Dcc busbar wiring

[Victor51]

I have just changed from a simple analogue layout (circular) to dcc. In order to do this, I fitted a bus bar with dropper wires. I'm new to all this and can't get the dcc Loco to run. I have linked the controller to the end of the bus bar, and also by separate wiring to the bus bar. I've run an electrical tester over the rails and these show as being live.

Can anyone offer any practical advice, otherwise I'm returning to analogue?

[bbishop]

Three thoughts:

 

Is it the loco?  Have you tested it on a rolling road or length of track?

 

You should not have a complete electrical circuit.  You need an electrical cut so it is, in effect, a circular end to end.  This may be an old wives tale, but better safe than sorry.

 

You have to be rigorous with your electrical breaks.  I wired up Beaulieu with a length of track in a crossover.  Easy, I thought, isolate at one end.  Result ***SHORT***.  I had to isolate both ends.

 

Bill

[Victor51]

I got the Loco to run on one piece of track, so I know it,s not this. The piece of track was in a siding, and not connected to the main circuit.

[WIMorrison]

You do have the correct address slected for the loco, I hope?

 

If you are using the default setting for the decoder this should be 3, however if it has been changed by someone(yourself?) then you will need to make sure that you use that address.

 

I suggest that you take 2 wires from your controller to the test track and get the loco to move up and down, then take that same pair of wires and connect to your main track to confirm that there isnt an issue with the track or bus. if the loco worked on test track and main track using the same wires then your issue is with the bus. If it works on test track but not on main track using same wires you have a track fault.

[Victor51]

Thanks. I was hoping not to have to disconnect, but I will. Crawling around on the floor at my age is undignified at the best of times.

I don't understand the concept of a break in the bus bar, how does the power continue? Please explain. Mine is a horseshoe shape already. And I have linked the dcc controller to one end - is this OK?

[WIMorrison]

I am not saying there is a fault in your wiring, I am just giving you some steps to isolate where the issue might be, then when it has been narrowed down to that single area that area can be investigate.

[atticombe]

Victor51

 

May I offer a web site which helps solve many model railway problems, I have used it many times and always found the answer I sought.

 

try http://www.brian-lambert.co.uk you won't be dissapointed

 

Michael

[DCB]

Text book example of why not to use one pair of bus bars for the whole layout. It applies quually to DC and DCC and reverting to DC will not make any difference at all.  If you Divide it into sections with isolating rail joiners and isolating switches and then you can progressively switch the sections on(or off) to find which on which section the fault is located.

 

Prising back railjoiners to create gaps and Chopping droppers is your only realistic alternative, starting again might be easier but wire up the first section and test it before adding any more, then test that and continue until the wiring is finished.  When it is all working and then fails that is when you need the switched isolated sections.  Faults can be anything from pins in point gaps, displaced point tags, track pins in loco motors, broken wires shorting (Clapham accident 12" to 1 ft scale) displaced layshaft shorting on a Q1.

 

 Faults are devious little sods and sometimes reappear after months or years of hibernation.

[Phil S]

Text book example of why not to use one pair of bus bars for the whole layout. It applies quually to DC and DCC and reverting to DC will not make any difference at all. If you Divide it into sections with isolating rail joiners and isolating switches and then you can progressively switch the sections on(or off) to find which on which section the fault is located.

 

Prising back railjoiners to create gaps and Chopping droppers is your only realistic alternative, starting again might be easier but wire up the first section and test it before adding any more, then test that and continue until the wiring is finished. When it is all working and then fails that is when you need the switched isolated sections. Faults can be anything from pins in point gaps, displaced point tags, track pins in loco motors, broken wires shorting (Clapham accident 12" to 1 ft scale) displaced layshaft shorting on a Q1.

 

Faults are devious little sods and sometimes reappear after months or years of hibernation.

[Phil S]

Whilst agreeing wholeheartedly with David's reply above, if you have one of those nice multimeter's I keep advocating everyone should have 8-).....

You CAN locate the short circuit on the layout by using the resistance range(s) and ( with controller and as much as practical lifted off or disconnected from the track ) search around the track for the lowest reading.... This is of course easier if the layout is already isolatable.... But I don't advocate the same sectioning as used for analogue cab control, but a more general / logical'area'based grouping such as through tracks or sidings.

