Shorts, Power
Districts, and the 1156 - Characteristics and Tests.
Test of the 1156 showing current
& resistance readings.
See Joe
Fugates video about using 1156s for short management.
Power Districts
When there is a short, typically
caused by an operator running “against” an incorrectly set Point or Turnout,
the power to the whole layout, shuts down. While this is satisfactory for a
single operator, it is very annoying when there are a few operators.
This annoying total interruption
can be eliminated by dividing your layout into Power Districts, achieved by using:
More Boosters – These are expensive and not really
required on layout operating approximately 10 or so trains.
A Circuit Breaker – Much cheaper (AS20 to A$25) per
section, making them a much cheaper alternative to Boosters.
An 1156 automotive lamp.
The $2, 1156 automotive 12
volt 32 candle power (27 watt) brake lamps that are not new to model railroads,
can be used to restrict the current to 2.0 amps when there is a short. The
booster does not cut out. It supplies the current to the 2.0 amp short power
district and all other power districts, thus operation on the other power
districts is not affected. The lamp does not
remove power to the short.
See Joe
Fugates video about using 1156s for short management.
Shorts in DCC.
There is a lot of
confusion here. The short that normally happens (99.9%), that trips the booster
or circuit breaker or that illuminates the 1156, is a short at the rails.
These include:
1.
An
operator running against an incorrectly set of points or turnout.
2.
The
back of a wheel contacting the closure rail on a turnout.
3.
Out of
gauge wheel sets going through turnouts.
4.
Bad
track alignment at turnouts.
5.
A
derailment.
Some of the above fault
conditions can be reduced by making your turnouts DCC Friendly, correcting the
track alignment and wheel sets. This leaves operator error as the main culprit
as the cause of the short.
Since the short is
at the rails, the only items affected are the wheels and track. This
short does not affect the DCC decoder and will not cause any damage to it,
contrary to what some have said. Continual shorts will cause pitting of the
wheels and track.
The reported short causing
a bogie or ties to melt, is when there has been a short and the booster or
circuit breaker has NOT tripped. Depending on how much current the booster can
supply and the amount of time the short went unnoticed will determine the
amount of damage. A 5 amp booster has the capability of supplying 60 70 watts
of power, transformed into heat, it is a very large soldering iron. This will
cause some damage and may cause a fire.
Adequate wiring is very
important to enable correct booster and circuit breaker operation. Use the Coin
Test to check all track wiring.
The 1156.
Using 1156 as a current
limiter, on our railroads is nothing new. The use of can motors in our
locos (last 15 20 years), that draw such small amounts of current compared to
open frame motors of the earlier design, means using the 1156 to manage shorts
and power division, is an ideal cheap device. Some of the draws backs of the
previous 1156 usage on earlier layouts, has found it way into this 1156 DCC
discussion. These draw backs are totally irrelevant now with our modern
railroads with the can motors for the locos. Using the 1156s will not melt the
ties as it has been reported. This is just another myth. The 1156 would only
let 2.1 amps flow and earlier locos draw more than 2.1 amps and I did not hear
any reports about the ties melting under the track while they were operating.
Present day locos equipped
with a decoder and a can motor, draw about 200 to 400 mAs of current,
while operating and 30 to 70 mAs while stationary. Sound locos only draw about
10 to 20% more. Two and three locos consisted together, including sound will
only draw about 500 too 800 mAs of current. Using these figures as a guide and
how you operate your layout, you can use the 1156 to divide your layout.
Exceeding three or four locos in a power district may cause operational
performance to be effected. Reduce the size of the power district. Remember
with a few operators, not ALL the locos are running at the same time.
The characteristic of the
tungsten incandescent lamp is that the cold resistance is about 10 to 20% of
the hot resistance of the lamp. If we operate in this cold resistance area the
1156 will not impact on the layout but when there is a short the current is
limited to 2.1 amps. This will allow total loco current draw of about 700 to
800 mAs before the voltage is robbed by the 1156 and starts to affect
performance. If operating locos slowly as in switching operations, this still
will not affect the layout. Reducing the voltage to the track affects top speed
and the brilliance of any loco headlights. See below for results.
