Hi,
To follow up my earlier post/thread, I've got a Digitrax zephyr coming in a couple of days to use as the power source for testing/maintenance of DCC locos.
Now I know that mixing DC and DCC is NOT recommended (especially by me) on a layout. But what about a 3 ft test track?
Said another way, if I have a test track hooked to the zephyr, and set a DC (no decoder whatsoever) on it, would it do nothing, operate as normal, or smoke and burn?
Thanks all, I'm sure others have tried this, but I have not.
ENJOY !
Mobilman44
Living in southeast Texas, formerly modeling the "postwar" Santa Fe and Illinois Central
Why not gaps the rails and isolate the DC test track from the rest of the layout just to be certain?
Rich
Alton Junction
The question is, what would happen if a DC loco was put on a test track that was connected to a dcc source?
The answer is, Don't Do It.
Mobilman44,
I don't know why, you would want, to test a DC, loco,with DCC, it will,hum and buzz. If you want to test a DC, loco, why not test it with a DC, power source? If you just want a test track, have both.DC and DCC, switched, with a DPDT, center off switch. You will only have one power source, working, at one time,that way.
Cheers,
Frank
Folks,
Please consider my question as one of curiousity ONLY - a "what if".
If someone on the Forum could give me a knowledgeable answer, it would be greatly appreciated.
This is a system-specific question, unfortunately. I have a Lenz system, and it supports running a DC engine as "Engine Zero," that is, select 0 as the locomotive ID on the throttle, and you can actually run the engine. You will note, however, that you are back to "running the track, " like in DC, and forward/reverse will revert to left-to-right vs. right-to-left, regardless of which way the DC engine is facing. (DCC engines will continue to work normally.) Auto-reversers will cause your DC engine to ping-pong, or maybe short.
Like I said, this is the way a Lenz system behaves. I think Digitrax works the same way, but I'm not sure, and I know that some systems don't support this option at all.
In any case, the DC engine will run slowly and will buzz loudly. There are anecdotal reports of DC motors actually burning out under these conditions, particularly if left idling for too long, but that's never happened to me.
It takes an iron man to play with a toy iron horse.
Mobilman,
I just gave you one, if you want to test a DC loco, for instance,before you convert it,to DCC, USE, DC, on your test track. You may also have,DCC, connected,to your test track,with a DPDT, center off switch, your test track will be controlled, by the switch,regarding,what system,you want to use.
mobilman, since you apparently did not like the responses that you already received, then take Mister Beasley's response as gospel truth. Sure, the Digitrax Zephyr has a feature that allows you to run non-DCC locos, at your own risk. But, yes, theoretically, your curiousity ONLY - "what if" question, can be answered in the affirmative.
It's very much a roll of the dice what happens. The general thing is that the "artificial DC" possible with some DCC systems (NCE does NOT support DC at all, for instance) is hard on motors.
That buzz that some mentioned will happen is the motor reacting to the quickly reversing polarity, which is biased in either F or R, depending on the direction of the loco. Some of the more sensitive -- and generally more expensive -- can motors can actually be destroyed by this effect.
An old BB Athearn? Probably not a problem. But if you aren't in the mood to research each and every loco you want to run this way, then you're rolling the dice on what effects DCC will have on it. And at most you can run ONE loco on DC at a time on a DCC layout on DC (assuming you're probably only going to run one at a time on the test track.) And you'd be well-advised not to let it sit idle on the layout under DCC power when not being used, as the buzzing effect continues even when not in motion -- it's simply balanced between F and R and just sits there, buzzing away.
Mike Lehman
Urbana, IL
mobilman44 Hi, To follow up my earlier post/thread, I've got a Digitrax zephyr coming in a couple of days to use as the power source for testing/maintenance of DCC locos. Now I know that mixing DC and DCC is NOT recommended (especially by me) on a layout. But what about a 3 ft test track? Said another way, if I have a test track hooked to the zephyr, and set a DC (no decoder whatsoever) on it, would it do nothing, operate as normal, or smoke and burn? Thanks all, I'm sure others have tried this, but I have not.
Below is a link about this for those who run a DC loco with no decoder with a controller that can run one DC only loco.
http://members.shaw.ca/sask.rail/dcc/DCC-waveforms/DCC_waveforms.html
The armature is slightly oscillating at the DCC frequency when the loco is not moving. Where the two brushes contact the armature segments, heat will develop. A few years ago I did some measurements with an infra red temperature scanner. The scanner could pick out this heat spot quite accurately. Bottom line, you don't want to do this. There is absolutely no reason to do this if the controller cannot run a DC only loco.
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.
Richg1998,
Thank you (and others that did likewise) for the meaningful answer. As I tried to explain earlier, I have no intention of doing this (run a DC motor with a DCC power source); I just wanted to know what would happen.
