1156 Automotive Bulbs

greenspun.com : LUSENET : Wiring for DCC : One Thread


The technical writer in me wants to warn you about the mixed message being sent by referring to #1156 bulbs as "Taillight Bulbs" (in the track wiring section).

The 1156 (as you know) is a relatively high candlepower bulb (as automotive applications go - something around 32 CP if memory serves) that commonly finds its application in automobile turn signals and brake lights (when not combined) as well as in back-up lights and other applications where a bright attention-getting light source is required.

Typical taillight bulbs are of a much lower candlepower (5 to 10 CP?) and serve in that capacity and occasionaly as other marker lights.

While I tend to agree that we should "...let Darwin prevail," please consider the consternation of the reader who, forgetting to jot down the number, runs to Pep Boys and returns with two dozen low-candlepower 'taillight' bulbs only to find that after painstakingly soldering them all in place, every one lights up quite easily the moment an engine is placed in the block (at least, I'm pretty sure that's what would happen).

Thanks for all the other great info, tho'!


-- Blaine Bachman (blbachman@aol.com), February 12, 2002



Thanks for sheding light on this topic! While I knew the bulbs on the back of cars were of different brightness and that brakes were always brighter than any other light, I never new that the bulb I tested and ultimately selected was not generally known as a tail light bulb. As they say, you learn something new everyday!

I'll add this to my list of web page updates. You are right, someone will succeed in buying just any old bulb and not get the desired result. You are right, a lower power bulb will light too soon - if not immediately!

Everyone please note: I ran tests on many bulbs. The 1156 worked the best. A few others worked pretty good, but the 1156 was also the cheapest of those that worked making it the winner. I don't specify, nor do I remember, the numbers of the others that worked. The key thing to note is that if you use a bulb that is too high in wattage (candlepower), it will not come on soon enough and limit the current to the short before the booster shuts down. A bulb too low in wattage (candelpower), will come on too soon.

As a few of you know (but not the thousands who send me hate mail on this topic), I didn't think up the bulb idea. Bulbs used in this way predate my birth and probably were used this way a week after Thomas Edison thought the darn things up! :)

Other people had run tests for model railroad use before I came along and put up my web page. ALL the bulbs mentioned in the previous articles were obsolete. So I started over from scratch and came up with the 1156.

Now, I'm starting to find the 1156 a little difficult to find. I used to be able to get orange or clear in large quantities. Now I can hardly find the orange and I can't always find a store that has a dozen packs that I can buy at a time.

I suspect in the next year or two, I will be doing this all over again. That's okay, maybe the hate mail will be frequent again and outnumber the junk mail that now fills my mailbox. :)

Definitely feel free to keep using the 1156. There won't be any crime to having your layout mixed with the 1156 and whatever I find to be its equivelent - same amount of current draw and cheap. It will just likely be shaped a little different and probably will mount differently as many of the newer bulbs do these days.

Don't worry about your 1156 burning out any time soon. I got an email a few years ago from someone who had been using automative signalling bulbs (how's that Blaine) since 1957 and he said he has yet to burn one out. My last car was 12.5 years old when I got rid of it and it never needed a rear bulb. Clearly, these things are designed to go on and off many more times than they ever will on our model railroads.

-- Allan Gartner (bigboy@WiringForDCC.com), February 17, 2002.

Is it me or am I reading something wrong.On one hand people are saying to use 12 wire for a system buss.The next thing is to feed the sections through a light bulb.Sure it will limit the current but why do I need a super heavy buss? Another thread says to put a feeder on each piece of track!! If I feed all of that with 1156 bulbs,when I have a short it will look like Christmas Vacation!!

-- Robert Terrano (orchid1@optonline.net), February 20, 2003.

A Christmas vacation? I like that. That would certainly make a short a festive event!

Seriously, let's see if we can straighten things out. 1. Yes, I SUGGEST #12. I do this to indicate simply that this is my main bus. I'm using the size of the wire as an visual indicator when I'm under the layout. I am not using it because I need an electrical wire that heavy. However, unless you have a small, bedroom size layout, I advise against using smaller than #14. Larger layouts have run into problems with #16 & #18 main buses. (Note: Outdoors, I use #10. This time, so that I am less likely to break it should I hit it with a shovel.)

2. Yes, I SUGGEST a feeder to every piece of track from the sub bus. There is only 1 bulb between the main bus and sub bus. See my wiring track section 5-6. http://www.WiringForDCC.com/track.htm

Following this approach, a short is a short. It is not a reason to break out the eggnog! The light lights up and tells you where the problem is.

Break your layout up into sub buses as you choose. I have my main broken into 15' sections so that I can block detect a train. Each block detected section, each spur, and each siding is on a bulb. Yes, that is a lot of bulbs. But problems are easily found! How you subdivide and use bulbs is YOUR CHOICE.

-- Allan Gartner (bigboy@WiringForDCC.com), February 20, 2003.

Robert and others,

With DC throttles we got used to constant adjustment of the 'speed' knob as the train ran around the layout. Each knob controlled one train. We accepted the fact that headlight brightness varied with speed. We didn't notice that when other engineers adjusted their train, it sometimes effected ours. With DCC our expectations and observations are different. We expect that the speed should remain constant (on a level layout) at a given throttle setting, and that it won't vary as other operators play with their train. So with DCC there are 3 new things we need to satisfy.

1. For good operation on DCC you need to maintain constant track voltage around the layout with a variable current load. The DCC bus under the table carrys power to all track sections simultaneously. A low electrical resistance is required to prevent a distant load from causing a voltage drop at your track section. Hense the trend/need for large diameter, low resistance DCC bus wire under the table.

2. Track rail is not the best electrical conductor. Rail joints sometimes make poor electrical connections. So to prevent train speed to vary as it passes from track section to track section, drop multiple track feeders down to the bus so that electric durrent doesn't need to flow through an unsoldered rail joiner. An alternate is to solder every other joint and drop 1/2 as many feeders. Leave some joints unsoldered for thermal expansion.

3. With DCC a track short will shut down the whole layout. [Booster over-current trip] Sometimes this may occur at turnouts. [See DCC friendly turnouts] It may occur by accident if there is more than one operator. At any rate it is annoying. One of the remedies is to protect each 'operator area' or likely track-short spot with a light bulb current limiter or fast acting electronic circuit breaker. [You don't necessarily need both.]

Note...Don't use light bulbs to isolate sub-bus areas AND more light bulbs to isolate track sections like turnouts. You will end up with multiple voltage drops in series which brings back unexpected sags in track voltage and interference between operators.

And of course...On a large layout it would be convenient if there was a way to quickly identify where an unexpected short circuit exists. splitting the layout into sub-busses with individual disconnect switches, circuit breakers or light bulbs does just that.

-- Don Vollrath (dvollrath@magnetek.com), February 24, 2003.

Moderation questions? read the FAQ