With a Radio Shack meter I’m measuring 19.9V on my HO DCC track. Some decoders, like Soundtraxx say not to exceed 18V. I’m using a Lenz Set-100 and according to the manual I can adjust the track voltage. Should I reduce the voltage? To what value?
Jerry
Most muilti meters will give you a false reading on DCC. The factory setting on my Set 100 is 16 volts at the track, which is fine for all BLI etc locos.
Ken.
Only you can answer that question. Our club reduced ours from the default of 17.5V to 15.5V just to be more friendly to stock lightbulbs in RTR locomotives and we were melting down lighted cabooses. At home I went even further and set mine to 14V, mainly because I have a bunch of lighted passenger cars.
You also realize you can set the voltage in the Lenz in two ways. It can be done with software or with a jumper inside the unit. I chose the jumper just so an accidental reset doesn’t jump it back up and fry my lightbulbs.
TZ I hadn’t thought about lighted passenger cars I’m going to bring my voltage down too, thanks for the wake up!![|)]
Ken.
Tony’s Train Exchange has special meter for getting real-time measurements of DCC track voltage. http://www.tonystrains.com/products/tteexclusive_measure.htm[](http://www.tonystrains.com/)
Eventhough DCC track voltage is half-wave DC, you can get an approximate reading (about ± 1.5v) with an AC voltmeter.
The nearly 20 volts is definitely too high. 14.5-15 volts is good for HO, 12v is better for N scale, and my HO runs fine with 12v on the track.
–Randy
Tony’s has a RampMeter that measures the DCC voltage ( pulsed DC ) very accurately, and the price is very reasonable. Anything over 14.5 V is tempting fate. I like using a constant voltage supply. The current will drop if things get out of hand, but the voltage stays clamped at 14.5V
At WIMRC we operate five to six HO locos at a time, some sound equipped, with “N” voltage setting on the DCS200 (8A), having found that “HO” setting produced "hiccuping in some loco’s.
Just got back to the train room. Thanks for all the input. I’ve set it at 16V and get a reading of 17.3V. Looks like that’s within the tolerance you mention.
Jerry
You might want to bring the 16v setting down a bit. Your lightbulbs (in those trains that don’t have LEDs) will last longer.
I just measured my track (NCE Pro) which is supposed to be 14.5 v and got 14.96vac on my AC meter. In my case the accuracy tolerance seems to be a little closer. The Ramp Meter would be the only way to actually confirm any of this.
Maybe someone out there that has one would do a test with the Ramp Meter vs. an AC volt meter and see how close they are.
The voltage that you get on an AC voltmeter is (usually)only accurate at 60Hz, especially your garden varity of voltmeter. The DCC waveform is in no way close to 60HZ, is it not 60CPS and it is not a nice sine wave. It is a pulsed square wave. When using a normal voltmeter your readings may vary depending on the number of messages being sent and some DCC sets can use an extended pulse to run a DC (not DCC) equipped device. The best thing a normal voltmeter can be used for is to check for comparative voltage drop or if there is a voltage there. The voltmeters specifically made for measuring DCC voltage is the way to go, or use an modern digital oscilloscope with a built in voltmeter, that will tell you peek-to-peek voltage, RMS, Average or what ever way you want to measure the voltage.
Paul
Dayton and Mad River RR
modelmaker51 & grayfox1119,
Both of you are claiming that DCC is actually a DC output, not AC. The only problem is that DCC is AC. It is square wave AC, but it is AC all the same. If you graph the DCC signal, it oscillates equally from positive to negative volts, which makes it an AC signal.
Paul A. Cutler III
Weather Or No Go New Haven
Paul3 DCC is “bipolar” DC, which is a "form"of AC, it is NOT a true sine wave as AC is. The DC power is modulated which allows for data to be encoded in the form of "1’s and “0’s”.
AC means “alternating current”. It has nothing to do with a particular waveshape such as a sine wave. The type of AC that we are used to in our homes IS a sinusoid (or a reasonable approximation depending on reactive loads) alternating at a rate of 60 cycles per second … but it is certainly not the only form of AC.
AC can also be a square wave, a triangle wave, a stair step and many others. It simply means that polarity regularly and symmetrically (well, not always either) alternates.
If DCC has equal amplitude positive and negative components then it is AC. If it is symmetrical from zero to some peak then it is AC with a DC component added to it to shift the average level.
If there is no repetition, then we have a pulse of series of pulses. (Which may or may not be a digital signal).
This is excerpted from one of my Cisco CCNA lectures. If it makes no sense let me know. If it does make sense then those four years at RPI paid off again. 
By the way, many companies make “True RMS” digital multimeters. Fluke is one of the best and most expensive but all brands work well enough. These should be able to measure the RMS voltage of DCC accurately for well under a hundred bucks. A 'scope is cool too if you can afford it.
I am no expert here, but do rely on them. I have been told by the technical folks at Digitrax, NCE, and Tony’s Train Exchange that DCC is NOT AC, but is what they call “half-wave” DC. Ask them.
(and if it is AC why can’t you read the voltage with an AC voltmeter?!)
Well, I’ll ask them, but according to what my college professors taught me back at Wentworth Inst. of Tech., DCC sure looks like AC to me (but then, I was in for Mechanical Engineering, not Electrical).
As for why you can’t read an accurate voltage with an ordinary multimeter on DCC track power, look above my first post, the one by train18393, where he states that normal meters are based on sine waves at 60 Hertz, and DCC is not either.
BTW, take a look at a real DCC “packet”. Note that the square wave has an equal positive and negative voltage…and that’s AC.
Paul A. Cutler III
Weather Or No Go New Haven
If it were half-wave DC it would not alternate around the common reference, but merely go from common to some positive potential. Since there is a negative component in reference to the common, it’s not DC.
As for not being able to accurately read the voltage, I would have to go into calculus to explain the concept of RMS voltage and the area under the curve. Suffice to say the area under the curve (ok a square wave is not exactly a curve) for a square wave signal is not the same as for a sinusoidal signal. Therein lies the difference in readings when using the common method of measuring. A more expensive true RMS meter will calculate properly for either waveform (and many others - like triangular). These meters are more expensive because they must process the input more to obtain the accurate reading.
–Randy
Randy,
I have an expensive Fluke RMS digital that gives just about the same reading as my Tony’s meter.
But here is my question. I also get the same reading using a $4.00 digital meter that I bought from Harbor Freight. In fact I bought 4 of them and monitor the voltage on each of my district’s. I operate them from a common wall wart. Are we/I missing something here?
Just hard to justify the cost of the RRampMeter. And since I own 3 different types of meters and get the same, + or - about 1/10 ,volt readings I am speaking with experience.
POOR MAN’S METHOD FOR READING DCC TRACK VOLTAGE
Watch the meter reading – you may need to reverse the leads if the meter reading goes below zero.
The volt reading is the DC voltage output of your DCC system (what decoders see), and that’s what you want to know.
When I use this method, I get a perfect 14 volts on my system.
Thanks Joe Yes I did that before I got my RRampMeter. It is just that I find a cheapo digital meter seems to read the track voltage just as accurately as the RRampMeter and/or my Fluke.