absolutely correct.
i simply said i have DCC locos that moved with PWM
and i explained there there a CV that enables such a feature
PWM may not be recognized as DCC, but sure can confuse the decoder in some way making it inoperable.
Who said âradioâ in this thread? Not me from what I recall.
Yes my throttles have 27 Mhz handheld radio controls, but the actual speed circuitry is a receiver base station hard wired to the track.
You mention low duty-cycle PWM possibly causing the processor to reset - the Aristo throttle is anything but low duty cycle - the pulse rate is 25 kHz. And is a very clean square wave pulse.
And it will not effectively control any dual mode decoder I have tried.
This high frequency PWM throttle provides speed control and slow speed very similar to DCC decoders - for locomotives without decodersâŚ
There is a wealth of technical info on the web about these throttles, I can direct you to it if you are interested.
Sheldon
i guess a poorly designed decoder can be confused. But a DCC signal is well defined as a sequence of pairs of polarity reversals that are nominall 100 or 58 usec in duration.
all packets require a preamble composed of a minimum # of ones and the packet has a error detection byte.
but despite all of this, i heard that some brands of decoders are prone to being reset.
no one.
S-9.2.2 Appendix-B lists it as a possible âPower Sourceâ
00000001 = Analog Power Conversion
00000010 = Radio
00000100 = Zero-1
00001000 = TRIX
00010000 = CTC 16 / Railcommand
00100000 = FMZ (Fleischmann)
Duty-cycle is not the frequency.
Duty-cycle refers to the % of time that the pulse is on during the PWM cycle. low duty-cycle (e.g. 10%) means the average DC voltage is low, 10% of the max voltageâŚ
and because the PWM is asymetric, it is not a square wave (i.e. 50% on and 50% off)
yes, DCC decoders drive the motor with a PWM pulse using an H-bridge
iâve provided links to many of these terms already
Here is specific info on the output signal of the Aristo throttle.
https://www.girr.org/girr/tips/tips3/pwc_tips.html#5471
Take a look at the second set of graphs regarding the ART-5471 Train Engineer.
The on/off time varies with the speed setting. The voltage is full on and then full off.
The on duration increases with the speed setting and the off time decreases.
There is considerably more info about the Train Engineer on this site:
https://www.girr.org/girr/tips/tips1/te_programming.html
And this one:
And again, it has confused every decoder I have ever tried to run with it. cheap Bachmann decoders, and fancy BLI decodersâŚ
And I have no interest in the detailed technical workings of DCC decoders, but I understand the original posters problem because I have seen it happen.
Sheldon
yes. it generates a convention PWM signal suitable for controlling a DC motor.
then why are you posting all these questions?
Because you seem to be challenging or questioning the cause of the OPâs problem, and the direct experiences of myself and others that demonstrates the shortcomings of many/most dual mode decoders in recognizing PWM as DC and/or recognizing/performing correctly with older poor quality DC signals.
Old power packs, before the 70âs had crappy waveforms, poor voltage regulation, the A/C transformers in them were cheap, with really bad regulation percentages. (open voltages 18-20, loaded voltages 12-14 at 1-2 amps), selenium rectifiers with no additional filtering. All things to drive any modern solid state circuit nuts.
The OP does not care one bit about all this science, he just wants his train to run.
The solution to his problem is to switch to DCC or get a newer, non PWM DC power pack with a transistor throttle circuit.
This question/problem was answered and solved 20 posts back, you just keep challenging the empirical evidence from me, the OP, the seller who used a cheap but modern DC power pack to run the loco successfully, and the experience and knowledge of others.
While I am by no means a DCC expert, I have been around DCC since its inception. I have and do operate with DCC on a regular basis on the layouts of a number of friends. I am well aware of their challenges and successes in learning/using DCC.
In my view and experience - using decoder equipped locos on ANY form of DC is a recipe for a poor quality modeling experience and an invitation to issues of all sorts.
As recently as a few months ago I picked up a Bachmann Consolidation that was DCC equipped with the Bachmann factory installed basic decoder (no sound).
On a 20 year old MRC transistor power pack (Railpower 1370 - basic budget pack) the loco ran poorly. Speed control was erratic, etc.
On my Aristo train engineer set to PWM it would not run, just hummed and sat there.
On my Aristo throttle set to âlinearâ (which puts a big capacitor across the PWM output) it ran better, but not perfect.
After I removed the decoder and replaced it with an 8 pin jumper plug, the loco runs perfectly on both of these throttles and has impressive slow speed and smoothness on the Aristo in PWM mode.
My next step was to remove the noise filter across the motor terminals from the factory circuit board in the loco which improved slow speed performance on the PWM throttle even more.
This too is a well known fact among many modelers that myself and others published on this an other forums more than 20 years ago.
Sheldon
2 Likes
iâm not. again, it seems like youâre fabricating an argument when there isnât one
again, i âabsolutelyâ agreed with you that not all decoders work the same. Again, i simply stated my experience, as you did,. But iâve tried to clarify several of your statements
You keep using that word âclarifyâ as if youâre actually trying to explain something better, when most of what youâre doing is seemingly willful obfuscation. I wish youâd stop that.
willfull?
obfuscation?
sounds like you also donât like being corrected when making rambling unsupported statements using techno-babble terms.
i often provide links to support these âclarificationsâ, for example NMRA standards or wikipedia pages providing better explanation.
if you disagree with something being posted, you should explain why you disagree.and provide supporting information
as an EE iâve had to diagnose many problems over my career. I learned not to jump to conclusions, to collect data, verify facts, to test my understanding of the problem to avoid making generalizations and assumptions to narrow the possible causes.
even âbizarreâ problems often have simple explanations or could just be a misunderstanding of how things work.
