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Measuring DCC current

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Measuring DCC current
Posted by fender777 on Friday, May 12, 2017 6:29 AM

Using my multimeter what reading should I get to make sure I have the right amount of juice on any one area of my track , I use a NCE power cab on my shelf layout. I assume I set the meter to DC'  Also when is a booster needed. Thanks for help.

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Posted by RR_Mel on Friday, May 12, 2017 6:53 AM

You need to use an AC scale for voltage and it may not be very accurate because of the square wave output of your Power Cab.
 
I built up a Paisley circuit to measure DCC current and it works very good.
 
 
Check out Rob’s site, he has a lot of neat stuff for model railroading that is easy to build.  He also sells printed circuit boards for his circuits as well as kits.
 
 
Mel
 
Modeling the early to mid 1950s SP in HO scale since 1951
 
My Model Railroad   
 
Bakersfield, California
 
I'm beginning to realize that aging is not for wimps.
 
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Posted by richhotrain on Friday, May 12, 2017 7:15 AM

As Mel indicated, you would measure AC, not DC, but a more reliable device than a multimeter would be a RRampMeter or a so-called "true RMS" meter.

The RRampMeter can be used in-line or portably, as opposed to in-line, to measure voltage anywhere on a layout. However, when using the RRampMeter to measure current, it must be used in-line, so it cannot be used portably to measure current.

I am not familiar with the operation or functionality of a true RMS meter.

Rich

Alton Junction

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Posted by fender777 on Friday, May 12, 2017 7:36 AM
Well I am not building anything to test' never heard of a ramp meter. I guess if my trains work I am good. So far they do. I thought their might be a standard No that the DCC controller puts out on the track when idle. Thanks
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Posted by peahrens on Friday, May 12, 2017 8:01 AM

You can read about the RRampMeter below.  I got one when I was setting up my 2012 (current) first DCC layout.  But I virtually never use it.  Some people install on the fascia to see their current demand.

https://tonystrains.com/shop/?s=rrampmeter

 

Paul

Modeling HO with a transition era UP bent

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Posted by yankee flyer on Friday, May 12, 2017 8:06 AM

Hi Fender

For small applications I don,t know of any way to measure current except, in line.

The thing is, there is no current untill something is turned on. if you have a light bulb and a 120V source there is no current untill the light is turned on so nothing to measure.

I remember an instructer that compaired electric to water, Voltage is the height of the dam and current is the amount of water coming out of your pipe at the bottom.

Cheers and have a good day.

Lee

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Posted by RR_Mel on Friday, May 12, 2017 9:10 AM

peahrens

 Some people install on the fascia to see their current demand.

 

 


I’m one of the nuts that use meters in my control panel.  I bought a couple of cheapo panel mount digital volt meters ($4) for my control panel.  I’m using Rob Paisley’s circuits, the panel meters are mostly for show.  The current meter will show increasing current as my trains climb my 3½% grades, again mostly for show.
 
My control panel is going through a massive redo for several new projects one of which is adding the DCC meters.
 
This is a drawing my proposed new control panel with the DCC meters.
 
 
PhotoBucket is down so I posted the picture on my Google Drive.
 
 
Mel
 
Modeling the early to mid 1950s SP in HO scale since 1951
 
My Model Railroad   
 
Bakersfield, California
 
I'm beginning to realize that aging is not for wimps.
 
 
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Posted by gregc on Friday, May 12, 2017 9:28 AM

fender777
I use a NCE power cab on my shelf layout

The PowerCab has an option to display current (amps).  see pg 59 of 1.65 manual

greg - Philadelphia & Reading / Reading

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Posted by SouthPenn on Friday, May 12, 2017 9:38 AM

A true RMS multimeter is used in the exact same manor as any other multimeter. The only thing special about them is that they will give you an accurate AC voltage measurement, even if it is not a standard 60 cycle (hertz) sine wave.

South Penn
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Posted by richg1998 on Friday, May 12, 2017 9:53 AM

I have used a Harbor Freight digital multimeter using the AC scale. I have the Power Cab and I measure about 13.6 vac. I check right at the cab output and then check along the layout. Since the power pack is 13.9 vdc, I know the readings are accurate enough.

