DCC with what the QSI airwire system can do, and I've been thinking about going to full-on DCC. 



So first, can I convert to DCC and continue to use the Airwire throttle? It wasn't cheap. Airwire makes, it seems, all the components needed for DCC. If I want to keep the Airwire throttle do I have to use airwire's command station/boosters etc.? Are they any good? 



Second, the real advantage of converting to full DCC, for me, would be the ability to easily do reversing loops and switches. I've been thinking about making a wye or a loop for a while now, but want it to be automatic and to be honest I don't really entirely understand how to wire/control a reversing loop for automatic operation. We invite a lot of neighbor kids to ruin on our layout and I'd want something that was basically invisible. Controlling switches with a wireless throttle would be cool too.


Third, we have a lot of buildings and cars lit with leds via track power. Would going to DCC interfere with that? I don't think so but I want to make sure. 

Thanks!



With any control system there are two parts, the signal and the power.

Airwire and Gwire sends the DCC signal over the air GWire can take the power from either the track or internal batteries while Airwire perfers batters. Track powered DCC sends the signal and power over the rails. There are also hybrid approaches that combine parts of each.

The AirWire throttle is actually a command station for sending the signal over the air. You can have it converted to work with several common track powered DCC systems. This conversion is a software replacement.

The reverse loop modules are easy to install, you isolate the loop at each end and connect the two track wires to one end of the reverse loop module and the other end of the module connects to the track.

Lights for buildings and cars may be a problem depending on your circuit but it is easily fixed. If your lights have a circuit to limit the voltage or current then you do nothing. If you are using raw track power then it may be that the lights work best at the common lower voltage used. DCC uses full track voltage all the time. If the lights are too bright simply place a diode on one lead and the voltage to the lights will be reduced by 1/2.

In selecting a DCC system select the one thaqt is the easiest for you to use.

 Hope that helps

Stan Ames
http://www.tttrains.com/largescale/


----------



## lownote (Jan 3, 2008)

Stan Ames wrote:

_"Airwire and Gwire sends the DCC signal over the air GWire can take the power from either the track or internal batteries while Airwire perfers batters. Track powered DCC sends the signal and power over the rails. There are also hybrid approaches that combine parts of each. 
The AirWire throttle is actually a command station for sending the signal over the air. You can have it converted to work with several common track powered DCC systems. This conversion is a software replacement."
_ 


Thank you Stan. Sorry to be dumb. I get the idea that the airwire trottle is a command station. If I wanted to have DCC sent over the rails, and control it with the airwire throttle, I could do that? How would I do that?--what software would I have to change?

I suppose alternatively airwire makes a block control unit which could automate an autoreverse, and I assume be triggered by the airwire throttle


----------



## Bill Swindell (Jan 2, 2008)

CVP makes a full line of DCC power components like command stations and boosters. They have version of the AirWire throttle that controls their track based DCC system. I would suggest that you call them directly and talk to Al about what you have and want to do.


----------



## Road Foreman (Jan 2, 2008)

lownote, 

The throttles are not the same, that is why Stan said you have to change the software.. CVP as Bill says make a complete system.. You can get the command station, boosters, & radio control receiver.. The autoreverser is a stand alone unit, 2 wires from the track & 2 wires to the circle.. You can get boosters that will autoreverse also.. If you wish to be able to run a non DCC loco you will need a system that has zero stretching.. 

BulletBob


----------



## Greg Elmassian (Jan 3, 2008)

Maybe the thing to realize here, is that DCC is standardized on the signal on the rails. 

Many DCC systems have wireless throttles, but the interface between the throttle and the receiver, whether a fixed base station or in a loco, is NOT STANDARD. 

AirWire is interesting in that what it puts over the air is pretty much the same signal as the DCC signal on the rails. 

Be that as it may, I repeat, there is not this level of standardization between the different brands of throttles. 

