Suzie

It is actually quite easy in DC. Just use the 'Bridge Rectifier' method from near the bottom of Brian Lambert's page. It is very simple, just isolate the reverse loop, and feed it via a bridge rectifier. The only limitation is that you can only go round the loop one way, but that is a small price to pay for very simple wiring.

Is there a suppression inductor left in circuit between the pickups and the decoder? This will create an awful lot of magnetic interference, and especially if it is near to the speaker audible noise while the loco is on DCC.

Interesting that it was not moved under its own power if not a failure. Did the loco need positioning too?

Does that mean for the modern steam loco cab interior we will need a cooking ring, a microwave oven and an electric kettle as part of the cab interior detail?

Surely an electrically driven heat pump would be so much more efficient than those 1940's immersion heaters. Probably so efficient that that an efficient steam plant might be more efficient than a straight electric loco... ...Now when off the wires perhaps a coal gas plant and gas engine somewhere in the 60' long tender...perhaps an articulated tender...

What about firing steam locos with LPG, or natural gas, or even town gas? Could have been a fun might- have-been with some interesting tenders and some novel firebox designs. The energy density being a tad lower than finest anthracite could make for some very big tenders I think.

If the motor has an interference suppression capacitor on it then the motor will be bypassed. It is possible that locos and stock with electronics in them might get a bit upset by a Relco (DCC fitted or with a brushless motor for instance) but a traditional DC motor will not be effected regardless of size if properly bypassed with a capacitor.

If you put the optocoupler at the servo end of the wire, yes it will make a difference electrically - but put it at the controller end? It should not make a difference. If it does it is well worth investigating why. I know that opto-isolators are cheap - but they are not necessary at the controller end - the microcontroller can easily drive the signal wire with an impedance much lower than the 1K source impedance you get with your opto-isolator circuit.

What you are seeing by adding the optocoupler is that you are generating a source with a source impedance of 1K or less (assuming that you are using a 1K resistor). This will overcome problems in the controller. These problems occur in two situations:- When you first power on and the controller has not configured the output to be a bipolar output. On many microcontrollers input is the default setting so it is important in the controller design to set the pin that is used to generate the servo pulses as an output. You don't need an optocoupler to fix this problem - just adding the 1K resistor should sort it. When a controller is configured to stop sending pulses or is designed to be used with a pull-up resistor that is not fitted. If you are seeing this fix work it suggests there is a problem in the design of the controller. It does not need an optocoupler to fix it, better firmware or a resistor will do it.

As Nigel has shown is the way to go to eliminate pickup of noise on the signal wire. The opto isolator must be close to the servo, but the supplied lead on the servo should be short enough to not need cutting any shorter. Just fit a 3-pin header near to the opto isolator to plug the servo in. The servos have a high input impedance which makes them prone to picking up interference, so the pull down resistor is essential between signal and 0V at the servo. This is a key component to reducing the interference. The lower the resistance that you can get away with the better from an interference suppression point of view, but reducing the resistance does have implications on power consumption from the 5V supply (most likely not a problem) and the maximum current rating of the transistor in the opto isolator. You should be able to use a 100R pull down resistor without any problem (50mA). There should be no issue with interference pickup on the 5V suppy or the 0V supply when using this arrangement. The transistor in the opto-isolator connects the signal wire to 5V when it is on, and the 100R resistor clamps the signal wire to 0V when it is turned off and both situations are local to the servo so making for a low loop impedance for the interference. Any interference will have to overcome the load of the 100R resistor when the transistor is turned off and this is not going to happen unless the interference is very excessive, in the same way that no interference will be sufficient to light the LED in the optoisolator. I have never had to go to the effort of installing optoisolators to remove interference problems, but doing this will fix the problem as long as it is not related to dodgy servos or controller problems.

Looks like you need two resistors - one in the black line and one in the red line. I suspect that the orange line has to drive hard to the supply rails in order to turn off the LED that should be dark and it cannot do this if you put a resistor in series with it.

We are now seeing a situation where the capacity of the railway is actually sufficient for the number of passengers - the way to get passengers back is to reconfigure the interiors to be a bit more spacious, comfortable, and healthy! Now that a lot of people have found that they don't need to travel it is time to make them want to travel.