 

Your search may also be helped if you can recall what, if any,train was moving at the time... Or point change that may not have properly switched.

 

Two historic examples which explain why my DCC loft layout has (4 power districts and sub districts within them ).... With a switch for each and an led (showing voltage on track) on the trackside of the switch. (So it lights up if a powered neighbouring section is bridged to that section by an item of rolling stock with metal wheels, or if a 9v battery was allied to the track section (either with the correct polarity, or better still, a bi-coloured LED )

Back in Zero-1 days my layout was 1 track section ( and 1_accessory section/bus ) .... A short occured ... Thankfully only 1 trainhwd been running.... But in plains he through a tunnel... I lifted the track at each end and the short was still there.... Running a finger in the ballast revealed a single strand of wire knocked by the moving train to short the rails. .....never again! .... Section switches ( and PSX intelligent breakers which retry every 2 seconds ) ever since.

My present loft layout, with a visitor present=: a train derailed.... 1st assumption was that where the short would be.. But it wasn't..... I had had a metal clad 9V battery in my hand when the derailment occurred.... And I simply put it down on the track to go and deal with the derailment.... But the short didn't clear as expected ...... That was when I looked carefully at the resistance (power off)... And the lowest value revealed theattery on the track.

Don't ever believe someone who says they never have a problem.... The solution is to build In diagnostics to help you locate a problem quickly...

Eg. Illuminated buffer stops show power on that siding. Streetlights or specific houses lit by a nearby power bus. Eg 12Vdc, 5Vdc, track-dcc, accessory-dcc, 16Vac accessory power .....

[Ray H]

I've just re-read the initial post in which the originator says "I've run an electrical tester over the rails and these show as being live."

 

Can we clarify how live the rails were and whether he tried at several places on the layout because - and I'll freely admit I may be missing the obvious - this doesn't sound like a layout short to me. At first glance this sounds like a problem with the (only?) loco (or something not set correctly on the decoder).

 

Can I suggest that the OP confirm whether his meter readings showed any difference in voltage readings with and without the loco on the track?

[Phil S]

Agreeing with the above, having re-read the original posting. Assuming that any suppression capacitors in the track feeds have been removed and the dcc-fitted loco is on its original number of 3..... ( a reminder that a 'dcc-ready'loco is NOT 'ready' until you have fitted a decoder after purchase!)

 

Check the loco: if placed on a separate piece of track,with a 9V battery touched across the rails; whether still an analogue (DCC ready) or a DCC fitted loco, the loco should respond and move ( forwards if the +be terminal is on the right hand rail ). (Although analogue running CAN be disabled in a DCC fitted loco, this is not how they are delivered... It is a user choice after purchase )

 

Reconnect your DCC controller to your layout. Using the track output

 

With your meter set to act volts - approx 20V range - check for a consistent value around your layout although it may not be an accurate value due to the meter.

 

Replace the DCC FITTED loco onto the track, and select loco number 3 to control. ....and report if it responds.

For further help.... Identify which DCC controller you are using, and the loco you are trying.

[Ray H]

. . . . . .

 

With your meter set to act volts - approx 20V range - check for a consistent value around your layout although it may not be an accurate value due to the meter.

 

. . . . . . 

 

May I be permitted to indicate that my (cheap) digital meter won't read DCC powered track voltage when set to DC, it only measures anything when set to AC volts and the lowest range there is 200V!

[Pete the Elaner]

May I be permitted to indicate that my (cheap) digital meter won't read DCC powered track voltage when set to DC, it only measures anything when set to AC volts and the lowest range there is 200V!

Would you expect it to read anything on DC? I wouldn't.

DCC is high frequency square-wave AC so average DC value will be zero.

You won't get an accurate reading on AC either because it is calibrated for RMS of sine wave. You will get a reading within sensible limits though.

 

It sounds like your meter auto-senses its range. It is best to start off with a high range anyway. Voltmeters are usually fine because they have such a large resistance, but (because of the way you need to connect it) you can blow an ammeter if you set it to low setting first.

