The Burford Branch

Tell us about your layout, where you put it, how you built it, how you operate it.
martin goodall
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Re: The Burford Branch

Postby martin goodall » Mon Aug 10, 2020 11:29 am

philip-griffiths wrote: I should also now ask for a degree in Ikea assembly....


I think we would all qualify for a degree (or at least a post-graduate diploma) in self-assembly furniture of various different makes! Fortunately, there was nothing of that sort this time, but when it comes to the main house move, probably next year, there's a large and awkward wardrobe to be taken apart and re-assembled. My wife and I still bear the scars of previous tussles with this piece of furniture, although we are now familiar with its faults and foibles.

Paul Hutfield
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Re: The Burford Branch

Postby Paul Hutfield » Mon Aug 10, 2020 12:30 pm

Pleased to hear the move went well and that Burford has safely arrived in its new home. Looking forward to the reassembly in the near future.

Best Wishes

Paul

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Re: The Burford Branch

Postby philip-griffiths » Mon Aug 10, 2020 6:32 pm

martin goodall wrote:
philip-griffiths wrote: I should also now ask for a degree in Ikea assembly....


I think we would all qualify for a degree (or at least a post-graduate diploma) in self-assembly furniture of various different makes! Fortunately, there was nothing of that sort this time, but when it comes to the main house move, probably next year, there's a large and awkward wardrobe to be taken apart and re-assembled. My wife and I still bear the scars of previous tussles with this piece of furniture, although we are now familiar with its faults and foibles.


Martin

We had to move an ikea bed in July. Unfortunately the ikea tools were lost but we had the instructions. So in assembling the beds, sideboards and shelves in a Nesta’s new place I used one of the boxes that came in the ikea packaging to hold all the Hex keys and manuals. Then wrote in big letters what it was on the lid. Considering that her place is only rented I can see myself potentially needing that box within 12 months....

Hope the move went ok.

martin goodall
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Re: The Burford Branch

Postby martin goodall » Sun Aug 23, 2020 5:22 pm

I have been making good progress with work on the underside of the layout, consisting of various changes to wiring and switching arrangements, which I had deferred until I could do this work without having to reach up under the layout (involving getting solder to flow uphill).

The changes are fairly mundane and are not easily illustrated, but one priority was to solder diodes across the coils of the electro-magnets for the uncouplers, to counter the backward ‘surge’ in the circuit that can occur when an electro-magnet is switched off. Paul Townsend has been trying to persuade me for several years to do this job, and the only reason for its not having been done sooner was that I was waiting until I could get the baseboards in front of me, while the layout is currently disassembled.

The first photo shows a SEEP electro-magnet with the diode soldered in place across the terminals. The cathode is wired to the Positive side of the circuit. I took the precaution of marking Positive terminals with red paint before doing this.

IMG_6496.JPG


The second shot shows a diode soldered across the wires of one of Ray Hodson’s ‘Magic Magnets’ solenoids.

IMG_6500.JPG


One of the other changes I made was to move an LED which I had already been using as an indicator when one of the uncoupling magnets is pre-selected, and to insert it in the electro-magnets switch panel immediately below the push-button that is operated to ‘fire’ a selected electro-magnet when a vehicle is standing or passing over it.

IMG_6504.JPG


I haven’t previously illustrated the sub-baseboard wiring arrangements, and frankly I am not at all proud of them or of the untidy way in which the wires run every which way, but I have not had any difficulty in identifying wires when necessary.

This shot shows the connections to the section switches panel (which was shown in an earlier post, when the layout was being dismantled). Only minor changes have been made, mainly in order to install an isolating switch in the milk dock / horse landing. The wires that are bundled together here are being led towards the inter-baseboard choc-blocks, while other wires are connected to track feeds on this baseboard.

