This question is just be cause I am feeling curious, I really can think why I would be important but I’ll ask anyway!
So today many DCC decoders are dual mode, meaning they run on but DC and DCC. Now most DCC systems can become ‘DC’ systems by running with address one. When running with address 0 the layout becomes DC and the DCC equipped locomotives don’t run at all. What I’m wondering is what a dual mode decoder will do when you run address 0. Will it run as a DC loco, or will it ignore the DC signal and sit still doing nothing.
Again just a curiosity, I don’t actually have a DCC system at the moment, though I do run on others systems.
Regards, Isaac
I model my railroad and you model yours! I model my way and you model yours!
Note that only some DCC systems support the address zero feature. My Lenz system does, but many do not.
It takes an iron man to play with a toy iron horse.
MisterBeasley Note that only some DCC systems support the address zero feature. My Lenz system does, but many do not.
Duly noted!
I am most firmiliar with Digitrax systems for the information of those replying.
I have 4 locos with dual mode decoders. 3 Atlas, and 1 Bachmann Spectrum. Since I turned my lay out over to DCC, I've never set it back to DC to try these locos on DC, to see how they work.
It's an easy switch for me, flip a switch, unplug one power system, and plug in another, and I can go from DCC back to DC.
I have run locos (analog) with out decoders on the DCC lay out, and my Digitrax manual says to set the address of an anolog loco at "00".
If I were to go to DC mode with the lay out, I don't know what the address of the dual mode decoders would set to, as acording to the instructions, there is nothing I need to do to the locos to run on DC. Their default address for DCC is "03".
I don't know if JMRI reads anything, or even works with DC. I have it, but it's not actively connected to the lay out, I use it as a "stand-alone" for decoder work, sometimes.
I would think that a dual mode loco, placed on a DCC system, would read only the DCC signal, and an address change to "0", the loco probably wouldn't work. But I don't know that for sure.
Not sure if I contributed to an answer to your question, or just rambled on with some thoughts on it all.
Mike.
My You Tube
No, the decoder will not run on address 0, because as soon as you set it on the rails, it will see the DCC signal and be in DCC mode. At most, you might confuse it and have it take off at full speed, which is one of the reasons I disable DC operation in all my decoders.
There are few if any decoders made today that are not "dual mode" and will work on DC or DCC.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
SPSOT fanNow most DCC systems can become ‘DC’ systems by running with address one. When running with address 0 the layout becomes DC and the DCC equipped locomotives don’t run at al
i don't believe a DCC sytem "can become a DC system".
I don't believe the layout becomes DC when address 0 (or 1) is used.
A DCC system can control a single DC locomotive using address 0 by skewing the DCC signal to have a DC offset.
i doubt any decoder can be programmed with address 0. You would select loco address 0 in the controller to control a single DC loco and can continue to control other DCC equiped locos using their assigned addresses.
or am i confused (not the first time)?
greg - Philadelphia & Reading / Reading
Correct on all counts Greg.
That's exactly what it's doing - stretiching out the positive half oor the negative half of the 0 bits in the DCC signal (since the definition of a 1 bit is a bit time less than some value, and a zero is any bit time over some other value, with a dead space in the middle). Assuming a loco wired per NMRA DC standards, positive on engineer's side is forward, if the phase of the 0 bit on the right rail is longer than the phase of the 0 bit on the left rail, there is a net positive DC offset to the right rail and the loco moves forward.
You can;t remove the negative somponent completely, or DCC decoders will not work, and DCC decoder equipped locos would only be able to move in one directions. So the DC motor still sees an AC voltage, just one that is more positive in one direction or the other. Hence the buzzing Stopped, there is an equal amount of postive side and negative side, so the armature doesn;t turn, but just vibrated back and forth. No airflow, basically a short through the windings , Depending on the motor, it will burn up in seconds (a coreless motor) to hours (a big heavy massive open frame motor) if left sitting there.
It's OK for a quick test run (except coreless motos) but not really suitable for long term running. Decoders are cheap, just put a decoder in it. Also, by extending the 0 bits to make the DC offset, it increases the time required to transmit full DCC packets to decoder equipped locos, slowing the response to throttle, direction change, and function control.
My first DCC system was a MRC2K that had three trottles on a panel and two on a lanyard. Throttle one on the panel was for DCC or a DC loco by design.
On the Bachmann EZ Command you press button ten for a DC loco.
I gave the system away and bought a NCE Power Cab that does not run DC locos.