About the same thing at the club that uses the NCE Five amp, power pro.

DCC you must know is sometimes called a form of AC.

With your meter, check right at the cab. Use that reading as a bench mark. Check at different points on the layout but make sure a loco is in that area because you need a load to see a possible voltage drop.

I remember a few post where the user said proper voltage everywhere but put a loco on the layout and saw slow downs. Need a load.

Try the AC scale and let us know what you see.

Remember, this is not rocket science, just model railroading.

The meter I use also makes a very good DCC amp meter using the 20ma DC current scale with a few extra components as someone has said. I have a high amoerage rheostat I clip across the railsand the booster trips at about 4.97 amps at the club.

Rich

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Posted by GrandTrunk-HO on Friday, May 12, 2017 10:12 AM

Accurately Measuring DCC V-AC Track Voltage

DCC uses a digital V-AC track power supply. As previously stated, to accurately measure digital V-AC you will require a RMS (Root Mean Square) V-AC volt meter. 

There are special multimeters available that will measure V-AC (RMS). Fluke sells True (RMS) multimeters, but they cost way over ($100.00's) each.

 

RR_Mel

I’m one of the nuts that use meters in my control panel.

I bought a couple of cheapo panel mount digital volt meters ($4) for my control panel. 

This is a drawing my proposed new control panel with the DCC meters.

https://drive.google.com/open?id=0B7gZp9MPvrm3SXJHeXVRMVpDbDA

Sorry RR_Mel to de-rail your plans, you can purchase a digital Amp meter, but you can Not purchase a digital Volt (AC-RMS) meter.

I presently have a RRampMeter that is manufactured by (DCC Specialties), that I purchased from https://tonystrains.com/shop/?s=rrampmeter

DCC Specialties 

http://www.dccspecialties.com/

They manufacture many different advanced DCC products and do not sell directly to the public, but only directly to Dealers. 

RRampMeter

The only inexpensive device that accurately measures DCC (track) Volts/Amps. 

http://www.dccspecialties.com/

There are (4) different versions available.

Learn More About RRampMeter

http://www.dccspecialties.com/products/rrampmeter.htm

RRampMeter Pictures

http://www.dccspecialties.com/products/rrampmeter-pictures.htm

You can use the RRampMeter to check your layout actual track V-AC power supply. (Not Amperage). 

Using a RRampMeter to check your layout Track Voltage and Track Amperage, this is how the unit is wired.

 

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Posted by RR_Mel on Friday, May 12, 2017 10:29 AM

GRANDTRUNK
 
As usual your info is inaccurate and miss leading!  I am using Rob Paisley circuits with cheapo digital panel meters that are as accurate as my $280 Fluke!!!!
 
Your gobbledy gook isn’t needed on this post.  I am a EE with over 40 years of experience in electronics.
 
 
 
Mel
 
Modeling the early to mid 1950s SP in HO scale since 1951
 
My Model Railroad   
 
Bakersfield, California
 
I'm beginning to realize that aging is not for wimps.
 
 
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Posted by richg1998 on Friday, May 12, 2017 10:39 AM

I paid about two dollars each for my meters and about maybe nine dollars for the amp meter parts.

If you have a layout with a couple boosters, cheap enough to cover both sections with it's own amp meter.

I installed at the club with an over head digital display so everone in the room can see the current easily. At the club, I used Paisley's voltmeter option.

I first did the meter like Mel did but realised the over head meter was better.

Yes the rrampmeter is nice but not absolutely necessary. It is nice if you do not like messing with electronics.

Rich

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Posted by richhotrain on Friday, May 12, 2017 1:38 PM

GrandTrunk-HO

 

RR_Mel

I’m one of the nuts that use meters in my control panel.

I bought a couple of cheapo panel mount digital volt meters ($4) for my control panel. 

This is a drawing my proposed new control panel with the DCC meters.

https://drive.google.com/open?id=0B7gZp9MPvrm3SXJHeXVRMVpDbDA

 

Sure you can. Home Depot sells one for $66.

Rich

Alton Junction

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Posted by GrandTrunk-HO on Friday, May 12, 2017 1:56 PM

Measuring DCC V-AC Digital RMS Voltage

RR_Mel

GRANDTRUNK

As usual your info is inaccurate and miss leading!  

