FORUM CLINIC: 12 years using DCC - SIGNIFICANT NEW INFO!

[jfugate]

QUOTE: Originally posted by ereimer

Joe , in your "DCC and Realistic Operations on the Siskiyou Line" DVD, one of the attendees raised the question of how does the 1156 bulb affect block occupancy using the current detection method . your answer was you hadn't gotten that far (in your detection / signalling project ) , but that the 1156 might cause a problem . any further info on that yet ?

ereimer:

Still no progress to report there. However, a lot of water's gone under the bridge since then around how the bulbs operate and do what they do, including some testing to determine what they do to the circuit when cold.

What I've seen so far leads me to believe the bulbs have virtually no effect on the circuit until the current reaches about 1.75 amps. Beyond that the bulb starts to limit the current flow, capping somewhere just under 2 amps. Between 1.75 amps and 2 amps the bulb starts to glow slightly .

If you have lots of locos in the train block and they make the 1156 bulb start to glow, you will start to notice the loco speed starts to flatten off. Cranking up the throttle doesn't translate into more current to the motor because the bulb is starting to limit the current.

With train length blocks and the typical current draw of a modern HO loco being around .2 amps or so, that means you can have somewhere around 8-10 locos on your train before you will start to notice this behavior.

Now with sound equipped locos, things start to get much more limiting. You will only be able to have about half the locos in the train block with Soundtraxx decoders, or about 1/3 as many QSI sound locos.

In other words, figure 4-5 Soundtraxx locos before the bulb starts to limit the loco speed, or 2-4 QSI locos. This is with train length blocks so we're talking per train.

The other option would be to wire two 1156 bulbs in parallel per train block, which should up the current limit to about 4 amps per train block.

[Anonymous]

Joe,

To see if I understand this correctly. The bulb is limiting the load to two amps or less per district or block. This will limit my locomotive loading to keep under the two amp "current limit". This means that I will have to have smaller districts than I might have if I were to be using 5 amp boosters as seperate power districts. My payoff is that the bulbs are quite a bit cheaper than boosters or breakers, will achieve the same effect and I can limit my shorting shutdown to very small areas. Roughly how many bulbs are on your layout and how are the laid out in terms of trackwork vs bulbs (ie. more for yards etc???)

[jwr_1986]

Joe, I retract my previous thought about the light bulbs. I just realized that because it was a high resistance load, neither would have protected the locomotive. I might just have to give this a try on our clubs layout. (The light bulbs not the melted locomotive) Thanks again for your clear and courteous responses.

Jesse

[jfugate]

QUOTE: Originally posted by Trainnut1250

Joe,

To see if I understand this correctly. The bulb is limiting the load to two amps or less per district or block. This will limit my locomotive loading to keep under the two amp "current limit". This means that I will have to have smaller districts than I might have if I were to be using 5 amp boosters as seperate power districts. My payoff is that the bulbs are quite a bit cheaper than boosters or breakers, will achieve the same effect and I can limit my shorting shutdown to very small areas. Roughly how many bulbs are on your layout and how are the laid out in terms of trackwork vs bulbs (ie. more for yards etc???)

Trainnut:

I have about 20 bulbs on my layout and the same number of train blocks. My mainline is 360 feet and I have about 1200 feet of track total.

A lot of this will probably become more clear once I do the wiring post.

You can have 5 amp power districts, just as you do today. You are assuming you won't draw any more than a total of 5 amps in that power district, so nothing changes there.

You then subdivide the power district up into 2 amp sub-blocks -- or 1.75 amp sub-blocks to give yourself a safety margin. This means you need about 3 sub-blocks in that power district, with the bus to each sub-block having an 1156 bulb in series on one of the feeds. You connect all the track feeders to the sub-bus, so that sub-block of rail is protected by the bulb.

If you have very many sound locos, you essentially need to double or triple your power districts to handle all that increased current. But per 5A power district, the process is the same - about 3 sub-blocks (gap both rails) protected by an 1156 bulb. That's an extra bus wire (12 guage wire) and $3 worth of 1156 bulbs to get this protection.

