How many volts do you have at the rails?

[cudaken]

 This is a new start to the post I started about making a Turnout DCC friendly I all so want to thank all the kind folks that answered it and will post there again.

  I talked with a Rep at Digitrax today about a driffrent subject, why they say a DH 163 will run LEDs on there site and it blew mine up real good. I will add I was told the DH163 does not drop voltage, it has to be a DH 165 like the kind folks here told me.

 I then brough up my decoder eating bench. He gave me a few ideas (he was not a fan of Athearn RTR I will add, said Athean spends a whole 50 cents per motor) and to check there PC board for slag before running.

 Before I have a decoder go bad, I do get some hours of run time on them. It not like I install one and it goes boom.

 I told him I have a MRC 8 amp booster, it said that could be the problem and not because of the amps. MRC stuff seems to put out to many volts. I was told that HO should never go over 12 volts and N scale never over 10 volts.

 I just tested mine, I have 14.5 volts at the rails with the 8 amp booster. I then tested the 1amp Bachmann E-Z with out the booster, it was 18.6 volts?

  Is 14.5 volts to high? Doing a slow cook on the decoders?

 So what volts do you folks at the rails.

                      Cuda Ken

[rrinker]

 You can;t get an exact measurement of the track voltage with a standard multimeter because of the square wave nature of DCC. Not sure if there is a gorund terminal on the MRC booster liek there is on the Digitrax ones, but the Digitrax way of measuring track voltage is from one rail to ground and then the other rail to ground, and add them. Should be equal on both sides, assuming address 00 is set to speed 0 - this is how runnign a non-decoder loco on address 00 works, it 'shifts' the apaprant DC voltage to one side or the other relative to the ground or common, so the DC motor 'sees' more voltage in one direction and can turn.

 At any rate, 14.5 volts is about right for HO, 18 is too high although most Digitrax decoders can take 22 volts, other can only take about 20 (large scale trains often run higher voltages - 18 for O, 20 for G. Smaller scales often use less - 8 volts for Z originally but I think most newer Z scale is at the 12 volt NMRA standard now). I'll ahev to see what my Zephyr reads on this particular meter, the Zephyr is rated to put 12.5 volts on the track. The bigger Digitrax systems have a 2 position switch, putting 12 volts out on the N scale setting, 14.5 on HO, and 18 on the O/G. The decoders can handle it - NMRA standards pretty much say they have to. The motor in the loco doesn't see that directly - like any semiconductor there are voltage drops in the transistors the drive the motor, so with 14.5 volts on the track the motor will see maybe a tad over 12 once the drops are figured in - just about right on. I wouldn;t be concerned about overvoltage if the ballpark figure you are getting is 14.5. More likely is that if you get a short that goes through the decoder at all, there's 8 amps hitting it. At 14.5 volts, 8 amps makes it 116 watts - LOTS of heat.

                                             --Randy

 

[mfm37]

 Did you get the tech rep's name? While I tend to agree with his opinion on what is a proper safe operating voltage for HO and N scale, those figures don't come close to matching the outputs of their own equipment.

To measure DCC track voltage accurately, you need a true RMS meter and the measurement needs to be done with a load on the output. A RRampmeter works quite well. We used a RRampmeter and a true RMS DVM to test voltage at the track for NTrak a couple of years ago. I can tell you that with a 3 amp load, a Digitrax booster (DCS200, DB200, and DB150) puts out 11.9 volts at the terminals with a three amp load applied. That's with the N scale setting on the booster and a 12 volt AC power supply. Raise the voltage of the power supply and the output voltage will rise even on N scale. I connected a 16 volt AC power supply to a DB150 and measured 12.3 volts on Nscale using the sme equipment..

The Zephyr's that I've measured using a 1 amp load have all been in the 13.9 to 14.1 volt range. Safe for HO but too high for N scale. All of those were being powered by Digitrax PS315's.

Martin Myers

[armchair]

 Ken, I just got My rampmeter 4 & checked the power at the rails ,Easy Dcc is putting out 13.9 volts to the rails. Although kinda pricey, the Rampmeter would proaboly be a good investment for You, given Your luck with electronics . I haven't had time to experiment with it but, it seems to be a great tool to add to the bulging tool chest. By the way You do have a fire extinguisher handy, don't 'Ya ?

[cacole]

With a digital voltmeter set to measure AC voltages, 14.5 to 14.6 Volts is exactly right and within the range specified by the NMRA DCC Standards and the voltmeter's inherent inaccuracy caused by the high frequency digital signal on the track.