IMG_6508.JPG


The next photo shows the choc block that feeds the electro-magnets switch panel. Changes here were mainly to accommodate a couple of additional LED panel indicators (not associated with the electro-magnets), which will be installed in the baseboard fascia when the layout is re-erected.

Although connections between the various switch panels and their respective choc blocks are colour-coded, most of the under-baseboard wiring is black. The red wires seen in this and other photos are the Positive returns in some of the circuits that are polarity critical, for example because in one or two cases LEDs are wired in parallel with those circuits. On the other hand, I didn’t colour code the Positive and Negative wires in the electro-magnets circuit, even though they too are polarity critical.

IMG_6507.JPG


Those wires that cross the baseboard joint are led to choc-blocks connecting the wires across the joint. As explained before, these ‘plugged’ choc blocks are an improvised version.

IMG_6511.JPG


Extra circuits will need to cross the baseboard joint in future, and I have installed a pair of proper plugged choc blocks for this purpose.

IMG_6506.JPG


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Baseboard B has now been set up in place of Baseboard A, so that I can start work on various minor wiring changes beneath that board.

IMG_6514.JPG


These under-baseboard photos also enable me to show the point control arrangements – a simple system of rodding and cranks driven by the small brass drawer knobs seen a few weeks back.

(The large square of plywood also visible in the next shot is the underside of the turntable well. The turntable has yet to be built, and the operating mechanism will have to be added below the turntable well, unless I resort to Power by Forefinger.)

IMG_6516.JPG


Changes of direction are effected by home-made aluminium cranks.

IMG_6517.JPG


The point operating mechanism incorporates micro-switches to change the polarity of the crossing vees. The arrangement of the micro-switches, together with the associated drive mechanism, is a simplified version of a design devised by Iain Rice.

IMG_6505.JPG


As soon as I have completed the minor changes to the wiring on Baseboard B, I should then be in a position to re-erect the layout.

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Re: The Burford Branch

Postby martin goodall » Sat Sep 12, 2020 9:12 pm

Work has been carrying on steadily over the past few weeks to complete the pre-planned work that had been scheduled while easy access could be gained to the underside of the baseboards.

This included revised feeds to the layout from the two transformers and the feeds to the controllers. The former involved the installation of a new choc block seen on the left of the photo below), and the latter comprised a replacement Din-socket (also seen in this photo) for the Modelex controller, which up to now had been connected to the layout only through a temporary lash-up.

IMG_6527.JPG


Another minor job was the installation of an additional isolating switch for the Carriage Siding (in case a railcar is parked there while a movement is taking place in the loop, which would not otherwise be isolated from it).

IMG_6525.JPG


I also installed an additional uncoupling magnet in the main line (seen in the next photo before it was wired up to its electrical feeds)

IMG_6528.JPG


Finally, a couple of extra choc-blocks were installed for cross-baseboard connections. The one seen here carries electrical feeds across the Baseboard B/C baseboard joint.

IMG_6541.JPG


After one or two final electrical jobs, re-assembly of the layout finally got under way in the past week. This involved a re-run of the emptying of King Tut’s tomb to make room for the re-erection of the baseboards. Before access could be gained to the walls of the royal chamber, all the grave goods had first to be removed, starting with the two chests of drawers that had been used to support the baseboards while the electrical work was under way.

IMG_6549.JPG


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Baseboard A was then positioned so that the baseboard legs could be re-fitted.

IMG_6552.JPG


and this baseboard could once again be set on its feet, when the lightweight extension at the back of this baseboard that carries the brewery buildings was also added.

IMG_6553.JPG


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Finally, the backscene was added to this baseboard.

IMG_6555.JPG


Baseboard B was dealt with in the same way.

IMG_6556.JPG


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The two main baseboards were then brought together.

IMG_6562.JPG


At this stage there was a discrepancy in the level of the two boards, but this didn’t faze me.

IMG_6563.JPG


It was simply a question of inserting chocks under the legs to even up the height of these baseboards, and to ensure that the baseboard surfaces were completely horizontal (checked with spirit levels).