It took me and one other guy three 8 hour days to rewire the Siskiyou Line to have the bulbs. We had to cut more gaps, run a third bus wire around the layout, and wire in a bulb between one main bus wire and the local train block sub-bus wire.

I knew the bulbs helped prevent shorts from registering booster but I was amazed to see how trains in other sub-blocks on that same booster kept on running even when one of the sub-blocks to the booster was shorted.

[Bikerdad]

Very informative Joe. I'm thinking I'll probably go with a combination of the electronic devices for breaking the layout down into power districts, and then bust each district down into power blocks using the latbubs. In part, I like this approach because it addresses the matter of reversing loops, which undoubtedly is going to be a topic down the road in this clinic.

I'm still unclear though on how to mount / fixture the lightbulbs.

[jfugate]

Biker:

I solder wires to the end and side of the bulb, add crimp spade lugs, and connect them to a terminal strip. I hang the bulb under the benchwork with a 3/4" plastic cable clamp and a 3/4" drywall screw.

I'll explain all this in more detail, plus photos, in my next post.

[Bikerdad]

Thanks Joe, I look forward to it.

[jfugate]

Since my video volume 3 on all things DCC releases in a few weeks, the distributor has moved the video clip on short management to the top and has made a large broadband version available for those with a fast connection.

See: http://mymemoirs.net/preview.php

You'll need Flash Player 7 to watch it ... most people already have that plugin installed in their browser. If you don't there's a link on the page to download and install it.

[ereimer]

happy birthday Joe !

i suggest everyone click on the link in joe's post . seems today is his birthday and he's giving all of us a present

thanks !

[Anonymous]

As far as a programming track, I use a section of my main track that is insulated and can be switched from normal DCC to the programming output of the controller. This works very good and I don't have to remove my locos from the track.

[Anonymous]

The secret to the "bulb" trick to protect districts from shorts is that a tungsten filament bulb has about a 13/1 hot to cold resistance. Therefore the bulb acts like a short circuit when cold (no short) and as a current control device with a short and when the short is bad enough, the bulb will light limiting current to the bad section.

[n2mopac]

Thanks for the video Joe. It was helpful to see it work, and it came through smoothly evenon my dial-up connection.

I think my answers are slowly getting answered, and I'm sure the wiritn post will help immensely. I am an electrical dummy, but do I understand right that with this process I need larger powere districts only for each booster, and not with breakers for electrical protection? I am also unsure how the bus stricture works withing each larger district aas it feed each sub district or block, but this will probably be covered in the wiritn post.

Thanks again for all this great info.

Ron

[SpaceMouse]

Can I assume that if I'm running 3 trains on a 4x8 layout, that I need only one bulb to protect everything?

[jfugate]

QUOTE: Originally posted by SpaceMouse

Can I assume that if I'm running 3 trains on a 4x8 layout, that I need only one bulb to protect everything?

It depends on how many locos per train and if any of those locos have sound.

Assuming 1 loco per train and nothing with sound, the normal short protection of the booster should be good enough.

The bulb is best used to mask the short from the booster with multiple train blocks on your layout or with sound locos on the layout.

You only need to mask the short if you have sound locos or if you have a large enough layout that you want to run more than one train and let it keep running even if other trains get a short. On a 4x8, allowing another train to keep on running is of limited value on the main because the train causing the short may be in the way of the other train.

However, if you have a small yard or significant passing siding on your 4x8, you might want *two* train blocks with each protected by a bulb. That way, the guy working the yard can keep on running even if you short something on the main, and vice versa.

But one light bulb and one big train block on the layout is only of value if you have sound decoder locos. The reason is because sound decoders on the layout can prevent a booster from resetting after a short since they have higher current draw than regular non-sound locos. The high current tricks the booster into thinking there is still a short so it won't reset.

The bulb prevents the booster from ever seeing the short so the booster stays up, even with sound locos on the track.

Make sense?

[SpaceMouse]

Yup, I like sound.

However, I must be missing a point here. I'm getting a Zephyr, which has a max output of 2.5 A. With the lightbulb, I'm limiting the output to 2A.

Why am I doing this?

[selector]

I am a convert. [bow] Drive me to Wal-mart, Master.