And there you go with âcorrectedâ, when most of what youâve contributed is either wrong or almost intentionally misguiding to non-technical people needing advice. Your adoption of personal insult further hints at some coping method rather than âclarifyingâ any sense of truth.
If you hadnât done this so often in other threads, I doubt Iâd be quite as upset about this one.
please provide an example along with a correction
huh?
where have i suggested that i feel insulted?
do you mean correct information when itâs not accurate?
seems you take offense, get upset when others donât take what you say as âgospelâ and provide contradicting information with links to accruate informatioin.
again, as an engineer trying to understand things correctly, completely and unambiguosly, i was always appreciative when someone âcorrectedâ me.
If you were an engineer trying to understand why a decoder that âautomaticallyâ discriminates between DC and Lena DCC is confused by some forms of PCM modulation, you would not respond with âCV 29 shuts off DC compatibilityâ. In the middle of asserting that PCM and DCC happily coexist, without discussing the particular cases under which it would, and then arguing with people whose firsthand experience indicates otherwise.
in particular, nothing youâve been saying is particularly relevant to the OPâs original problem. Describe to him exactly what setting CV 29 does, and how it would make his engine run smoothly on MRC Ampack-waveform DC. Indicate with diagrams, and a parts list, how to build a large LC filter on his variable-DC output to get actual, low-ripple DC from his rheostatjcally-controlled output. Nitpicking that a pot used as a rheostat is variable resistance, which is singingly obvious to us, does not contribute to the OPâs perception of his control difficulty.
seems like youâre reading more into my responses that what i posted (please quote)
i just said that i turned that bit off so that my DCC locos didnât respond to the PWM i used to test DC locos. (i wasnât trying to run DCC locos with PCM. I just observed that they did)
where did I say DCC and PCM "happliy coexist. I simply pointed out that thereâs a feature in the spec. I also pointed out that it is unclear what the âPower Sourcesâ listed in Appendix-B were
nothing?
isnât OP is trying to use the above featrure.
iâve pointed out that thereâs a CV bit for enabling the featrure which may be relavent
i posted a link to the spec for that CV. i only said that i found it confusing.
did you?
i donât know what the OPs technical abilities are
but now that you asked, mayeb the OP should try using these DC motor controllers from ebay:
- PWM controller
- looks like a regulated DC controller
where did i make such a suggestion
please stop putting words in my mouth
What is there to clarify? I did not do exhaustive doctorate level research on the conditions I have observed.
The important facts include:
The locomotive does not work with the 1960/70âs power pack the OP has. (I asked right away what kind of power pack)
The locomotive does run fine on the inexpensive but more modern Bachmann power pack that the seller used.
My personal facts:
I have purchased more than 50 DCC locomotives of various brands over the last 25 years, most advertised as dual mode decoders and not one has operated successfully on the form of full voltage pulse width modulated speed control from my Aristo Train Engineer throttles.
I am unclear from your statements if you have ever operated a dual mode decoder loco on any form of DC, including any form of PWM.
I have also seen/tried operating dual mode decoders on various older MRC power packs with no satisfactory results - again this is why I asked the OP âwhat kind of power packâ.
I have a basic understanding of why this problem exists, I donât need a college dissertation on it. The OP only needs a solution, without clouding the issue or challenges to the known solution that will not help him.
And again, just my opinion based on my 56 years of experience and 25 years of some exposure to DCC.
If you want sound go DCC and be done with it.
If not, if you donât want DCC, take the decoders out like I do.
Sheldon
3 Likes
The 200Hz PWM controller is guaranteed to not work and to be noisy with DC powered locos.
That is why the Aristo Train Engineer works at 25 kHzâŚ
Sheldon
Thanks for all the practical suggestions that folks have offered to help troubleshoot the problem. I have a plan to move forward so lets give this a rest. Iâm going to play guitar for a while. Hope you all have a great rest of your day.
1 Like
Well, that was a bunch of useless blah, blah, technical mumbo jumbo
Anyhow, if my internet search was proper it appears that the loco has a SoundValue decoder supplied by SoundTrax.
From what I read, the flashing tender light could possibly be an error code.
Some of that is discussed here:
Good luck.
Oh, and a call to Soundtrax could possibly be of some value.
He does not need a better âPWM controllerâ for his problem; he either needs low-ripple, non-interrupted DC to prevent confusing his built-to-a-price decoder, or specific instructions on how to set CV29 on a Bachmann decoder correctly. Claiming you pointed him to a link to CV29 documentation is disingenuously useless if he knows little or nothing about DCC â you might as well send him tech specs to a PWM controller and tell him to e-mail Mouser to send him a parts spec.
One of the points of applying a large LC filter to the output of his MRC control is that it removes any potential source of âinterferenceâ with a device looking for DCC modulation at startup. Iâm not enough of a ham to tell him where to find appropriately large inductors and capacitors cheaply, and Iâd defer to a degreeâd EE as to the correct values to use on a variable-DC output (from, say, 0 to 22V nominal, which rules out many combinations of supercaps).
I have seen suggestions that he open the locomotive and substitute a jumper board to allow direct DC motor and lighting control. I have no direct idea how he should do this, other than it would let him operate with his existing MRC or with the Tech II he plans to get, and then simply replace the decoder if he âgoes DCCâ in future.
then i guess most decoders donât run at the frequency. i thought most operate above the human hearing range of ~20kHz. i think you would hear 200 Hz.
who said he did
i assume he would use DCC if he had a DCC controller that he could program the CV with. DC is enabled by default on most decoders
that sounds like a good option
iâve seen flashing headlight when i tried using an Arduino to generate DCC that wasnât quite right. the polarity reversals were outside the 100/58 usec tolerances (i.e. corrupted DCC packets)