Circuit Breakers & Boosters not resetting after a short with sound
equipped locos.
Mark Gurries’s
technical explanation.
Rex Beistle PM42
solution that I have used in the PM42 diagram.
Operators
in the U.S and here (
I had this problem when I was building a DCC
demonstration module and I fitted an EB3 from NCE, a 3 channel electronic
circuit breaker. I searched the DCC Yahoo Groups and at Tony’s Train Exchange,
I found a statement that, when there are Soundtraxx equipped sound locos on the
layout, that there were problems with the Power Shields resetting. Power
Shields and EB3 are similar.
I resolved my problem with the EB3 after getting
advice from Mark Gurries on the Yahoo NCE group, to fit a lamp in parallel with the
circuit breaker, as shown in the photo and diagram below.
Why?
- The circuit breaker cannot differentiate between a short circuit and the
larger “inrush current” requirements of few sound locos. The more sound locos
in a zone, the more current is required in this “reset 2 seconds”. Increasing
the trip current jumpers on the EB3 only marginally improved the reset
operation. Adjustment of the trip response time more than the default 1/10th
second may cause the booster to trip and not the EB3, when there is a short.
Using
a 5 Watt lamp, Hella Part No W125, similar to the 168 available in the U.S, I
found that I could have 6 sound equipped locos in the same power district and
the EB3 reset automatically. If locos were idling with sound on, then I had to
increase it to 10 watts. See table below and Auto Lamps in DCC for the wattage
of the lamps I have used. Experimenting with lamp wattage until particular loco
density requirements have been fulfilled, will enable the EB3 to reset
normally.
Tests - EB3 reset times after the short is removed
Without bypass lamp.
1 sound loco – 2 seconds
2 sound locos – 5 to 40 seconds
3 sound locos – Would not reset (still not reset after
5 minutes).
With a 12 volt 5 watt Hella W125 or “168”
bypass lamp.
3 sound locos – 2 seconds
4 sound locos – 2 seconds.
5 sound locos – 2 seconds.
6 sound locos with idle sounds - 8 to 40 seconds.
Use
a 10 watt 97 lamp for 5 or more locos in the same power district.
The
use of 1156s for this “work around” will give a very bright visual indication
with a current of approximately 2.0 amps flowing through the short.
Unless you have more than 10 sound locos in the same power district, no need to
use an 1156. Note: I use 1156s for short circuit and power district management
on my layout. There will be no problems using these lamps, IF the short
is rectified immediately and not left unattended. See my article on Using the 1156s.
Note: I have spoken to Jim Scorse and he has tested the EB3 with a 168 wedge
lamp and is happy with using this lamp to allow a reset of the EB3s. Remember
this problem does not happen on all layouts.
Fitting
the parallel lamp fix with each circuit breaker channel, as shown above, has
provided correct operation of the circuit breaker, but will allow a current of
.35 amps for a “168” lamp to flow, when there is a short, thus the EB3 does
not disconnect the power to that power district (layout) .
This lamp effectively provides a parallel path for the current. With the
EB3 under normal operation, negligible current flows through the lamp due to
the higher resistance parallel path. When there is a short circuit and the EB3
trips, now there is current flowing to the short as determined by the wattage
of the lamp, the higher the wattage, the more current. When the short is
removed and the EB3 is attempting to reset (circuit breaker is determining if
there still is a short for 2 seconds) the lamp current provides the major
portion of the initial large inrush current for all the sound decoders, 
so when the EB3 “closes”, it supplies the remainder of the inrush
current. This EB3 sensed inrush current is less than the “trip current”
settings of the EB3. So now the operation of the EB3 is automatic.
Figure 1
Some
modellers might say, why not just use 1156s and remove the EB3 or other circuit
breakers (I do on my layout, I only use 1156s). Using 1156s, do create voltage
drops and thus a maximum of about 3 to 4 locos including sound, operating in
one power district. Using the EB3 and Power Shields with the 168 parallel lamp,
gives the best of both worlds – operating without a voltage drop (limit on
locos) and allows automatic resetting.
A benefit of using this “parallel lamp fix” for ALL
circuit breaker installations is that the lamp can be located remotely, say 20
or more feet away from the EB3. The lamp if located in a suitable line side
building becomes a very effective visual warning of a short. This visual
warning is a great way to indicate whether the train operator has a short
(lower photo), instead of dirty track (upper photo) when his train stops.
