Author Topic: Stay Alive Circuitry  (Read 12968 times)

Alan

  • Conductor
  • ****
  • Posts: 1042
    • LK&O Railroad
Re: Stay Alive Circuitry
« Reply #45 on: July 29, 2016, 07:53:34 PM »
Quote
At this point, I probably only have about 100' of track laid with only 6 pairs of track feeders. ... I can take voltage measurements anywhere on the layout and get the same reading.

Are you taking the measurements under load? If there is no load on the system then you will always get the same voltage measurements regardless of length.

Place a significant electrical load say an 1156 tail light bulb (= @15V 8 ohms 30W = 2 amps = 4 unit lash-up pulling really hard) on the rails at a feeder point. Measure the voltage at the bulb. Then place the same load 8' away (midway between feeders). Measure voltage at the bulb again. The difference in readings will show you the the effect of wide feeder spacing. Not saying it is a bad thing. Not saying it won't work. Just saying there will be a measurable difference. In the ideal world we want the loaded voltage to be exactly the same everywhere. Closely spaced feeders facilitate this. 16' is pretty wide spacing.

I did the same test on my system except under a load greater than I knew would ever be realistically expected on the rails at any one place. For a load I used an automotive headlight which draws about 4.5 amps @ 15V. The voltage measurements varied slightly from location to location but at worst were only 1.2 volts less than the unloaded power supply voltage of 15.1 volts. I now know that even with a lot of locos in a lash-up pulling really hard they will always receive at least 13.9 volts.

In both cases we are actually measuring the voltage drop of the entire bus and feeder system while under load. Regardless of wire gauge or number of feeders, this is the final answer that matters. It is what your locos will see.

The popular quarter test mentioned earlier is a test to determine if your wiring will allow enough current flow to trip the circuit breaker in the power supply. A good test. But it tells you nothing about what voltage the train will operate from under normal conditions. You really need to know both.

Why you ask? The breaker test is obvious - prevent damage. The voltage test because it feels really good to set the speed of a loco and watch it traverse the entire layout without one iota of speed change. Like your locos to creep at walking pace all the way around without stalling? Keep the voltage even. Ahhhhhh feels so good.   
Alan

LK&O Railroad website

When I was a kid... no wait, I still do that. HO, 28x32, double deck, 1969, RailPro

Josephbw

  • Conductor
  • ****
  • Posts: 191
Re: Stay Alive Circuitry
« Reply #46 on: July 30, 2016, 06:31:11 PM »
Hi Alan, I've taken measurements w/o load, with several engines idling, and with 6 engines pulling a train. The voltage varies a little between testing methods, but the voltage is consistent all around the layout.

The track that I have laid up to this point is mostly permanent, without gaps. At some point I will gap and install feeders at most likely every 6' to facilitate block occupancy detection.

Slow speed control is one thing that I'm really impressed with using the RP system. We use Digitrax at the club and we don't get the same control with the engines there.

Joe

Dean

  • Conductor
  • ****
  • Posts: 192
Re: Stay Alive Circuitry
« Reply #47 on: July 30, 2016, 09:10:25 PM »
Interesting reading.
On a DCC system if you got power from the wheels, ran it through a full wave rectifier, then to a battery, and then to the normal power connections of a LM-2, wouldn't that cover all needs? It could be run as dead rail and would have a built in keep alive on DCC systems.
BTW, did you use heat sink compound between your resisters and the aluminum heat sink?
Dean

Alan

  • Conductor
  • ****
  • Posts: 1042
    • LK&O Railroad
Re: Stay Alive Circuitry
« Reply #48 on: July 30, 2016, 09:44:26 PM »
Quote
On a DCC system if you got power from the wheels, ran it through a full wave rectifier, then to a battery, and then to the normal power connections of a LM-2, wouldn't that cover all needs? It could be run as dead rail and would have a built in keep alive on DCC systems.

You would need some sort of battery management system to prevent overcharging the battery.

Quote
BTW, did you use heat sink compound between your resisters and the aluminum heat sink?

Yes
Alan

LK&O Railroad website

When I was a kid... no wait, I still do that. HO, 28x32, double deck, 1969, RailPro

TwinStar

  • Conductor
  • ****
  • Posts: 506
  • Modeling a 1961 Rock Island Twin Star Rocket
Re: Stay Alive Circuitry
« Reply #49 on: September 13, 2016, 05:02:53 AM »
I again had the opportunity to run on a nice Free-mo layout this weekend. While the DCC ran very well the track was still subjected to rapidly becoming dirty. Intermittent interruptions of power and the stalling of the locomotives and restarting of the sound has kept this technology at the top of my want list. I'll be making my desires to Tim known again.

The RailPro ran flawlessly as one would expect. My Broadway Limited EB-7 not so much.

Jacob Damron
Modeling late 1950's Dallas Union Terminal in Free-mo+ modules

Texas Railway Modeling and Historical Society trmhs.org
trmhs.org