More on power districts

[ON28]

Per the good discussion, I am planning an engine terminal with a turntable, a half-dozen enginehouse stalls and fueling/ready tracks that in total can accommodate more than 20 idle locos. Since I use 90% keep-alive locos, I'm planning on/off switches for most tracks. Can I put the terminal in the same power district as the yard, which will have up to an additional four locos live at a time? I'll assume crews have to be careful about leaving tracks electrically live...

Also, I have a paper mill complex with turntable that wil see a maximum of two locos at a time, and a port with same loco traffic. Can they share a power district with auto-reverser/circuit breaker even though they are physically nowhere near each other? 

[Alan]

Per the good discussion, I am planning an engine terminal with a turntable, a half-dozen enginehouse stalls and fueling/ready tracks that in total can accommodate more than 20 idle locos. Since I use 90% keep-alive locos, I'm planning on/off switches for most tracks. Can I put the terminal in the same power district as the yard, which will have up to an additional four locos live at a time? I'll assume crews have to be careful about leaving tracks electrically live...

Yard and engine service areas can have a lot more locomotives in use than can main lines because the locos aren't under load. They aren't drawing much current compared to locos trying to haul long trains at speed. The biggest concern will be when the layout is first powered up. Lots of keep-alives will be charging at the same instant which could exceed the breaker trip point or power supply capacity. Your on/off switches will solve that issue. In a worst case situation you could use a "soft start" circuit that would allow the power system to come up gradually. I've long been curious why DCC manufacturers don't include soft start in their equipment given all the trouble sound capacitors seem to cause. Here is a $7.00 example: https://www.ebay.com/itm/UPC1237-Dual-Channel-Speaker-Protection-Circuit-Board-DC-12-24V-Boot-Mute-Delay/173320804854?hash=item285ab999f6:g:HT4AAOSw~NRdL9qF. Place a high wattage resistor across the relay input/output and viola, startup surge problems solved.

Also, I have a paper mill complex with turntable that wil see a maximum of two locos at a time, and a port with same loco traffic. Can they share a power district with auto-reverser/circuit breaker even though they are physically nowhere near each other? 

Physical location doesn't matter. Electricity moves at the speed of light so as far as electrons are concerned your entire layout resides in one tiny spot. Both the mill and port can be on the same district and on the same breaker but it is probably dangerous to share auto-reverser. If the insulated joiners/track gaps were bridged at the paper mill and the port at the same time bad things will happen.

[G8B4Life]

Ok Alan, I've gotta ask... I know you don't use sound or keep alives and that ringing is different to too much inrush current but you say

Place a high wattage resistor across the relay input/output and viola, startup surge problems solved.

so what does the board you linked to do over the simple Big Honkin' Resistors that you use by themselves? and lack of locomotives with capacitor in them to charge aside, if you'd been wondering why manufacturers don't include it why didn't you build in a soft start for the power on the LK&O? Just curious.

- Tim

[Alan]

Ok Alan, I've gotta ask... I know you don't use sound or keep alives and that ringing is different to too much inrush current but you say

Place a high wattage resistor across the relay input/output and viola, startup surge problems solved.

so what does the board you linked to do over the simple Big Honkin' Resistors that you use by themselves? and lack of locomotives with capacitor in them to charge aside, if you'd been wondering why manufacturers don't include it why didn't you build in a soft start for the power on the LK&O? Just curious.

- Tim

Two different problems, two different solutions.

My big honkin' resistors reduce over-voltage spiking (ringing) on startup. The eBay board + relay resistor reduces inrush current on startup. My big honkin' resistors are in parallel with the load, the eBay board resistor is in series with the load.

If you recall from our private messages, I was without oscilloscope when installing the LKO power system (Note to all: don't spill coffee on an operating oscilloscope). I was forced to rely on a SPICE simulation that showed considerable voltage ringing. Since that time my wonderful wife gave me a new oscilloscope as a Christmas present. A nice one to boot. Hands off, she's all mine.

With the ability to actually measure the system I have discovered the voltage ringing is not nearly as bad as the simulation indicated it would be. It's there but much, much less than predicted. Probably due to the various loads installed since (30 occupancy detectors, 52 Tortoise machines, hundreds of LEDs, etc.). These loads were not included in the simulation. I am now considering removing the big honkin' resistors. With concerns of voltage ringing abated, the resistors are really nothing more than a parasitic load on the system. It's a shame too, because they look so cool. 

[atsfguy]

Alan,
 Disconnect the big honking resistors from your system and leave them in place as eye candy.
Cecil

[Alan]

Might even put a mirror down there so they can be seen while operating the layout.     

[ON28]

Thanks to Alan for answering my questions! Your comments on soft start-up are interesting, and thanks for not scolding me for my non-logical cheap thinking: Save $50 on a circuit breaker while putting hundreds of dollars worth of motive power at hazard!

Also, I have seen one DCC user who added an uninterrupted power supply to avoid what he says could be damage to sensitive DCC components from power outages/spikes. What do you think?

[Alan]

Thanks to Alan for answering my questions! Your comments on soft start-up are interesting, and thanks for not scolding me for my non-logical cheap thinking: Save $50 on a circuit breaker while putting hundreds of dollars worth of motive power at hazard!

Also, I have seen one DCC user who added an uninterrupted power supply to avoid what he says could be damage to sensitive DCC components from power outages/spikes. What do you think?

Not a DCC user so cannot speak definitively but my initial reaction is won't do much. An outage should just turn everything off and power spikes will be seen only by the power supply so doesn't make it to anything DCC.

[G8B4Life]

Thanks Alan,

I think you'll need to do an update blog post now that the Big Honkin Resistors are not actually needed.

Back to soft start and manufacturers not building that in, I wonder if that's because they never did before (even Ring didn't build this in) and perhaps Keep Alives have inrush current limiting built in these days (I haven't seen a commercial keep alive circuit diagram to confirm this). I rekon with the fancy microcontroller built in and the very long charge time that Ring's PBM does.

- Tim