Do I need a power booster?

[RAF96]

17 minutes ago, Oldddudders said:

A cheap digital multimeter, perfectly good enough for most modellers' purposes, is less than £10 on Amazon, probably cheaper on Aliexpress if you can wait a few days. A most useful diagnostic tool. I'm no amateur electrician - still less a 'professional', of course - but it serves me well. 

Screwfix and Toolstation and on occasion Aldi and Lidl sell them for around a tenner. It is worth checking they can cope with up to 10 amps DC current as some meters have a 200mA limit which precludes their use for motor stall current checks.

 

@melmerby do you have a link file for use with your USB scope to translate the binary commands into text. I wrote one initially but never got it finished.

Apologies for the fuzzy screen grab.

 

[RikkiGTR]

7 hours ago, Andymsa said:

The poor op must be getting really confused by all the tech talk of specifications…

Correct 😬

 

My images are too big to upload from my phone but hopefully I can describe it well enough - 

Track is N Gauge, all Peco. 

Fiddle yard is a basic 8-track (4 up and 4 down line) configuration. The only part of the layout that uses set track points (the rest is code 55 finescale). 
I have droppers on each track before they enter the fiddle yard from either side and one on each fiddle yard track as well. So 12 droppers covering the fiddle yard (or 24 if you want to count red and black individually). 

Edited May 4 by RikkiGTR

[YT-1300]

29 minutes ago, RikkiGTR said:

Correct 😬

 

My images are too big to upload from my phone but hopefully I can describe it well enough - 

Track is N Gauge, all Peco. 

Fiddle yard is a basic 8-track (4 up and 4 down line) configuration. The only part of the layout that uses set track points (the rest is code 55 finescale). 
I have droppers on each track before they enter the fiddle yard from either side and one on each fiddle yard track as well. So 12 droppers covering the fiddle yard (or 24 if you want to count red and black individually). 

Try reducing the resolution of the images, they will help the community help you.

 

With DCC its best for each piece of track to have it own dropper, for instance if you have 3 lengths of flexi on each road in your fiddle yard, you'll need 6 droppers for that road (both rails).   Each point also needs a power feed to the toe of the point, the reason for this is because fishplates aren't reliable enough to carry the power needed.  I view fishplates as a means to hold the track pieces in alignment only.

 

DCC is often quoted as 2 wires to the track, however its more 2 wires to every piece of track!

 

As has been mentioned, a cheap multimeter is an essential tool.

[young37215]

I model 00 and have a large (14m x 3M) layout with 30+ sound fitted locos. According to the DCC Concepts Alpha Meter I installed a year or so ago, I draw around 1Amp with 5 or 6 sound locos running at any time. There is a Youtube video from Charlie at Chadwick which shows a similar outcome. 

 

I used to use a Guagemaster Prodigy to control the layout and never had any power issues. Based on what the OP has stated and my experience, it does seem that the problem is resistance and voltage drop rather than an under powered controller. I suspect that the answer to the ' do I need a booster?' question is no. I would be going down the multimeter route as better qualified people have suggested as the next step in my problem solving efforts.

 

 

[GrumpyPenguin]

12 hours ago, RFS said:

 

Suggest you have a read of this article to get a better understanding of the purpose of doing the coin test for DCC systems.

Read it before & it goes against everything I was taught/practice as an electrical engineer.

[GrumpyPenguin]

10 hours ago, melmerby said:

IIRC Digitrax actually recommend this.

The McKinley Railway used this as it was being built to verify the wiring.

That's entirely up to them, i stand by whjat I have already said.

[GrumpyPenguin]

10 hours ago, melmerby said:

But you are not a DCC engineer.

Are you an electrical engineer ?

 

AC, DC, DCC - the principles of electrical current is still the same.

[jamesed]

I'm sort of with you @GrumpyPenguin on the coin test thing although I can see that it works - in a crude way.  It just feels completely wrong to be deliberately introducing a short circuit into any powered circuit. I won't use frog juicers or similarly powered auto-reversers for exactly the same reason - even though they clearly work.  Having said that, there are plenty of occassions when I manage to create inadvertent short circuits!  Nothing is ever a substitute for good wiring system design followed up with methodical fault tracing with a multimeter when necessary - as has previously been said a cheap meter will do the job well enough. However, if the wiring spec isn't up to the job no amount of fault finding will fix all the potential problems. 

