Simple Electrical Questions

[The_Ghan]

Please forgive my ignorance.  I search and search and search here ... and don't find the answers I'm looking for. I've spent 3.5 hours on line this evening.  I started with a single website: www.wiringfordcc.com and things only got worse.  I ended up with 8 different websites open and totally confused.  Frustration is starting to surface my end, so, here are a few questions:

 

1. Why doesn't the equipment we buy come with circuit protection built in?  According to the Digitrax website I need to add my own circuit protection.

 

2. Can I use 5A automotive blade fuses as circuit protection?

 

3. Can I use 5A automotive circuit breakers (resettable)?

 

4. Does anyone use automotive light bulbs for protection?  http://www.wiringfordcc.com/track.htm (this is a VERY CONFUSING website) and seems like an unreliable method of circuit protection.

 

5. Where do I put my circuit breakers? Between power supply and boosters? Between boosters and track?

 

6. I have  a BDL168 LocoNet Occupancy Detector  on order.  It detects up to 16 sections.  How do I wire the track power to those sections?  I was about to daisy-chain one loop around the track and then realised I'd be shorting all my isolating joiners via the power loop?  Do I need to power each section via a PM42?

 

7. I'm confused between "Blocks" and "Sections" are these the same thing?  I thought my subway might be 1 section containing a dozen or so blocks.  I therefore thought my booseter would power the whole subway through 1 connection on my PM42 and the track would be divided into 12 sections by isolating 1 rail only.  Then I thought the BDL168 is wired to each "Block".

 

Some help and advice would be greatly appreciated.

 

Cheers.

[CaptOblivious]

Ghan,

 

Frustrating is right! I spent so many, many evenings looking for similar information, and banging my head against the wall. The result has been that I have determined to build my own DCC system from the ground up, rather than try to figure out some of this stuff. Anyway, these are good questions you have. I will try as best I can to help answer them.

 

1. Not sure. Cost and flexibility are a couple of reasons. I find Digitrax's circuit protection system somewhat boggling, myself: Why can't it be built into the booster? There's no answer forthcoming to this one, I'm afraid. It's just a brute fact.

 

2. Yes.

 

3. Yes.

 

You'll have to buy or make holders for either the regular fuses or resettable fuses, but there's no reason you can't walk into O'Reilly Auto Parts and pick up some fuses for 50¢. Not a problem at all.

 

4. That website is terrible, as far as organization goes. I don't know anyone who uses bulbs, but it's not a terrible idea, because you get an instant visual indication that a fuse has blown. It is a terrible idea if you don't want a ton of bulbs generating a ton of light and heat under your layout, though.

 

5. Anywhere between source of current, and thing you want to protect from too much current. The closer to the thing you want to protect, the better. So, I say: Put them between the booster and the track.

 

6. That is the very question that drove me to just design my own system. Digitrax's manuals on the subject are readily among the worst-written technical manuals I have ever come across. I still have no idea. And God help you if you want to add transponding! Ken likely knows how this is supposed to work, though.

 

7. I'm confused about Digitrax's use of those terms ("block", "section"), too. I think that a "block" is a larger section, corresponding roughly to what prototypes call blocks: A stretch of track upon which only one train is permitted at a time. But we often want to do detection at sub-block resolution: Is a train entering a block? In the middle of it? At the end? So Digitrax breaks blocks up into "sections", each of which have separate detectors. This way, you can detect trains at a finer grain than blocks, which are rather large. Each block is powered independently of the others, and hence uses double isolation; each section within the block needs only one rail isolated for the detectors to work. I think. I may have the terms reversed. As you say: It's damned confusing.

 

I don't know how helpful all that was. At least knowing that there are others here just as frustrated with this stuff as you are maybe helps some, I hope.

[railzilla]

Please forgive my ignorance.  I search and search and search here ... and don't find the answers I'm looking for. I've spent 3.5 hours on line this evening.  I started with a single website: www.wiringfordcc.com and things only got worse.  I ended up with 8 different websites open and totally confused.  Frustration is starting to surface my end, so, here are a few questions:

 

Just make a break. I am Electronic and Electrical Engineer and also need some time to get into.

