I just don't want to have more than 10V on the track - better safe than sorry. How many times did you have problems with your PC? :angry: Bill Gates says it is 100% perfect... OK - what you are doing is controlling the voltage by using first 25% of the curve well, I would like to be able to use all 128 steps rather than first 29...:teeth: why don't you go directly to the guy in Austria - just pay into his account and he will send you the goodies I doubt if such a new stuff will already be available in US Chris
Tony (Zmon): While NCE (and all others) use pulse width modulation (PWM) to control the motor speed, it still sends the maximum track voltage (after the decoder's internal losses) during the "on" cycles. Due to duty cycles of the PWM, the motor effectively sees a lower amount of power but still the same maximum. In general, these won't hurt the motor, unless of course run at 100% duty cycle = 28/128 speed. While NCe does have runaway protection, it still could happen so a diode drop like Chris is doing gives that confidence that it aint goign to happen. Someone get me a schematic of the PowerCab an I am sure I can change a resistor to set it. Obviuously no pot like the ProCab. I'll check on the NCE forum.
Hi Guy's Its Friday, November 24th, and i will be hearding to SLC to taday to hand out with Chris my CE dealer. I plan to go into gtreater depth on this voltage issue today. We are planning a bit of meter testing and more detailed progarning on the PC. I'll report more when i learn/know more.. Tony B....
You're up early Jeff! I'm adding decoders to 3 more SD45's this morning before packing up for the show. What time are you heading down to Pleasanton?
:thumbs_up: I have sent an e-mail to NCE (no reply so far...) and asked the question on Yahoo group: http://groups.yahoo.com/group/NCE-DCC/message/30643 unfortunately, for some reason (maybe I was asking wrong question?) didn't seem to excite any response on the group thanks for your help Chris
Hi Tony, make sure your dealer knows of the special requirements of some of the Z Scale motors. In HO and N Scale, a motor might be able to take 12-16 volts without incident other than a bit of heat, but some of the Z Scale motors can burn out over 8 volts, and some over 10 volts. Some of our motors are coreless, and you need to disable the back EMF feature to avoid premature failure, as $50 a pop, and months lead time for a coreless motor is a real hassle. I have seen many runaways, on different NCE systems, probably on the order of a dozen a year. NCE is not immune to runaways. At .7volts drop per diode, 5 or 6 would drop 3.5 to 4 volts what your decoders will ever see, and be much safer for your low voltage motors. Your system will work just fine if you blow this mod off, it's just a bit riskier.
Rob, your picture seems to be in conflict with what is shown on: http://www.members.optusnet.com.au/nswmn/excess_voltage.htm here is the diagram I am referring to : would you care to comment on the differences? to avoid somebody simple (me :shade doing something stupid... thanks Chris ps btw this is a great page! and I recomend it to other DCC newbies like myself
There's no conflict, but they are dropping more voltage. It is not necessary to build the circuit on both legs of the track power, because all the current goes through all the diodes lined up in the direction of current, then when it reverses it goes through all the other diodes. That circuit drops 5.6v, and the one above it drops 3.5v. -Robert
thanks, better ask than be confused I wasn't sure whether you had to drop equally on both legs or dropping everything on one leg was OK As for the value and number of diodes - I have measured voltage with my RRampmeter before and after until I got the value I wanted. And that will depend on diodes used - voltage drop vary with type. Chris
Fellas i'm getting a bit confused... i worked on this yesterday for several hours, and i think all i did was confuse myself. Follow with me and tell me if i'm crazy. I strung several dioded together to build the voltage reducer and of cousre it worked in tests. But heres my problem. The mulit meter readings i took directly off the factory supplied NCE transformer was 13.55 volt DC. However the reading on my test track wothout the diode reducer installed was measured at 10volts AC. I understand from the dealer that DCC uses AC signals to feed the track and carry the DCC information, is the decoder then converting this AC sign wave into DC at the loco? What is the diode reducer going to do to the AC signal? I just am not getting this concept. If the output from the power cab is in AC, then what good is the diode reducer? On addition, i am a bit confused as to why there is need for diodes to be arrange both in a foward and backwards position on the hot leg of the track power. Is this because DCC uses feedback? or is this to compensate for reverse power opperation. Please help, i don't trust anyone not involved in Z, as otheres just don't understand what we Zer's are real all about. I agree with you all that i too do not want to melt down my lovely little locos, but thi AC vs DC busness is confusing me. HELP!!!!!!!! Tony B...
