ATLANTIC CENTRAL gregc MRC tech 2500 is PWM http://cs.trains.com/mrr/f/744/p/269380/3053917.aspx#3056485 (i put the above link between <url> </url> tags, replace < with [) Well, by that description it is cheap and dirty 60Hz PWM at best. I have not scoped any of them, I am only going by their own description. In any case, the OP now understands that his comparison was not valid in the first place. And I have no dog in this fight since I am happy with my Aristo PWM throttles which have a high frequency PWM output similar to a DCC decoder and work great. I may have a Tech 2 2500 laying around here, a friend gave me a bunch of power packs when he converted to DCC years ago. If I am correct, my recollection of its performance is not anywhere near as good as the Aristo Train Engineer, which of course is also wireless radio. Sheldon
gregc MRC tech 2500 is PWM http://cs.trains.com/mrr/f/744/p/269380/3053917.aspx#3056485 (i put the above link between <url> </url> tags, replace < with [)
MRC tech 2500
is PWM
http://cs.trains.com/mrr/f/744/p/269380/3053917.aspx#3056485
(i put the above link between <url> </url> tags, replace < with [)
Well, by that description it is cheap and dirty 60Hz PWM at best.
I have not scoped any of them, I am only going by their own description.
In any case, the OP now understands that his comparison was not valid in the first place.
And I have no dog in this fight since I am happy with my Aristo PWM throttles which have a high frequency PWM output similar to a DCC decoder and work great.
I may have a Tech 2 2500 laying around here, a friend gave me a bunch of power packs when he converted to DCC years ago. If I am correct, my recollection of its performance is not anywhere near as good as the Aristo Train Engineer, which of course is also wireless radio.
Sheldon
"Older" is not particularly descriptive. The earliest DCC decoders often did not support running on DC. At all. For example, early Atlas Gold DCC locos had a jumper plug on the board, in one position, it was DCC, in the other, DC. Because the decoder couldn't run on DC. Early sound decoders also did not work on DC. At all.
Even with DCC decoders that CAN run on DC - they can be configured to not respond to DC.
And DCC motor only decoders that work on DC behave completely differently than DCC+Sound decoders that will work on DC, for reasons previously explained with regards to voltage and making the sounds work.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
ATLANTIC CENTRAL I will suggest again, just go DCC or stay DC, being on the fence is full of pitfalls.
+1
Either DCC do yes or DCC do no or else squished, just like grape.
-Kevin
Living the dream.
Lastspikemike ATLANTIC CENTRAL A few more thoughts: I think MRC knows that TRUE high frequency PWM will not work with dual mode DCC decoders. Their market for DC power packs requires DCC dual mode decoder compatiblitly. They are trying to get the best DC control they can without loosing that market segment. If you put a dual mode decoder DCC loco on my layout with my Aristo throttles, one of two things happen, it has two speeds, full speed on and off, OR it sits there and buzzes, because the decoder is confused by the high frequency pulse of good PWM. Testing of more than a dozen different DCC locos has always had one of those two results. MRC has made it clear that the "DC to DCC transitional market" is important to them, with their dual mode packs that cost as much as DCC starter systems....... Sheldon Hmm. That's very interesting. My Tech 7 powerpacks seem to operate exactiy that way. The Tech 6 "dual mode" on the other hand does not seem to. Current DCC decoders run the same in DC or DCC on the Tech 6 but older ones definitely do not. Mind you the whole point of the Tech 6 is you don't need to have the capability to run DCC in DC mode.
ATLANTIC CENTRAL A few more thoughts: I think MRC knows that TRUE high frequency PWM will not work with dual mode DCC decoders. Their market for DC power packs requires DCC dual mode decoder compatiblitly. They are trying to get the best DC control they can without loosing that market segment. If you put a dual mode decoder DCC loco on my layout with my Aristo throttles, one of two things happen, it has two speeds, full speed on and off, OR it sits there and buzzes, because the decoder is confused by the high frequency pulse of good PWM. Testing of more than a dozen different DCC locos has always had one of those two results. MRC has made it clear that the "DC to DCC transitional market" is important to them, with their dual mode packs that cost as much as DCC starter systems....... Sheldon
A few more thoughts:
I think MRC knows that TRUE high frequency PWM will not work with dual mode DCC decoders.
