Junctionmad

1 hour ago, AndyID said:

 

So don't use LEDs with different specs. The one thing you can guarantee is that they will all pass the same current and it's the current that determines the light output, not the voltage.

While there is definitely some difference in illumination , in many cases it’s irelevant ( mimics etc ) for example for blue , red, green and yellow I use 1k8 on 5V. Works fine 

Or use a CDU design that doesn’t pass the activation current through the switch ! 
 

There are several published designs where a transistor switches the output of the CDU and the switch simply switches the transistor. This removes the arcing and high current pulses from the switch 

Or use a CDU design that doesn’t pass the activation current through the switch ! 

11 hours ago, Crosland said:

 

The problem is that the converse is also true. Applying a higher voltage will cause a higher current to flow.

 

If one LED is mismatched and generates a higher Vf, at a safe working current for that particular LED, then that Vf is also applied to the other LEDs which may then be operating at an unsafe current. Another LED pops, the Vf gets even higher, ...

 

Yes, it's a corner case, but it can happen, and is one of the reasons why parallel connected LEDs are always used with individual resistors by anyone doing it for a living.

 

It’s such a corner case it’s around the corner

in real life electronics with similar leds , one resistor will “ work”   Yes it has certain specific drawbacks but in practice it actually works. Yes it’s not a Recommended approach but for leds  from the same family operating well into their safe current zone  it will work  

and no I’m not recommending  it  

I have done this also , here Les the fusion 360 cad , I just finished the software 

On 19/09/2020 at 21:31, AndyID said:

 

Even if there are no disconnects it's not a good idea. If all the LED's are the same colour they will not have the same forward voltage. Some will "steal" more current and be brighter than others. In the most extreme case one or two might steal most of the current and become Flame Emitting Diodes (although that's fairly unlikely).

 

If you look at the characteristic curves of leds the VF rises with current , Hence your sceanario will not occur 

My experience is I don’t rely on the peco wires and i solder on my own 

I would always recommend bonding the switch blades to the stock rail and switching the frog as the optimum approach, but as has been said the points will work out of the box also. 

If you points and signals are electrically operates then , other then having a particular interest , there no advantage in building mechanical interlocking 

in our case we have a bicolour led at each lever , red locked , green unlocked , red flashing , lever out of position 

simple and easier to understand 

I presume this is a 2x1 braced with ply baseboard.

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There's no fancy circuitry about a computer PSU. They are just another switched mode power supply which are  readily available for all sorts of supply voltages

Modern PC low voltage psus are actually quite complex , as any perusal of their schematics will testify 

4 hours ago, DavidCBroad said:

I have several computer PSU's stockpiled in my scrap drawer.    I am pretty cavallier about electrics but no way would I use anything like a 5 amp supply anywhere near model railway equipment. I have had wires glowing on a lot less than 5 amps and I wouldn't risk any more than a 1 amp power unit for accessories except possibly for throwing points with 1950s point motors and momentary contact.   Several separate 1 amp wall warts plugged into a proper 220/240 volt ring main properly installed by someone who knows what they are doing, (not necessarily a professional electrician as one nearly killed my son by wiring a metal patress box to a live feed) has to be the better solution. Even better use model railway power units with a decent 1 amp cut out not a modern 2.5p  1 amp Polyswitch.    If you must use a 5 amp monster then 0.25 amp Polyswitches on the individual feeds should delay the onset of the fault which burns the shed down.

I don’t know what you’d think of our big O gauge DCC layout with 2x10 A and 2x8A switchers feeding it  !! 