1% metal film resistors are only about tuppence each anyway in reasonable quantities nowadays so no real need to worry too much about tolerances or need to bother with ye olde carbon film resistors. https://www.rapidonline.com/1k-0-25w-royal-ohm-metal-film-resistor-100pc-cut-tape-62-3450

LEDs are easily powered from a 5V USB charger. The USB-C types should be able to supply 3A which will be sufficient for quite a lot of lighting. You should be able to obtain a USB-C charger locally at reasonable cost, or from online sources with a plug that fits your local socket. A 3A USB charger should be good for at least a hundred and fifty LEDs, probably much more - if you have less than fifty almost any USB charger will do, you might have one lying around. When using a 5V power supply you will not risk damaging the LEDs if you wire them the wrong way round - they just won't light. Since LEDs vary in their forward voltage from around 1.8V for most red LEDs all the way up to nearly 4V for some of the white ones you will probably have to experiment a bit with the series resistors required to get the brightness you want. Running the LEDs at the typical 20mA will often result in a lot more brightness than you really want so expect to need to use a much bigger resistor than the 68R - 150R that LED resistor calculators would suggest you need. 1K resistors are usually a good starting point. Get a big box of them and you can play around and see how you get on. Initially just put one 1K resistor in series with the LED and see how bright it is. If too bright put another in series, if too dim wire two resistors together in parallel and put them in series with the LED. When you want to buy more resistors you can be a bit more targeted and see what values you have from this table:- 2x 1K in parallel = 500R (470R nearest E6 preferred value). 3x 1K in parallel = 333R (330R nearest E6 preferred value). 5x 1K in parallel = 200R (220R nearest E6 preferred value). 2x 1K in series = 2K (2K2 nearest E6 preferred value). 3x 1K in series = 3K (3K3 nearest E6 preferred value). 5x 1K in series =5K (4K7 nearest E6 preferred value). Rapid are a good source of components mail order in my experience.

I think it is safe to say that the lack of recruitment (that would have commenced when Series 2 was shown before the current pandemic crisis) indicates that someone needs to pitch a new programme idea to keep railway modelling on prime time television. Since four in a bed has been consistently popular for over a decade, how about we get four model railway clubs, and send a delegation of modellers from each club to try out the other clubs. We can call it 'Four in the Club' as a nice click-bait style title. There will be plenty of tea drinking, swearing, and sulking to to keep the general viewers happy, and we might get to see an awful lot of layouts at a very early stage of construction.

If you are using servos then you have a couple of options:- Use a servo controller with built in frog switching. The Peco/ANE PLS100 solution uses an add-on to switch the frog polarity at the same time that the servo moves, or you can use something like the Signalist SC2 which has frog switching as standard. Use a servo based motor that integrates the switching with microswitches. There are quite a few simple mounts available, and you can probably make something suitable from a bit of sheet aluminium, but if your controller is prone to twitching a servo motor that limits the movement and uses the full range of travel of the servo can be a good idea, and it will have plenty of torque to operate the microswitches. Here is a Signalist SB1 motor which can actuate a pair of microswitches (one at each end of travel). It can be mounted below the baseboard and be fitted with a pin too.

Looks like there are some 132KV pylons being removed from Raleigh (two runs). Don't often see them being removed apart from upgrades.

LBSC AC electrification was 25Hz the same as the American Pennsy and Newhaven systems but a lower voltage 5.6KV - half of the 11Kv then standard in the USA, later 22KV) probably due to bridge clearance problems. The 25Hz power generation was used to power the 750V DC system after conversion using rotary converter substations with a 25Hz AC motor driving a DC dynamo. I think that the Midland Lancaster system was 25Hz as well. These early low frequency systems were chosen so that synchronous AC motors could be used, especially applicable to 3-phase systems like the Italians had. 16 2/3Hz made for lower speed motors than 25Hz. 50Hz motors would be too fast and not enough starting torque to be fitted directly to the axle unless the wheels were tiny - too small to be practical. It was later found that DC motors could be made to work on the low frequency AC. Post grouping the AC systems were not on the government approved list - there was only 1500V DC overhead, or 750V DC third rail so it was inevitable that Woodhead would be 1500V DC. It was not until the 1955 modernisation plan that operational 50Hz AC experience from the rest of the world (specifically South Africa, India, Turkey and France I believe) that 25Kv 50Hz was adopted to replace 1500V DC in the UK immediately following the completion of Woodhead as we know it, probably putting a spanner in the works for further expansion of 1500V DC at the time if it was likely it would have to be converted to AC at some point. I am sure that had there been a much bigger extension of Woodhead that later conversion would still have used the EM2s but fitted with transformers and rectifiers, and the catenary would have remained the same apart from bigger insulators. Look at Luxemburg as an example where they are changing the insulators on the 3KV DC system ready to change over to 25KV AC but the wiring is all still the same so this might work if modelling a later 25KV Woodhead style system.