The baseboard fascias were then added together with the various switch panels, controllers and inter-baseboard connections. Most of the buildings were also placed on the layout, although I have omitted some of these pending some work on the track – a couple of minor repairs and adjustments and then the addition of point rodding and ballasting of the track (a job that has been waiting far too long).

A couple of minor cosmetic repairs will be required, but the layout survived the move remarkably well.

IMG_6569 (2).JPG


IMG_6572 (2).JPG


[The proper layout lighting has not yet been installed; hence the rather odd lighting seen in the two shots above.]

Although there were no real problems, all this took quite a lot of effort (with some very welcome help from my wife), and I fervently hope that the exercise won’t have to be repeated for a good few years. It is slightly frustrating that all this work has simply restored the layout to the state it was in before dismantling started some months ago, but I knew from previous experience that this is unavoidable when a semi-permanent layout has to be moved.

martin goodall
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Re: The Burford Branch

Postby martin goodall » Tue Oct 06, 2020 2:03 pm

I haven't had time to do much on the layout in the past few weeks, due to other calls on my time, but one job I did get done was to connect the wires from the transformers to the layout. I showed a photo a few weeks ago of the new choc-block under the baseboard after it was wired up. The final job was to wire up the other half of this pair of plugged choc-blocks carrying the feeds from the transformers, bundling these together in a flexible cable-tidy.

IMG_6602.JPG


I have also installed a “Power On” indicator (a yellow LED) in the baseboard fascia, on the left of the switch panel controlling the electro-magnets (as there happened to be a spare hole here in the baseboard fascia, as a result of a previous change). Few people are likely to find such an indicator necessary, but past experience has taught me that it will provide helpful confirmation that power is actually connected to the layout, as well as a reminder to switch everything off at the end of an operating or testing session.

IMG_6598.JPG


One job that still awaits attention is to make good the gap between the backscenes behind the two main baseboards. As the photo below shows, I didn’t succeed in closing up the backscenes as effectively as I would have wished, despite the baseboards being tightly and accurately screwed together. As before, in addition to sticking the mill chimney in place over the joint, I shall have to paper over the crack in the sky above the chimney and touch up the painted smoke on the backscene (supplemented again by a wisp of teased out cotton wool).

IMG_6605.JPG

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Re: The Burford Branch

Postby martin goodall » Mon Oct 19, 2020 8:53 pm

An LED conundrum

Some time ago, I decided to add a panel indicator to the switch panel that controls the electro-magnets for uncoupling the magnetic couplings on the layout. At the time, there was a risk that a switch might inadvertently be left on (as I was not using push-buttons for this purpose at that time), and so an indicator seemed to be a desirable precaution. More recently, I have installed a single push-button to ‘fire’ the preselected magnet, but I decided it would still be useful to retain the indicator to show that a magnet had been selected.

IMG_6598 (2).JPG


The panel indicator takes the form of a red LED, rated at 12v. This came ready wired, and I suspect a resistor may be wired in to knock the voltage down to less than 12v. Whatever the arrangement, the LED duly glows brightly when an electro-magnet has been selected. However, I have noticed that when none of the switches is ‘On’, there is still a faint glow from the LED (which is not a reflection in the lens from the layout lights, and so is entirely absent when the transformer is unplugged), but I just can’t work out what is causing this.

I should explain that the circuit for the LED is entirely separate from the circuit that provides power to the electro-magnets. In fact, power for the electro-magnets is supplied by an entirely different transformer. Even when that other transformer is unplugged, the faint glow from the LED can still be seen. In case there might be some form of inductance from the power source itself, I re-wired the LED to a different circuit, but the faint glow from the LED could still be seen when no switch was connected.