Running a DC loco on stretch zero is hard on the motor. I did temp measurments with an infrared scanner with the loco in a test stand some years ago. Motor brushes where they contact the armature get hotter when the motor is stopped and DCC still applied.
https://sites.google.com/site/markgurries/home/technical-discussions/dc-loco-on-dcc
Motor and light decoders are about $20.00 each depending on place you get them.
Many just do not want to seem to do any research but make assumptions. The Internet is loaded with info on this subject.
Rich
If you ever fall over in public, pick yourself up and say “sorry it’s been a while since I inhabited a body.” And just walk away.
SPSOT fan ... So today many DCC decoders are dual mode, meaning they run on but DC and DCC. Now most DCC systems can become ‘DC’ systems by running with address one.
...
So today many DCC decoders are dual mode, meaning they run on but DC and DCC. Now most DCC systems can become ‘DC’ systems by running with address one.
I have never seen this stated. I can't disagree, but I have yet to see a thread on this forum, or on any other, where this is discussed and/or taken as a given. I do know that entering Add "00" on my Digitrax DT400 throttles with a DB150 backing them will allow me to run DC-only locomotives. I only tried it once. That was plenty. No, really...
SPSOT fan When running with address 0 the layout becomes DC and the DCC equipped locomotives don’t run at all. What I’m wondering is what a dual mode decoder will do when you run address 0. Will it run as a DC loco, or will it ignore the DC signal and sit still doing nothing.
When running with address 0 the layout becomes DC and the DCC equipped locomotives don’t run at all. What I’m wondering is what a dual mode decoder will do when you run address 0. Will it run as a DC loco, or will it ignore the DC signal and sit still doing nothing.
I don't know about "0", but "00" is what we are asked to enter for an address if we want to run a strictly DC motor using the Digitrax systems. I don't think our systems support the address "0" or "00" for DCC operations because the default for all decoders that are NMRA compliant is "03". So, to address your question, a DCC-enabled decoder (set in CV29), should do nothing if you go to Add "0" or even "00" and attempt to get any powered decoders to do something...anything. They will power up, and do everything in neutral that you had them doing the last session (I'm pretty sure), but they should not turn lights off/on, sound the horn, turn the drive mechanism, consist, etc.
SPSOT fan Again just a curiosity, I don’t actually have a DCC system at the moment, though I do run on others systems.
Address one on a digitrax will not operate a DC loco, only 00 will. I have a DCC loco with address 01 and it runs on DCC. I'm not sure fan has his facts straight.
SPSOT fanNow most DCC systems can become ‘DC’ systems by running with address one. When running with address 0 the layout becomes DC and the DCC equipped locomotives don’t run at all.
A DCC system does not become DC. You can run a DC loco on DCC, as I stated, Digitrax says to set the address to "00".
But the system does not "change" into DC, and a DCC loco will run, as it should.
floridaflyer Address one on a digitrax will not operate a DC loco, only 00 will. I have a DCC loco with address 01 and it runs on DCC. I'm not sure fan has his facts straight.
It seams I have caused some confusion by accidently saying address one instead of address zero. I am aware that address zero is the one that runs DC locomotives (at least on a Digitrax system). Apologies for any confusion, the title has been corrected.
i thought it was your statement that the system/layout becomes DC and DCC equiped locos no longer work that was inaccurate.
A DCC decoder can work on a DC layout if enabled to operate in DC mode.
nope ..
the DCC system sends out packet information for DCC first, which the decoder can accept ..
it is only after this that it sends out the DC information, which if the DCC was valid, the decoder cannot accept .. simple ..
SPSOT fan When running with address 0 the layout becomes DC and the DCC equipped locomotives don’t run at all.
Wrong. On my Digitrax DCC DB150 with the DT400 throttle, I can run a loco without a decoder on one throttle, and a DCC loco on the other.
The DCC system does not become DC.
mbinsewi SPSOT fan When running with address 0 the layout becomes DC and the DCC equipped locomotives don’t run at all. Wrong. On my Digitrax DCC DB150 with the DT400 throttle, I can run a loco without a decoder on one throttle, and a DCC loco on the other. The DCC system does not become DC. Mike.
I had no idea you could run a DC locomotive and DCC locomotive at the same time! Are you sure that would work well? The speed the DC locomotive is running at would determine the maximun voltage either could recieve (as DC locos speed is controlled by the amount of colts applied to the track). So if the DC is running slowly the DCC locomotive could only run the same speed as the other DC engine or less. Correct me if I’m wrong, hope I make sense...
Tell ya what, when I get back here later this am, i'll set it up and try it. I have two throttles on the DT400, so I can control 2 seperate locos.