[jrbernier]

Ken,

  I just measured the output of a Digitrax DCS100(Chief) and a DCS050(Zephyr) with  unit.  System powered on with 2 Sound/DCC engines on the track.  The measurements were with a 'multmeter' and with a RRampMeter.  Here are the results:

System        Multimeter    RRampMeter       

DCS050       13.0                     13.6

DCS100       13.5                     13.9

  I suspect your 1 amp EZ Command system was 'unloaded' to register that high of a voltage.  That 8 amp booster is a little high.  It may not be the total output voltage, but maybe 'surge/spikes' getting out to the track.  I have a number of Athearn 'RTR' engines with DH163 series decoders and they have run for hours at club open houses.  Now, maybe a really old 'BB' engine could draw enough.  But a little cleaning/lube/adjust brush spring tension and it should not draw more than .75 amps.  As mentioned, you need the Digitrax DH163L0 or DH165L0 decoder for the P2K engines - they will handle the P2K light package.

Jim

[cudaken]

armchair

Ken, I just got My rampmeter 4 & checked the power at the rails ,Easy DCC is putting out 13.9 volts to the rails. Although kinda pricey, the Rampmeter would probably be a good investment for You, given Your luck with electronics . I haven't had time to experiment with it but, it seems to be a great tool to add to the bulging tool chest. By the way You do have a fire extinguisher handy, don't 'Ya ?

 I do have a fire extinguisher handy, but I have been strapping Hot Dogs on top on the engine as heat sinks and work well.

 Darn, I was really hoping that the MRC booster was the problem at this point! Is the Rampmeter the one that Tony's Train World sells?

 Guess I am back to the turnout's being a problem and adding circuit breakers.

 I am thinking about hooking up a MRC 2500 to the B line and hooking in my cheap multimeter in line to see if there and power spikes. Would that work? When I had the MRC 9500 there where no power spikes, but that was over a year ago.

 Building a 11 second engine for a 3500 pound car is easier than this has became.

                  Cuda Ken

[maxman]

cudaken

Guess I am back to the turnout's being a problem and adding circuit breakers.

If you want to experiment and don't want to make a large initial cash outlay to get a breaker, you can try the tail light bulb temporary fix.  Basically you put a tail light bulb in series with one of the leads between your booster and your track.  The bulb acts as a current limiting device and offers some limited over current protection.  An 1156 bulb will limit current to about 2.1 amps, based on some published experimental data.  When a short occurs, the bulb will start to glow. At least you'll know when something is happening.

There is a downside to using these things.  If you have a number of engines in consist, the current draw will start the bulb to glow.  You will be limited to what you can run. I tried it and didn't like it, but it'll only cost you a couple dollars if you want to experiment.

The following link discusses how all this is supposed to work, how to do the wiring, some of the downsides, and has a table of current values for various combinations of bulbs.

http://siskiyou-railfan.net/e107_plugins/forum/forum_viewtopic.php?3026

Regards 

[mfm37]

cudaken

 I am thinking about hooking up a MRC 2500 to the B line and hooking in my cheap multimeter in line to see if there and power spikes. Would that work? When I had the MRC 9500 there where no power spikes, but that was over a year ago.

 Building a 11 second engine for a 3500 pound car is easier than this has became.

 

 

That may work as long as the meter holds up. It may not be dead accurate but would definitely show spikes and variations.

 

BTW, is that a '70 Cuda? I had a '73.

Martin Myers

[cacole]

 Cheap digital voltmeters don't react fast enough to voltage changes to record spikes, but will show only long-term fluctuations.

[cudaken]

Martin, if you mean in the Icon I use, it is my money pit 69 Charger R/T with a big Bore GMC 6-71 Blower. Getting close to spending the same as the Blower on decoders! (not really, melting decoders is way cheaper)

 My Cuda is a 1970, 383 car with Hockey Stick strip, Go Wing, Rally Dash, Buckets and Slap stick shifter. 383 is warmed over with DB 4 intake, 750 Holley, Headers, MSD 7 AL TSI 3500 stall, Hemi Clutch can, 5.0 Kick Down, TCI valve body with 3:23 sure grip. Not a fast car, but a great street peeler, runs 14.35 at it 98.5 MPH in the 1320.

 Cuda Ken

[Texas Zepher]

cudaken

what volts do you folks at the rails.

I used to use Railcommand which puts out 15VDC to the track plus a 2.5V carrier signal for a total of 17.5VDC to the track.    When I went with DCC the Lenz unit by default puts 17.5VDCC to the rails, so I ran that for a while.  After some calculations for LED and lamps I and decided it was too high.  The Lenz allows me to choose output, so I set the track voltage to 14.5.   I am now thinking about reducing it again to 13.

[cudaken]

 Martin, you have a Mopar PM.