 

1. Why doesn't the equipment we buy come with circuit protection built in?  According to the Digitrax website I need to add my own circuit protection.

 

The have a protection built in but maybe you do not want your whole layout shut down because of a single short circuit. Such a short circuit can happen when a loco passes a turnout which is set wrongly. Your home has also a set of fuses and not one for all

 

2. Can I use 5A automotive blade fuses as circuit protection?

 

3. Can I use 5A automotive circuit breakers (resettable)?

 

That should be possibly IMHO worth trying but for N scale 5 Amps is to high. Also DCC is  a high frequency AC signal where car electric is DC.

 

4. Does anyone use automotive light bulbs for protection?  http://www.wiringfordcc.com/track.htm (this is a VERY CONFUSING website) and seems like an unreliable method of circuit protection.

 

Thats a cheap and unreliable method maybe suitable for larger scales.

 

5. Where do I put my circuit breakers? Between power supply and boosters? Between boosters and track?

 

Between Boosters and Track. You should use a separate power supply for each booster. But your chief has enough power for a large N-Scale layout.

 

6. I have  a BDL168 LocoNet Occupancy Detector  on order.  It detects up to 16 sections.  How do I wire the track power to those sections?  I was about to daisy-chain one loop around the track and then realised I'd be shorting all my isolating joiners via the power loop?  Do I need to power each section via a PM42?

DO NOT USE A DAISY CHAIN. It is very troublesome for troubleshooting. Use a "star " or "tree" architecture instead. I isolate both rails even only one is enough but troubleshooting with double gapped rails is  much easier. For your example use one pair of cables (Loudspeaker cable) between the booster and PM42 the four pairs between PM42 and BDL168 and than sixteen pairs to each track block. In this example of four blocks together are one section and a section is separately fused. So if there is a short in block 6. Block 5-8 will have no more powerd because the fuse triggered but blocks 1-4 and 9-16 are still working. But you also could use only less four exits of the PM42 just make teh sections larger. You can only use one so all 16 blocks of the BDL 16 are on the same fuse.

 

7. I'm confused between "Blocks" and "Sections" are these the same thing?  I thought my subway might be 1 section containing a dozen or so blocks.  I therefore thought my booseter would power the whole subway through 1 connection on my PM42 and the track would be divided into 12 sections by isolating 1 rail only.  Then I thought the BDL168 is wired to each "Block".

One section is one block, means thats the part of the track you can detect an occupancy.

One zone contains one or more sections. Zone means separately fused and/or connected to a reverse unit. E.g. a reverse loop can consist of multiple blocks.  You have to find the balance between reliability (each block has its own Fuse) and cost (use one fuse for all blocks.) For a double tracked subway i would recommend at least two blocks. Simplest for your equipment is 4 Blocks = 1 section means one PM42 and one BDL168 for every 16 Blocks.

 

Some help and advice would be greatly appreciated.

 

Cheers.

 

I hope i didn't add to the confusion,

Regards

 

Edit: checked up digitrax manual definition they use detection zones and detection section

[inobu]

Ghan,

 

It appears that you have entered into the DCC abyss. Because there are so many opinions and view you will often find contradictions that become quite confusing to the beginner. The interpretation of principles often dictates the mindset that the builder uses to create. You will adopt your own views and mindsets that some will agree with and others will not. What is important is that you adopt principles that enables you to create and manage a safe and functional system.

 

With that said I will attempt to answer your questions and give some insight to better understand the environment. I went through this a few years back.

 

1. Because layouts can be wired in a multitude of configurations, circuit protection is subjective. Digitrax provides the power and you manage a power distribution network conducive to your layout design. I have seen everything from systematic wiring to a rats nest of shielded copper yet both of those layouts were functional one to my surprise. The need for stand alone boosters normally indicates a larger layout, which means customized wiring and circuit protection which requires an open source booster so to speak.

 

2&3. Too much current is a killer for any electrical component. There is a balancing act between usable and available current that you must maintain. Your decoder will draw what it needs but a short will draw all the current available. The problem is providing enough current for your trains to operate at the same time managing potential shorts that could destroy your decoders and everything else. You must work your way up to this level meaning working out all the bugs on your layout. The last thing you need is 5 amps on a troubled infested layout. The convenience of having a resettable fuse is just an indication of repeated failure. The goal is to reduce the likely hood of trips and isolate them to areas or blocks to limit damage.

