I built a DCC control panel and my Digitrax PM42 is not fast enough.

This is my new DCC control board for my Unitrack layout


I ordered a NCE CP-6, but I had this Digitrax PM42 for a couple of years and never even opened up the package. I decided while I’m waiting for the CP-6 I would give it a try and wow this thing does not work fast enough. My NCE PowerCab trips before this does making it useless.

Anyway about my control board, I have another DS64 to be mounted for the rest of the turnout control, but I still have to run wires to the turnouts. And I’m going to make a short cable for the USB adapter and get rid of the Coiled cable. Then after I make up the wires for the turnouts I’ll install the second DS64 and hopefully I’ll have the CP-6 by then.

Since I’ll now have two more power districts available, I need to maybe think of adding a few more insulated joiners. I’m having troubles right now with my Unitrack connections anyway and I’m not looking forward to pulling it all up. I wish I could just notch the track and solder on feeders to the side like I’ve done on my Code 80 layout.

 

The PM42 is adjustable (and I assume the CP-6 is too). You probably have it set for too slow of a trip/too high of a current for it to work the way you intend it. Check out the manual - pages 10 and 11 - or get it off the Digitrax website if you don't have it.

 

The PM42 uses mechanical relays which results in a slower response then the sold state relays used in the DCC Specialties products. While setting the trip current lower will result in the circuitry starting the process of throwing the relay at a lower current, it can't make the relay move any faster.

 

As has been mentioned, the PM42 is adjustable. The default setting is 3 amps, so no, out of the box it will not work with the 2 amp Power Cab. Unfortunately in your case, you are supposed to use a Digitrax throttle to change the settings on the PM42. It probably wouldn't be worth the trouble since you have a CP-6 on the way, but I think you can program the PM42 using the DS64. The DS64 can be configured to activate routes, and when it does it sends switch commands through Loconet. By configuring the DS64 to send the commands to set the options you want on the PM42, you should be able to configure the PM42.

 

I don't believe the PM42 can be adjusted low enough to trip before the PowerCab.

Corey, the CP6 is a bank of six automotive type lamps that act as current limiters in over-current events. Available in 1A (standard) and 1.7A (optional) per circuit.

 

That’s too bad, because that just renders this useless. I was hopeful when reading CSXRoberts post about adjusting it because I would have liked to use the CP6 on my yard module.

I actually bought the PM42 as an auto reverser a couple of years ago to use as 2 Short Circuit Managers and 2 Auto Reverse Controllers as shown in example “D” of their manual, which would have been great because I could do everything I wanted to do with only one board. Then I read on Digitrax site that it was not recommended so I bought the two PSX-ARs instead.

Well I don’t know what to do with thing now. I’ve been talking about buying the new Zephyr Xtra, maybe I’ll just keep this until I do.

 

It is my understanding that there is NO circuit breaker that is made that will trip as quick as a Power Cab. NCE was going to make one but I have never seen it come out. This is also true for auto reverse loop circuits, the Power Cab will trip before the
auto reverser toggles.
I had a reverse loop on my layout and I could not get any reverse loop circuit to work. I upgraded my Power Cab with the new smart booster (SB3A).
Now I have a 5 amp system and the auto reverse loop works.

 

No amount of tweaking or increase in system amperage will ever do anything to improve the performance of the 1970's relay technology used in the PM42. You are better off selling it and getting a solid state unit like the PSX units from DCC Specialties. They work with any system and are about as fast a breaker as you can get. In the end, you will have a device that is more resuable than the PM42 could ever be. The slew rate of a solid state device, the speed it has to shut off, is on the order of a couple hundred nanoseconds. The relay is a couple hundred miliseconds. That is a sixth order of magnitude difference or about 100,000 times faster.

 

Wow! You mean my PSX-ARs aren’t going to work either. I haven’t had a chance to really check them out because I discovered that I need a few more power feeders to a double crossover feeding my loops.

I can buy the old Zephyr right now cheeper than the SB3A. Man I’ll tell you I just don’t have anything that works right starting with the so called “fool proof” Unitrack to the power management, then the Auto reversers, and now NCE system itself.

