PWR-56 limitations and possible adjustments?

[TJMac]

Using RailPro to run 2 rail O scale I'm a little concerned 4amps isn't enough as I have several Atlas engines that draw just over 1.2amps each. A consist of three engines would be pushing it. I decided to try a Mean Well LRS-100-15 turned up to 16v for a total output of 112 watts (double the PWR-56). When I run this through the PWR-56 I'm still only seeing 14v at the rails. Hooking the Mean Well direct to the rails and I see the full 16v (plus/minus).

That said, does anyone know if it's possible to adjust the voltage regulator in the PWR-56? Is it even worth messing around with it?

[CPRail]

I have a similar set-up for my HO layout (different unit than your Mean Well), but I'm pretty sure I have mine BETWEEN the PWR-56 and the layout. I'll try and get a photo tonight.

[CPRail]

As promised, here is my set-up. The Red and White wires go to the track (I really need to remember to attach those to the upright in the photo...)

[fishindogwood]

With those different separate power supplies, do you even need to use a PWR-56 at all in the circuit?  It’s not like there is any encoded signal being put onto the rails like DCC.   

[William Brillinger]

With those different separate power supplies, do you even need to use a PWR-56 at all in the circuit?  It’s not like there is any encoded signal being put onto the rails like DCC.

No, you do not need a PWR-56 at all. Put 14 to 16 volts on the rails and you are good to go.
The benefits of the PWR-56 are it's repeater function, and its ability to give feedback through the HC about the status of the power system.

[Michael Larson]

Some thoughts from an electronic standpoint.

The desired result of adding an external power supply with greater voltage and current capability, in both examples given where the PWR-56 feeds, or is fed by, said external supply, in reality will not gain you much, if anything.

In the second example (AC->Brick->PWR-56->Ext), the PWR-56 is feeding what appears to be a DC to DC supply.  In this configuration a higher track voltage will be achieved, but the current capacity is still governed by whichever supply has the lower over-current protection point.  If it's the PWR-56, the track output will still be limited to 4 amps.  If the external supply's over-current point is lower, say 3 amps, then the track output will be limited to 3 amps.

In the first (original poster's) configuration (AC->Ext->PWR-56), there are some potential risks.  If the over-current protection of the PWR-56 is located within the unit shown in the picture, again, 4 amps is all that will be available to the track.  Also, as the OP noted, the PWR-56 output voltage is 14 volts and likely can not be adjusted easily, if at all.  In short, this configuration achieves neither desired goal of increased voltage or increased current capacity.  In the worst case scenario, if the PWR-56's over-current protection circuitry is in the brick power supply that comes with it, then feeding the PWR-56 with a supply capable of 7 amps (the LRS-100-15) could conceivably, and more than likely will, damage the PWR-56's output circuitry should a short circuit occur.  Even operating within the capabilities of the external supply, continuously drawing 5 or 6 amps through an unprotected PWR-56 may also damage it.  That is a risk I would not be willing to take.

Conclusion: Adjust the LRS-100-15 output voltage to 16 volts (it will go that high, as I have done this on my LRS-100-15 I use to power my Digitrax 8-amp Super Chief Command Station) and connect it directly to the track.  You'll get 16 volts with up to 7 amps available to run those O scale trains.  If you still need the repeater function of the PWR-56, just place it where needed, plug it in, and don't worry about connecting the output to anything.

[William Brillinger]

The unit that CPRail is showing is not a DC power supply. It is a 12V-46V (8A) DC-DC Boost Converter. It is being used to increase the voltage on the rails from 14V DC to 15.5V DC in order to eliminate the under power voltage that you see on older LM's when using a bridge rectifier in line with a keep-alive.

[CPRail]

Thanks Bill, I couldn't remember the exact name, but you recalled the situation I was trying to rectify perfectly!

[LVRR1856]

My plan is to set up several power districts, 4 districts, use 4 Pwr-56s and 4 CB-1. All sections would be isolated with plastic rail joiners or use the old DC method with common ground and isolate the positive sides into blocks.

This will also allow me to use DC locos (separately of course). Using a DPDT switch to use dual power. Sim to a dcc/dc layout.

Will using multiple PWR56's be a problem ?