 

4. A short is a sudden draw of maximum current. The bulb will limit and consume the current. Wired up to individual blocks will allow you to identify the shorted area on your layout. That bulb can provide that split second needed before the breaker trips to save a few components. This is old school modeling. The PM4 is the new wave.  

 

5. Distribute your power to individual blocks and place the breakers (PM4) between the selected track area and the booster. The power company refers them as grids (same mindset) and principle. Manage your booster like the power company by supplying power to different areas/blocks on your layout. A short on the east side of the town should not shut down operations on the west side. This is power management

 

6. The A and B rails from the booster connects to the left and right rails of the track layout. This serves as a complete track power configuration. When you insert the BDL168 into the power configuration it will receive the B rail feed from the booster and redistribute it via the 16 Detection Zone outputs labeled DS1-DS16. Here is where the confusion starts but I will clear it up.

 

Lets create an oval layout that is 32 feet by 12. We will break the oval into 4 blocks. East and west blocks are 12 feet and North and south blocks are 32 feet. In order to isolate the blocks or power districts we have to insert the black isolators onto both track rails A and B at each corner on the oval.

 

Now lets focus on the North block. Remember it is a straight run 32 feet long with isolators on all track ends. Were are going to identify this strip of track as North Block Zone. The BDL168 has 4 Zones A-D with 4 detection sections per zone. We are assigning Zone A-D (DS1-DS16) to the North block.

 

Let make the first connection to the track. Wire Rail A from the booster to the A side if the track. This leaves us with the B-rail. The B rail will connect to the Zone common of the BDL168. In essence the BDL168 is taking one B rail input and distributing it into 16 B rail outputs. Being that we identified the north block as NBZ we will have 16 (detection) sections. We need to break up the North block into 16 sections. Being that we have the B rail open we will divide the B rail into 16 parts or sections. Every 2 feet we will insert an isolatoron on the B rail of the track giving us 16 Detection sections. The A rail is the common side and the B rail is the segmented side that is fed by the Zone's DS outputs on the BDL168 completing the tracks circuit.

 

Now, you can see how the block is created by isolating both A and B rails and how the sections are created by isolating the B rails within the block or power district.   

 

The PM42 Quad Power Manager divides one booster output into 4 power sub-districts/blocks it acts as a circuit breaker. Using the PM42 you can add 3 more BDL168 and complete the other blocks giving detection abilities to the complete layout.

 

7. There are detection sections, transponder detectors and power districts or blocks.

 

Detection sections:

 

For Occupancy detectors and Transponder detectors

 

A section is a area of track gaped on one or both rails and connected to any type of occupancy detector. The detector can sense the presence of a loco (or other specially equipped cars) in that section of track.

 

Resistance method -

 

The wheel resistor is one method of occupancy detection that normally used resistance to identify the presents of rolling stock or natural resistance from locos (uses BD4 Digitrax) on the track.

 

Transponders method-  

 

Some decoders are equipped with Transponders which broadcast out for transponder receivers (RX1) to detect its presents. This detection method can provide more detailed decoder information than the simple presents of induction.  

 

Transponder detectors

The BDL168 and the RX4's are wired into a specific power district or block. It is the RX1 that creates zones for individual transponder detection. Transponder activity (Decoder) is monitored via the transponder receiver(RX1) in a particular section of a block. It's information is reported back to the command station via the BDL168 on the locobus. The trains are identified by the decoders/transponders installed on them.

 

Blocks /Power Districts

 

The booster and PM4 : delivers power to the tracks which creates the power districts or blocks.

 

Clearing up the mud.

 

You can have 1 booster on one layout with all parts of the layout associated with one another. If you have one issue anywhere on the layout,the whole layout shuts down. This is because your layout is one block or power district driven by one input from the booster.

 

You can add a PM4 and break the layout into 4 blocks. The PM4 will take the one input from the booster and divide it into 4 independent outputs. You will need to isolate your layout into 4 blocks or 4 power districts. You will have both rails isolated on each end of your track run creating a  individual power districts or block.

