DCC Railways

Which in service failures are they? You are still missing the point about recharge times being fast enough.

MBQ

Thay already understand the issues perfectly well.

Nothing Jeff says violates any laws of physics.

Exactly which bit do you have a problem with?

Maybe we can help.

MBQ

I'll let others read the rest of that post, that you snipped, and come to their own conclusions.

MBQ

I don't need to address the points made by Jeff, as I am in agreement with him.

Talking about yourself again, Jerry.

MBQ

The electricity companies use the principle all the time, if it were not the case then there would be horrendous losses in the supply system. Stepping the voltage up and down with transformers is essentially a lossless process, apart from the small losses in the actual transformer core.

The National Grid is stepped up to EHT voltages, up to 400kV, because the resistive losses in the lines will be lower for a given power consumption. However, the *POWER* will remain the same, and when the EHT is stepped down to lower voltages the current will go up, *but* the power will still remain the same, (less any losses in the transformers). This works for both stepping up and stepping down in voltage, the current changes but the power must remain the same due to conservation of energy.

DC is a different matter as you can't use transformers, so in order to step DC *UP* you must convert it to AC (as in a switching regulator/psu). To step it down you can dump the excess voltage, but it has to go somewhere, and that is in heat, as in a simple linear regulator, or even a series resistor; or you can again use a more efficient switching regulator.

When you step up to a higher voltage in a CDU the step up is not 'inefficient' the additional current is needed because you are putting more current through the coil (for a short period), which is you aim in order to make the point move quickly. There is no, or at least, very little penalty in the transformation process itself.

The situation when you charge a CDU capacitor is entirely dependant on the charging circuit. If you have a 12V supply & capacitor voltage you need some series element to protect the psu from seeing a low impedance as the capacitor discharges, and also to keep any recharge current within the capabilities of the psu, & to prevent high in-rush currents into the Cap. & to prevent a high continuous current into the coil.

If you step up to a higher voltage you either need a a higher voltage dc psu, or some means of transforming a lower voltage up. An AC psu and transformer would be the easiest, but a voltage doubler circuit would do, but are generally capable of lower current outputs (which would slow the re-charge time) and are somewhat more inefficient. A switch mode regulator would be efficient but is more complex. Either way you still need current limiting for the reasons given above. If you pulse the motor at a higher voltage the peak current will be higher through the coil (the whole point of the exercise), so more energy will be taken from the cap, so for a recharge will either take longer for a fixed input power or more power and a higher current will be required, however, the transformation to the higher voltage is not 'inefficient', the higher current is required merely because you are putting more current through the coil.

Regards Jeff

Sounds like the Hornby unit is well designed. Does it take power from the track or a separate input?

Has a seperate DC output but only one DCC, so same connection as track.

Cheers, Simon

You made a mistake in responding to the obvious troll :(

Just for reference a lot ex BR PSB interlockings use a battery bank to do a similar job as the CDU does for the modeller so that when a route is set all the points can move at the same time, at least on Southern where I worked on the S&T.

For my fiddle yard I use a CML DAC10 that allows me use inputs to set routes and allows you to adjust CDU pulse time for each motor and recharge time afterwards so when I set a route I see the points switching one after the other. It has Loconet interface for feedback to controllers or computers connected to the network if you need that.

I'm too willing to give him the benefit of the doubt, and a chance to prove he can change. It seems I was wrong again.

MBQ

I had debate on this forum with him before as have many others have with similar results. There are unfortunately a few people around like him and in the extreme can effectively close down newsgroups.