End Decoder Problems With A Snubber (243)
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- čas přidán 3. 07. 2024
- Whenever folks hear or see the word "Snubber" they seem to assume it is some semi-magical device that can do something special, although they usually have no idea what. So in this video we'll take a look at what a snubber is, what it can do, how it works, how to know whether you need one, where you can get them, and where to put them. Plus I'll even show you how to make your own for mere pennies. So let's get started!
Here is a link to Mark Gurries website. Beware as it can get a little deep in places but he does provide a lot of information for free!
sites.google.com/site/markgur...
And here are the parts for the RC filter with their All Electronics part numbers. Remember that just about any source of electronic parts will do, I just like All Electronics.
Resistor 100 ohm 1/2 watt (1 watt for O scale and larger) #293-100
Ceramic disc capacitor 0.1 uF 50VDC #104D50 - Jak na to + styl
I was wondering about the clock too, I was scared to ask. lol love the videos Larry. Thanks for all the information on DCC.
Thank you for posting a very informative video. I am having problems with certain locos on my layout not responding to commands and it mainly happens to be at the far ends of my room sized layout. I was thinking of using the NCE snubbers but as you've shown that a simple resistor and capacitor can be used, I'll be off to the electronics store tomorrow to get some and hopefully solve this problem!
Besides being a model railroader, I am also an amateur radio operator, so this video rang bells in my head. The problems discussed in this video are part of electromagnetics called "transmission line theory." The DCC feed lines and the tracks form a group of transmission lines on the layout. Even without sources of interference the lengths of the lines themselves can distort the DCC signals. Thanks Larry for discussing solutions that help to mitigate these problems. Also, I really like the scope captures. I'll have to try hooking up my scope to the track and see what the signals look like.
Absolutely right! The correct term for this circuit element is a _terminator,_ not filter or snubber. The issue is that an open ended transmission line reflects signals, and the very fast DCC edge signals when reflected add to the incoming signal producing those narrow spikes seen on the oscilloscope trace. Terminating the line with a capacitively coupled 100 ohm resistor (equal to the approximate characteristic impedance of the transmission line), prevents these reflections and eliminates the spikes. I need to be convinced that you need as much as 0.1uF though, it may work with 0.01uF with less loss, but I need to experiment to be sure.
Snubbers are used for supressing voltage and current spikes resulting from switching - there is no switching here causing the spikes so I suspect Snubber is a customer friendly term for the end result. Rather than matching the track characteristic impedance, another way to look at the same thing could be that it is a filter designed to attenuate higher frequency components which comprise the spike. As you will know, the cutoff frequency of a filter using the given components is 16kHz at the -3dB points (ie power of the waveform on the track would be attenuated by half if the waveform is at 16kHz). The DCC signal is at about 8kHz fundamental and so would be slightly rounded off (perhaps very rounded off) as the higher harmonics are attenuated, but the spike would be completely removed as it is about 1/50 duration of a single cycle of the DCC, so comprises many high frequency components. The cap value of 0.1uF seems high (overdamped) and I think your suggested starting point of 0.01uF is probably about right. I wonder if manufacturers have copied each others' values ?
Thanks for posting this, Larry- saving one engine or one decoder makes these a great investment
Thank you Larry! This problem can happen on small layouts, too. I’ve witness the runaways, blown (for no apparent reason) decoders and loss of control on a six by ten layout. Mine is double track, three continuous loops plus sidings and spurs. I just blamed the sporadic mishaps on the decoders. Now I know better and snubbers will be installed!
Another mystery solved, thanks Larry.
Just like the condenser in a set of ignition points. They were installed to stop radio frequency interference caused by the engine ignition system. Same old thing; now, a new (old) use. Bravo!
Thanks for sharing info about snubbers (RC circuits). I was the person who asked last week about the NCE version. I bought a set of 2 for $7.99.
Thanks so much for sharing Larry. Great video as always.
Thank you for sharing. Great information and well explained.👍👀
That was a very interesting presentation. I didn't know these filters actually existed. Thank you for your information - much appreciated.
Thanks for the useful video. I was not aware of the problem thinking most systems ran fine by themselves.
Another interesting video. Thank you for info!