SPSOT fanthe speed the DC locomotive is running at would determine the maximun voltage either could recieve (as DC locos speed is controlled by the amount of colts applied to the track).
A DCC system changes the polarity of the track voltage to send packets. The average voltage is normally zero.
It can control a DC locomotive by stetching a positive or negative cycle so that the average voltage is not zero. While a DC locomotive may run, there's a lot of wasted AC current (the signalling for DCC decoders). Address 0 is used to control this DC value.
To operate a DC locomotive on a DCC system, a technique called "Zero Stretching" is used. Usually referred to as Address 0, an address isn't allowed in DCC. All the DCC locomotives will continue what they are doing, as they just ignore that packet.
Not all systems support Zero Stretching, as it not part of the DCC standard. For those that do, they simply alter a null packet by making one rail high (energized) for a longer period of time than it would normally be. The longer it is held high, the faster the DC motor will turn. Speed is determined not by voltage, but by time.
In a DCC system there are no AC voltages, nor are there positive and negative voltages. Just a sequence of high and low voltages on each rail, where one is energized (high) and the other is not (low). It is a digital system, after all.
While Rail A is high, the current flows through the motor to Rail B (at zero volts), and it turns, providing motion to the locomotive. In this case, Rail A is more positive than Rail B, so current flows from the energized Rail A to B and back to the source. To reverse direction, Rail B is held high, current flows from B to A and the motor turns in reverse. Rail B is now more positive than Rail A, so it will turn in reverse. Repeating this packet this fast enough keeps the motor turning.
When address 0 is in use, it generates a lot of packet traffic which can bog down system response. Even when set to speed step 0. To power a DC locomotive a lot of packets have to be sent at address 0.
Under normal DCC operation, the high frequency of the pulses on the rails cause the effective flux in the motor to cancel, as the direction of current flow changes rapidly. This can result in overheating, and some motors, such as coreless types, can be quickly damaged. The motor is also going to make some noise as the torque vector keeps reversing, causing the amature to vibrate.
Quote. In a DCC system there are no AC voltages, nor are there positive and negative voltages. Just a sequence of high and low voltages on each rail, where one is energized (high) and the other is not (low). It is a digital system, after all.
The full wave bridge rectifier in the decoder produces DC voltage because there is AC voltage. The filter caps smooths out the pulses like any rectifier circuit. Alternating current. Not what we see from our outlets in the house because of the digital data. Use your definition. I will use mine. Just a higher frequency power supply feeding more electronic circuits. The digital data is sent to the microprocessor.
Equal Positive and negative going pulses like AC has. I have used my Scope many times.
Before our power gets here the AC looks pretty bad also.
As I said I would do yesterday, today, I put an Athearn loco, no decoder, on the lay out, set it's address at 00, on the same track, I had a loco with a decoder, with address set at 03, and I had independant control of both locos.
Moving the throttle on one, did not affect the other, as it would be if I had 2 locos on the track, with seperate addresses.
I use an old Digitrax (2004) SEB set, with a DB150 and a DT400 throttle, which gives me seperate control of 2 locos, using 2 throttle knobs.
betamaxNot all systems support Zero Stretching, as it not part of the DCC standard.
stretched "0" bit is described in S-9.1
betamaxAll the DCC locomotives will continue what they are doing, as they just ignore that packet.
a stretched 0 bit is allowed in a valid packet. No need to "just ignore the packet". The width of a zero-bit half-cycle (time between polarity reversal) needs to be >= 100 usec, so it can be as long as necessary to establish the desired DC voltage.
betamaxIn a DCC system there are no AC voltages
betamaxthe direction of current flow changes rapidly.
while DCC is certainly not like the old Lionel AC transformers and is not sinusoidal, the fact is that current to each rail does alternate direction and is therefore AC.
betamaxnor are there positive and negative voltages.
when describing a voltage, it helps to define the reference that the voltage is between. (this is why high voltage line worker can touch 765,000 volt lines).
So while there is just 12V between the terminals of the booster supply, the H-bridge in the booster continually alternates the routing of current from the supply (+) to the rails such that with reference to one (either) rail, the voltage on the other rail is changing polarity from + (higher) to - (less than).
betamaxWhen address 0 is in use, it generates a lot of packet traffic which can bog down system response. Even when set to speed step 0. To power a DC locomotive a lot of packets have to be sent at address 0.
no additional packets (at least one) are sent. By stretching a zero-bit, one packet can be very long.
Wow, I had no idea you could run a DC loco and a DCC loco at the same time. My grandpa told me you couldn’t run DCC locos while you used address zero. Thanks for the info everyone, very informative!