Their market for DC power packs requires DCC dual mode decoder compatiblitly.
They are trying to get the best DC control they can without loosing that market segment.
If you put a dual mode decoder DCC loco on my layout with my Aristo throttles, one of two things happen, it has two speeds, full speed on and off, OR it sits there and buzzes, because the decoder is confused by the high frequency pulse of good PWM. Testing of more than a dozen different DCC locos has always had one of those two results.
MRC has made it clear that the "DC to DCC transitional market" is important to them, with their dual mode packs that cost as much as DCC starter systems.......
Hmm. That's very interesting. My Tech 7 powerpacks seem to operate exactiy that way. The Tech 6 "dual mode" on the other hand does not seem to. Current DCC decoders run the same in DC or DCC on the Tech 6 but older ones definitely do not. Mind you the whole point of the Tech 6 is you don't need to have the capability to run DCC in DC mode.
You keep saying this about how "current" or newer decoders work. But have you exhuastively tested all the decoders currently on the market?
And so what if the new ones do work better on DC than the older ones? People are just supposed to throw away all their older DCC locos and buy newer locos so they can run them on DC?
No offense to ANYONE, but I will suggest again, just go DCC or stay DC, being on the fence is full of pitfalls.
I know how the Tech 6 works........
And I know how dual mode decoders do not work on true high frequency PWM DC.
I have 140 locos, and no decoders..........
All my trains run fine. I run 3-4 unit diesel lashups, I double and triple head steam locos of different wheel arrangements from different brands. My headlights come on before my trains move, and I walk around with a wireless throttle in my hand - all without DCC.
I run 4 trains on a double track mainline, and I don't flip any block toggles........
I seriously considered DCC several times, rejected it every time. But for most peoples needs, DCC is the best choice.
rrinker Remember the Tech II 2500 is some 40+ years old. I got my 1500 for my N scale layout around 1978. There was no DCC dual mode to worry about - it was more MRC building to a price the market could support. You can see it in the disassembly shots, and other brands aren't any better. They aren't exactly finely crafted devices with lots of attention to detail. But people weren't going to pay $100+ for a single throttle power pack. --Randy
Remember the Tech II 2500 is some 40+ years old. I got my 1500 for my N scale layout around 1978. There was no DCC dual mode to worry about - it was more MRC building to a price the market could support. You can see it in the disassembly shots, and other brands aren't any better. They aren't exactly finely crafted devices with lots of attention to detail. But people weren't going to pay $100+ for a single throttle power pack.
I should have been more clear, I was refering to the fact that MRC has yet to build a true high frequency PWM throttle.
SeeYou190 This is hllarious... We had two seperated conversations, both spiralling down in this thread. Tom asked us to only talk about one of them. Then we started talking about Ernst Gears, clickable links, and Tech II 2500 power packs. At least the conversation has become civil and not full of bad information. -Kevin
This is hllarious...
We had two seperated conversations, both spiralling down in this thread.
Tom asked us to only talk about one of them.
Then we started talking about Ernst Gears, clickable links, and Tech II 2500 power packs.
At least the conversation has become civil and not full of bad information.
Well agreed, but the Tech 2 converstation relates directly to the OP's question, since that is the DC power pack he is using to formulate the comparison he asked about.