Thank you!
Actually a simple answer would have been, a DC motor will not run on AC and under certain conditions be damaged, burnt out.
I did figure it was curiosity. Obvious Man told me that very quickly.
Love some of the replies.
Everyone here should store the link and study the issue. I can see some here have no clue.
My experience is different, at the club we had a member, now deceased, that run all his loco on DCC address Zero. In fact he never had a loco with a decoder in it. He used to do that for 10 years without any ill effect or collateral damage to either his locos or the DCC system, of course he was not leaving locos idle on the layout. He became so good with running DC locos on a DCC system that he could even cross a reversing loop without stopping or creating a short. He could reverse direction on his throttle on the precise moment to avoid problems.
I think the wording that you can only run one DC loco on DCC is misleading. One can run as many locos as he wants as long as the amp. of the system support them. They will behave as they would on a DC layout, that is they will all go the the same speed and direction.
So my experience is you can run DC locos on a DCC layout as long as you run them and don't leave them idling on a powered track.
Jack W.
It is very obvious that you can run more than one DC only loco. It all depends on the capability of the controller which many are not aware of. Also, if the different locos run at different rates with the same voltage, Obvious Man says, don't do it.
Manufacturer's of a controller that can run a DC loco usually say, runs one loco for that reason so the answer is not that misleading.
Atlas installs a small resistor on their factory DC boards that doesn't affect anything when running on DC, but when the engine is placed on a DCC layout, it will shut down the system (presents a small short) preventing you from running it on DCC. This was done because they got tired of all the fried motors that were being sent in to be replaced.
You have to figure if Atlas does something like that, and some DCC systems now won't even allow address 0 to be accessed, there must must be a good reason to avoid doing it.
Mark.
¡ uʍop ǝpısdn sı ǝɹnʇɐuƃıs ʎɯ 'dlǝɥ
A long time ago, I learned the best thing about running a DC loco on your DCC layout:
It makes you want to install a decoder and do it the right way.
Rich,
I don't keep up with all the latest and greatest in DCC, in particular any extended DC capabilities. I'm an NCE guy and long ago just got used to the idea it's not a big deal to put a decoder in a loco -- any loco.
Perhaps my wording would be more accurate to say most DCC systems that do have DC capability can only control one DC loco, presuming you could of course run a consist of up to the amp capacity of the system. Splitting hairs there, I would say. If the union consider a lashup as one loco these days, I got no problem doing the same.
Now if there are DCC systems that control multiple DC locos in different directions and speeds, that's news to me. I presume you gotta know what to ask for and assume it's something of a premium to get such things over and above the cost of a regualr ol' DCC system. I'd have to ask WHY? though, because you can do that a whole lot easier and cheaper by using, ummm, DCC and decoders in each loco...
Pretty sure I wasn't trying to "mislead" anyone in any case.
The OP says that he is looking for a meaningful answer but it seems like a meaningless question.
If you set up a test track and connect it to a Digitrax Zephyr and set a non-decodered DC loco on the test track, will it do nothing, operate as normal, or smoke and burn?
If you set a shaving cream can near an open fire, will it explode? Maybe yes, maybe no.
But, why do it?
The clear consensus seems not to do it.
mobilman44Said another way, if I have a test track hooked to the zephyr[DCC], and set a DC (no decoder whatsoever) on it, would it do nothing, operate as normal, or smoke and burn?
I believe the Zephyr is one of the systems where you can call up channel zero and run it.
Why do you think you want to do this?
I thought my question was pretty straight forward and it truly was meaningful to me. I'm still a relative newbie to the world of DCC, and honestly didn't know what would happen if a DC loco was plugged into DCC power.
Even though I had/have no intention of doing this, I just don't see the problem in getting a straight answer.
However, comparing the placement of a can of shaving cream near a fire source with my question IS truly meaningless. That doesn't even rate "an apples & oranges" response.
But, I will tell you this, there isn't a person on this forum that wouldn't get a kick out of seeing what would happen if a can of shaving cream was put near a fire source!
All that being said, my question has been answered, and I thank those that took it seriously.
I think we all took your question seriously and gave a serious response in each case.
But when you came back and said that you only wanted knowledgeable and meaninful responses, that put those of us who had already responded on the defensive.
You had already indicated that you knew that mixing DC and DCC is not recommended. So, when you asked what would happen if you connected a test track directly to your Zephyr, and then set a DC loco on it, your question was met with a flurry of cautionary responses.
If you sit a DC loco on a track powered by the Zephyr, it will buzz. Leave it there for a few hours and you might burn out the motor. Select address 00 and run it back and forth a few times, and it will be fine. I've test run plenty of locos without decoders and never had a problem.