Your Grandpa is telling your this? I guess your much, much younger than I thought you were. , or, lets say, had an idea of.
I'm 70, well entrenched in the grandpa age, kid....
mbinsewi Your Grandpa is telling your this? I guess your much, much younger than I thought you were. , or, lets say, had an idea of. I'm 70, well entrenched in the grandpa age, kid.... Mike.
Yes, I am very young (I’m in my latter teens). Your not the first person to tell me I seem older, I usually babble so much about trains people interpret from my knowledge of railroads (and a cornucopia of other random topics) that I’m much older! I’d assume my grandpa couldn’t understand how you could run both a DC engine and a DCC engine simultaneously. Some of the “Old Heads” seem to take forever to understand even the smallest things about electronics! Though even I didn’t get how you ran a DC loco on DCC until just now...
SPSOT fanSome of the “Old Heads” seem to take forever to understand even the smallest things about electronics!
Easy now.... ....there are things electronic about all of this that I may never get to the top of the learning curve, and it doesn't bother me at all!
I can handle CV's and run my trains. And if I get tired of all the DCC stuff (not), I can easy flip a switch, unplug my Digitrax, plug in my MRC 2500, and go back to DC.
As long as we're all haveing fun, getting along, helping each other, and doing just what your signature lines says..... It's all good.
But I digress,
mbinsewi Easy now.... ....there are things electronic about all of this that I may never get to the top of the learning curve, and it doesn't bother me at all!
Just joking around! I honestly don’t want to stick around on stereotypes of different generations. While I might quickly understand how to program CVs, that doesn’t mean I like it, sometimes I feel like people assume my generation are tech wizards, and while that mostly true, I detest CVs! Can’t wait till I learn how to use JMRI!
mbinsewi As long as we're all haveing fun, getting along, helping each other, and doing just what your signature lines says..... It's all good.
Can’t agree with you more (hey, we’re getting along!). No offense intended, just having fun!
I wrote that signature just in case something came off too harsh, glad someone caught on to it!
richg1998 Quote. In a DCC system there are no AC voltages, nor are there positive and negative voltages. Just a sequence of high and low voltages on each rail, where one is energized (high) and the other is not (low). It is a digital system, after all. The full wave bridge rectifier in the decoder produces DC voltage because there is AC voltage. The filter caps smooths out the pulses like any rectifier circuit. Alternating current. Not what we see from our outlets in the house because of the digital data. Use your definition. I will use mine. Just a higher frequency power supply feeding more electronic circuits. The digital data is sent to the microprocessor. Equal Positive and negative going pulses like AC has. I have used my Scope many times. Before our power gets here the AC looks pretty bad also. Rich
Your scope is fooling you. But it isn't lying either.
You clip the "common" (reference) lead (usually the one with the gator clip) to rail B , and clip the probe to rail A.
Rail A is energized to +14V, current flows from the probe through the scope and returns to B, as it should. The display shows a trace moving in the positive direction.
Then Rail A is held to "0" and B is energized to +14V. The probe is less positive than the common and current flows in reverse through the scope, resulting in a negative trending trace.
Since the booster only has two wires supplying power to it, it cannot create a negative voltage. One of those wires is the common, the other is the "positive". To create a +/- 14V output, you would need a 28V power supply to create those voltages internally, or an external 14V power supply with plus, minus and common wires.
Since decoders pick off the digital stream via a diode, how would that affect operation if a negative pulse is on the rails?
betamaxSince the booster only has two wires supplying power to it, it cannot create a negative voltage. One of those wires is the common, the other is the "positive". To create a +/- 14V output, you would need a 28V power supply to create those voltages internally, or an external 14V power supply with plus, minus and common wires.
I think what you're trying to say is that if you measured the voltage between either rail and the common (less positive wire providing DC power to the booster) you would measure (half) the supply voltage on one rail and zero volts on the other. You would never measure a negative voltage.
but the decoder in the locomotive only sees the voltages between the rails and it sees the polarity of that voltage changing -- the voltage on one rail alternately becoming larger and then lesser (minus) with respect to the other rail.
betamaxSince decoders pick off the digital stream via a diode, how would that affect operation if a negative pulse is on the rails?
are you suggesting that the DCC signal on the rails simply changes between zero and some positive voltage? Zero volts is not at the bottom of each waveform below, zero volts is the dotted line thru the middle. From S-9.1
The NMRA baseline digital command control signal consists of a stream of transitions between two equal voltage levels that have opposite polarity.