Question if i switch over to the Zepher right now would there be any more problems with any of this?

I don’t know how many times this came up, but I really wish I would have went with the Digitrax in the first place.

 

I don't think that the PXS-AR will work with the stand alone Power Cab.
If you change over to the Zephyr I am unsure.
David might know as he is a Digitrax user I believe.

 

Should I pay the extra money for the new Zephyr Xtra?

Thinking about trading in my NCE PowerCab and buying a Digitrax Zephyr . I found a really good clearance deal on the older Zephyr and was just wondering which one should I get?

The only differences that I can see between them are the following:

Zephyr Xtra Digitrax compared to old Zephyr
1) Control 29 functions compared to 10 functions
2) 3.0 Amps with 13VDC compared to2 .5 Amps with 12VDC
3) Run up to 20 addresses and 20 throttles compared to10 addresses and 10 throttles

I don’t know of any more differences, but the extra 19 functions might come in handy and a .5 amp difference doesn’t sound like much.

Now I’m not sure how 10 more Address will help me and I don’t ever see having that many throttles.

So is it worth the extra money to have an extra 19 functions?

 

I would say not, especially since if you add a DT series throttle(or use a JMRI throttle), you can have access to those functions with the original Zephyr.

 

Thanks that’s what I’m going to do then.

Also I just found out that the power supply might not be included with this, but its still agreat price and I’m wondering if I can use another power supply that I happen to have. It a 13 VDC 1A power supply that I belive has the same plug.

I realize that it’s going to reduce the total power, but will it get me going for now until I find another one. I read somewhere that I could also use a computer laptop type power supply that has the same voltage and I think I also have one of those someplace.

 

Short answer is no. You need a power supply that will supply at least as many amps as the unit is rated. Less will not allow the Zephyr's short circuit protection to work.

As far as no power supply included... Unless you are not located in North America, the Zephyr should include a PS315 power supply (3 amps, 15 volts). Personally, if that now obsolete Zephyr will cost more than $100 without a power supply, I'd pass on it.

Martin Myers

 

I must confess that it seems somewhat odd to be putting power districts on a 'starter system' at all. I wouldn't think the power available warrants it and you can't have a lot of operators, so the odd short shouldn't cause much mayhem.

As has been alluded above you need a fair amount of power available from the command station to allow the breakers below it to operate first - at risk of winding Rick up, technically this is called discrimination and involves both current and time. Adding more power to the existing system (SB3a + bigger power supply) would make more sense to me than changing to another limited starter set. (Ye gods - a Brit telling an American he needs more muscle ... )

 

Well I don’t know what it is going to be like with the Zephyr, but my PowerCab certainly needs something. The SB3A smart booster would probably do the trick, but for the extra money I can have LocoNet which has been my goal ever since I learned of it.

I planed my whole yard with its 46 DCC controled Switches around LocoNet.

I’m usually running two passenger trains with lighting and A&B units. I also have sound on two of the locos. My NCE trips about every 10 to 15 minutes when I decide to move some locos around on my sidings. Sometimes I might run a third single loco on to the main to crossover to another siding. I’m just getting feed up of having the whole layout shutting down every time I forget to throw a switch or start moveing locos around to line up for their turn on the main.

 

This is one section of the layout that I’m working on now showing the power districts. And yes it doesn’t need all these but the CP-6 has 6 circuits so why not use them? It is a 3x8ft modular portable layout that I can pick it up and move it. It connects to another 3x8ft module through a 2.5x5 ft module. Oh the red track is not in yet, it was a christmas idea that I never got around to because i didn't have enough track.

I’m also going to add a helix and a shelf above these layouts, but I haven’t worked out the details on exactly how to keep the shelf unit and helix modular.
This is what it’s going to be after everything is done.

 

SleeperN06, if you're serious about building the layout in your previous post you might be better off not switching to another starter system. If your plans will exceed the Zephyr's capabilities by the time you get part way through your expansion you might be better off going straight to a bigger system.