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Voltage Meters
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 Posted: Fri Jun 3rd, 2011 10:35 pm
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Bronco_6
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Ladies and Gentlemen:

In the old days of DC power, it was a good idea to have a 0 - 15 volts meter on your power panel. It enabled you to trouble shoot and also see the drain on your power supply. An Amp meter wasn't a bad idea, either.

In the new age of DCC, how important is the use of these gauges on the power feed? Is it easier to have a hand-held multi meter for troubleshooting?

The layout is to the "I Got The Wood" stage and am working on the track plan.

Bronco :cb:



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 Posted: Sat Jun 4th, 2011 12:30 am
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Huw Griffiths
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I think I'd better say, from the outset, that I don't have a DCC layout (or any other layout, for that matter - space constraints).

Instead, I hope you don't mind me looking at this as an electrical engineer.


I must admit that I haven't come across many controllers (of any sort) with meters on them.


Edit: The ones I did come across were laboratory bench power supplies, being pressed into service as DC controllers - a bit of an overkill to be honest. I don't recall taking much notice of what their meters were telling me - but I don't think I actually needed to - the RTR locos I was using were good runners.


Certainly, I'm not sure what a meter could tell you, if it were permanently connected to a DCC controller.


However, a hand held meter (especially a DMM) could have loads of uses on any layout - particularly if you're testing loco motors (with decoders temporarily replaced by blanking plugs), or if you're testing track wiring - in both cases with the controller temporarily replaced by a 9V battery.


If you often have to do track wiring tests (perhaps on a portable layout), it might be easier to get an LED track wiring tester and see which LEDs light up when you apply the "juice".

These things are actually very easy to build yourself. (I should know - a number of years back, a major UK model railway magazine published my design for a posh one. Unfortunately, a few gremlins crept in at their end - so what they actually printed was a load of nonsense. This was a real shame, as I quite like the guys who run / ran this magazine. I know they got my emailed correction - probably best to put that episode down to experience ...!)


If it comes to checking if anything's getting to the track (and there are no shorts) on a DCC layout, I can only think of 2 instruments that would tell you much - an oscilloscope (which most people don't have access to) or a loco with a decoder (which you probably wouldn't want to risk if you had any doubts about the wiring).


Edit: The scope would show a waveform for the DCC signal - the waveform would be recognisable as DCC - however, it would tell you nothing about how much current is being drawn by whatever is on the track. For that, you'd need to put a low value, high current, resistor between one of the controller terminals and one side of the track "circuit" - and put the scope terminals across this resistor. Personally, this strikes me as a very expensive (and complicated) way to take measurements.

I've mentioned LED track wiring testers - these consist of one (or more) LED connected each way round, with a series resistor(s) between one side of the LEDs and one side of the track. I believe DCC signals swap polarity many times a second, so one of these testers will act as if it's connected to low voltage AC (all the LEDs will light).



My gut feeling is that most trouble-shooting on DCC layouts would probably be best done with the controller disconnected and replaced by a battery. However, I'm sure there are plenty of people here who'd know better than me on this question.


Regards,

Huw.

Last edited on Sat Jun 4th, 2011 01:13 am by Huw Griffiths

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 Posted: Sat Jun 4th, 2011 02:57 am
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W C Greene
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Wow-I use my voltmeter along with my old power pack as boat anchors. Maybe I had better buy a new meter.....Naaaaaw!

                       Woodie-glad I am wireless



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 Posted: Sat Jun 4th, 2011 03:41 am
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Herb Kephart
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Not a answer to the question that you asked, but on a straight DC layout an ammeter is far more useful than a voltmeter.

It will tell you if you have no connection to the loco (0 reading with power on) It will tell you if you have a short (meter all the way over to max). It will tell you if your motor is working too hard, before the dreaded smoke appears.

A volt meter will tell you what the voltage is---so?


Herb  :old dude:



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