Wiring the layout
using the 1156.
Some modellers wire each
point frog feeder with a lamp.
My layout: I have divided my layout into 8 power
districts, one per major operating area like a yard or station area. I will
make smaller power districts when the operational need arises, if ever. This is
easy to do, just make the district smaller.
Joe Fugates Siskiyou
Lines layout: Joe divides his layout into train length power
zones. See his video about using the 1156 at:
http://mymemoirs.net/preview.php
Click on the screen to start the video.
See http://siskiyou.railfan.net/model/constructionNotes/wiring.html
for a wiring diagram about the 1156 installations.
My club layout: When
I joined the NMRA SIG group here in
This layout is powered by a
single NCE 5 amp booster. Operating nights have 6 to 8 train crews. This will
mean about 8 to 12 locos as some trains have double headed locos. Broadway Ltd
and Soundtraxx sound locos also are being used. Generally one train crew or
maximum two in one module, each 1156 will only have at maximum 4 locos under
its control. The 1156 is able to handle these loads.
I have installed an
ammeter and it shows a maximum 1.5 to 2.0 amps during the operating session. At
the moment, this gives us plenty of amps headroom with no need of an extra
booster. Installing a full time ammeter at a convenient location, will allow
you to monitor layout current (amps) demand. When the booster shuts down due to
a short, the ammeter will be showing 3.5 to 4.5 amps while operating. This is
when an extra booster is required.
I prefer to place the
1156s in a line side building as shown. If the operators loco stops, he will be
suitably warned that he has a short. This illumination of the building will
certainly attract his attention and he will remedy the fault immediately. This
very visible warning will NOT go unnoticed for too long, thus preventing any
problems. Some have asked that the light creates a lot of heat and is a little
dangerous. 1156s are located in millions of motor vehicle tail lights and this
is a similar small non vented enclosure has not caused a problem there. This is
ideal manager certainly tells us what is going on when the loco stops. A loco
stops and there is no bright visual warning, then it is dirty track that
stopped the loco, upper photo. With a short, no problem missing the warning,
lower photo. On my own layout, dirty track is a problem as I share the garage
with two cars.
My own layout.
My 30’ x 30’ Double Deck
layout is divided into 15 Power “town” Districts, each controlled by an 1156.
Power Division for $30 and I have installed an Ammeter to
monitor layout current demands. You will be surprised at how little current the
layout uses.
Adding a PTC (Poly Switch) to the 1156.
Lately I have been modifying
my 1156s that I have on my layout, after reading an article by Dick Bronson
where he shows how to add a Poly Switch to a dual filament lamp. After approximately
40 seconds or so, the Poly Switch “cuts in” and now only allows about .4 Amp to
flow through the Short. Click here for Dick’s
Short Circuit article.
More Theory and Tests
The theories of how a lamp
works see http://home.howstuffworks.com/light-bulb2.htm
To restrict the current when
there is a short to about 2.0 amps we could use a 6 ohm 25 watt resistor, but
using an 1156 lamp has the added benefit, that while it’s hot resistance is
about 6.0 ohms, when the lamp is illuminated brightly, its cold resistance is
only 0.5 ohm. This makes it a variable resistance resistor, with a range of 0.5
ohm to 6.0 ohms.
What this gives us model
railroaders, when operating a few locos and drawing, say 700mAs (2 to 3 locos),
the voltage drop across the 1156 lamp is about 1.0 volt. With a resistor this
would be 4.2 volts. This voltage drop is robbing our layout of voltage. This
affects the performance of locos namely top speed and eventually when the
voltage at the loco (track) is at 9 volts DCC, the Soundtraxx decoders sound
starts cutting in and out but non sound decoders will still operate to about 7
volts. The top speed will obviously be reduced, slow operation will be ok.