Great video Larry. I enjoyed the technical explanation and the solution(s) that could be used to correct the problem. Thank you.
Excellent video. Thankyou.
Nice update lots going on. Thanks for sharing David.
Thanks very much for replying to my comment. It's nice to see other people's work to get idea to improve my Channel. Take Care DD.
Very informative Larry
Thanks for sharing!
Interesting. Thanks for that Larry. I hadn't heard of this before.
This is the most helpful train video Ive ever watched. Ive had these problems for years and had no idea where to begin. As it was somewhat sporadic I ignored it but it always caused frustration. I cant believe Im going to fix this problem for less than a plastic horn hook coupler. Thank You DCC Guy!!!!!
How did it go? Did this fix what you hoped?
Thanks for a great video. I have problem #1 and I should have what I need to make a few. Time to heat up the soldering iron and go to work.
Thanks Larry.
Great video thanks
Thanks for the information. I've had an intermittant problem with some loss of control after a loco crosses over a return loop gap when another one is already in the loop. It hasn't caused any damage yet, but it's been a little concerning. Considering the cost of the pre made Digitrax ones, I'll give them a try.
I have a DCC++ setup on my test loop. I was having problems with runaways on certain decoders and I tried everything you said to no avail. The solution was to upgrade my 12v 1.5A supply to a 15 V 4A supply. The problem is completely solved. Not sure if the issue was with the current or the voltage.
I have added one snubber to each power district for my layout. I had a MRC wireless system and a constant problem with a Proto 2000 GP38-2 with a TCS LL8 decoder. I used the problem my ghost driver, it would just take off like something out of the movie poltergiest. A number of the features of the system later failed and I decided to replace it. Fast forward to my current DCC system, NCE Power Cab with Smart Booster and decoders were still failing. TCS M-1 decoder in a Proto 2000 SW-9 the light would stay on and nothing else. A TCS in a Bowser U-25B turned into a real time version of a "GE Toaster". The decoder was cooked and heat damage to shell! Called NCE with an attitube, "I can't afford this anymore" NCE's response, "Snubbers"! Bought two of them, one for each power district, at this time, no issues!
Works great!
at least the U25 realistically weathered itself!
The combination of a 100 ohm resistor and a 100nF ceramic disc capacitor gives a frequency cut off at the 3 dB point of 15.9 Khz. The 94 Ohm resistors give a frequency of 16.9 Khz.. Be aware that resistors have a error percentage. Anything around 10% is normal. Check your resistors resistance with a meter if you want to be more precise. As a note on Capacitors.....they can have an error of 80% plus or minus which could be an issue, if you have the means test them to find the closest to 100 nF but i doubt you need to be that choosy. I shall need some RC filters as my N gauge layout is over 30 feet but as a radio amateur this all makes sense to me. Thanks Larry
Yes, that combination of components was selected by the folks at NCE who strongly recommend its use. Jim Scorse is a great EE so so I trust his choice.
I have 4x9 foot Ho scale layout and a bachmann dcc controller but I have an athearn dcc sound locomotive that had a short that burned out some leds and afterwards whenever I give it power I take off like a rocket and dosen't respond to any commands. But when I run it with DC power (which I ran on prior to the short) it runs just fine. I have reset the decoder several times and it hasn't fixed the problem. I'm pretty sure I have to replace the decoder...
Sounds like you cooked it. Did you try a reset by programming CV8 to a value of 8? If that doesn’t work you may be able to get it repaired by Digitrax, check their website. The fact that it runs on DC simply means that track power is passed through the decoder to the motor and your DC throttle is controlling the voltage getting to the motor. With DCC power on the track at constant voltage of about 14V the motor is getting full voltage and taking off.
I have had some of the problems you talked about, my locos not responding to speed commands, bell works one minute, then doesn't,. I have my layout divided into blocks with a power bus. But after watching this video and the symptoms related I know that my bus wire in a couple of my blocks are more than 30 ft. I have even had an issue with blowing a decoder on my loco in this block that is considerably longer than 30 ft. So without checking it with an oscilloscope. I should probably install an rc filter in the blocks I have that are exceeding that 30 foot mark. Thanks for the info. Great video as always.
Chuck
Check your track voltage if the control losses are occurring in the same areas. You may need to beef up your track feeds in those locations.