Ernst seems to no longer be around, Walthers lists them but it's all out of stock. Searches find nothing but some forum posts of people complaining they were loud - they just didn't installt hem correctly. I had an S12 I put a set in. The trick was to use tooth polish, like Pearl Drops, to lap the gears, run it a while in both directions, then take it all apart and clean it out, then reassemble with proper lubricant. Witht he worms off, my loco would roll on smooth surfaces rather than slide, even with all those extra gears. Standard Athearn BB motor tune up technics quieted the motor. That thing could pull anything I tried, and ran at a nice realistic top speed, and quieter than it came out fo the box. Having the motor and flywheel RPM higher for a given speed of the loco makes it more likely to coast over dead spots, and allowing a higher voltage for a given ground speed makes for smoother starts, so there definitely advantages to gearing down fast running locos.
But if the loco already runs at realistic speeds, the only way to improve performance is to reduce as much as possible any friction in the drive line, and use a power source most conducive to getting the motor to turn over as slow as possible while not stalling.
gregc tstage Let's make that link clickable: how?
tstage Let's make that link clickable:
how?
Greg,
I copied your URL link, pasted and opened it in a new tab in my browser (Firefox), copied that URL link (again), then created the link as you described. I've found that copying the URL directly from someone else's post and creating a link from that doesn't work on this forum. So, I copy & paste it in a new tab, copy it from that, then insert it between bracketed urls in the text body of my post.
Tom
https://tstage9.wixsite.com/nyc-modeling
Time...It marches on...without ever turning around to see if anyone is even keeping in step.
Rich
Alton Junction
tstageLet's make that link clickable:
greg - Philadelphia & Reading / Reading
gregcMRC tech 2500 is PWM http://cs.trains.com/mrr/f/744/p/269380/3053917.aspx#3056485
Let's make that link clickable:
rrebell I guess the only way is if I used the exact same engine. That will not happen and after futher testing of just DCC engines, I have two exact ones of the same engine, one runs twice as good as the other and I can find no diferences that would make it so.
I guess the only way is if I used the exact same engine. That will not happen and after futher testing of just DCC engines, I have two exact ones of the same engine, one runs twice as good as the other and I can find no diferences that would make it so.
DCC locos are subject to all the same mechanical variations that make any two DC locos run different. PLUS, they have those pesky decoders that can have different CV settings.
In theory two new out of the box identical DCC locos should have the same CV settings and run the same.........
But manufacturers do sometimes change decoder suppliers, change base line CV settings, settings get changed by shop owners before the sale, or with used locos you have no idea who has reset CV settings..........
So until you check that, again all comparisons are worthless.
SeeYou190 ATLANTIC CENTRAL Correct, the Tech 2 does not use PWM, I don't think MRC has ever built a PWM throttle of any kind I was under the impression that the MRC Tech II 2500 produced a PWM output. CMStPnP Just curious, long ago in the 1980's I think they used to sell regearing kits so you could change the gearing ratio on some locomotives to get them to run slower or smoother. Basically by changing the gearing ratio the engine drive spins faster but the wheels move slower. Do they still sell those kits? Just curious. They come up on eBay fairly frequently. Usually the sell in the $5.00-$10.00 range at auction, but people sell them at $25.00 and up for Buy It Now. I only installed one Earnst Super-Gearing kit is an Athearn SW switcher. Then it was just a little noisier and much slower. It was a good improvement for a switcher. -Kevin
ATLANTIC CENTRAL Correct, the Tech 2 does not use PWM, I don't think MRC has ever built a PWM throttle of any kind
I was under the impression that the MRC Tech II 2500 produced a PWM output.
CMStPnP Just curious, long ago in the 1980's I think they used to sell regearing kits so you could change the gearing ratio on some locomotives to get them to run slower or smoother. Basically by changing the gearing ratio the engine drive spins faster but the wheels move slower. Do they still sell those kits? Just curious.
They come up on eBay fairly frequently. Usually the sell in the $5.00-$10.00 range at auction, but people sell them at $25.00 and up for Buy It Now.
I only installed one Earnst Super-Gearing kit is an Athearn SW switcher. Then it was just a little noisier and much slower. It was a good improvement for a switcher.
I don't think so. It is not a true full voltage pulse width modulated throttle.
With true PWM, all voltages applied to the track are full voltage square wave pulses, which start out widely spaced and become longer in duration to increase speed.