Regards, Greg


----------



## Road Foreman (Jan 2, 2008)

Greg, 

I think you are correct.. A friend uses the AirWire receiver to drive Digitrax DS 64's for turnout control.. The AirWire receiver will not act like a command station, it is just a booster with the voltage out being what ever the battery voltage.. 

BulletBob


----------



## Greg Elmassian (Jan 3, 2008)

I think we are in agreement Bob. 

It's interesting that AirWire chose to send DCC over the air, and I have no assurement that it is a COMPLETE command set, it seems that many DCC commands are sent over the air. 

Now, the AirWire receiver will "pass through" certain DCC commands, we know that Function commands work, and it looks like accessory commands work. What probably does not get generated OR pass through is motor control commands. Since the QSI/Gwire combination works, it seems possible that the motor control commands are transmitted. 

Interesting, I know there must be some exceptions/limitations in the "DCC" that is sent by an AirWire transmitter. 

Some day someone will do these tests, maybe. 

Regards, Greg


----------



## Bill Swindell (Jan 2, 2008)

What do you think is missing from the AirWire DCC? I know for a fact that the necessary signals to run a motor decoder are present in the DCC output from the AirWire receiver. You can program CV's with both OPS & SVC code programming.


----------



## Greg Elmassian (Jan 3, 2008)

I'll revise my last sentence, there may be some limitations or omissions. 

Bill, have you found that all commands pass through, even speed up and down and momentum and consisting? 

Regards, Greg


----------



## Bill Swindell (Jan 2, 2008)

The AirWire receiver & transmitter fully support modifications to speed curves, momentum and consisting.


----------



## Road Foreman (Jan 2, 2008)

Greg, 

My friend is running a NW-2 with a Digitrax 583S decoder by his AirWire receiver & a booster.. Says everthing works fine.. He has also ran a small loco with decoder from the output from the receiver but cautions about the 1 amp DCC output of the receiver.. He will soon be running 3 DS-64's off of the receiver.. 

BulletBob


----------



## Greg Elmassian (Jan 3, 2008)

Bob, that sounds like a good combination. It might not make CVP happy, since the combination of the receiver and a $45 DS-64 is way cheaper than their linker and activator. 

I wonder if some enterprising soul will try hooking the Gwire receiver ($80) to a DS-64? That should work also, and be even cheaper. 

What do you think? 

Regards, Greg


----------



## StanleyAmes (Jan 3, 2008)

Posted By Greg Elmassian on 01/04/2009 6:56 PM
I'll revise my last sentence, there may be some limitations or omissions. 

Bill, have you found that all commands pass through, even speed up and down and momentum and consisting? 

Regards, Greg


Greg

I have had a scope on the output of a Qwire receiver. The Gwire is simply the receiver chip and a very small booster (power station). The bit timing for the one bits is just a little off but other then that this is pure DCC. What DCC packets are supported is only dependent on the feature set supported by the Air Wire transmitter. For example the transmitter does not, at this time, support the functions from F12-F27 so the receiver will not transmit those functions. If some future command station upgrade is done the Gwire receiver would support this feature with no change.

Note these out of spec 1 bits may cause some problems with some decoders but most operate is this range.

A simple experiment for you would be to hook up the Gwire receiver directly to a normal DCC power station and operate your railroad through the Airwire command station.

As to passthrough for the AirWire receiver, the output must have a continuous packet stream so it would be much more difficult to try to filter out the packets then to simply pass them all through.

The only real idfference is that the booster is much larger on the AirWire receiver then the Gwire one. Thus I would expect all the packets to be available on this outpur as well.

Hope that helps

Stan
http://www.tttrains.com/largescale/


----------



## Greg Elmassian (Jan 3, 2008)

Thank you Stan. 

I was not putting AirWire down, but since their only intention was to support their receiver and an attached sound decoder, I suspected that there might be things that are not supported. F12-F27 are not a big deal to most people. 

Also interesting, but not surprising is the "little off spec" of the timing. Again, if I was manufacturing it, I would manufacture it for my own sales, not to make it a universal component. 