Thanks, ever so much, Joe. I will have to spend some time getting this to solidify, but the the video is clear proof of concept.

So, if I understand, the more locos drawing current (volt-amps) in a given district, the more potentially lethal the short. The bulb offers a sink to the shorted power by glowing brightly and minimizing the detection of the short by the booster. Locos keep running and they stay cool. Only the one loco in that particular feeder block encounters the short.

Is that right?

[jfugate]

QUOTE: Originally posted by SpaceMouse

Yup, I like sound.

However, I must be missing a point here. I'm getting a Zephyr, which has a max output of 2.5 A. With the lightbulb, I'm limiting the output to 2A.

Why am I doing this?

Chip:

Yes, that's my point. Just putting a lightbulb on a single block feed to your entire layout will do just what you said -- limit your 2.5 amp output to 2 amps, for no real benefit.

If you don't use a lightbulb, you get the full 2.5 amps output to your layout, and the booster will "beep beep beep" when you get a short and then reset once you remove the short.

BUT -- and this is a big *but*, if you have from 2-4 (or more) QSI sound locos on the track and you get a short, once the short is removed, the QSI's have a high "inrush current" and the booster will think there is still a short on the track and won't reset until you start taking QSI locos off the track until the booster finally resets.

Now if you put a lightbulb in one of the two track feeds to your 4x8 layout, when a short occurs, the booster won't shut down at all, so things come right back after the short, even with 4+ QSI locos on the track.

However, you still have the 2.5 amp output but the 2 amp limit of the bulbs. If you bust your 4x8 in half, with 2 train blocks, *each* connected to a bulb, you get 2 amps per half. If you have 2 amps worth of locos on one half of your layout, you can have .5 amps worth on the other half and the bulbs will like that just fine.

In other words, by busting your layout up into train blocks (all still wired to the same booster), you are assuming you won't have more than 2 amps worth of locos in any one train block protected by the bulbs. You spread your full booster output across several 2 amp limited train blocks.

By making each sub-block the size of a train, you are assuming no one train on your layout will need more than 2 amps, which is a pretty safe assumption unless everything is QSI locos and you run more than 3 QSI locos per train.

Typical HO loco current draw:
non-sound = 0.2 amps
Soundtraxx = 0.4 amps
QSI = 0.6 amps

The other thing you can do, Chip, since you just have a 4x8 is to connect two 1156 bulbs in parallel on one of your track feeders, which will up the current limit to about 4 amps instead of the 2 amp limit of a single bulb.

Then you will be protected from shorts shutting down the layout when you run sound equipped locos, and you won't have to gap anything. However, a short will shut down all trains since you won't have any separate train blocks to isolate the effects of the short. But you will get the full 2.5 amp output of your system to the track with the two bulbs in parallel.

Yet the booster won't see the short so it will recover immediately even with lots of sound locos on the track. So you have options.

[jfugate]

Selector:

You got it right ... just think "loco consist" instead of a single loco. All locos in the one train block are affected by the short because the bulb will suddenly absorb about 2 amps and let almost no current get to the locos, so they will come to a stop.

Once the short is removed, all locos in that one train block will resume running and the booster will not think there ever was a short -- just a spike in current, as if you suddenly put a whole bunch of locos on the track at once.

[selector]

Thanks for the quick response, Joe.

In a way, I am set up like Chip is; we have monolithic layouts with feeders to reduce voltage drop, and that is the limit to our sophistication. In my case (unsure of Chip's), I have no gaps. So, I could merely cut some gaps between each of my 3 sets of feeders, thus creating blocks (not 'districts', because each should have a booster). Then, wire a single bulb into each, in series, and since I only run a max of two trains (currently, each with sound), the single bulb per block will do the trick with ease as no more than two locos will ever be on any one block by chance. A loco fortunate enough to be on another block when the short appears will continue on its merry way because no resisting bulb is sucking that block's current up.

Sorry if I seem to be monopolizing the thread just now, but if you answer in the affirmative, I am on my way.