The table below the first 3
columns the current through the 1156 was with a DC Power Supply. The resistance
of the 1156 was calculated by using Ohms Law R = E/I
My NCE DCC PHP system has 14.0
DCC at the output. I have an ammeter in circuit full time that uses a bridge rectifier
connected in one track feeder. There is a voltage drop of 1.5 volts across this
rectifier. I operate with 12.5 volts at the track with a 1156 in series with
one power feeder to each power division.
For the last column of reading
I adjusted my booster to give me 14.2 volts DCC at the track. The booster was
adjusted to 15.6. There is a 1.4 volts DCC voltage drop across the bridge
rectifier.
For DCC voltage measurements I
use the DCC Tester from Pricom at www.dcctester.com
What can be seen as mentioned
above, the 1156 gives you variable resistance and much less voltage drop than a
6 ohm 25 watt resistor that would restrict the current flowing to 2.0 amps when
there was a short.
When the 1156 is used with our
DCC layouts we can run about 3 - 4 locos (700 mAs) per power zone. If this
creating some problems with the ammeter installed full time do as I can do,
bypass the ammeter while operating and only have it in circuit when measuring
loco current or layout demands. Alternatively adjust the booster to give you
14.2 volts at the track thus compensating for the ammeter (bridge rectifier
voltage drop). I adjusted the booster for the last column readings and now back
to 12.4 at the track.
Some modelers have reported by
lowering their DCC track voltage has resulted in less problems with runaways
and decoders. I operate at slow speeds with switching and no fast passenger
trains, so I prefer my voltage lower.
Using an 1157 a two filament lamp
with both filaments being used will provide a higher current about 2.5 amps and
using two 1156s in parallel will increase the current to 4.2 amps. This may
cause a problem with the booster sensing the short before the lamps restrict
the current to the 4.2 amps. Experiments will have to be done here on
individual systems as booster capacity and response times will be different.
This shows how good the 1156s
are for our DCC layouts. A very effective power dividing device that is cheap.
The basic property of a tungsten filament of the 1156 acts as a variable
resistance, that a normal resistor could NOT provide as it is a fixed
resistance. Operating the 1156 in the range .1 to .9 Amps only creates a 2.2
volts voltage drop. A very acceptable condition that would allow 2 to 3 locos
to operate, including sound, in that power district.
Using 1156s for Tonys
Power Shields or the NCE EB3.
Experiment with 12 volt lower wattage lamps to
provide the bypass lamp for the work around for these circuit
breakers, to enable them to reset with sound locos. Using the lower wattage
lamp will only allow a smaller current to flow through the short. 1156s will
not cause any problems with decoders or wheels and these act as a very visible
indictor of a short, that will be easy for operators to identify where the
short is.
Bye the way, Jim Scorse at NCE
recommends the 168 lamp for the bypass fix for the EB3s.
|
Current flowing through the
1156 |
Voltage Drop across the
1156 |
Voltage
drop 6
ohm 25W resistor
by Ohms
Law |
Resistance of
the 1156 by
Ohms Law
R=E/1 |
DCC
track voltage With
1156 and Bridge
rectifier Ammeter
installed |
NCE
DCC booster voltage adjusted
(15.6) to give 14.2 volts at the track with ammeter and 1156 installed |
|
200
mAs |
0.1 |
1.2 |
0.50 |
12.2 |
13.9 |
|
300 |
0.17 |
1.8 |
0.57 |
11.9 |
13.8 |
|
400 |
0.26 |
2.4 |
0.65 |
11.7 |
13.5 |
|
500 |
0.43 |
3.0 |
0.86 |
11.3 |
13.1 |
|
600 |
0.7 |
3.6 |
1.17 |
10.9 |
12.6 |
|
700 |
1.1 |
4.2 |
1.60 |
10.2 |
12.2 |
|
800 |
1.6 |
4.8 |
2.00 |
9.6 |
11.4 |
|
900 |
2.2 |
5.4 |
2.44 |
9.3 |
10.4 |
|
1.0
Amp |
2.8 |
6.0 |
2.80 |
9.1 |
10.0 |
|
1.1 |
3.6 |
6.6 |
3.30 |
|
9.0 |
|
1.2 |
4.2 |
7.2 |
3.50 |
|
|
|
1.3 |
5.0 |
7.8 |
3.85 |
|
|
|
1.4 |
5.7 |
8.4 |
4.07 |
|
|
|
1.5 |
6.7 |
9.0 |
4.47 |
|
|
|
1.6 |
7.6 |
9.6 |
4.75 |
|
|
|
1.7 |
8.5 |
10.2 |
5.00 |
|
|
|
1.8 |
9.5 |
10.8 |
5.28 |
|
|
|
1.9 |
10.5 |
11.4 |
5.53 |
|
|
|
2.0 |
11.6 |
12.0 |
5.85 |
|
|
|
2.1 |
12.7 |
12.6 |
6.05 |
|
|
1156
illuminating with 3 locos & causing locos to slow
up too much.
