Long time model railroader here who moved into a condo in my retirement and I'm about a month or two away from finishing laying track on a new folded dog bone w/reverse loops plus a point to point extension layout in a 15' x 16' room.
I made the decision to say goodbye to my old pal Hogger plug-in DC control and get my feet wet with a Digitrax DCC system. In doing my homework I can't find any mention of the DB 150 load/track feeder terminal maximum wire size on the Digitrax website. I'm going to feed a PM 42 from the DB 150 for (4) short protected power districts along with (2) AR1 reversers for the return loops. I know the favored buss size is #14 .... so, again, my question is will the DB 150 terminals accommodate #14 wire?
Also, am I correct based on the product pictorials there won't be any problem soldering #14 buss wires to the PM 42 plug in connector?
Thanks in advance!!
I don't know about the PM42, but for sure the DB150 can take 14 gauge wire. I use that gauge on mine. I would expect the PM42 to be similar. Hopefully you'll get the straight goods about that shortly.
Crandell
Appreciate the reply, thank you. One question put to rest. As an aside, this is a link to a Feb 2012 early stage photo of my layout that I posted in the layout construction forum.
http://cs.trains.com/mrr/f/11/t/202466.aspx?sort=ASC&pi314=2
#18 is the biggest you'll get on the PM42 edge connector terminals, and even that is tough. But short lengths of smaller wire will not cause a problem - voltage loss is a cuntion of length of the wire as well as its size, so there will be no real measureable drop if you run short lengths of #18 from the PM42 and then connect to the #14 bus.
Here's my setup:
That's #14 from the DB150 terminals to the terminal strip, and #14 fromt he terminal strip there to the one on the side of the PM42. The wires fromt he PM42 to the other terminal strip are #18. The input power wires to the DB150 fromt he strip are doubles up, I think it was some #20 I had in black. The power feed to the PM42 fromt he 4 position strip is a single piece of the same wire, since the PM42 doesn't need much power.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
You might want to look at the Breakout Boards offered by LWH3 (http://www.lwh3.com/products.htm). They look like they can make hooking up to Digitrax boards less of a chore.
Joe
Randy, thanks for the photos. Helps me visualize the setup. Digitrax's website info is specific about using a separate power supply (a PS14) for a PM 42 (and multiples of them each with a PS14). I see you didn't or I'm missing something?
Bottom picture, top 2 terminals on the left strip are the connection for the PM42's power supply.
Somewhere on the Digitrax site there is a discussion on hooking up the 150 unit to a PM42 and the recommended wire is 16 gauge
Firstly, I'm going to second JoeinPA's advice about breakout boards. Here's a link directly to Accu-Lites where I buy mine. They also have break out boards for the SE8C and BDL168. If you're going down the transponding route with RX4's then you will have more flexibility with the multi zone breakout board for the BDL.
Secondly, with regard to the size of the wire, the thinner the wire gauge the higher the resistance and the greater the loss of voltage and DCC signal over distance. By using breakout boards, you increase the maximum wire gauge to #10, which is what I'm using. Yes, AWG #12 or 14 will do fine, but I happened to have access to 300' of red and black #10. You can read about the different wire gauge sizes and their resistance here: http://www.picwire.com/technical/paper9.html Note that AWG #14 has 2.5 times the resistance of #10.
Of course, #10 might well be twice the price of #14 ... I've never actually checked.
If I had more than one, I might go breakout board - or more likely make some up myself, since solder tail 44 pin edge card connectors standing upright on a perf board are easier to solder to than the eyelt type supplied witht he boards - or I could use a right angle mount type. Those premade breakout boards seem excessively high priced to me given a 1-off run at one of the circuit board factories could make 4 or maybe even 8 of them (2 per physical sheet) for maybe $75 tops, and the parts aren't terribly expensive to populate them with.
As for wire size, remember the drop is based on length AND current draw. If you have access to cheap or free #10, absolutely do NOT go out and buy something else. However, if you have to buy the wire - figure on the length of each bus run and how much current will be pulled through it. My layout is around the walls in about a 10x15 room, the longest buss run goes halfway around, about 25 feet (didn;t measure, but it's actually less since the track isn;t against the wall border). Even is all 5 amps from my booster went through there, that's a .63V drop. Not really noticeable. ANd 5 amps CAN'T go through there, the PM42 sections are set to 3 amps each, so the maximum voltage drop I really could have is less than .4V. Not noticeable. Normal loss is even way less, since I can't run more than maybe 2 trains in a section at a time, and that's pushing it. Key factor is the quarter test passes everywhere. If I had longer runs, I'd use #12. A 50 foot run of #12 (100 total wire feet - complete circuits, remember!) will still be under .5 volt at 3 amps, and I wouldn;t run a single bus run more than that, if I had that big a layout I would distribute my power more so that the supply was somewhere near the mid point of the wire run, so that even with a 50 foot long string of wire, the furthest distance from the power source would be 25 feet or so.