 

Recap the power flow

 

The booster feeds the PM4. The PM4 distributes the power into 4 separate outputs with independent circuit breakers.This gives you the ability for direct control over your power distribution.

 

The next goal is to manage and identify the activity within each block or power district. The BDL168 interfaces with the command system of the booster and can preform Occupancy detection or Transponder detection. There is a difference in Occupancy detection and Transponder detection. Occupancy detection is simple induction detection where the device looks for resistance on the track. Transponder detection requires the BDL168 to uses the RX4 to manage transponder zones within the block.

 

 

 

 

Inobu

 

I only use Digitrax to avoid cross functional conflict with other products. Although Digitrax's information is somewhat convoluted its product and applications are far more in-depth than other manufactures. As far as the documentations is concerned I think there are two generations of documentation that uses different terminology. The different kinds of technical writers also play their role in conveying information. DCC is still evolving and I don't think the documentation is being updated or rewritten which cause a disconnect.

[KenS]

1. Why doesn't the equipment we buy come with circuit protection built in?  According to the Digitrax website I need to add my own circuit protection.

 

I agree with most of what the others have said, but I'll add a couple of comments.

 

All of Digitrax's Command Stations and Boosters come with self-resetting circuit breakers built in.  However, these may trip at fairly high amperages on the larger models (the Zephyr trips around 2.5 Amps, I think).  Stand-alone circuit breakers trip at lower currents (the default for the PM42 is 3 amps, which is also the maximum safe limit for the BDL168 as well as being the rated maximum for a section of Kato's Unitrack), so these are useful to reduce the probability/severity of damage to a model in a short.

 

Note that you may also require a fuse or circuit breaker between the power supply and the command station or booster, if the supply is rated higher than the device.  Digitrax's PS2012, for example, can put out 20 Amps, and Digitrax recommends using their cables with built-in resetting 5-amp circuit breakers between the PS2012 and a command station or booster.  This doesn't have anything to do with a track short, but will protect the power supply (and minimize the risk of a fire) in the event of a short in the wiring.

 

You don't need that protection if the size of the supply is matched to the requirements of a single command station or booster.

 

5. Where do I put my circuit breakers? Between power supply and boosters? Between boosters and track?

 

6. I have  a BDL168 LocoNet Occupancy Detector  on order.  It detects up to 16 sections.  How do I wire the track power to those sections?  I was about to daisy-chain one loop around the track and then realised I'd be shorting all my isolating joiners via the power loop?  Do I need to power each section via a PM42?

 

Digitrax recommends putting the PM42 between the command station or booster and the BDL168.  The BDL168 can be wired to as many as four sources (i.e., the four outputs of the PM42) if your power needs are great enough, or entirely to one (by connecting the same PM42 output to all four power inputs on the BDL168).  This arrangement protects both the BDL168 (and any associated electronics) as well as the train on the layout from a track short.

 

As noted above, the circuit breaker allows you to use a lower trip current, reducing the severity of shorts.  It also serves a problem isolation function, as it limits the effects of a short to one area of the layout, making the cause easier to locate.  Finally, it can serve to protect occupancy detectors like the BDL168 (which aren't cheap).  I didn't have circuit breakers on my old HO layout (and probably didn't really need them with a Zephyr, but there were times I really wanted their help in problem isolation).  I am installing PM42s on my N-scale layout, which uses a DCS100 and BDL168s.  That's still under construction though, so I don't have any experience with them yet.

 

You can run a power bus from one command station entirely around the layout (I'd avoid connecting it in a loop), and drop feeds off of it to PM42s (or directly to BLD168s if you aren't using PM42s) where needed.  As noted, a problem in that bus can be hard to track down, and star wiring may be easier to debug.  But a simple loop, particularly if you can open it in a few places when trying to isolate problems, isn't too complicated.  One power bus around the entire layout wired directly to track (often recommended in DCC books) could be a nightmare to debug though.

 

Where you need to separate things are between boosters (or boosters and command stations) if you have more than one.  Each of those is a separate power zone (or whatever you want to call it) and must have both rails isolated.  The isolation permits the circuit breaker in the station or booster to reliably detect a short because there is no other return path (e.g., through the rails to the other booster). The two boosters must, however, be connected through their grounds to permit current to flow between them while a train is crossing that boundary (grounds must be at least as big as the bus wiring for that reason).