Ok, I never thought of that. My feeders are 22 gauge. I don't have as many feeders on the same section which is on an upper loop coming off my helix whereas a bus wire would be visible so I have soldered all the fishplates for better contnuity.
Rails have much higher resistance than copper wires so voltages can drop off fast in them With code 83 I use feeders every 6-8’, every 3’ with code 70 rail.
Ok, good to know. I'm using Atlas code 100 rail. I try to have feeders about every 3 to 5 ft
Acculites also makes a rc filter also
Hi Larry
Can you please provide the info on the 14 Gauge (audiotek?) wire you use for your DCC bus. Looks a lot easier than twisting two wires. I assume that you just separate where you need to connect feeders? Thanks Marc
Exactly, I just slip a knife in there and open it enough for a suitcase connector.mThe great thing about it is it keeps the two conductors the exact same length which doesn’t always happen with twisted wires. I have seen some that basically were one straight wire with the other one twisted around it. If you order it make sure to get the OFC (oxygen free copper) vs the CCA (copper clad aluminum). This is the one I get:
www.parts-express.com/Audtek-SKRL-14-100-14-AWG-OFC-Speaker-Wire-100-ft.-100-021
They also sell other lengths and diameters.
Thanks for the video Larry. I find what you do very informative and well done. Can you use the NCE snubbers with a Digitrax system?
In their manuals Digitrax says not to use capacitors alone, but don’t say anything about the RC filters. That said I did it back before I replaced my old wires with zip cable. Matter of fact the lead photo I used was at the end of a 40’ bus on the layout with an 8 amp booster. As always you should only use these if you are experiencing the symptoms I listed.
Thank you Larry. I have an unrelated question from your previous videos. I watched your video on building a keep alive for the loco using a diode, zenier, resistor, and capacitors. I also watched the video for adding a 12v led strip to the passenger car which used a bridge to get DC, resistor to limit in rush current and capacitor. so my question is does the stored energy in 12 passenger cars with lights cause a problem to my Digitrax system.( i.e.feedback)? I am using 5-2.7v super capacitors a 100 1/2 watt Resistor and a small bridge same is in the video and my track voltage setting is set to 14.5 v
I use them with my Digitrax system, people have been using these for years without any problems. Just be aware that the lights and any other accessories you power using your track power takes that my away from your locos.
@@TheDCCGuy Thanks for the quick reply
Hi, Larry. I have followed your videos with great enjoyment and have learned a LOT! Thanks! Since basic electrical seems to be the current trend, I'd like to learn just how a DCC "booster" works. It can't just be upping the power supply voltage is it? I am running an NCE Power Cab and they say the current limit is 1.5A. What ever magic is involved seems to be after the command station output. Thanks.
At the most basic level the command station creates a low voltage/amperage version of the DCC signal I showed in the oscilloscope scans. The magic with the boosters is that they literally boost the DCC signal to the voltage/amperage desired. Some systems just bring it up to whatever level they get from the power supply while others can be set to a specific voltage but the amperages are usually specific to the booster. These also have their own proprietary designs that do the magic of creating a stable, and hopefully noise free power bus. They also have built in ability to sense a short circuit and shut down. If you’re interested here is a link to a website with a 3 amp booster circuit that may be more than the basic info you were looking for.
Thanks, Larry, I assume the filter would affect current occupation (what is the current draw of filter) , where would be the best place to locate the filter in this case. Does it do any good if you place it near the booster or would you need a small section of un-occupation track detected track at the end of the bus
Yes they do draw a small current and their wattage as I said is 0.25-30 watts so use ohms law to calculate the amperage based on your voltage. Also as I said in the video they go at the end of the bus first then can be added at intermediate points. They would be useless near the booster as most already have some type of noise suppression filters built in.
Good video. I am using block detection (Circuitron BD-2). Will a snubber cause these to detect a short? There are adjustments on them, just not sure how these will work with block detection...?
Yes, the BD20 instructions tell you how to desensitize the device so you won’t get false detects. However as I said in the video if you aren’t seeing any symptoms you may not need the RC filers in the first place, especially if you have twisted your wires or are using zip cord.