Other then the consumption of wire there is no other drawback to a low voltage ring main , however twice the number of connectors  etc give opportunities for poor installation and hence unexpected resistances 

if you size your wire right , you don’t get any issues with voltage drop anyways and wire is expensive , ring mains are essentially simply doubling the conductor area 

( the ring main has largely been replaced by radials ) 

At the cost of those levers , using them for dummy operations is a rather expensive peccadillo. 
 

as a builder of a 72 lever frame , my view is

dont bother with dummy levers unless you have a penchant for absolute fidelity and mechanical interlocking , there are tablets you can take that help this condition 

include levers to make your layout work as required , a model railway will never be a facsimile of a real railway. 
 

if the frame is large , evaluate the operator workload. ( especially if you add bells and what not. ) 
 

16 hours ago, The Johnster said:

Point taken, but I am working in DC and a large DC layout with electrofrogs must be wired to a very high standard for reliability (if anyone makes large layouts with DC any more).  DCC simplifies matters considerably.  It is not just a matter of reliability and a high standard of work, but ease of fault finding if things do go wrong,  Electric circuitry connected by soldered joints is vulnerable to handling mistakes when the layout is being transported, or the van being driven over potholes, or extremes of temperature or humidity.  At one show I attended many years ago, all sorts of modelling was featured and the layout took several significant blows from R/C racing cars that had got out of control of their owners at high speed and crashed into the legs, derailing stock, damaging couplings, finding dry joints, and generally causing problems.  This stopped after one of our operators accidentally trod on a Mclaren with extreme prejudice...  

 

Layouts are not porcelain, but generally need handling with due respect to give of their best.  Another problem with the club I was with was a reluctance to keep a layout in operation between shows, as the space was usually needed for work on the next layout, but I felt that we needed to practice operating and that as well as being able to put on a better show for the punters use of the layout between shows would identify the most likely trouble spots, and give us a better chance of eliminating them!  But the general culture of the club was building layouts, not running them, not the only reason we parted company but one of them.  

 

DCC has not only reduced the sheer amount of wiring needed, it has increased the physical resilience of layouts as well.  The down side is that the complication and problems are moved onto the locos and away from beneath the baseboard, and of course the cost.  Without playing the OAP on a limited and fixed income violin excessively, I have 13 locos, which will be 14 next week and 15 at the end of the year (I keep saying I have enough locos but I'm not convincing anyone any more; another 2 are on the cards for next year).  Converting to DCC is something I would certainly consider very seriously indeed were I able to pay for it; the idea of a constant 12vdc of current supplied to locos is attractive for someone who sets a good deal of store in reliable and controllable slow running.  But it is well beyond my means and likely to remain so.        

At £20 a decoder for a basic but high quality brand from Zimo and controller solutions from £150 up , why not buy 1 loco next year and convert the remainder 

13 hours ago, Derekstuart said:

 

 

I have to agree with Peter. Whilst I do use browser bookmarks, I have never once had to send my diary away to a forensic laboratory to reconstruct my hard drive; none of my back up software automatically records them.

Obviously not on a mac with iCloud then , you poor thing , not only are my bookmarks backed up , they automatically transfer across all my devices ( 7) 

2 hours ago, The Johnster said:

 

I can recall exhibitions being huge fun but very stressful, and often excuses for very heavy drinking sessions.  They are not good for me and I don't do them any more.

When I designed the big O gauge now at 20 baseboards  , it was always intended to be an exhibition layout. 
 

I was determined to ensure that past mistakes weren’t repeated and that the goal of a complex but reliable layout could be conceived. This extended to running reliability etc. 
 

Yes this needs a bigger budget and a careful and controlled process with one person in charge of that process , even if many people contribute to the work 

The result is a layout that can be erected and basically operational  within 1 hour. And to date the record for dismantling and  truck on the road ( we use a full size commercial truck ) is 40 mins. 
 

At a recent 3 day show.  Beside track cleaning it ran faultlessly for the period 

result no stress , huge fun. 
 

it can be done, electricity isn’t voodoo 

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le and reliable.  I hand operate my points, an acceptable method on a small BLT.  Involvement with club layouts in the past has convinced me that the more wiring you have, and the more complex it is, the more likely some poor sod is to spend a show underneath the boards with solder dripping in his eye, irrespective of how thoroughly it was all tested before the show...