I am using Rob Paisley circuits with cheapo digital panel meters that are as accurate as my $280 Fluke!!!!

Your gobbledy gook isn’t needed on this post.  I am a EE with over 40 years of experience in electronics.

Mel

Hello RR_Mel

So you claim to be an EE (electrical engineer) and also using a Rob Paisley DCC digital panel meters.

This Posting (DCC Meters)

DCC V-AC digital track Amperage can use Any type of Ohm (resistance) meter.

DCC V-AC digital track Voltage requires a V-AC (RMS) Voltage meter.

Fact (DCC Amp Meter)

DCC Circuits And Related Pages

http://home.cogeco.ca/~rpaisley4/CircuitIndex.html

1.) 5 Amp - DCC Ammeter (ZXCT1009) (PCB)

RR_Mel

Could you please inform all of us in this posting.  Where has Rob Paisley posted on his web site, how to build a  DCC digital V-AC  (RMS) voltage meter (project) to measure actual V-AC (RMS) track voltage?

 

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Posted by RR_Mel on Friday, May 12, 2017 3:11 PM

GrandTrunk-HO

 

GRANDTRUNK

As usual your info is inaccurate and miss leading!  

I am using Rob Paisley circuits with cheapo digital panel meters that are as accurate as my $280 Fluke!!!!

Your gobbledy gook isn’t needed on this post.  I am a EE with over 40 years of experience in electronics.

Mel

 

 

 

I’m not going to get this post locked arguing with you.  As far as I’m concerned it would be much better if you moved to another forum, if they will allow you.  All of Rob’s circuits that I’ve used over the last 15 years have worked very good.  The Rob DCC meter circuits are accurate to better than .1 volts according to my Fluke and that’s all I care about.  I will not respond to any more your disrupting posts!  
 
 
Mel
 
Modeling the early to mid 1950s SP in HO scale since 1951
 
My Model Railroad   
 
Bakersfield, California
 
I'm beginning to realize that aging is not for wimps.
 
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Posted by richg1998 on Friday, May 12, 2017 3:27 PM

Yeah, Rob's circuits have always worked for me.

Generally the only ones who say the meters are not good are those who don't use them.

Again, this is model railroading, not rocket science. I worked at a NASA facility for fifteen years and worked with the best equipment.

Rich

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Posted by RR_Mel on Friday, May 12, 2017 3:35 PM

richg1998

Yeah, Rob's circuits have always worked for me.

Generally the only ones who say the meters are not good are those who don't use them.

Again, this is model railroading, not rocket science. I worked at a NASA facility for fifteen years and worked with the best equipment.

Rich

 

I’ve used dozens of Rob’s circuits and all are excellent.  I normally make my own circuit boards but I bought the DCC current board from Rob.  I did a slight mod to it to expand the range.
 
His signaling system circuit is great.
 
 
Mel
 
Modeling the early to mid 1950s SP in HO scale since 1951
 
My Model Railroad   
 
Bakersfield, California
 
I'm beginning to realize that aging is not for wimps.
 
 
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Posted by selector on Friday, May 12, 2017 6:16 PM

fender777

Using my multimeter what reading should I get to make sure I have the right amount of juice on any one area of my track , I use a NCE power cab on my shelf layout. I assume I set the meter to DC'  Also when is a booster needed. Thanks for help.

 

What do you mean by "juice?"  If you mean voltage, then any digital meter that has the appropriate range in an "AC" mode (say 20 volts) will give you a good estimate....good enough to know that you're getting good scale voltage to the rails.

If you mean 'current', which is amperage, you need to make something work across the two rails.  As mentioned, something like a tail light bulb drawing about 2-2.5 amps, or a locomotive drawing a string of cars behind it while it's in motion.  Technically, some bit of current is being taken up by a decoder and a headlight, but most of us want a locomotive to be in motion so that we can see what it draws with two, six, twenty cars, or what difference it makes if it's on level tracks, a curve, or on a grade and climbing.

I'm by no means an expert in this, but I understand that you do need special measuring devices to accurately measure current draw across the rails, and one of those is the popular RAMPmeter.