I have double-checked the circuit; the LED is definitely wired the right way round, and there are no stray connections or reverse paths by which current could reach the LED when it is not switched on (and it wouldn’t work at all if the polarity of the circuit was not correctly observed.) I cannot identify any source from which any stray current could be leaking, whether by inductance or otherwise. But if the transformer powering the LED circuit is plugged in, the faint glow from the LED is present, even though no switches are ‘On’.

So can anyone who knows a lot more about electricity and electronics than me suggest the cause and also propose a solution?

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Re: The Burford Branch

Postby grovenor-2685 » Mon Oct 19, 2020 9:34 pm

If you post thr circuit here then maybe we can see something.
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Keith
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Re: The Burford Branch

Postby martin goodall » Tue Oct 20, 2020 2:48 pm

At Keith’s suggestion, I have prepared a simplified circuit diagram, which shows the entirety of the circuitry for the LEDs powered from the 12v DC output from the controller. I don’t understand electrical and electronic symbols, so please excuse the crude form in which this diagram is presented.

LED Circuit.jpg


The Yellow LED is wired in parallel with the circuit powering the Red LED. It is rated at 3v, and so a resistor is wired in series on the Negative (feed) side to reduce the voltage reaching this LED. (I have simply shown this as ‘R’ on the diagram.) This Yellow LED serves as a ‘Power On’ indicator, showing that the transformer is plugged in and switched on. [The transformer, an ancient H&M ‘Safety Minor’ unit, provides power from its other windings for the 14/16v AC feed to the controllers, and a variable 0 – 12v DC feed which is now used solely to provide power to a Seuthe smoke unit (set at about 11v).]

The Red LED is fed through one or other of six DPDT switches, of which I have shown only two on the diagram for simplicity. The other side of these DPDT switches carries a 13.8v DC supply from a totally separate transformer to feed the uncoupler electro-magnets. There is therefore no connection between the circuit for the electro-magnets and the circuit for the Red LED, but when a DPDT switch is On, it performs two separate and independent functions – (a) switching on the Red LED and (b) connecting the 13.8v DC supply to the electro-magnets; but note that no power flows in that other circuit until the push button switch on the panel is also pressed to ‘fire’ the selected electro-magnet.

When a DPDT switch is On, the Red LED glows brightly. However, when no DPDT switch is On, there is still a faint glow from the Red LED, if the H&M transformer is plugged in and switched on, even when the other transformer (powering the electro-magnets) is unplugged.

I rather doubt whether the Yellow LED affects the situation, because the red LED exhibited the same faint glow, even when it was connected through a completely different circuit to a separate power source (a smoothed 12v DC supply from the bonfire power board, powering only the flame flicker, but not the smoke of the bonfire, which obtains its power from the 14/16v AC supply from the H&M unit).

Do these details help anyone to spot the problem?

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Re: The Burford Branch

Postby grovenor-2685 » Tue Oct 20, 2020 2:56 pm

Could you temporarily substitute the H&M supply with a 9V PP3 battery and see if you get the same effect?
There is possibly some capacitative leakage through the switch wiring which should not occur with a smooth DC like from a battery.
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Keith
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martin goodall
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Re: The Burford Branch

Postby martin goodall » Tue Oct 20, 2020 3:13 pm

Thanks, Keith.

I'll try that. I'm currently 90 miles away from the layout, so it will have to wait until next week.

(By the way, just to show my complete ignorance of electricity, I had gained the impression that current flows from the negative terminal of the power supply to the positive terminal, but should that be the other way round? Maybe it doesn't matter so long as the Positive terminal is correctly identified, and polarity sensitive components are wired into the circuit the right way round.)

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Re: The Burford Branch

Postby grovenor-2685 » Tue Oct 20, 2020 3:59 pm

martin goodall wrote:By the way, just to show my complete ignorance of electricity, I had gained the impression that current flows from the negative terminal of the power supply to the positive terminal, but should that be the other way round? Maybe it doesn't matter so long as the Positive terminal is correctly identified, and polarity sensitive components are wired into the circuit the right way round.