if you are asking, than you are clearly not :teeth: DC is not the way to measure - you need special meter for DCC, or way of correcting the reading for your multimeter. Read very good page on this (and many other DCC) subjects: http://www.members.optusnet.com.au/nswmn/meters.htm what do you use to measure? see above - this is simply confusing you roughly, that is my understanding (btw it is not sine wave, it is square) nothing (apart from dropping the track voltage) - and that is the whole point - if it was doing something, it would be causing problems. That is why we use very fast recovery diodes, so that the signal is distorted as little as possible so that you don't chop off half of the signal, one direction works on one half, the other direction works on the other half of the AC wave there is not such a thing as a "hot leg" - see below from Rob - you can have the dropper on either leg (or both, which is the way I have done it) Chris
I am pleased to report that we have "power up" in UK: I have used "ultra fast" diodes, with a total voltage drop of 3,7 V (or 0,46 V per diode) Track voltage showing on the RRampMeter is very safe 9,8 V The only problem with this is that for voltage that low, RRampMeter requires separate power supply(black/yellow cables on the picture) Chris
Chris; Eureka!!!! finally a moment of clairity!!!! I now understand it, i had read those other pages about meters and all it did was confuse me till now. Off to prevent problems... Thank you so much for being patient with me, and my lack of comprehension. Tony B...
Smaller Decoder Arrived Today... I spent the day at the GTE Train Show, running DCC no less, and when I got home, there was an unexpected package with 2 decoders inside. The Uhlenbrock 73400 Comfort Mini, and the CT Elektronik DCX74zD deocders, sent as free samples from Oliver Passmann of http://www.passmann.com I had a chance to install the Uhlenbrock 73400 inside an AZl SD70, and programming in paged mode with my NCE went quick and easy, and the decoder functions flawlessly. The CT Elektronik DCX74z deocder is even smaller, and it is a 4 function decoder I plan on using with a ditch light configured loco, so it will take me a few more days to get to this decoder. Here is the size comparison pictures:
Robert, I follow your lead and cancel my order with Tony, then I place a order with Tom's gadget. They still had three drop in decoders left. I also order the Procab. I hope have my dcc equipment next week.
GadgetToms has some fast shipping. I placed an order for a couple of drop-in decoders on Monday and they were here on Friday. With service like that they will keep my business.
Hello Chris, Robert and all; With the great advice from this thread as well as the multiple links to further info, I am happy to report that i was able to finally understand what was/is going on. I built, tested and ran the prescribed diode voltage reducer, and found that it worked as described. Further experimenting with the amp draw, and voltage tests dicussed in the meters link all worked and were very interesting. my GP35 drew 0.01 mA in forward and 0.02 mA in reverse. This leads me to beleive that the 2amp power supply with the power cab should be more that ample for a medium sized layout. Thanks again for the great advice. Tony B...
Quote from way back on page one... Could this capacitor be used by itself with regular DC? or would it take extra circuitry to work in the same manner? Also if the center is foam instead of regular carbon could the shape of the cap be re-worked to fit in tight spaces? For instance 8mm is about as wide as our motors so could we slightly flatten it down a bit to reduce the width one way?
Chris, have a look at this page! (if you haven't seen it already?): http://www.members.optusnet.com.au/nswmn1/USP.htm somewhere on the web I have also seen short films demonstrating this in action - right now I can't remember where... (old age is painful:angry Chris