The MRC instructions say the pulse rate is 60Hz, and that the pulses disapear as speed increases as I described above.
That is not PWM, which uses much higher frequencies (more rapid pulses).
Example, with my Aristo throttles, the headlights of DC locomotives light up at nearly full brightness before the loco even starts to move, because of the full voltage high frequency nature of the pulses.
PWM is a long time well known way to control DC motors, if they were using it, they would call it that, rather than making up their own new name, "proprtional tracking control", which by description is just old fashioned half wave pulse power that turns off automaticly around half throttle.
ATLANTIC CENTRALCorrect, the Tech 2 does not use PWM, I don't think MRC has ever built a PWM throttle of any kind
CMStPnPJust curious, long ago in the 1980's I think they used to sell regearing kits so you could change the gearing ratio on some locomotives to get them to run slower or smoother. Basically by changing the gearing ratio the engine drive spins faster but the wheels move slower. Do they still sell those kits? Just curious.
Overmod If I remember correctly, the original Helix Humper was a regearing kit for things like steam locomotives with a worm on the motor shaft and a bull gear on a driver axle. The kit used a humongously larger-diameter multiple-start worm and a bracket arrangement that tilted the replacement motor up to fit.
If I remember correctly, the original Helix Humper was a regearing kit for things like steam locomotives with a worm on the motor shaft and a bull gear on a driver axle. The kit used a humongously larger-diameter multiple-start worm and a bracket arrangement that tilted the replacement motor up to fit.
Yes, and they also sold can motor kits for Athearn locos. In my RDC shown above, the motor came from Helix Humper, the gear kit from Ernst.
If I remember correctly, the original Helix Humper was a regearing kit for things like steam locomotives with a worm on the motor shaft and a bull gear on a driver axle. The kit used a humongously larger-diameter multiple-start worm and a bracket arrangement that tilted the replacement motor up to fit.Could that be the 'kit' you were remembering?
gmpullman CMStPnP Do they still sell those kits? Just curious. We almost lost them but Northwest Shortline is the go-to source for drive-line parts. https://nwsl.com/collections/regearing-repower-kits I had contemplated getting their gear set to increase the speed of the old Life-Like Proto 1000 RDC but in the meantime Rapido produced some "quicker" designs. Regards, Ed
CMStPnP Do they still sell those kits? Just curious.
We almost lost them but Northwest Shortline is the go-to source for drive-line parts.
https://nwsl.com/collections/regearing-repower-kits
I had contemplated getting their gear set to increase the speed of the old Life-Like Proto 1000 RDC but in the meantime Rapido produced some "quicker" designs.
Regards, Ed
I think he might be refering to the old Ernst kits to regear various Athearn Blue Box locos?
They also offered a gear conversion for the Athearn RDC.
I try to avoid 80' long passenger equipment, so I like Athearn's selectively compressed RDC.
CMStPnPDo they still sell those kits? Just curious.
Just curious, long ago in the 1980's I think they used to sell regearing kits so you could change the gearing ratio on some locomotives to get them to run slower or smoother. Basically by changing the gearing ratio the engine drive spins faster but the wheels move slower. Do they still sell those kits? Just curious.
Overmod ATLANTIC CENTRAL It is not clear to me that the two locos are same make and model? It was my understanding that he took pains to get the two locomotives as 'alike' as possible, other than one being DCC with decoder and the other 'pure DC' to the motor. He also specified both his DC and DCC control and power equipment, although I don't know enough about the specific DCC equipment to tell what difference that might make to his 'decoded' low-speed 'fidelity' or responsiveness. Here is the manual for the Tech 2 2500. My understanding is that this does speed (and braking and momentum simulation) entirely in the voltage domain, but with 'pulsed' additional voltage boost (at nominal 60Hz fixed frequency) at times. (I am amused that in the power domain this appears to correspond to a kind of 'amplitude modulation' to get a load moving...) It does not mention anything about PWM being used to produce either the voltage control or the additional-voltage pulses. The slow-speed performance from a good modern decoder will have some additional control both over the delivered PWM 'voltage control' and by reading the back EMF from the motor. I would not at all be surprised to find the slow-speed regulation 'better' on DCC for a given drivetrain BUT I'd also expect that the best smoothness vs. performance might require quite a bit of tweaking and optimization, some with poorly or inadequately documented CV settings that may influence each other.
