reducing power on yard tracks

Hi Bill,

that's why I wrote "... current ... almost double." In my practical experience, two diodes in parallel will handle more current than a single diode. There are certainly commercially available circuits with eight diodes as bridge rectifiers. I presumed that the paralleling was for greater current carrying capacity, but I'd be interested to hear other explanations.

Regards, Greg.P.

You've highlighted the real problem with diode voltage dropping! Train A might require 12 volts to maintain a scale speed whereas train B might require 4 volts to maintain scale speed. If you drop 1.4 volts Train A will get 10.6 volts (88%) and will barely slow whereas train B will get 2.6 volts (65%) and may well stop completely.

One can even that sort of problem out a bit by installing series diodes in locos that run too fast, or by remotoring. It's also possible to build a seperate controller feed from the track supply to deliver a percentage of the track supply, but that is most likely getting too complex for most people.

Regards, Greg.P.

Higher rated diodes tend to cost considerably more than two lower rated ones. I have here a Black and Decker drill which uses pairs of diodes to form a bridge rectifier, so I'm not the only penny-pincher around.

Greg.P.

Greg Procter wrote in news: snipped-for-privacy@ihug.co.nz:

You're probably better off going to DCC to even things out. You can adjust CVs to make the locomotives run together better, or put in a detecter of some kind at the entrances to your yards to tell the DCC controller the train's in the yard. Your DCC controller (probably a computer) would then slow the train.

Digitrax decoders on Digitrax systems have a feature called something like "transponding" where the system can guess where the train is. This could be the beginning of a easy and reasonably inexpensive automation system...

Puckdropper

DCC works differently to block control - block control is the concept being discussed here. DCC also doesn't have any provision for slow-down blocks. While analogue control doesn't at present have any in-loco control setting modules on the market, these are quite practical to devise.

Regards, Greg.P.

Greg Procter wrote in news: snipped-for-privacy@ihug.co.nz:

What you would be doing is shifting from physical blocks to logical blocks via the DCC controller. Now most DCC systems aren't set up for automation, but I'm sure it could be implemented with a computer system. (Please don't confuse this with trying to sell the guy on DCC; I'm just pointing out another way to solve an automation problem. Sometimes you turn the nut, other times you turn the bolt head.)

You want analogue? How about a permanent magnet at the entrance to the block and a reed switch in the loco. When the switch gets set, the loco would then slow down via a series of diodes or resistors. At the other end, another magnet would reset the switch and the train would suddenly speed up. This would allow you to tailor the slow down amount to the locomotive(s).

Puckdropper

The "logical blocks" are the same as those which would be set up for train control by the railway if the model layout were full scale.

Certainly, but the whole concept of DCC is to eliminate blocks - when the layout owner is trying to establish control blocks. An additional layer of technology, not normally catered for in DCC, has to be added.

I respectfully suggest that you haven't offered another solution. You have suggested a change from analogue control to DCC, but you haven't said anything that affects the problem.

I personally would not recommend reed switches and loco mounted magnets because they are not 99.9%* reliable, which any train control system needs to be. (*100% minus allowance for nuclear attacks, cats asleep on track etc)

This will work with current detection actuators. With an analogue controller with momentum/brake, the actuator (reed, current etc) can actuate the brake circuitry to bring the train to a slower speed. Removing the external brake signal/actuation will cause the traction current voltage to increase back to the controller setting.

Regards, Greg.P.

From: Donut know who wrote what:::!!! ....... beginning of thread is gone!!!

Are the two blocks -- Main and Yard -- from a different power source? If yes, then the power the train receives could be additive which produces a speedup momentarily as the loco bridges the blocks.

Jim Holland PRCoModels (@) P-R-Co.com

From: Donut know who wrote what:::!!! ....... beginning of thread is gone!!!

Are the two blocks -- Main and Yard -- from a different power source? If yes, then the power the train receives could be additive which produces a speedup momentarily as the loco bridges the blocks.

Jim Holland PRCoModels (@) P-R-Co.com