We have a very electrically complex layout , using MERG Cbus , etc , one disconnected wire in 6 exhibitions , 

its not the complexity that causes unreliability , it’s the poor standard of typical electrical installs  that causes the issues 

Don’t use mains twin and earth , it’s like wrestling with a snake 

buy a few metres of decent stranded  cable 

On 06/09/2020 at 22:00, AndyID said:

I usually use solder but I think you could use wire nuts without any problem. They are used extensively for mains wiring in the US and they make very reliable connections. Might be a bit hard to find in the UK?

 

https://en.m.wikipedia.org/wiki/Twist-on_wire_connector

 

 

 

They are not acceptable terminations for 230-240VAC systems , US wiring code is about at 1950 compared to European standards , they are not specifically banned but difficult to make compatible with most European safety codes 

they can of course be used on low voltage systems 

Since a wagon turntable is unlikely to be motorised , surely just wire up the track using dropper wire , you could still do 90 degree turns etc once you return the the normal direction via the reverse route. 

The GM500 will work with the PM10 point motor , but if using the additional decoder  board as in the PM10D , you will have  to break into  the three wires from the decoder board to the actual solenoid and attach the GM500 as per its instruction manual 

I would recommend the book Model Railway Signalling by the renowned  C. J. freezer , it’s available 2nd hand online 

I

Aimed  at the railway modeller , it cover the compromises that arise in MRs around signaling 

unfortunately too many boosters are created on the basis of being “ added” to the existing dcc output ( be it a booster or command station/booster ) , ie by running another dcc feed bus. 
 

this is problematic where you already have multiple baseboards and an installed dcc buss 

Most  boosters simply typically duplicate the rating of the existing command station , this isn’t any use of you can’t easily add additional dcc buses 

additional busses are no use equally if you can’t easily identify seperate track zones  so that the current can be split , you may find you simply need more current in all track sections. 
 

hence there is a dearth of big boosters , the merg One is the only one I know of that capability 

there are three types of booster interface 

(a) proprietary , ie loconet , Zimo can , Z21 can etc 

(b) CDE ( command data , error ) this is a logic level interface to the booster devised by Lenz , it’s a simple dcc interface with short circuit feedback 

(c) direct dcc connection , a few boosters support simply connecting to the output of the command station directly , ie the dcc track output 

while you can use those boosters (C) in parallel with the command station ,but feeding shortage dcc busses ,  it’s also useful to completely supplant the command station with the new booster.  This is the easiest upgrade ASSUMING your bus wiring is rated fir the new booster 

note that in (C) short circuits are handled in the new booster and status is not fed back to the original command station , which it is in (A) and (B) 

If you are using Railcom ( C) may not be a wise choice as typically the cutout is not propagated by the booster 

6 hours ago, That Model Railway Guy said:

 

Ah fantastic! I was hoping that it was possible to use just the power from the booster as you described but being very new to DCC I didn’t want to assume anything. Thanks for that information, that’s really helpful.

 

The 10amp MERG DCC booster kit sounds great. Even taking the membership fee into consideration that’s a very good price. How tricky is it to put together? I’d certainly put myself more towards the beginner end of the spectrum with this sort of thing! 

 

Not difficult to build at all , all big chunky components. Lots of help on the merg forum 

you need to add a suitable power supply 16-18v dc. Many low cost switched mode units available on eBay 

7 hours ago, AndyID said:

 

Hi John,

 

Could you share a bit more detail on your wire in tube? Tube size, wire size, type etc?

 

Thanks

Andy

 

PS - I'd try avoid chocolate block connectors. The screws work-harden the copper wire and it is no longer "elastic" at the point of contact. After a while the connection is no longer gas-tight. Ultimately corrosion sets in and the connection fails.

 

You might get barrier strip connectors that have a captive metal plate between the screw head and the wire. That spreads the load over a much greater length of the wire to prevent it deforming and hardening.

+1 , Re chocolate blocks. That’s exactly what happens. Over time the wire then loosens and causes intermittent connection issues.