Can 2 conductor twisted pair shielded cable be used
If you can find it in large enough sizes. I have stripped twisted pairs out of old Cat5 cable to use with connecting my NCE Button Boards and Switch8 accessory decoders to switch machines.
Hi Larry
Could this also affect decoders with Keep Alives fitted? The symptoms I’m experiencing are that locos fitted with keep alives (TCS KAT24s) run then stop for a moment so as I approach the loco to see if it needs any attention, it will just suddenly continue on as if nothing happened. It doesn’t run away per say or stop responding to commands. It just stops, then moves off as if nothing happened. I suspect it’s voltage spikes but it’s a symptom not on your list so I’m curious to know if there’s anything else going on?
Ally
Not likely unless so e CV was reset that impacted on the Keep Alive function. That’s usually the type of behavior you see without a Keep Alive installed! I suggest you recheck the connection and if that is not the issue then call the TCS techies, Dan knows these well.
Thank you for the quick response. I have emailed Dan as suggested and will get back if there is a solution. To confirm, this is not a spiking issue?
I wouldn’t think so.
Should one of the RC Filters be installed on a new layout that hasn't experienced any issues as a precaution? I spilt my power bus wires to cover my layout that has one set going in opposite direction from the other . Would I use one at each end of the bus?
I would if the bus is longer than 30’. And yes you would put one at each end if each exceeds 30’. Generally though fir shorter runs my recommendation is to install them only if you experience the issues I listed.
Larry, I love your informative videos and I've gotten a great deal of wonderful information about my system. My problem is that I've never seen anything on my personal system. I purchased a Digitrax Evoloutuin system with the DT500d duplex/radio/infrared throttle. I've looked everywhere on CZcams but I can't find any insight into my system. I have been finding occasional problems with the system especially with losing programming on my decoders from time to time. Any information you could provide me on the Evolution and especially the DT500D would be greatly appreciated.
I’ll see what I can do.
Hi Larry. Great video with very useful information. Do modern DCC command stations not have this protection built-in?
Yes they do and that is why the first oscilloscope scan I showed had such a perfect waveform. However its the wires, motor and wheel arcing, intermittent shorts outside the command station/booster that interact with the DCC power/signal and create the problems.
The command station will generally have circuitry (diodes) that send spike voltages back into their own power supply so their output is relatively clean. As the signal passes along the track reflections from the far end bounce back and at result in ringing. Close to the command station, the diodes within the command station will (along with any other filtering present) remove most of the spike. Further away the ringing may be present at significant levels.
Wondered how motor suppression is carried out on DCC systems. On conventional controlled systems, it's by a parallel 220nF capacitor at any power clip or track power feed in point. Don't know if these are removed when installing DCC control. RC snubbers are used with mains triac/thyristor controllers.
I remove them from all my UK models. The only US models I have seen them on are Bachmann. Some of the UK instruction sheets actually point out that it may be necessary to remove them from the motor leads for good DCC operation. They can interfere with BEMF and create poor performance although most of the better decoders now apparently can deal with it. I did a video, #79, “Are your decoders being choked” on this subject.
Regarding installation of the snubber, my DCC bus is shaped like a V, in that the bottom of the V is the booster and the legs of the V proceed down the layout and do not touch each other because of a removable bridge. So, should each end of the bus have a snubber installed ?
Yes
@@TheDCCGuy Thanks !
Great Video, Is there any right or wrong way to wire the resistor and capacitor as the resister only allows flow one way. an if using more then 1 RC Filter or would low reverse the flow on the 2nd RC Filter.
I have never seen anyone suggest they all should have the same orientation. And if you think about it it doesn’t matter since there is power on only @A@one rail at a time. Current flows from the on rail to the off rail through the RC filter not both ways at the same time as would occur if power was on on both rails all the time.
So would a snubber roughly equate to a passive CAN Terminator in an ISO-BUS system as used on heavy machinery?
Sounds good.
I did some checking. Accu-lites makes snubbers too and actually call those that. DCC Concepts has Power Bus Spike Suppressors as their product. Have you looked into those versions? Any of these you recommend over the other?
Thanks for that feedback. Not surprising since there is nothing especially secret about these. They probably don’t get much promotion since they likely don’t have a big profit margin and it is so easy and cheap to make your own.
