Digitrax PM4 for operating a reverse loop.

[SpaceMouse]

Our club has 4 PM4 units and in addition to using them for short detection, we want to use them for reversing power in reverse loops.

Now this is all second hand. We can wire them on the unit, but we can figure out how to tie them into the system.

So, help me out. What is the funtion of the PM4? Can you explain first what we are trying to accomplish with the PM 4 and then how to go about it.

[rrinker]

First off, are the PM4's or the newer PM42's? The major difference is that the PM42 can be programmed for trip current and trip time. Regardless, they both function the same otherwise.
Each PM4/42 has 4 sections. Each section can be EITHER a circuit breaker for a power district, OR a reversing controller for a reverse loop. But not both at the same time.
There are some combinations of reverse sections/breakers that don't work properly, but that shouldn't be a problem.
All connections are done via the 44-pin edge card connector. In addition to the track inputs, the PM4/42 also need a power source to operate the device - the PS12 or basically a 12 volt wall-wart power supply will do. Since they are already functioning as circuit breakers, I will presume they are currently wired properly.
To use a section as a reverse loop controller, it should be fed from another section acting as a breaker. For a breaker, the track output uses both pairs of pins ont he edge connector. For a reverse loop controller, you connect the leads to the track to only one pair on one side of the edge connector. The Digitrax website has the PM4/42 instruction manual with wiring diagrams that show this. It's easier to just look at the picture than for me to explain it. One important thing is that the GND of the PM4/42 should be connected to the GND on the booster with a suitable size wire (basically the same gauge as your track bus).

--Randy

[MisterBeasley]

Are there any limitations when using the PM42's? The Digitrax page says it "divides" the booster power into 4 districts. Can the PM42 handle the full booster load on one single district, as long as the total current doesn't exceed the booster rating?

I think I need 2 reversers, one for a loop and another for a turntable. MRC makes a reverser, as do other manufacturers. Digitrax makes the AR-1, which is both cheaper and more powerful than any of the others I've seen. How do these compare? I'm running a Lenz DCC system, so are there any compatability issues?

This is getting a bit deeper into specifics of layouts, but my turntable will be off the reversing loop. Are there any issues with "cascading" reversers?

[rrinker]

There are no limits as far as districts - one booster could drive a dozen PM42's if you want that many power districts. Obviously the total current load on the track cannot exceed the booster's rating, or the booster will trip.
Do not cascade auto-reversers. Try to arrange things a little different;y so the turntable does not connect directly to track that is controlled by the loop's autoreverser. If two autoreversers are on adjacent segments of track, they will end up fighting each other to reverse the polarity when the train crosses the gap. If you have a lead coming off the loop trackage - insulate that at the turnout and power it via a regular power district, not one controlled by the reverser.
Personally, I think the Tony's Powershields are technically the best product out there. All solid-state, there are no relays like in the others. They work with any DCC system - and the PS-Rev reverser also incorporates short protection. The standalone autoreversers like the AR-1 do not, and when you configre a PM42 section as autoreverse, it does not work as a circuit breaker so you need to feed the reverse section from another PM42 secton acting as a breaker. Plus they all have annoying relays.

--Randy

[Tom Bryant_MR]

You might also look into the Automatic Reversing Section controller from Loy's Toys.

http://www.loystoys.com/loystoys/arsc.html

A few more $ but look into the tech details. I have two and love them - no shorts needed to change polarity.

[SpaceMouse]

QUOTE: Originally posted by Tom Bryant_MR

You might also look into the Automatic Reversing Section controller from Loy's Toys.

http://www.loystoys.com/loystoys/arsc.html

A few more $ but look into the tech details. I have two and love them - no shorts needed to change polarity.

Thanks, but our club already has 4 PM4's.