As mentioned in the text the lamp
will start to glow with about .8 1.0 amps flowing through the 1156. With 0.8
amps and the track voltage at 13.8 volts DCC this would cause a reduction in
track voltage to 9.6 volts DCC. Depending on current draw of locos, if double
or triple heading locos with a heavy load could cause locos too slow too much.
If this is happening then the 1156 resistance could be DECREASED by adding
another lamp in parallel with the 1156.
An 1156 is a 12 volt 32 Candle
Power (approx 27 watts) automotive lamp and connecting two in parallel would
INCREASE the current when there is a short to 4.2 amps. While this would double
the amount of locos before the two 1156s would impact on operation, it may
cause the booster to trip out before the lamps restrict the current. Boosters
trip in about 1/10 of a second. Also I am loathe to recommend a short circuit
current of 4.2 amps continually running while there is a short. While there is
normally no power dissipated at the short (wheels and track) there will be a
bigger spark that will cause pitting of the wheels and track.
If your type of operation
causes your locos to slow with one 1156 there is a couple of alternatives.
1. Add a
5, 10 or 15 watt lamp in parallel with one 1156 to increase the current a
little bit more. Experiment here start with a 5 watt lamp first.
2. Wire
two 21 watt lamps in parallel giving 3.4 amps as below. This does NOT cause the
NCE booster to cut out and would be suitable.
3. Buy a
1157 lamp which is a twin filament stop/park 32/5 CP lamp and wire both filaments
in parallel.
4. Adjust
your booster DCC track voltage a little higher. See your system manual. NCE
have a potentiometer that can be adjusted from the rear.
Try what solution is more
suitable for you. If operating with 3 locos that cause the 1156 to illuminate
dimly and slow locos that you cannot accept, it may be more appropriate to use
circuit breakers like NCEs EB3s or TTXs Power Shields, as there is operating
limitation with the light globe solution and the purpose of the lamps was a
cheap alternative for power division and short management, but if the 1156 is
affecting your operation, then this is not an effective alternative.
To
connect two lamps in parallel:
Connect both the lamp bases
together by soldering a link between the two lamps. To solder to the bases,
clean the area with a file to enable solder to weld to the base.
Connect both solder contact
tips together.
Solder a wire to each of the
base and the contact links and connect in SERIES with one track feeder to the power
district. It does not matter which track feeder you connect this lamp into.
Yellow heat shrink from a previous test.
In electrical terms,
SERIES means in line with a circuit and there is only ONE path for the
current to flow through like the early Christmas tree lights, one globe blows
and all lights extinguish. Ammeters are connected in series.
PARALLEL means across the circuit, two or more paths for the current to
flow. All the lights in your house are connected in parallel, one blows, and
all others will still work. Voltmeters are connected in parallel.
Happy experimenting with 1156
lamps or similar, for power division and short management. I find the 1156
method a great indicator for showing why a loco stops and have them located on
my layout in view in a line side building.