 

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Posted by rrinker on Friday, May 12, 2017 7:58 PM

 A cheapy Harbor Freight meter will in most cases actually be MORE accurate than en expensive brand True RMS meter. Why? Because with a square wave the peak is the actual voltage, unlike a sine wave where the peak is square root of 2 times the average. You need calculus to prove it (area under the curve - or box in the case of the square wave). A True-RMS meter will measure the correct values for sine, square, and triangle waves, however they usually don't go up to DCC frequencies. I have an old Fluke 8060 that was designed to be used by audio engineers so it does True RMS up to 20KHz, but more modern ones often top out at around 1Khz.

 The main reason for the RRAmpmeter is for the current measuring, the voltage is easy enough to do without special circuitry. Most meters have relatively inaccurate AC amp readings, even of standard 60Hz stuff. The circuitry used in the RRAmpmeter is available for DIY from Rob Paisley. At one point he was offering a circuit board of the DCC amp meter with the current sensor pre-soldered (it's a surface mount part only) so all you have to do is basic part soldering to complete the circuit.

 Measureing curretn around the layout when it all comes from the same booster doesn't tell you much of anything,. Measuring voltage will help pinpoint poor wiring though. You don;t even need an accurate measurement for that - measure right at the booster terminals and then compare that reading to ones taken from the rails. At the farthest point away it should still be no more than .5V less. Exact reading in unimportant, it's the relative change that matters.

 

                                             --Randy


Modeling the Reading Railroad in the 1950's

 

Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.

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Posted by gmpullman on Friday, May 12, 2017 8:20 PM

Like Paul, above, I don't use my RRampmeter as often as I thought I would.

One thing that I do when I use it to read voltage, though, is attach an automotive 1156 lamp as a ballast load. Reading voltage without any load is not really going to pinpoint any weakness as near as I can see.

Weather you use the RRAMPmeter or not, this data sheet is helpful in this discussion:

http://www.tonystrains.com/download/rramp-appnotes-df.pdf

Page three addresses the ballast lamp.

Imagine going around your house and poking volt meter test probes into the outlets. Chances are you'll get 115 to 120 volts, in North America anyway.

Does that mean you can plug a 5000 watt space heater into the outlet you just read good voltage from? Read the voltage again after the heater is turned on!

Actually the old Digitrax "Quarter Test" will let you know if you have any weakness in your feeders or rail joints.

Good Luck, Ed

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Posted by RR_Mel on Friday, May 12, 2017 8:32 PM

Randy is right on about buying the board with the ZXCT1009s soldered to the board from Rob, the two surface mount parts are not much larger than the head of a straight pin.
 
 
Mel
 
Modeling the early to mid 1950s SP in HO scale since 1951
 
My Model Railroad   
 
Bakersfield, California
 
I'm beginning to realize that aging is not for wimps.
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Posted by graymatter on Friday, May 12, 2017 10:16 PM

Just my two cents...I put a ampmeter between the 13 volt 1.8 amp NCE power supply and the NCE power panel. I spice the meter in the positive wire between the DC power supply and the NCE power panel.

I am going to add an ampmeter to each power supply/booster I add.

EDIT: what I am suggesting is measureing the DC current from the DC power supply. Measuring the DCC signal can be done with an Ocilloscope and if the amplitude of the DCC signal drops... that would indicate the DCC system is being loaded down. 

It would be much simpler to watch the current draw from the DC source that supplies power to the DCC system.

If you have an analoge meter you can make markers on the face. 

Marks for the average current draw of one locomotive. A mark for two etc.

and a mark for the max current your DC power supply can safely handle.

if an ampmeter needle twitches wildly when the locomotive is in a particular location, that could indicate a trouble spot on the track or switch etc. This is why I prefer analogue to digital ampmeter.

Mark R is correct the analogue meter would not give an accurate reading of the DCC current. Just the DC current from the power supply going to the DCC PCB.

 

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Posted by Mark R. on Friday, May 12, 2017 11:03 PM

graymatter

Just my two cents...I put a ampmeter between the 13 volt 1.8 amp NCE power supply and the power panel. I cut the positive wire and conected it to analogue made in America ampmeter. 

I am going to add an ampmeter to each power supply I add.