Great information. Does it matter which wire to the two terminals on the snubber? Thanks.
It does not seem to matter.
Good Video. But... The RC filter cannot be used when current sensing track detection is in the circuit. The club I belong to has Digitrax BDL168 track occupancy detectors. I believe these are current sensing. The wiring has a common line and multiple feeders coming from the BDL168. The longest feeder may go 30 feet. Any suggestions on how to deal with this situation?
I think the BDL168 uses diodes for sensing occupancy in a block and since these draw some current they may result in false detects. With current sensing based detectors there is a work around but I don’t know of any with the diode based ones. Since it sounds like you don’t have long wire runs you may not have any problems, do you see any of the symptoms I mentioned? What size wire was used? What amperages are being used?
I was guessing the big black lumps near the hook up board were CT coils. Guess not. We have had some strange CV settings, and a couple blown decoders. Wire size is 14 awg. The feeder wires leave the BDL168 and go just a few feet up to almost thirty feet.
I am not sure whether you can adjust the sensitivity of the BDL168 like you can with a BD20. With those you can make onboard adjustments and cut down on sensitivity so the false detects are eliminated. So take a loo at the BDl168 manual and see if there is a similar way. Also those may not be sensitive to the current draw of the RC filter since it only uses a 100 ohm resistor. It would only take a few minutes to wire up a RC filter, install it, and see if the detector lights up.
I just read through the manual and it does tell you how to adjust sensitivity so you might take a look at that if the RC filter does give you false detects.
If you twist the bus wires (or use the speaker wires that are tightly bound together like you do and I do), you shouldn't need the RC filters. Am I correct?
That’s right, and as I said in the video if yours is a small layout you might even get away without twisting.
Thx for the video. Can I just install a snubber - w/o knowing if it's needed? Can just adding one cause any harm?
Shouldn’t be a problem. I even have one on my 8’ long modular layout.
Great video Larry, besides twisting the DCC bus, does wire gauge play a factor as well?
Should you put one on every block?
You should always use the correct size wire for the scale, rail code, and length of the run. As I ad in y video pit one at the end of the power bus and maybe a second midway if symptoms remain in some areas.
My bus wires go from the DCC booster about 25 feet in both directions. I used 10 gauge solid copper plastic conduit house wire (Romex) as that is what I had available. How does the gauge factor in on this issue?
The thickness of the wire mainly affects how much voltage loss you get as you get far from the base station. With your 10 ga wire, you will get very little loss but adding RC filters at each end a good idea as is cheap insurance.
You should have few problems with that arrangement. However if you see any of the symptoms I mentioned then try the RC filter bandaid.
Hi. I am a member of a club in Norway and we have a rather large layout that is divided in two parts, one part is DCC and the other part is Märklin/Motorola-system. We hav experienced many of the problems you listed in the video and we are planning to try out the RC-filter to see if that will correct the problems. But my question to you is: Do you know if these filters also work on the Märklin/Motorola system?
I have never looked at this system so have no idea as to whether these would work. However the folks at DCC Concepts in the UK sell a unit similar to the NCE snubber and their electrical engineers may have considered this. I suggest you send them an email inquiry via their website dccconcepts.com .
Larry what would us "Soon to be smokers" do, w/o your Expertise. What's your recommendation on say a main that encompasses 100' or more break into 4~25'ers using dealer wire & a cap~res. On each End?
I believe in a stepwise approach. First are you having problems? If not then do nothing. Some systems and wiring configurations are more prone to these issues than others. If you see the symptoms then try the RC filter. If that doesn’t take care of the problem then breaking the 100’ run into shorter ones however remember you still will have to count the full length of each wire run from the booster. If you can put your command station booster i the middle of the layout and fan out your buses that would be the best configuration. Or you could break it into 2 50’ runs with a booster in the middle of each, so your 50’ runs would in effect be subdivided into 2 25’ ones. Divide and conquer!
@@TheDCCGuy Larry I finally got time to sincerely thank you for the tips as I progress so does my, How-To knowledge all the while trying to remember "Now. Which end goes In The Cement?! 😆
Why don't you show a waveform after you attach the snubber?
I don’t own an oscilloscope.
