It's really simple ...

It's really simple - you just cut the wire that's going to the frog and connect each end of the cut wire onto one of the poles of the bulb. In other words, the electricity going to the frog is now flowing through the bulb first since it's now wired in series.

What's happening is the electricity is flowing through the bulb filament when a loco rolls over the frog, but it's not enough current to light the filament, ordinarily. A cold light bulb filament doesn't affect the circuit much at all - it's like it's not even there - it's just more wire.

However, if you get a short, suddenly the current jumps to the limit of the filament (2.1 amps) and the bulb lights up - limiting the current. In an ordinary short, the full current capacity of the booster is flowing through the short - if you have a 5 amp booster, then 5 amps are flowing. If your DCC system supplies 14 volts (as many do) then you now have 14 x 5 or 70 watts being released at the point of the short.

Just imagine what putting a hot 70 watt soldering iron on the location of the short could do as to damage and you get the idea. By limiting the short current to 2.1 amps, you now have only about 29 watts being released at the location of the short - still enough to do some damage but it will take much longer before it gets serious. Generally, the extra time this gives you coupled with the very obvious light from the bulb makes it possible to remove the short well before it will do any serious damage.

I have a circuit diagram for this in my video volume #3, along with many other pointers and circuit diagrams. If you subscribed to MRH, you got a $10 off coupon code and can save $10 on the price of this video - or if you go download the early bird bonus goodies that go with the current issue, you can get a $15 off coupon code - making the price of this one video only $10 (plus shipping).

1156 Bulb Short Management

Thanks Joe. I will go and do it now.

Cheers and thanks for the rapid response. It only took my Lunch break.

Stewart.

Short Circuit Management

Hi again,

Yes it works. I have installed 6, only another 16 to go.

Cheers

Stewart.

DCC Short Management

Hi,

My name is Marcelo and I´m a Southern Pacific fan writing from Toledo Province in Spain. I saw the Joe´s video about DCC short management but I´ve a problem when I try this.

I connected a 12V 21W bulb like Joe show in the video, but when I try to make a short in order to test the connections, the lamp lights for a second or less and the DCC central show a short. I have a Roco Multimaus DCC central with two cabs. Is there a bulb problem or I forgot another thing?

Thanks in advance.

Marcelo

Toledo - Spain

Depends on your booster short reaction speed

Depends on your booster short reaction speed - if it's too fast, the bulbs don't help. You need a booster that reacts at about 250 milliseconds or longer. Anything faster and the booster wins, not the bulb.

On a Digitrax system, you can set the short delay to 500 milliseconds, at which the bulbs work great. If your system lets you change short reaction time with a setting, then you're good. Otherwise, nope, doesn't work.

Lenz, for example, is too fast except for their oldest LV100 boosters, meanwhile the EasyDCC boosters are the other way: the older EasyDCC booster cards don't work. NCE works great, and so does Digitrax with the booster short delay setting at 500 milliseconds.

Booster Reaction

Thank you very much Joe,

Unfortunately my DCC (Roco 10764) is not able to set the reaction time to a short circuit, so I must find some other way to handle this problem. Is it possible to connect a component due to the lamp?

Thanks again

Marcelo
Toledo - Spain

Different Bulb is needed sometimes!

I use an 1142 bulb that draws 1.44 amps  instead of an 1156 because my DCC system is an MRC Express rated at 1.6 amps total.  Using the 1156 bulb drew to much amperage so that was my solution. In the end I get the same protection.  As soon as I upgrade to a full power system I will change them over to the 1156.  I will also be adding sockets for the bulbs as this will make wiring them in much easier,  All my bulbs are above the layout so we can see them quickly!

Another Use for Tail Lights

Tail lights are also handy for controlling low amperage motors with a rheostat.  My layout is a torture track with steep grades and sharp curves and an assortment of motors from old open frame motors to low-draw can motors.  The big old motors on the grade have cooked transistor throttles to death, so I use a rheostat throttle on the mainline. 

Since rheostats control motors by dividing the voltage between the rheostat and the load, some low draw motors are not well balanced with the rheostat.  I have wired a tail light bulb (I don't know the number and I doubt that this application is picky) in parallel to the track.  This way, the voltage is split between the rheostat and the bulb, and the low-draw motor inherits the voltage of the bulb with which it is wired in parallel.  Locomotives that used to start and stop too abruptly on the rheostat now start and stop smoothly and at lower speeds.

When I am running a high current motor or a double header, I do not want the light bulb in the circuit, so I wired a switch to the bulb to shut it off.