 

Likewise, with a PM42, both rails of  a section of the PM42 must be isolated from both rails of the adjacent section, and each PM42 has a ground that needs to tie back to the other grounds.  This is for exactly the same reason.

 

Digitrax isn't very clear in their manual, but I believe that when using a BDL168 with multiple separate PM42 outputs, the "detection common rail" is isolated between the detectors connected to each (i.e., if the inputs for section 1 and section 2 are on separate PM42 outputs, then DS1-DS4 share a detector common rail wired to that the first PM42 output, and DS5-DS8 share a common rail wired to the second PM42 output).

 

I wouldn't use lightbulbs as a circuit-breaker replacement, as they aren't as reliable a method.  But others swear by them, and if you don't have circuit breakers (or can't afford them initially) they're likely better than nothing, and will help isolate problems.

[The_Ghan]

Gentlemen,

 

I greatly appreciate your reply.  Here is my shopping list (currently in the mail) from Hiawatha Hobbies:

 

245-SCF Digitrax, Super Chief Premium set 5amp  $309.99  1  $309.99

245-PS2012 Digitrax, Power supply 20 Amp f/DCC  $143.99  1  $143.99

245-PM42 Digitrax, Quad power manager auto rev  $63.99  1  $63.99

245-DS64 Digitrax, Stationary decoder 4 output  $47.99  2  $95.98

245-BDL168 Digitrax, LocoNet Occupancy decoder  $119.99  1  $119.99

245-SE8C Digitrax, Signal decoder  $99.99  1  $99.99

 

I've also bought some blade fuses (2A and 5A) and automotive fuse box from Ebay.  I've got 6 rocker switches to turn sections on and off. 

 

I'm going to be running 2 loops of track which split into 4 platforms at the front and 8 sidings at the back.  This will emulate a subway station.  Later I will cover this with more board and there will be a window at the front to view the subway station.  I'll build my above ground layout over.  See sample plan attached.  I've colour coded the different sections require for occupancy detection.

 

So as I understand it, my power will be going from Power Supply to Booster, then from Booster to PM42 or fuses, I then split it into two sub-districts (inner track and outer track), within each sub-district I use the BDL168 and wire as shown in the Digitrax documentation.  Wherever I place a fuse I'm going to add a rocker switch to enable manual isolation of sections.

 

Then ... I get down on my knees and pray!!!

Temp-subway.pdf

[railzilla]

Hi Ghan,

i counted:

22 Blocks or section 4+8 for station 4 for each loop and 2 for the stub tracks in the back. But you do not net occupancy detection everywhere or you could combine the running tracks together.

You have 22 Turnouts so your 2 DS64 are not enough, even you combine some turnouts like the crossover to one turnout. Are you using the original Peco switch motor coil or a servo motor like a tortoise? If you use Kato or Tomix double crossover instead four single peco turnouts you could save a lot of switch motors and decoder outputs (2 instead of 8). Do you have all the track and turnout material. For the storage yard Kato or Tomix switches might be actually cheaper than peco turnouts plus needed accessories.

 

For the time you have all necessary equipment to start.

 

For what do you want to use the SE8C?

 

I assume you want to use the other two exits of the PM42 for your top layout.

 

Using switches is a good idea, especially for the storage tracks, no need to power your trains all the time.

 

Regards,

[inobu]

Ghan,

 

Make sure you understand the whole layout wiring and Direct Home wiring concept.

 

Good luck

 

Inobu

[The_Ghan]

Hi railzilla,

 

OK, the reason I appear to be short a few things has to do with the post and tax.  If my package arriving in Australia is valued at over AUD$1,000 then it is liable for duty.  So, I always order around US$850 worth of gear.  Allowing for the 0.88 exchange rate that keeps my order just below the magic $1k.  The extra DS64s will be in the next order along BDL168s, RX4s and a few other things.