Depends on how deep you want to get into the physics, convention is to think of current flowing from +ve to -ve and polarity sensitive devices such as LEDs (in your case) need to be connected accordingly. Usually the londer lead is the positive. If you dig down to the next level where current is to be defined by the movement of electrons then electrons have a negative charge and are attracted to the +ve thus flowing in the opposite way to the conventional current. Dig even deeper and things get more complicated and I'm not going there. That is moving from the realm of electronics towards that of nuclear physics.

With regards to your LEDs, they operate on current rather than voltage and that is why a resistor is needed, to limit the current, most modern LEDs give a good light on 5 mA and should not be run over about 20 mA. In this range of currents red/green/yellow LEDs will have a voltage of roughly 1.4 Volts across them, White and blue LEDs usually a little over 3 Volts. Any LED specified as 12 V will have a built in resistor.
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Keith
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Will L
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Re: The Burford Branch

Postby Will L » Tue Oct 20, 2020 6:38 pm

You are not alone. I recently replaced the bulb in the light beside my bed with an mains voltage LED bulb. Much to my surprise the bulb now glows slightly when switched off. To stop it doing so I have to unplug the lamp completely.

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Re: The Burford Branch

Postby Alan Turner » Wed Oct 21, 2020 7:37 am

Will L wrote:You are not alone. I recently replaced the bulb in the light beside my bed with an mains voltage LED bulb. Much to my surprise the bulb now glows slightly when switched off. To stop it doing so I have to unplug the lamp completely.


It's glowing because it is picking up a current from capacitive effects of your Mains wiring.

You can fit a neon indicator across the bulb to eliminate the problem which is easily achieved by fitting a socket with integral neon indicator.

regards

Alan

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Re: The Burford Branch

Postby martin goodall » Wed Oct 21, 2020 9:05 am

As I mentioned yesterday, I won't be able to try the battery test suggested by Keith until next week, but I should perhaps make it clear that the dull glow from the LED when it is switched 'off' doesn't greatly bother me in itself. My real concern is whether the 'stray' current that makes the LED glow faintly could be damaging the LED in any way. If it really isn't anything to worry about then I can live with it.

If I were to pursue my usual 'suck it and see' approach to mechanical and [low voltage] electrical issues, I suppose I could just let things carry on as they are, and wait and see if the LED fails. I've got a couple of spare LEDs if that were to happen.

However, I shall be interested to see the result of the battery test next week, and will report back on that.

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Re: The Burford Branch

Postby Will L » Wed Oct 21, 2020 10:03 am

Alan Turner wrote:It's glowing because it is picking up a current from capacitive effects of your Mains wiring.

You can fit a neon indicator across the bulb to eliminate the problem which is easily achieved by fitting a socket with integral neon indicator.

Nice idea Alan, and I had read something similar else where, I tried it but it didn't work. I was aware that in general the underlying problem is that these diodes work on very small currents which can show up in ways that don't fit in with a school boy understanding of electronics.

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Re: The Burford Branch

Postby Tony Wilkins » Wed Oct 21, 2020 4:36 pm

Hi Will.
If it is a touch lamp, i.e. one of those that can be turned on or off by touching a metal part, then the control circuit relies on the filament of a conventional bulb for its return current. This could be enough to make an LED bulb glow. They don't work at all with florescent bulbs as they don't conduct unless on.
My wife got a touch lamp from a boot sale only to discover it was faulty and the body was live when plugged in. The control circuit had blown. I removed it completely and rewired it as a conventional lamp, now safe.