 

 

That meter may not work as expected. Installing it the way you are describing would require a high frequency (more costly) type of AC ammeter as the DCC signal functions at a much higher frequency that standard AC current. It may not work correctly or may even be damaged.

Mark.

¡ uʍop ǝpısdn sı ǝɹnʇɐuƃıs ʎɯ 'dlǝɥ

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Posted by richg1998 on Saturday, May 13, 2017 1:02 PM

That is why I answered with results.

Any scientist worth their salt will attempt to do an experiment to see if a person’s experiments are valid.

Rich

 

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Posted by lifeontheranch on Monday, May 15, 2017 9:41 AM

The Not Secure warning is a result of the web site having not implemented SSL. Nothing to do with ads on the site.

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Posted by betamax on Monday, May 15, 2017 4:56 PM

Said website is owned and operated by TorStar Corp. (The Toronto Star's publisher). 

 

That being cleared up... Can we stop the silliness?

 

The easiest way to measure the current flowing in your DCC system is to connect an ammeter in series with the power supplied to the booster.

Yes, some current will be consumed by the booster in the form of heat being dissapated by various semiconductor and passive devices.  But, Kirchoff says what goes in must come out, so the amount indicated is the current being demanded by the booster and all loads connected to it.

Simple and doesn't add any problems or complications to the track circuit.

 

 

 

 

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Posted by RR_Mel on Monday, May 15, 2017 5:39 PM

betamax

Said website is owned and operated by TorStar Corp. (The Toronto Star's publisher). 

 

That being cleared up... Can we stop the silliness?

 

The easiest way to measure the current flowing in your DCC system is to connect an ammeter in series with the power supplied to the booster.

Yes, some current will be consumed by the booster in the form of heat being dissapated by various semiconductor and passive devices.  But, Kirchoff says what goes in must come out, so the amount indicated is the current being demanded by the booster and all loads connected to it.

Simple and doesn't add any problems or complications to the track circuit.

 

 

 

 

 

That sure beats the way I did it and no calibration needed.  There is only 220ma used by my DCC controller with a 387ma DCC load, my Fluke measured 607ma at 15.1 volts DC in.
 
Thanks Betamax
 
Mel
 
Modeling the early to mid 1950s SP in HO scale since 1951
 
My Model Railroad   
 
Bakersfield, California
 
I'm beginning to realize that aging is not for wimps.
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Posted by mfm37 on Monday, May 15, 2017 8:19 PM

fender777
Well I am not building anything to test' never heard of a ramp meter. I guess if my trains work I am good. So far they do. I thought their might be a standard No that the DCC controller puts out on the track when idle. Thanks

You surmise correctly. If they are running OK, you are good. Your DCC sytem already has a booster. Every DCC sytem has one to power the track. The booster is built in to your PowerCab. It will "put out" the listed voltage - check your manual. You can measure the output with an AC meter. Your reading may not be exact depending on the meter. It will be in the ballpark and close enough for most. Current draw is dependent on what is running. Nothing on the track, there's no current draw to measure. If your trains are running OK, then the POwercab is putting out enough voltage. Parked engines with decoders  draw a negligible amount of current. Light bulbs and leds will also draw current.

When current draw begins to exceed the rating of your Powercab (1.5amps IIRC) the trains will stop because the powercab's internal overcurrent protection will trip. That is when it will be time to add a booster that supplies more current. None needed until (if) that should happen.

You can do the "quarter test" around your layout. This involves simply shorting the two powered rails to see if the Powercab's internal breaker acts. It should trip immediately when the rails are shorted. If not, increase bus size or/and add feeders. When the breaker trips immediately all over the layout, you are good. BTW, it's called the coin test because at least in N scale, a quarter works well to make the short circuit across the rails.

You can add gauges if desired. Many like the extra info.

I prefer simplicity: Run trains, fix problems if they arise, Run some more trains.

Martin Myers

 

 

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Posted by lifeontheranch on Monday, May 15, 2017 8:51 PM

mfm37

You can add gauges if desired. Many like the extra info.

I prefer simplicity: Run trains, fix problems if they arise, Run some more trains.

Martin Myers

You have to admit they look cool. Cool

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