Crosland

There's always been a fixed charge in addition to the percentage. It's 2.9% + 30p.

One assumes the agreement with eBay will cover them using the DD for refunds.

Where are you measuring the voltage, and what with? You should not see any voltage drop anywhere under normal operating conditions. What DCC system? If the voltage drops at the command station/booster output then your system is not up to supplying the current being drawn by the layout. Check whether the power supply input is dropping under load. If so, and the system supports it, replace the PSU with one with a higher current rating. Otherwise, split the layout and add a booster to power half the layout, leaving the remainder connected to the command station. If the voltage drops by varying amounts around the layout, especially on that gradient, then your wiring is not up to the job. Have you created a track bus around the layout with lots of droppers to the track? What sort of wire did you use?

What's generating the overvoltage "of siginificant duration"? The problem with DCC is high frequency spikes due to poor wiring (another poster mentions the inductance), which an RC snubber will deal with. I wouldn't say they are obscure in the UK. The topic comes up reasonably often. The general consensus is that they do work. Decoders will sometimes (often? always? I'm not sure) have a zener clamp to protect themselves. You can't treat a DCC layout as a transmission line. It would be futile exercise, the main problem being that the loads have a habit of moving around.

Why? You can't read back, which can be inconvenient, but you can only program one loco at a time. Are you confusing it with some "train set" systems that do service mode programming on the whole layout and can reprogram every loco?

I have to ask why? This is not normal practice for a DCC layout. The DCC track voltage can be greater than 17V, depending what system you are using. It is more usual to fit an RC snubber circuit to remove high frequency noise.

The person you are replying to is not in the UK and may not benefit from the DD guarantee.

I Note that a SPROG can adjust the CVs related to sounds but cannot load new sound projects. You need proprietary hardware for each brand to do that. Andrew Crosland sprog-dcc.co.uk

It's everything to do with current. The thicker core sizes can carry heavier currents. It has to be thick enough to have a small voltage drop at those higher currents but, as I said above, what is small voltage drop in a 240V circuit (a few volts) is a large drop in a 12V circuit. Using an under-rated cable means (a) it may get warm (b) the appliance may not see the intended voltage. The voltage rating on cable refers to the insulation breakdown voltage, which you allude to but, even for lowly hook-up wire, this is generally in the 100s or 1000's V range. Thin conductors are perfectly safe for mains, they don't need to be "mains rated", depending on the application. Think of an old fashioned transformer. The low voltage secondary wiring can be thicker than the mains wiring as it carries more current. There was one very well known DCC retailer (I'll spare their blushes) who used to multiply the insulation breakdown voltage by the supposed current rating to come up with an enormous power rating for their cable [I've discovered my favourite emoji]

True. Nickel Silver rails are much poorer conductors than copper wire, add in dodgy rail joiners and you see why it's recommended to connect droppers to every piece of track for all but the smallest layouts.

The command station (or booster) will have fault protection to cutout in the event of a short circuit. It takes a finite time during which ohms law determines the current that will flow. The level at which the booster trips will be set by design and component tolerances. The problem with poor wiring is that the resistance is too high which limits the current. The current could be above the maximum rating for the booster but not enough to trip it, allowing a high current to flow for an indeterminate time. Moving away from layout wiring, the worst case is poor wiring in a loco where all of the resistance is concentrated in a small length of wiring (or other conducting path). All of the power is dissipated in a small area leading to the pictures of melted bogies.

You just need to be VERY careful that the DC and DCC never meet and think carefully about how everything is isolated and switched when operating. The upper most rail in your picture, for example, is common to both circuits (gauges). Personally, I wouldn't do it Having seen the standard of your work, however, you might make it work ...

Sorry, and I know I can be a bit of a pedant but droppers have to be able to carry the full overload current in the case of a short circuit, especially if a single dropper feeds an isolated section of track (such as a frog). It's only the short length that allows thinner wire to be used.

Whilst you don't want any appreciable voltage drop during operation the crucial aspect is what happens when you get a short? If the wiring is not good enough (too high resistance) it may not be detected. A current rating is basically meaningless, unless you know how it was measured. The only useful rating is the resistance per unit length. Use that with the maximum length wiring run (remember to count out and back from the booster) to calculate the total resistance. Only then, knowing your nominal track voltage, acceptable voltage drop and maximum current, can you determine if that wire is suitable for your application. For a typical UK layout, however, 1mm^2 is probably adequate Even with "mains" cable you need to know what you are doing. Cooker cable is much thicker, not just because of the higher current but to guarantee only a small voltage drop (yes, I know current, voltage and resistance are linked). A few volts drop in a much thinner 6A lighting circuit is neither here nor there. Put 6A through the same cable in a 12V DCC system and the voltage drop becomes significant. To keep things simple it's better to over specify and not have to worry about the maths. Use the thickest cable you reasonably can for the bus. The droppers can be much thinner. They are much shorter and will drop very little voltage even when pushed beyond their supposed current rating. There was an amusing post once (not here) where someone tried to claim thin droppers would cause your layout to catch fire

I've always understood those are the worst way to do it as they do not completely empty the sump.

If plastic it's just a spacer, otherwise probably ferrite to add some inductance. Is the buyer really likeley to know?

Wouldn't touch them due to their high prices. If weight and value allow, I always use Royal Mail. Otherwise, UPS are much more competitive, about half the price of Parcel Farce for equivalent weight/declared value. My own recent experience suggests UPS are suffering a few days delay to the EU (Brittany), RM much worse, e.g. two weeks to Italy and still stuck in Italian customs. These could have been particular local difficulties so treat with caution. The US charges are nothing to do with, and pre-date, Brexit, before anyone blames it. The cost to send, e.g., a 1.5Kg small parcel to the US by Royal Mail went up about 50% a few months ago due to the US post office imposing higher "final mile" charges on international deliveries. This was to counteract the cash they were bleeding by having to, in effect, subsidise parcels traffic from China. The US is now in a zone of it's own for RMs pricing. Other RM international charges have gone up recently due to normal price rises, certainly not skyrocketed like the US charges.

LOL, what will they think of next? I'd like to see them get USB-IF certification for that Nothing at all if you have suitable receiver modules. BUT you need to have a very robust protocol to avoid interference. A lot of people have had issues using WiFi throttles at shows due to congestion on the airwaves.

Yes, OK , but only enough to light the LED in the opto-coupler at the input.

The booster requires its own power supply, it does not draw any power from the Powercab. I doubt very much the Powercab has Loconet DCC output. NCE do not use Loconet.

The "Track" book. Build some of the simple jigs. Worth its weight in 2mm track materials

You never answered my first question, what's the DCC track voltage? The max. voltage at the motor will be a volt or two less due to losses in the decoder. In comparison, what DC voltage are you using?

Earthing blocks are a LOT cheaper, e.g., https://www.screwfix.com/p/4-way-earth-block/12386

It's a DC voltmeter trying to read an AC voltage. It's clearly not OK otherwise the Op wouldn't have asked Adding a large capacitor after the bridge rectifier, as shown in your circuit, changes the controller from pulsed to smooth DC. This may, or may not, be what the OP wants.

Given the controller output is rectified AC, do you want the peak voltage or the RMS? To measure the peak, feed the output (before the reversing switch) through a diode into a capacitor. The cap will charge to the peak on each cycle and give a smooth reading. A few uF will be enough as the voltmeter will not take much current and will not discharge the cap very much between cycles. For a crude RMS measurement, create a peak measurement and use a couple of resistors to make a voltage divider to read 0.7 of the peak. Use Rs in the 10s of Kohm to avoid discharging the peak capacitor too much.