Electronics and DCC

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.

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

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.

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.

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.

Thanks Joe, I look forward to it.

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.

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 !

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

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

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?

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?