With the price of copper these days, even #12 wire is getting rather expensive. Last time I looked I think it was over $200 for a spool that in the past I paid under $100 for. #10 I haven't even looked. So - if you cna find a free or inexpensive source, use what you can get. If you have to buy new, at some point it becomes cheaper to just add a booster and power supply halfway around the layout and use the smaller wire size, end result being the same or less actual voltage drop.
THE_GHAN.... First I've heard (and seen) of these "breakout boards"....just illustrates further my unfamiliarity with DCC. Can't tell from the picture what wire size the terminals will accommodate but it is the lesser of two evils where you just plug the PM 42 into the board and hook up the power district feeders vs having to solder wiring to the eyelets and then to a terminal strip.
But as Randy mentions in his post the cost for just one is half the cost of the PM 42. Just to mention I'm no stranger to soldering, wire capacities, etc., as this was my stock in trade so to speak early on in my working years (should have mentioned this prior I guess but it didn't come up) so I'm comfortable wiring the PM 42 connector as an option.
I find it odd that Digitrax hasn't configured the PM 42 connector as an all in one with (4) sets of terminals like the breakout boards. Probably the cost factor which would push the price above $100 vs their list price for the current model.
But all said, I appreciate you making me aware of the breakout board which, as I said, I wasn't aware of.
Oh, forgot to mention in my post that the loss in those short, couple of inch pieces of #18 wire are absolutely meaningless. I don;t think even my fancy desktop meter, which CAN tell the difference between 100 foot spool of wire and a 50 foot spool of the same wire, could even measure the difference between 6" of #18 vs 6" of #16.
I guess if it really is an issue you can skip the edge connector and solder right to the PM42. Voids the warranty though.
I've soldered 12 ga to a couple of 44 pin connectors. It can be done but puts a lot of strain on the lug. Most of the ones I've assembled with 18 ga wire running a short length to a terminal strip or bus bar. My larger bus cable continues from there.
HO rail joiners make excellent connectors, btw. They slide on the lug. Open the other end a little with a screwdriver. Slip your wire in and close the joiner over the wire to hold it. Then solder the whole works. If you find that a wire needs to be removed, just heat the end at the lug and slide off while the solder is fluid.
Don't forget to slip a piece of shrink tube over the wire before soldering.
http://bantrak.net/images/switchboxcoverremovedpreview.jpg
Martin Myers
Randy: I agree with your math regarding voltage drop across the wires. Remember that the resistance in the table on my link is Ohms per Thousand Feet .... but it illustrates the value of going up just one gauge size to anyone thinking about skimping on cost by buying small gauge wire.
What hasn't been covered is the DCC signal loss over distance. My philosophy is to minimise signal loss whenever possible, starting at the Command Station. Thus, good connections, connectors (such as motorcycle connectors) and good feeder wires are also important. I don't have the tools to measure the DCC signal strength but I know a guy from another forum who does ... and has. His results were enough to convince me of the importance of these things. Of course, you only need to follow manufacturer recommendations with wire gauges.
Over50: These breakout boards happily take wire sizes from #10 down. I don't think #8 would fit in the terminal holes. Very small gauges, such as #30 can be accommodated because the screw terminals have a flat bar to clamp the wire and don't rely on the screw itself (possibly one reason for the cost), although we don't usually use wire that small.
When considering the cost of breakout boards you should offset the saving from not needing the bus-bars or terminal strips, plus the time saved in not having to solder #18 wires to the pins and wire them to the terminals. For me, time is always an issue .... seriously so! Neatness also counts and the breakout boards are very forgiving in that regard.
Cheers
The_Ghan
That's the beauty of DCC - the voltage is the signal, so there's really not much signal to lose anywhere.