[RikkiGTR]

 

May be hard to see but I've marked on the plan where I have feeds for the fiddle yard.

Truth be told it may be an issue with under-gauge wire used for the main bus - I got it from Amazon and it is Chinese, it does feel quite flimsy and is probably not 32/0.2, so I'm going to remove the entire bus and replace it with much heavier wire and see if that sorts out the issue.

Edited May 4 by RikkiGTR

[Crosland]

19 hours ago, melmerby said:

The RS Pro cable has 17A rating, several other brands show 10A or more

Most DCC suppliers sell it for bus wiring and IMHO 10A is perfectly adequate.

 

Current ratings are meaningless unless you know the voltage drop per unit length at a given current.

 

Cable sold for mains wiring has a current rating, but it's rated such that the voltage drop will be within allowable limits for mains. At the same current in a 15 V DCC system, the same voltage drop would be a show stopper.

[Andymsa]

1 hour ago, GrumpyPenguin said:

Read it before & it goes against everything I was taught/practice as an electrical engineer.

I get where you’re coming from, but the let’s say you have a short for what ever reason how will you know the layout will shut down track power? Digitrax command stations and boosters are capable of outputting 8 amps. That’s a disaster waiting to happen even fire as your track melts. So you need to know things will shut down when needed, the only way to test is introducing a test short ie coin test.

[Andymsa]

45 minutes ago, RikkiGTR said:

 

May be hard to see but I've marked on the plan where I have feeds for the fiddle yard.

Truth be told it may be an issue with under-gauge wire used for the main bus - I got it from Amazon and it is Chinese, it does feel quite flimsy and is probably not 32/0.2, so I'm going to remove the entire bus and replace it with much heavier wire and see if that sorts out the issue.

replace with 2.5mm mains wire. 

[melmerby]

49 minutes ago, Crosland said:

Current ratings are meaningless unless you know the voltage drop per unit length at a given current.

So 60 ohms per km and current rating at a given temperature isn't a good enough description?

 

 

Edited May 4 by melmerby

[melmerby]

2 hours ago, Crosland said:

Cable sold for mains wiring has a current rating, but it's rated such that the voltage drop will be within allowable limits for mains

It also is dependent on installation.

e.g. open wiring, clipped to wall, buried in plaster, bunched in conduit etc. All are different ratings for the same cable.

 

I'm bemused by all the talk of even minimal voltage drops needing to be eliminated for a booster to work correctly and cut the power on an overload

Every piece of track on my layout is feed through 2 diodes* which drop the voltage in the range 1.2 - 1.4 volts, yet the booster cuts on the slightest hint of a short circuit, it is set to 4.5A trip and is fed from a 110W DC power supply.

 

* for occupancy detection.

[Oldddudders]

4 hours ago, GrumpyPenguin said:

Read it before & it goes against everything I was taught/practice as an electrical engineer.

Oh well, as they say in Spain, hacienda that, then. 

[RAF96]

20 hours ago, Crosland said:

Cable sold for mains wiring has a current rating, but it's rated such that the voltage drop will be within allowable limits for mains. At the same current in a 15 V DCC system, the same voltage drop would be a show stopper.

I use 2.5mm ring main wires for my bus and 0.75mm lighting flex for my droppers and my RRAMP meter shows 15.4 volts across the whole layout - single garage sized folded-8, twin track powered by an Elite controller on a 4-amp PSU. Absolutely no power issues to date 5 years down the line.

[Andymsa]

I think people are getting too hung up with volt drop and resistance. As RFS says 2.5mm mains wire is absolutely fine, I have never had power issues with my very large layout.

[GrumpyPenguin]

21 hours ago, jamesed said:

I'm sort of with you @GrumpyPenguin on the coin test thing although I can see that it works - in a crude way.  It just feels completely wrong to be deliberately introducing a short circuit into any powered circuit. I won't use frog juicers or similarly powered auto-reversers for exactly the same reason - even though they clearly work.  Having said that, there are plenty of occassions when I manage to create inadvertent short circuits!  Nothing is ever a substitute for good wiring system design followed up with methodical fault tracing with a multimeter when necessary - as has previously been said a cheap meter will do the job well enough. However, if the wiring spec isn't up to the job no amount of fault finding will fix all the potential problems. 

 

21 hours ago, RikkiGTR said:

 

May be hard to see but I've marked on the plan where I have feeds for the fiddle yard.