 

We think alike it seems, because I too did the math on the cost of track etc.  I get my Peco gear out of eHattens in the UK.  International shipping means I enjoy the 14.89% discount, which is usually more than the cost of the freight.  Including freight, my Peco gear arrives at my door 35-40% cheaper than I can get it in Sydney.  Straights and curves work out at around AUD$3.50 per metre with Peco as against $6.70 per metre with Tomix Fine Track.  Peco points end up costing me about AUD$3.00 more because I wire them up with a molex plug for hot swapping.  But the REAL reason I’m using Peco in the subway is I don’t want ballast.  I want the “concrete sleeper bolted to concrete foundation” look.  Peco will give me this look.  All my visible track up top which requires ballast will be Tomix Fine Track.

 

The SE8C is so that I can get started with signalling.  I’m going to locate signals in the station section, which will be the only part visible to all when the layout is finished.

 

Inobu, I’m planning to use Direct Home Wiring rather than Whole Layout.

 

Now, something I’ve forgotten about altogether ... LocoNet cables.  Do I just need standard 6 wire RJ12 throughout?

 

Cheers.

[inobu]

Yes, RJ12, Get the crimper kits and a spool to run exact lengths on all of your wiring runs.

 

The wiring aspect plays the most important role is having a solid layout. Most of us end up bundling the access wire under the layout giving us headaches in the long run. Because of the complexity in laying out the detectors, you want to make sure your wire installation is traceable for easy trouble shooting.

 

Put the wiring diagram on paper and use the Digitrax cut sheets. They help organize your plan.

 

Don't forget about your terminal blocks, (hind sight for me) I should have made my own terminal block instead of buying them. The number of positions always came up either too long or too short and I had to share blocks breaking up the wiring grouping. Next time I will go with Plexiglas, drill press and a box of screws for a custom install.

 

Last thing is wire identification. Label maker and a color coding scheme works wonders. 

 

As you wait for your material to come in, get the plan on paper.

 

Good luck

 

Inobu

[railzilla]

Hi railzilla,

 

OK, the reason I appear to be short a few things has to do with the post and tax.  If my package arriving in Australia is valued at over AUD$1,000 then it is liable for duty.  So, I always order around US$850 worth of gear.  Allowing for the 0.88 exchange rate that keeps my order just below the magic $1k. 

So you government is quite generous in Switzerland the limit is much lower so it is not worth sending multiple parcels.

The extra DS64s will be in the next order along BDL168s, RX4s and a few other things.

Note that the RX4 only will work with Kato and Digitrax decoders. i Also bought two of them but are not that convinced, or better i do not like vendor lock in.

But the REAL reason I’m using Peco in the subway is I don’t want ballast.  I want the “concrete sleeper bolted to concrete foundation” look.  Peco will give me this look.  All my visible track up top which requires ballast will be Tomix Fine Track.

For the visible parts you can use motors instead of coils then the turnout will move slowly like the prototype. It will need some space under the layout and is more difficult to mount.

 

Keep us updated. The projects seems well planned.

Regards,

[KenS]

245-SCF Digitrax, Super Chief Premium set 5amp   $309.99   1   $309.99

245-PS2012 Digitrax, Power supply 20 Amp f/DCC   $143.99   1   $143.99

245-PM42 Digitrax, Quad power manager auto rev   $63.99   1   $63.99

245-DS64 Digitrax, Stationary decoder 4 output   $47.99   2   $95.98

245-BDL168 Digitrax, LocoNet Occupancy decoder   $119.99   1   $119.99

245-SE8C Digitrax, Signal decoder   $99.99   1   $99.99

 

How are you planning to power the accessories? Some of them can use track power (e.g., DS64), but some (like the PM42, SE8C and BDL168) need a separate power supply.  You can use a spare output of the PS2012 as an accessory supply, but Digitrax warns against using the same supply that you use for SE8C and BDL168 devices for other things (like the PM42). You can apparently share one supply between them (per the SE8C manual).

 

It's possible that the concern is just about variations in voltage, and wiring them independently back to the PS2012 would minimize that, but the issue could be something else, like electrical noise, and you may want to consider a separate supply  like the PS14 (300 mA, enough for both the SE8C and BDL168, although you'd need to cut the end of the wire off and solder it to the two edge connectors). I'm actually planning to do the independently-wired-to-PS2012 approach, but I don't know if it will work.

[The_Ghan]

KenS,

 

I was planning to use a handful of existing transformers that I own.

 

Cheers.