If you want to be fancy, pick up a cheap DC power pack, like an MRC 370. And a DPDT toggle switch with a center off. Center off is important. Radio Shack used to have a small DPDT knife switch, that would be even better, and add a cool factor. At any rateh, connect one side to the DC pack, one side to the Zephyr track output, and the center to the rails. Now you cna switch back and forth between DC and DCC power, with no chance of both being applied to the rails at the same time, which would be extremely bad and fry something, probably the Zephyr.
But unless you are working with coreless motors, a quick run back and forth on the test track using address 00 will not hurt the motor.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
rrinker If you want to be fancy, pick up a cheap DC power pack, like an MRC 370. And a DPDT toggle switch with a center off. Center off is important. Radio Shack used to have a small DPDT knife switch, that would be even better, and add a cool factor. At any rateh, connect one side to the DC pack, one side to the Zephyr track output, and the center to the rails. Now you cna switch back and forth between DC and DCC power, with no chance of both being applied to the rails at the same time, which would be extremely bad and fry something, probably the Zephyr.
Yes, that's the way to do dual power on the test track -- but only if it's completely separate from layout trackage that will have DCC on it.
IF you use a spur or section of other trackage that is part of the layout, then you really need additional protection from a double set of gaps separated by a length of track that is longer than your longest loco on which the power can be turned off.
Why?
If there is only a single set of gaps, the loco under test or a loco on the layout could bridge that gap with its wheel between DC and DCC. Then the smoke is released by the Zephyr...
It's best to have that intervening stretch of dead track or it'll be really easy for you to forget and then regret it.
That's the whole point of his buying the Zephyr - a completely isolated test track in his workshop, which is in a different room from his layout. No connection.
Some of our well intentioned brethren may have been confused by the question. I suspect they're focusing on the practical rather than the theoretical aspect of this question. Since there's no practical reason to do such a thing it probably registered as a "What the What the" moment.
What a given DCC system will do to a given DC loco depends on how much voltage at what frequency the motor sees. I don't know DCC systems and what they put out, but a loco will happily ignore all kinds of voltage at a high enough frequency, like above 25000 Hertz. That was the basis of the old "high frequency" lighting boosters hobbyists used to build. They put out 5-6v., but at 25K the "alternating" part of the current was too fast for the motor to notice. The light bulbs responded quite well. No mods (to rolling stock) were required as long as the booster was low power, but you'd loose the directional part of your lighting. You did have to provide a "choke" and diode protection for transistor power packs though.
Anyway, long story short, AC at 60 Hertz, bad news for DC motors, high freq. ok.
Lou
rrinker That's the whole point of his buying the Zephyr - a completely isolated test track in his workshop, which is in a different room from his layout. No connection. --Randy
Apologies, Randy. I saw the other thread, but didn't read it and the context wasn't quite that clear here. Thought I'd mention it just in case it was a potential issue for anyone reading it later.
The argument for or against always seems to come down to what system the person has - those with systems that do not support zero stretching, address 00 to run a DC loco, are all almost firmly in the "don;t ever try this' camp, and those of us that have systems that can do this generally are of the opinion that you can do it and it's just fine, though the running characteristics might not be what you'd want.
In all cases, just letting a non-decoder loco sit there and cook is definitely NOT good.
Other than slight variations in track voltage, all DCC systems put pretty much the exact same thing to the rails - after all, the waveform and data contained therein is part of the NMRA spec, and if one system put out a vastly different waveform, it would be hard to use any decoder with any system.
mobilman44Said another way, if I have a test track hooked to the zephyr, and set a DC (no decoder whatsoever) on it, would it do nothing, operate as normal, or smoke and burn?
A motor is an interesting device. superficially, it's just a lot of wire. But when it turns inside a magnetic field, a induced current is generated.
when an enternal current is pushed through a wire within a magnetic field, opposing magnetic fields create forces that turn the motor which in turn creats an opposing current. There is a balance between how fast the motor turns, producing an opposing current and the current being pushed through it by an external source and the mechanical load resisting its rotation. In other words, less current flows through it the faster it rotates inside a magnetic field. The greater the mechanical load, the slower it turns, less opposing current, more external current and more force.
but the bottom line is when a motor doesn't turn, it's really just wire and the wire resistance is the only thing limiting the current. this is not the same as a locomotive stopped with its wheel spinning.
since the track polarity of DCC is changing quickly (10 kHz), the motor never has a chance to rotate, looks like simple wire, maximum current flows, the motor gets hot and can become damaged. The buzzing heard is the motor vibrating due to the DCC frequency.
greg - Philadelphia & Reading / Reading
A person who keeps asking the same question over and over, just changing the wording, has already made up his mind he is just trying to find someone who will confirm it.
Dave
Lackawanna Route of the Phoebe Snow