We experienced locomotives intermittently change direction or change speeds during a train show but only at that particular train show location. And repeated again year later same train show location. No where else. Will the "snubber" resolve these issues different from your problem list? Perhaps be we have different issue. 😳
Interesting phenomenon that I have never seen happen in almost 30 years of DCC. The fact it occurred at the same place might suggest some external EM noise interaction, or it just might be the configuration of your layout each time. If it has never happened anywhere else ever before or since it would suggest the local issue. But if elsewhere as well then the snubber might help. These are so cheap and easy to make and install a test would be easy enough.
How do you actually fit them?
You have the two wires coming out of the controller to the track, but only two terminals.
Do you come in with the two wires and come out with two wires from the same terminals?
As I said in the video beginning at 18:55 they are connected between the two bus wires of your DCC bus.
Been thinking about your video on DCC spikes and snubbers for a while. Experimenting with an Arduino PWM scheme to run and animate a small "critter" engine on a short piece of DC ... not DCC ... track. On my scope, I see lots of similar spikes so I was interested in the snubbers. Then I noticed MOV varistor transient spike protectors can be purchased with voltages like 10-18V (AllElectronics). Question for you ... and for anyone out there. Might a low voltage MOV be used to kill unwanted track voltage spikes? For DC, maybe just place across track rails. For DCC, maybe place two ... one between each rail and ground. Welcome your thoughts. All the best ...
I would think a transient voltage supression diode would work well to remove the spike, but would need to be sized for the DCC voltage in use. These are used to clip superfast voltage spikes like this. Say if your track volatge is 14V, then an 18V 1W TVS would be worth trying (across the rails). Too low a voltage would cause a short all the time and the diode would fail. Too high and the spike will not be gone. This would be a good option along with the snubber, but I would use 100 ohms 1/2W in series with 0.01uF.
Would you recommend these on a small layout or should these only be used if you find problems
Only if you have problems, which usually means with DCC power bus runs of 30’ or greater. That said poor wiring and other issues may complicate this guideline.
Hi Larry, My friend has a VERY large layout with a main line of approx 150+ feet. Using Digitrax for command station and about 5 boosters. There are about 15-20 NCE Switch 8 (original version) stationary decoders for operating the Tortoises. We have a recurring problem whereby the Switch 8 fails to respond to the throttle signal. We shut down the whole system for about 30 seconds. After we power back up the Switch 8 works again. I've never thought to notice if this problem occurs immediately after someone shorts out somewhere on the layout. I recently replaced two of the offending Switch 8's and installed 2 of the latest Switch 8's (which are sooo easy to program). So far no problem. I'm wondering if installing RC filters could correct the problem. Thanks for any help you may be able to give. Tom
First, how are they powered and how are you controlling them?
@@TheDCCGuy They are powered from the DCC BUSS. We “talk” to them using the Digitrax throttles.
Has anything changed on the layout, for example a new command station or boosters? I assume all those boosters are powering individual blocks?
Hello again Larry, In a way things have changed over the years. It started doing this from the very beginning since the change from NCE system to Digitrax. I don't know if it did it under the NCE system as it was just before my involvement in Bobs layout. Through the years (6 or so) we have added boosters and went from DCS100 to DCS240.
Tom-With so many changes it makes it difficult to isolate a single problem but several, things come to mind. First I know that some products reportedly have trouble with the late model Digitrax command stations such as the DCS240. The NCE Light-It won’t work with their commands according to the manual or website. I really have not used throttle commands with my Switch8s so can’t comment there, I just use the Button-Board and pushbuttons. So it could be the change from NCE or it could be signal issues or it could be noise on the bus. The snubbers are cheap and easy to make and would be a quick test to see if something is going on with the square wave shoulders.
Recently I had the opportunity to visit a large home layout that exclusively uses RailPro DCC controllers and decoders. I haven't seen any articles in MR or videos by you on this manufacturer. Do you have any experience with it as far as pros and cons regarding its use?
If they want to send me a setup I’ll be happy to give it a test drive, but I know nothing about their system.
@@TheDCCGuy Okay. Hopefully they'll send you a system to evaluate. Thanks for answering me.
I’ll send them and email and see what……
Another excellent Video Larry, thank you for sharing.