I know some systems reccomend putting a snubber on the ends of long bus runs, but Digitrax doesn't and I've never had an issue, My layout is too small for that. But the club modular layout is a giant 28x135 donut and we have no problems there either, and no snummbers. Power is supplied by 4 boosters approximately equally distributed plus another one in the engine facility (which cna have a couple dozen sound locos sitting in it at any given time - and never has an issue recovering from shorts). Command station is dedicated - it's track output is not used for anything. Bus runs are all #12 with PowerPole connectors at the end of each module. Like current N-Track standard, the bus wires are not cut anywhere under a module. In fact for a new one we make up a wire harness with the Powerpole connectors and attach it to the module frame, then feeders are tapped off. Plus the whole thing is detected and signaled in accordance to current NORAC standards, with a dispatcher panel in JMRI.
Lot of great info here and appreciated. Took note of the idea of slipping rail joiners over the PM 42 connector solder pins, etc., ....slick idea. Still, the more I think about it the ease of a breakout board vs hand wiring is looking better and better even at $32.
All said, I'm well aware of wire size to amp capacity ratio and voltage drop to resistance. What seems to me as over kill - and pointless - is running #12, 10 or larger buss wire on a home layout in a 12 x 15 room or less.
If you're feeding a 30 foot run of track in a power district every 6 feet or less to ensure consistent amperage and digital data flow with #20 wire feeders where wire resistance IS a factor of length then you're essentially bottlenecking any larger size buss feeder capabilites - and rendering it pointless. Now, if it's a club layout with hundreds of linear feet of trackage per power district then I agree voltage drop would become an issue at 14 VAC.....but an average home layout of 300 to 500 square feet or less broken down into power districts? Methinks the whole concept of bigger is better in terms of buss wire is akin to if a little grease does some good then a lot of grease wil do a lot of good...which isn't the case.
I agree with you. My own experience is with NTRAK. Iwas one of the group that developed NTRAK's new wiring standards. Most home layouts will run fine with 14 ga or even 16 ga bus wires. Smaller home layouts should be fine with 18ga.
We found that the signal degrades quickly when voltage falls below 10 volts. Strange things occur at lower levels. HO scale is running at 14 volts so there is more room for the drop. N Scale runs at 12 volts so the drop will occur over shorter bus lengths. The rail cross section is smaller as well. We also needed to make allowances for varied electrical skills. 12 ga bus' became a safe size that would let us run about 80 foot power districts reliably on a booster.
Home layouts have the advantage of being stationary with the wiring being done by a single individual. This also applies to fixed club layouts. There is usually an electrical guru or three that the other members are happy to allow to wire it all up.
Main thing is to not skimp on the electrical system to save a couple of bucks. It only needs to be done once and will give trouble free performance for many years. It doesn't show, so wiring tends to be forgotten. Even that "temporary jumper" tends to become permanent once trains get rolling.
Yes, there is often a tendency towards overkill - 8 amp boosters to run a max of 4 locos in HO, or even worse, N scale. Wire thick enough to run the whole house for a 20 foot run. Skimping is bad, indeed. Overkill just costs extra money. Some people may have a free or very low cost source of wire, if this is #12 or #10 where #16 would be more than adequate, it's not really overkill - free #10 vs paying for #16, I think I'd put up with the extra effort and run the #10. Free #20 vs buying #14 for a 10x20 layout? Have to spend the money. #20 is fine for feeders, but not for long bus runs.
As to the unreliability at 10 volts and below - this is pushing the lower limits of the NMRA spec, I would expect decoders to start getting flakey when the driving signal level gets below 10V. Definitaly more of an issue when starting with a lower voltage, but somewhat compensated for by the generally lower power draw of N scale locos - of course with the extra room you then promptly consist 6 of them and pull huge trains while we stick with 2 units and shorter trains.
And on temp shortucts - indeed, I think there's still one of our modules that gets a pair of alligator clip jumper wires on it every time it gets used. Thing is it's one of the ones that gets left out when we can't set up the whole thing, so it never gets fixed. We do maybe 2 shows a year where we can actually put up the entire layout, the rest get a shortened configuration and this module is left on the cart. Think we are usually next to you at Timonium. And always next to those other guys who swamp our simplex radio with their NCE radios
rrinker Think we are usually next to you at Timonium. And always next to those other guys who swamp our simplex radio with their NCE radios --Randy
Think we are usually next to you at Timonium. And always next to those other guys who swamp our simplex radio with their NCE radios
Note, information on wiring the PM42 found on the Digitrax site
http://ikm.digitrax.com/questions.php?questionid=814
Wish this was included with the PM42
DON7 - Thanks for the link. Found one other Digitrax link on wiring the PM 42 is my initial search but obviously missed this one which has specifics. Also confirms Digitrax recommended buss size as #14.
This thread as a whole has a lot of great info thanks to all who took time to reply and, again, thank you!