Doug, You say the problem is not that of the Zephyr. Fine. With the 1 K resistor in place, the Zephyr is looking at two electrical circuits in parallel across the track: the resistor and the decoder. The Zephyr will deliver a greater total current to the combination because the resistor and the decoder both draw current; but it cannot deliver any greater current than before to the decoder because the decoder's electrical characteristics have not been affected. I hear 'you' say this fix works, but it didn't for me and I cannot see how it can work. What am I missing?
Greater total current delivered to a decoder and resistor in parallel: True Same current to the decoder in either case: Also true Decoder's electrical characteristics unchanged: True again BUT... (there's alway a "but") The above depends on the Programmer recognizing the presence of a decoder in the first place. Lenz decoders (and others of similar design) simply do not draw enough current by themselves during the acknowledgement pulse for the programmer to recognize their presence, hence the "d nd". The added resistance in parallel with the decoder causes more current to be drawn from the programmer, which then recognizes the presence of a "decoder" allowing programming to proceede. See paragraph D in http://www.nmra.org/standards/DCC/standards_rps/rp923.html
Doug, According to your reference, if I'm reading it correctly, the presence of the decoder for Service Mode instructions (programming) is acknowledged by a pulse it returns to the programmer. I fail to see how a passive resistor across the track can generate that response or cause it to be generated. Doug, you say: But Mike Sheridan seems to disagree: Perhaps the cause of the problem does lie in wave shape and the 1K resistor somehow affects it, although I can't see how without a CRO. I have been wondering if, perhaps, my Zephyr power supply might have something to do with my inability to program the decoders. I was told (unsubstantiated) that the Zephyr should not have a supply greater than 15V AC fed into it. The supply I'm using is a transformer with both a 12V/3A and a 15V/3A tapping. Unloaded, the 12V winding produces 13V and is the supply for my Zephyr. Because the 15V winding produces an unloaded voltage of approximately 16.5V, I am not using it because of the warning to avoid excessive voltage. The only problem I have found using the 12V winding is that I cannot program the Bachmann decoders. Does anyone have any thoughts on using one or the other of the transformer windings? I could give the programming one last try. If it fails again, then it might be a case of opening the purse and fitting alternative decoders that I know will work.
I had a few minutes free just now and decided to look at Bachmann, USA, web site. Their discussion forum had the following two posts (the second post is a response to the first): It does seem that the 1 K resistor across the track is a recognised fix for the programming problem. I am now very interested to see what thoughts you have on the Zephyr power supply voltage before I give the 1 K fix another try.
My input was purely my way of understanding/explaining what seems to happen. I think doug has a much better knowledge of this matter than me and you should probably take his advice over mine
The acknowlegement "pulse" is not sourced by the decoder, but sinked by it, i.e., the decoder increases the current that it draws from the programmer for a short period. The programmer monitors the total current being drawn and sees this current pulse as a positive acknowlegement. The additional parallel resistance causes the total current drawn from the programmer to increase (hopefully) to a level that the programmer recognizes as an ACK.
Hello , here's my 2 cents worth, to save your self a lot of trouble getting 4 digit adressing enabled try this www.digitrax.com/kb/index.php?a=1267, it's a two page doc, please read both pages and do the 2 examples show. believe me it works. I have a Lenz system and using Digitrax decoders was a pain, but to program cv17, cv 18 and cv29 on most decoders try this method...
Oh yea someone new to DCC wil understand all the stuff here! http://www.nmra.org/standards/DCC/standards_rps/rp923.html This is the problem with this hobby, a new person to model railroading needs "Help" and right away they get overloaded with "information" they don't understand! What they need is someoe to show AND tell them how to fix or do something. I don't understand all that NMRA standerd stuff, But I can SHOW and tell someone how decoders are programed! If your thinking about getting into DCC, look at how the manual says how to program a decoder. If you have to " turn this knob and flip this switch and hit this button" kind of stuff, and use a hex decimal converter chart .....lol. If your local hobby shop only has one brand of DCC system there's going to "sell" you on that one. And people who bought thiers that way are going to say there's is the greatest too! The most expensive system is not the best for everyone. My point is not about which brand is the best, but what brand is right for you, the person considering changeing to DCC, and "helping" fellow model railroaders. Model Railroading.......IS fun.
I agree that the referenced standards are not for the uninitited, but GeeBee asked a specific technical question and obviously has enough electronics knowledge to understand the concepts involved. There not being a separate forum for those with more than average electronics acumen, I opted to answer on this one. The reference was offered to help explain how a 1 K resistor would help resolve the "d nd" issue with Lenz decoders. Most folks would not care why or how it would work, but as GeeBee asked, I felt an answer would not be out of place. I would not offer the same answer to someone who didn't care about the technical details (although my wife might disagree <G>), but try to tailor my responses to the specific questioner. If GeeBee said he had a frammitz that went "klunK" instead of 'klink", I would have tried to help un-klunk it using approriate terms and references (based on my limited frammitz expertise). Standards can be a tough read, but a little time invested (if you are interested) can shed a lot of light on why and how this stuff (oops, technical term, sorry) does what it does.