Edited September 20, 2017 by Pete the Elaner

[Enterprisingwestern]

I know it's a bit late now, but this is a classic example of not testing each bit of wiring you do as you go along, saves the headless chicken mode at the end.

Also, re Multimeters, cheap and nasty ones are ok for basic circuit continuity testing, but as others have said, not much cop when you are in deeper waters, buy a good quality one and save yourself some hassle.

 

Mike.

[Ray H]

Pete

 

My immediate thought when I read Phil S's post (No. 13) and his reference to 20V range was, because my meter only has that figure in the DC range, that it referred to a DC setting.

 

I was just attempting to clarify that the reading needed to be on the AC range, something that recent converts from analogue to DCC might not have appreciated

[Pete the Elaner]

I was just attempting to clarify that the reading needed to be on the AC range, something that recent converts from analogue to DCC might not have appreciated

Worth mentioning, especially after I had someone on Facebook insisting DCC was a DC signal & telling me what a **** I was because I told him he was wrong.

[Phil S]

Phil S: Slight apology:  'act 20V'  was meant to read '  ac 20V '   ... an extra t appeared from somewhere [spelling auto mis correct ] , and i didn't notice until reading these comments.  Of course dcc is an alternating square wave ....and only has any 'dc' value if 'loco 0' is allowed and is moving.... a horrible method which alters the average ac value to be non-zero.. not recommended and not allowed on many systems.

 

the only 'dc' references i made was to a simple check with a 9V dc battery       the suggestion of a '20V {ac) ' range was simply to ensure a suitable range for a dcc signal which was likely to be 12-16V ac but which some meters may show too high or too low because they were primarily or simply designed to measure 50-60Hz sinusoidal ac.

[shibushe]

It is important to only use two wire colours from Bus To Track. Never use these colours for any other wiring on your

Layout.

So, Have you accidently crossed say, A red outer track wire to an inner Black. Just a thought.

[Crosland]

Before wiring, buy or make a very simple continuity tester with a battery and a buzzer. Clip this across the rails. Now proceed to wire the layout. If the buzzer sounds then you have created a short.

Edited September 20, 2017 by Crosland

[WIMorrison]

Just wondering if points could be the issue?

 

You say it was a DC layout and you have installed DCC on it and I wonder if all your points are DCC friendly or whether you have them wired and once is closed causing a short?

 

Theoretically this should cause the controller to shut down but as we don’t know any details we don’t know if this is the case - perhaps the normal default settings have been changed and rather than cutting off the power what has been set is for the system to remain powered and the locos stopped due to short?

 

Would be good to see a track plan and know where your feeds are together with knowledge of what DCC system you have purchased and which decoder you have installed into the loco

[Crosland]

Before wiring, buy or make a very simple continuity tester with a battery and a buzzer. Clip this across the rails. Now proceed to wire the layout. If the buzzer sounds then you have created a short.

 

Conversely, create a deliberate short occasionally. if the buzzer doesn't not sound you have an open circuit (or too high resistance).

[Pete the Elaner]

Before wiring, buy or make a very simple continuity tester with a battery and a buzzer. Clip this across the rails. Now proceed to wire the layout. If the buzzer sounds then you have created a short.

What a simple, effective tool to have when wiring.

As most good wiring practices, useful for DC as well as DCC. This could easily be step #1 in any wiring manual!

[DCB]

Before wiring, buy or make a very simple continuity tester with a battery and a buzzer. Clip this across the rails. Now proceed to wire the layout. If the buzzer sounds then you have created a short.

Excellent idea, I used a door bell for years to continuity check vehicle wiring. where I couldn't see such as stop lights.  I'm not sure bells work on AC but a series diode would sort that.

[Pete the Elaner]

Excellent idea, I used a door bell for years to continuity check vehicle wiring. where I couldn't see such as stop lights.  I'm not sure bells work on AC but a series diode would sort that.

I think you mis-understand how simple this idea is. There is no AC involved.

The idea is to connect the battery & bell instead of the controller/command station. The layout then acts like a big switch which should remain open. A short-circuit closes the switch which rings the bell.