Can you expound a bit more on the continuous packet stream? I'm pretty sure that certain DCC decoders or functions require this, but not sure which. 

Regards, Greg


----------



## Road Foreman (Jan 2, 2008)

Greg, 

Hooking up the G-Wire receiver to a DS-64 will probably not work because the G-Wire works on 5 volts & the DS-64 probably has to have a minium of 7 volts.. But I could be wrong!! You also have to power the DS-64 with the external 12 volts DC..


----------



## Greg Elmassian (Jan 3, 2008)

I was assuming the separate power input. The question will be the minimum DCC signal level on the TRKA and TRKB inputs. It's worth a try. I searched the Digitrax forum for an answer, but could not find one. Stan did run an ordinary Digitrax mobile decoder (right Stan?) from the Gwire, so I would assume the input design might be similar. 

Regards, Greg


----------



## StanleyAmes (Jan 3, 2008)

Posted By Greg Elmassian on 01/05/2009 12:34 PM
I was assuming the separate power input. The question will be the minimum DCC signal level on the TRKA and TRKB inputs. It's worth a try. I searched the Digitrax forum for an answer, but could not find one. Stan did run an ordinary Digitrax mobile decoder (right Stan?) from the Gwire, so I would assume the input design might be similar. 

Regards, Greg 




Greg

I think there may be some confusion here so let me try to explain it better. In classical track powered DCC the power is transmitted along with the signal. No signal no power. Thus the AirWire receiver must not only transmit the signal but must also be able to provide enough voltage for the attached sound decoder to sound good. It also has to ensure that the signal is sent continuously as it if stops sending the signal the power is removed as well. The reason this all works is because AirWire is indeed DCC. I fully expect you could hook most any decoder to an AirWire’s DCC output and all the functions including motor control would function properly. Note however that the power output in terms of amps is not sufficient to power Large Scale models which is why the restriction to sound or function decoders only.

The concept behind Hybrid DCC is that the signal and the power are no longer combined.

The Gwire receiver uses this hybrid assumption. It assumes the decoder has power from another source so it only is concerned with transmitting the signal. The DCC standards only describe the signal properties in the +- 4 volt range so any edge detection decoder should work just fine even though the +-5 volt Gwire signal is less than the minimum spec level of +-7 volts.

Sampling decoders should also work so long as the sample detection threshold is less than 5 volts.

As for bit timing there should be few if any problems.

“Digital Command Station components shall transmit "1" bits with the first and last parts each having a duration of between 55 and 61
microseconds. A Digital Decoder must accept bits whose first and last parts have a duration of between 52
and 64 microseconds, as a valid bit with the value of "1"”

My notes are old on this but I believe the GWire was a shad shy of 55us, less than the spec requires for command stations. Note it is also possible my notes are wrong on this and the signal is closer to 56us ( I did this several years back). Either way this should not be a problem because it is still well within the range decoders should accept.

I have indeed hooked up several decoders to a Gwire receiver and they work as one might expect since the signal is simply a very low power DCC signal.

There is no packet that cannot be transmitted, the only limitation being the feature set the AirWire transmitter has decided to support. Change the transmitter supported packet set and the dumb Gwire receiver will transmit those packets to its attached decoder.

Stan http://www.tttrains.com/largescale/


----------



## bobgrosh (Jan 2, 2008)

I gather from these comments that:

If you take an Air-wire receiver out of a loco, and connect the DCC out of the receiver to any brand name of booster, then you could run the booster output to the track and run DCC equipped locos on the track.
Anyone tried this?
Any limitations?
B0B


----------



## Greg Elmassian (Jan 3, 2008)

I don't know anyone, but it should work, subject to the out of spec timing that Stan Ames saw. 

Regards, Greg


----------



## Road Foreman (Jan 2, 2008)

Bob, 

A friend of mine is doing that.. Not sure of the booster but I think it is CVP's.. He has run a NW-2 with a digitrax decoder.. Says it runs fine.. 

BulletBob


----------