From the uninformed What I've leaned about the people on TRAINBOARD in two days: Some of them build some realy nice railroads. Some of them know a hundred times more than I do. Some of them will let you know it! None of them said hello and welcome aboard(except an adminstator). Same experence I had at the local model railroad club here in Tucson.......
Chubak_007, Thank you for the reference. That helps a lot. I looked at using CV17 and CV18 when I was programming my other locos and couldn't quite see how to do it. Mind you, I didn't spend too much time on it because I didn't really need it at the time. As for any in-depth explanations in trying to help me, I'm sorry you thought it might be information overload (I'm a retiree with a background in electronics). When I decided to post on the Forum, I wondered at the depth to which I might have discussed my problem and was pleased to find someone with technical knowledge who responded. Reference to the NMRA specs was not a problem, but I did not delve into them too far as they take time to digest. The recommended fix had not worked for me so I needed assurance from a knowledge of how it was supposed to work. Doug, Yes, I should have seen that. It has clarified somehat how this fix could work (there's still an element of doubt until it works for me) and is what the NMRA specs said in somewhat different terms: the motor current is increased for 60 ms (if I recall). Even now, I'm thinking that the programmer has been fooled into believing there is a decoder there, how then is it able to write to the decoder. Obviously, without returning to the NMRA specs, the write requirements are quite different from the decoder detection requirements and a 'high decoder impedance' is no longer a problem. All, So far, no-one has commented on the possibility that my Zephyr power supply voltage is too low. Thoughts anyone?
Hi Chewie! Hi GeeBee! I actually don't often look at total posts to see who is a newbie and who isn't, as anyone may have been on another board for years. In any event, welcome aboard guys!
Don't forget, to enable 4 digit engine # , cv17 ,cv18 AND cv 29 have to be programed, cv29 is a multi function cv, but it has to be programed to enable 4 digit engine #'s. I dont know anything about Digitrax system, but on my Lenz you have to use a programing track to write to cv17, 18 & 29 and others as well. If you want your engine to run short hood (or cab forward) enter 034 in CV29 if you want to run your trains on non-dcc railroads too enter 038 If you want engine to run long hood foward enter 035 in CV29, if you want to run engine on non-dcc railroads too enter 039 in cv29 Note: if after programing you're engine, it runs in wrong diretion, just swap : 038 for 039 or 034 for 035
I haven't been well these past couple of weeks so I haven't had a chance to have another try at programming my Bachmann locos until last night. I increased the input voltage to my Zephyr from 12 V AC to 15 V AC to see if the voltage was the reason for my previous unsuccessful programming attempts. Unfortunately, I have to report that I am still unable to change the loco addresses. Admittedly, I tried programming only one of the three locos with which I'm having trouble, and, as two of the locos are the same (different engine numbers), I assumed none of three would program. I have to be honest, at this point, I am still sceptical of the '1 K resistor across the track' fix, in spite of at least one person saying on this forum that it works. Thank you all for your input.
Note that when you program an "Ad4" with the Zephyr, not only are CVs 17 and 18 programmed, but CV29 is also updated (This of course assumes the Zephyr recognizes the presence of the decoder in the first place <G>). I have one Atlas loco with an OEM Lenz decoder and it required the 1K resistor to program. All my other decoders (so far) are Digitrax, and have presented no problem. BTW, My Z is powered by the furnished PS315 (15 VRMS AC). Hope you feel better.
The 1K resistor works. Doug explained why, I just use one when needed and it works. If you want to go to really dark territory with your Zephyr, You need to try "Blast Mode" Blast mode is an undocumented feature of the Zephyr that turns its programming outputs into a full current broadcast programmer. (Like the Empire Builder) To enable Blast mode programming close option switch 7 on the Zephyr. Remove all locos from the track. Place only the one you want to program on the program track and have at it. When finished, Change option switch 7 back to "thrown" Frankly though, the 1k ohm resistor is much easier. Martin Myers
Well it will work, but when you look at the recommanded supply by Digitrax it's 15V. Don't be fooled by the non-load voltage of a transformer, this is always higher than under load. Just add the Zephyr and have again a look at the output and it will be around 15V. As an indication, I use a Roco 16V/50VA transformer without any problem already more than 2 years to power my Zephyr. An other option is an universal notebook powersupply. These allow you to select the DC voltage you need (most time with 1V increases). These are small but powerfull. I use one (set at 15 VDC /5A) for the DCS100 Gino