ATLANTIC CENTRAL It is not clear to me that the two locos are same make and model?
It was my understanding that he took pains to get the two locomotives as 'alike' as possible, other than one being DCC with decoder and the other 'pure DC' to the motor.
He also specified both his DC and DCC control and power equipment, although I don't know enough about the specific DCC equipment to tell what difference that might make to his 'decoded' low-speed 'fidelity' or responsiveness.
Here is the manual for the Tech 2 2500. My understanding is that this does speed (and braking and momentum simulation) entirely in the voltage domain, but with 'pulsed' additional voltage boost (at nominal 60Hz fixed frequency) at times. (I am amused that in the power domain this appears to correspond to a kind of 'amplitude modulation' to get a load moving...) It does not mention anything about PWM being used to produce either the voltage control or the additional-voltage pulses.
The slow-speed performance from a good modern decoder will have some additional control both over the delivered PWM 'voltage control' and by reading the back EMF from the motor. I would not at all be surprised to find the slow-speed regulation 'better' on DCC for a given drivetrain BUT I'd also expect that the best smoothness vs. performance might require quite a bit of tweaking and optimization, some with poorly or inadequately documented CV settings that may influence each other.
Correct, the Tech 2 does not use PWM, I don't think MRC has ever built a PWM throttle of any kind.
Most of their products in recent decades have been simple transistor throttles, with various features, braking, momentum, pulse power.
Sometimes the pulse power, typically just half wave DC, fades into full DC as the voltage increases.
I long ago stopped following the details of each of their products.
Yes, many/most decoders now use BEMF to improve motor smoothness. It is the reason some locos perform slightly better with DCC than they do on the Aristo or other DC PWM throttles.
I have found these differences so small, and often in consistant, so as to not be important to me.
I have also learned variations in factory "DCC ready" light boards can effect DC performance. Sometimes the light boards are a plus, sometimes not.
And locos like Bachmann have noise circuits that must be defeated for best performance, DC or DCC.
Just my view, but to restate - any minor difference between the performance of any given loco with no decoder on a top quality PWM throttle and that same loco with a premium DCC decoder, is so small as to not be consistantly measurable or of any practical importance in actually operating a layout.
That is the goal after all, to run trains.
Having no interest in onboard sound, I am very happy with DC control.
tstagehow 'bout someone start a separate thread on the former.
Since we have two separate conversations traveling on parallel tracks and the discussion on explaining DCC in "non-lawyer" terms keeps pushing the OP's thread to a siding, how 'bout someone start a separate thread on the former. So, from this point forward all posts will be relevant to rrebell's question on his DC/DCC locomotive experiment and any competing conversations will be relegated to the scrap yard - Thanks.
Overmod Lastspikemike The DCC signal varies in frequency. That's how it works. That's not at all how it works.
Lastspikemike The DCC signal varies in frequency. That's how it works.
That's not at all how it works.
ATLANTIC CENTRALIt is not clear to me that the two locos are same make and model?
Here is the PDF manual for the Tech 2 2500:
https://www.modelrectifier.com/v/vspfiles/resources/dc-ac/Tech%202%202500%20AF130.pdf
My understanding is that this does speed (and braking and momentum simulation) entirely in the voltage domain, but with 'pulsed' additional voltage boost (at nominal 60Hz fixed frequency) at times. (I am amused that in the power domain this appears to correspond to a kind of 'amplitude modulation' to get a load moving...) It does not mention anything about PWM being used to produce either the voltage control or the additional-voltage pulses.