You can get a type of double pole switch which is an ON-ON-ON type and this will do what you need. It is basically two 2-way switches where in the middle position one is one way and the other is the other way so they can both be on at the same time. Example switch here:- https://uk.rs-online.com/web/p/toggle-switches/7347202/

Times have changed now, back in the 1940s diesel was not a as an attractive option as now, and electrification was the only realistic way to modernise. The benefits of electrification would be efficiency (fewer locomotives required, fewer maintainence staff, better reliability...) and post war with lots of worn out locomotives just fit for scrap it was probably the best time to make a decisive move to modernise a key route and concentrate what was left on the lesser routes. With long term stability (no threat of government interfering to spoil the long term prospects) there would have been the possibility of investing for the long term to reap the eventual benefits. Doing nothing was not going to reap any short term benefits!

You can use a DCC decoder, most have the capability to work on DC and will operate the directional lighting, and make use of the stay alive. The better the decoder the better it will work on DC so you really need to spend at least £20 and get a Zimo (MX600p12) or similar. If you fancy having a go at making your own the DIY Decoder Project function decoder will do the job well and you should be able to make it fit in the 121 and fit a small capacitor after the rectifier to give stay alive capability. The directional lighting will then light correctly at full brightness as long as there is a small voltage on the track. http://dccdiy.org.uk/function.html In practice it is hard to get good results for directional lighting with stay alive on DC without using a computer to control the lighting so using a small PIC like the 12F629 used in the DIY decoder is a good way to do it, and operating the lighting on a lower voltage such as 5V means it can take a while for the capacitor to discharge before the voltage drops low enough to dim the lighting.

Of the big four only the Southern and LNER had active electrification plans in progress, so to say that the LNER would not electrify is a mistake since both the Great Eastern suburban and Woodhead main line 1500V DC schemes were in progress over a decade before nationalisation. Orders for a lot of mainline EM2s had been placed suggesting that a much larger main line program was going to happen on the LNER, the likes of which were not seen under BR(E) until 1985 after Woodhead had closed, some fifty years later. That gives an example of how far back nationalisation put the railway, completely depriving it of justifiable investment. The LNER might have been short of a few bob, but it knew what it needed to do in order to become more profitable by investing wisely in efficient technology. The success of Woodhead and Shenfield would have enabled more finance to be available from investors and the LNER would have been on a roll electrifying Newcastle to York then to Kings Cross, and probably a whole lot more too during the '50s and '60s (but probably not the GC extension though).

I think that the Lenz can provide 300mA on the 'L' wire. Overload it and the Lenz will crash (this is what happens when you plug a Multimaus in sometimes due to the inrush). Probably best to run the whole layout Expressnet from a separate 1A 12V supply - use just the 'M', 'A' and 'B' wires from the Lenz and feed the 'L' and 'M' on the bus with 12V from an independent 12V supply. You will still have the 5-pin DIN socket on the front of the Lenz in case of emergency, or you can use that for the interface like you have done. Not sure how many handsets can be powered from 300mA.

Was the USB interface connected by any chance? This I suspect will connect both the 'T' and 'M' terminals of the Lenz (they are electrically the same) to the 0V of the USB cable, and thence via the computer to mains earth.

This is where having plenty of capacity is key, and reintroducing a dedicated, or primarily, freight route would help things so the slightly incompatible traffic flows do not intermingle so much. There must be some considerable value in removing freight from the Great Eastern main line having to cross all four tracks on the flat at Stratford to get to the North London line. The amount paid out when that goes wrong must be humungus - and it does go wrong...