Truth be told it may be an issue with under-gauge wire used for the main bus - I got it from Amazon and it is Chinese, it does feel quite flimsy and is probably not 32/0.2, so I'm going to remove the entire bus and replace it with much heavier wire and see if that sorts out the issue.

Looks like the bus cable/wire could very well be the issue.

2.5mm mains cable is single strand & diffecult to work with - stranded from someone like RS or CPC will be much better.

(cue : those who have used mains cable "without problems" & the skip scavengers).

[Steven B]

All this talk of wire diameters isn't helping solve the problem.nIf the rest of the layout works without fault then there's nothing fundamentally wrong with the wiring.

 

As the voltage drop is affecting the whole fiddle yard then my guess is that there's a dodgy joint between where the fiddle yard wires join together and the command station.

 

Steven B

[GrumpyPenguin]

This discussion is a perfect example of "a little knowledge can be dangerous".

 

I've made my points as a professional electrical engineer who spent most of his time fault finding/putting other peoples work right (a lot of it on 12v display lighting so working in similar voltages as being discussed here but far, far higher currents, up to 50a) but apparently I don't know what I am talking about.

 

My layout (24' x 10') has had the wiring installed & tested as I've already described & never felt the need for crude "coin tests" as I'm confident with my work. As it happens I've had the odd derailments at the futhest point from the boosters & instant trip out.

I'm using a Z21 & 2 x Lenz boosters.

 

I'm now finished with commenting, other people looking for advice can make their own choices based on what they read.

 

Enjoy the rest of your Bank Holiday Weekend.

[melmerby]

58 minutes ago, GrumpyPenguin said:

This discussion is a perfect example of "a little knowledge can be dangerous".

That comment is a perfect example of arrogance,

"I'm a professional and I know best"☹️

[melmerby]

On 04/05/2024 at 08:51, RAF96 said:

 

 

@melmerby do you have a link file for use with your USB scope to translate the binary commands into text. I wrote one initially but never got it finished.

Apologies for the fuzzy screen grab.

 

 

Sorry. No I don't

The odd occasion when I've had the scope on the layout I was just looking for a good signal that the Picoscope would resolve properly.

The main concern was ringing (following comments elsewhere on RMWeb) which "Bus Terminators" are supposed to cure, but I didn't get any on my 20' x12' layout with 100s of feet of track and numerous sidings.

 

The only thing I found was that a Digikeijs DR5000 had a less clean waveform than either a Lenz 100 system or a Roco Z21

 

[Andymsa]

3 hours ago, GrumpyPenguin said:

This discussion is a perfect example of "a little knowledge can be dangerous".

 

I've made my points as a professional electrical engineer who spent most of his time fault finding/putting other peoples work right (a lot of it on 12v display lighting so working in similar voltages as being discussed here but far, far higher currents, up to 50a) but apparently I don't know what I am talking about.

 

My layout (24' x 10') has had the wiring installed & tested as I've already described & never felt the need for crude "coin tests" as I'm confident with my work. As it happens I've had the odd derailments at the futhest point from the boosters & instant trip out.

I'm using a Z21 & 2 x Lenz boosters.

 

I'm now finished with commenting, other people looking for advice can make their own choices based on what they read.

 

Enjoy the rest of your Bank Holiday Weekend.

im sure the builders of the titanic were confident of there work, but look at what happened there 😁 your an electrical engineer and you know your stuff, just because it goes against what your taught doesn’t make the coin test crude or wrong. Us modellers have varying skill levels, some might not be as confident as us in their wiring and need to test if the layout will shut down safely. There  is an excellent website called wiring for Dcc maybe worth a look for you, there are many examples of layouts failing to shut down during shorts on the internet. You mention you tested your layout wiring, what tests did you do to prove the layout will shutdown if you did not do the coin test?

[Oldddudders]

The late Mark Gurries would be shaking his head at some of this. 

[Michael Hodgson]

On 04/05/2024 at 11:14, jamesed said:

I'm sort of with you @GrumpyPenguin on the coin test thing although I can see that it works - in a crude way.  It just feels completely wrong to be deliberately introducing a short circuit into any powered circuit.

 

It seems to me that model railways frequently introduce a short circuit into their traction supply.  Whether that's deliberate or inadvertent as is normally the case when operating is irrelevant.  The circuitry needs to be able to cope with it without causing any damage.  Something that confirms the ability to do so has got to be a good idea.