[tsasala]

Joe,

I've been researching DCC for a while now, and with my system on its way, I happy to see all this information in one place. Although I've been able to cobble together the same basic information by going to tons of web sites and reading a lot posts, it was a lot of work and very hard to put all the pieces together. This series really helps codify everything and provides a very nice "big picture" view. Where were you 6 months ago! ;) Kudos and thanks for all hard work!

-Tom

[SpaceMouse]

Okay, Joe, now I gotcha. I can split the inner loop from the outer loops with no problems, which is consistant with usage and should ONLY TAKE ABOUT A DAY to do.

But then again this layout is my learning layout so I'll do it.

[jfugate]

Selector:

You got it! Should work just as you describe.

[jfugate]

All:

I hope to post the wiring installment tonight ... that should help more of you get an "ahah!" from all this light bulb discusssion.

[jfugate]

TOPIC THIS POST: Wiring details for 1156 bulb train blocks

Here's a typical DCC layout with three power districts, each powered by their own booster.


(click to enlarge)

Let's zoom in on the wiring for a single power district and then see how we “upgrade” it to add the 1156 bulb short management.


(click to enlarge)

Here we are zoomed in on our power district. Let's go through the steps to add the 1156 bulb short management protection.


(click to enlarge)

To add the 1156 bulb short protection to the power district, you first need to cut gaps in both rails to break the track up into train length blocks. Here we can see this gives us 8 train blocks.


(click to enlarge)

Next, we need to run a third bus wire for each train block thereby creating an 1156 protected bus feed for each train block. For each block we add a feed from the main bus to the third bus, through a SPST toggle switch and an 1156 bulb. If you wire a SPST toggle into each train block bus feed, you can kill the power to the block for debugging purposes, like when looking for mystery shorts. This is what I have done on the Siskiyou Line and it has come in handy more than once.


(clcik to enlarge)

You can now add the toggle and 1156 bus feed to each train block bus, and run track feeders to each rail section for a given train block from its associated third bus and the block will be protected from shorts by the 1156 bulb.


(clcik to enlarge)

Once you add all the toggles, bulbs, and track feeders for your power district, here's what you get. This is the complete wiring to add 1156 bulb short management to your layout.


(clcik to enlarge)

HOW THE WIRING ACTUALLY LOOKS ON THE LAYOUT
Here's how I wire in the bulbs. I solder wires to the terminals on the bulb, add crimp spade connectors so I can wire the bulb into a terminal strip. I mount the bulb using a plastic 3/4” cable clamp and a drywall screw.


(clcik to enlarge)

And here's how it all looks under the benchwork at a train block location on my Siskiyou Line.


(click to enlarge)

TOPIC NEXT POST: All about DCC friendly turnouts

[selector]

All very clear, and clearly a lot of work!!![:O] I can see that you get great benefits from all that work, but....whew..that must have taken many days to do, Joe. I'm glad that my 'salvation' will be done in about two hours.

[jfugate]

Selector:

It took one other guy and me 3 eight hour days to rewire the Siskiyou Line to be set up this way. That was back in the summer of 2000 and it was the best thing I've ever done wiring-wise to the Siskiyou Line. It was time *very well* spent.

[jfugate]

Before we leave the 1156 light bulb short management, have we answered everyone's questions? Do the two posts make it clear why and how?

[Bikerdad]

Yup, makes things clear. Thanks a lot. Any thought to perhaps creating a little more "standoff" for the bulb to reduce fire risk from "microscopic" to "infantesimal"?

[rrinker]

You certainly could - just use scraps of dimensional lumber fromt he benchwork to make 'stands' to lift the bulbs out of direct contact. Or you could (at great expense) buy actual sockets for the bulbs which would put the base of the bulb near the benchwork and the globe well above it.
Keep in mind in their intended application, these bulbs are inside a tightly closed plastic space - and I don't hear very many reports of the taillights in cars catching fire. Given that a 12v short in a car is far worse than even a 10 amp booster shrting out, I don't think there's much issue there.

--Randy

[ereimer]

QUOTE: Originally posted by jfugate

Before we leave the 1156 light bulb short management, have we answered everyone's questions? Do the two posts make it clear why and how?

i think so Joe , even i understand how the bulb works now [:D]
now we just need someone to test the block detector issue to see if they will work