Hi Martin.
LEDs will glow on rather less than 5m Amps. A diode test with a multimeter will make one glow dimly when forward conducting (forward biased in the vernacular) The other important thing with LEDs is the maximum reverse voltage, which is typically not more than about 5 volts and should not be exceeded.
If there is no reverse voltage present then the LED should suffer no ill effects whatever is causing the fault, but it would be nice to understand the cause of the mysterious glow. Could be worth testing for any AC Volts across the LED with a multimeter.
Regards
Tony.
Last edited by Tony Wilkins on Wed Oct 21, 2020 7:20 pm, edited 1 time in total.

martin goodall
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Re: The Burford Branch

Postby martin goodall » Wed Oct 21, 2020 5:44 pm

Thanks, Tony.

I was thinking of looking at it with my multi-meter, and this is something I'll do next week, in addition to the battery test mentioned above.

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Re: The Burford Branch

Postby martin goodall » Sat Oct 31, 2020 5:15 pm

I have had very little time for any hobby activities in the past few weeks, due to having to spend all my time completing a professional writing project to meet a tight deadline. I did, however, find the time to do the battery test on the layout suggested by Keith Norgrove. With no electrical equipment of any sort plugged in, I attached the leads for the two LEDs which serve as panel indicators to a 9v PPG3 battery. The yellow LED, which serves as a ‘Power ON’ indicator, glowed brightly, as it should, but the red LED which serves as an indicator that a switch for one of the uncoupling magnets has been turned on also glowed dimly when no electro-magnet was selected, as it did before. This LED then glowed bright red, as it is designed to do, when one of the DPDT switches for the uncoupling magnets was turned on. So the mystery of the dim glow in this LED, due to some stray (but very low) voltage somehow being connected across it, remains.

I didn’t have time to start poking around with the multi-tester, and I have in fact taken an executive decision to leave it at that, and not to investigate this mystery any further. The dim glow from the LED when the circuit is disconnected is hardly visible, especially now that the layout’s ceiling-mounted light fitting has been re-installed in the layout’s new location (see below), and floods the layout with bright ‘sunshine’. If the panel-mounted LED were to fail at some date in the future, then I would investigate further before replacing it, but for the time being I am prepared to live with it.

Getting the layout lighting sorted out was the only significant event that has occurred in the past few weeks.

IMG_6640.JPG

My wife thinks this lighting rig is ‘ugly’, but my answer to that is that you’re supposed to be looking at the layout, not at the ceiling.

This light fitting has served the layout in its several homes for some 35 years, and now that it is fitted with four modern LED bulbs that are rated at only 13.5 watts each, but flood the layout with more than 6,000 lumens of light, the scene is constantly bathed in bright sunshine. These new bulbs are a big improvement on another well-known make of LED bulb that I previously tried out. If you have followed this thread, you may recall that I complained that those other bulbs seemed to give the layout a yellowish cast (especially in photographs), and they failed after only a very short time.

The bulbs now in use clearly give a much more even spectrum of light and I can thoroughly recommend them. They are ‘Tungsram’ 13.5 Watt (Warm white) LED bulbs, with a colour temperature of 2,700K, and each bulb delivers 1,521 lumens. According to the manufacturer, they should work for 10,000 hours, and should withstand being switched on and off 50,000 times. I bought them from Waitrose. They are made in Hungary, so I took the precaution of buying some spare bulbs (even though I don’t expect to have to replace them for some time to come). If you think you could use some of these bulbs yourself, you’d better buy them before the end of the year. The complete 'Horlicks' the government is making of Brexit is likely to lead to major logistical problems in the New Year, which could seriously impede the import of goods from the EU.

These are a few photos taken after the layout lights were installed in the new railway room, showing the bright sunshine in which Burford perpetually basks.

03.JPG

I still haven’t had time to put the mill chimney back in place, and to paper over the gap in the backscene to restore the ‘smoke’ that issues from the chimney.

IMG_6642.JPG


IMG_6643.JPG


The government is expected to confirm in the next few minutes that we shall all be going back into lock-down for a month [if not longer], which means in practice that I shall be unable to do any further work on the layout itself for at least the next five weeks. However, this comes as no surprise, and I had already taken the precaution of keeping back several buildings that can be worked on away from the layout, if I end up being ‘exiled’ 90 miles away from the layout for a month or more.

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Re: The Burford Branch

Postby Tony Wilkins » Sun Nov 01, 2020 7:58 pm

martin goodall wrote:I have had very little time for any hobby activities in the past few weeks, due to having to spend all my time completing a professional writing project to meet a tight deadline. I did, however, find the time to do the battery test on the layout suggested by Keith Norgrove. With no electrical equipment of any sort plugged in, I attached the leads for the two LEDs which serve as panel indicators to a 9v PPG3 battery. The yellow LED, which serves as a ‘Power ON’ indicator, glowed brightly, as it should, but the red LED which serves as an indicator that a switch for one of the uncoupling magnets has been turned on also glowed dimly when no electro-magnet was selected, as it did before. This LED then glowed bright red, as it is designed to do, when one of the DPDT switches for the uncoupling magnets was turned on. So the mystery of the dim glow in this LED, due to some stray (but very low) voltage somehow being connected across it, remains.


Hi Martin.
Thanks for the electrical test report.
The fact that the fault behavior is the same with a pure DC source means one can safely discount any AC effects.
What appears to be happening is that there is a high resistance path somewhere allowing a very small current to flow through the red LED when all the switches are off. What I suspect is going on is a phenomenon called tracking.
You mentioned earlier that many of your solenoids are / were not fitted with quench diodes to kill the high voltage spikes caused when breaking the circuit of a magnetic coil. Over time, this voltage spike can break down carbon based materials and cause a relatively low resistance path across the insulator known as a track. I suspect this has happened to at least one of your switches. This used to be a common problem with car HT systems and damp mornings.
The only way to confirm this would be to disconnect the feed wire to L and the return to L1 and see what resistance reading you get across the switches in parallel when off. I would expect to see a resistance reading in the range of 10s of K ohms. It should of course be open circuit. To find out which one would mean further dismantling.
I can think of no other logical explanation for this behavior.

Regards
Tony.

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Re: The Burford Branch

Postby grovenor-2685 » Mon Nov 02, 2020 3:22 pm

I agree with Tony on this. Its safe enough to just ignore it.
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Keith
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Re: The Burford Branch

Postby martin goodall » Tue Nov 03, 2020 9:46 pm

Thanks, Tony, and also Keith.

The original switches for the electro-magnets couldn't handle the 3-amp demand placed on the circuit by these particular electro-magnets, so they were replaced with higher-rated switches, which I largely avoided using other than for testing , before the diodes were installed across the coils of the electromagnets a little while ago. So I don't think the voltage spike would have broken down the carbon based materials in these particular switches so as to cause a low resistance path across the insulator.

But I suppose it can't be entirely ruled out.

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Re: The Burford Branch

Postby grovenor-2685 » Tue Nov 03, 2020 10:03 pm

Since you have enough current leaking though for you to see the LED lighting up, and it cannot be induced when using a battery there has to be a resistance path much lower than it should be. I would estimate somewhere between 4700 ohms and 20000 ohms which should be easily measurable with a multimeter.
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Keith
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Re: The Burford Branch

Postby martin goodall » Tue Nov 03, 2020 10:37 pm

Keith wrote "....................you have enough current leaking though for you to see the LED lighting up, and it cannot be induced when using a battery.............."

Just to clarify:

(1) The LED glows only very dimly when power is supplied to the layout, unless one of switches for this circuit is turned on, when it glows brightly (as it should).

(2) The dim glow in the LED is also induced when using a battery.

However, I gather that you both agree that it's safe enough to just ignore it.

Tony Wilkins
Posts: 419
Joined: Tue Mar 20, 2012 3:57 pm

Re: The Burford Branch

Postby Tony Wilkins » Wed Nov 04, 2020 11:59 am

In a nutshell, yes at the voltage in use it can be safely ignored.
Regards
Tony.


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