Not
everyone has the problem Different layouts have exhibited varying results for sound loco circuit
breaker reset operation, so fit either circuit breaker (EB3 or Power Shield)
and see what happens. If everything operates without any problems with the
circuit breaker resetting, don’t do anything.
NCE’s
EB3 intermittent or no operation.
A few modellers have reported that their EB3s did not work at all when
installed or had intermittent operation.
The
problem is that one or more of the 2 term terminal strips, (4 off) have dry
joint or bad connections to the circuit board. Inspect and re-solder these
joints and check for operation.
Power
Shields from TTX. The Power Shields have a
similar problem with sound resets and this is rectified the same
way, with a parallel lamp. Connect the lamp from DCC 2 (Input) and Rail 2
(Output) connections as shown below. Only one lamp is required. Use the lowest
wattage lamp possible to get the results you need. I have not tried this “fix”
on the Power Shields. A few modellers have told me the 1156s work on the Power
Shields.
This interim fix, will enable
layouts where circuit breakers have been fitted and operating with sound locos,
to operate correctly until manufacturers (decoder, circuit breakers and
boosters) have modified their products, to take into consideration the higher
inrush current requirements. There is no problem with circuit breakers with non
sound locos.
This problem happened with me with Soundtraxx equipped
locos and BLI operators in the
The
reason that this problem surfaced now, was that when the circuit breakers and
booster were designed, the NMRA Standards never stated an “Inrush Current”
value. With non sound locos there were no problems and everybody was happy.
With
the increasing popularity of sound locos ever since Broadway Limited released
ready to run locos with sound, this “Inrush” has appeared on more and more
layouts and users are reporting the inability of the circuit breaker or
booster, to reset without removing power to the layout (or booster).
With
later releases of sound decoders, circuit breakers and boosters, hopefully this
problem will be resolved by manufacturers improving their circuits for charging
capacitors and sensing currents for shorts/inrush. Only time will tell if this
happens.
If
a DCC system that only has boosters and no circuit breakers, then you cannot
add a parallel lamp to the booster. Circuit breakers will have to be introduced
to eliminate the booster from cutting out. If there are problems with the
circuit breakers then, then parallel lamp can be fitted.
Power
Shields from Tony’s Train Exchange are advertised now to allow more sound locos
to be in the same power district before the circuit breakers exhibits problems
with resets after a short.
Tony’s Power Shield Four:
PS-4s are two PS2 assembled onto one board.
The booster inputs to the PS-2, if fed from one
booster are joined together shown with the green lines.
The lamps for each section shown as Lamp 1 through
Lamp 4 are connected from “DCC 2” to each “Rail 2”.
This gives a parallel path for the current through the circuit breaker section
for each of these sections.
As
with the EB3, experimenting with lamp wattage until the particular loco density
requirements have been fulfilled that will allow the Power Shield circuit
breaker channel to reset automatically. Start with a 168. If the Power shield
does not reset with the amount of sound locos you have in one zone, then
increase the lamp wattage to a 1141 (18 watt) or an 1156 (27 watt). I don’t
have any Power Shields but others have told me the 1156 works great. See Auto Lamps in DCC for auto lamps
in DCC and the numbers. If you don’t want to experiment just use the 1156.
Photo of Tony’s Shown below is a Power Shield Four
(PS-4) setup with “barrier” terminal strips courtesy of Vince Vargus,
(16 Apr 06) showing how two PS-2 are assembled
together to form one PS-4. Thank you Vince.
Vince has shown his wiring method of terminating the PS-4 using barrier
strip terminal boards.
On the left is the terminal board to connect the DCC
from the booster.
On the right is the terminal board to the 4 power
districts.
Note Each PS-2 is treated separately. If he feed for
the PS-4 is from one booster, then the two pairs of black and red wires on
the left are linked together.
For each circuit breaker section, the “sound reset
lamp fix” lamps would be connected between one black wire on the “DCC 2”
to the other black wire on the right “Rail 2”. Two lamps are
connected to each of the black wires on the left, the DCC input.
Digitrax
PM42s and PM4s:
Rex
Beistle has said that the PM42s and the PM4s have the same problem and can be
fixed by the same parallel lamp fix. Thanks Rex.
The
PM42 &PM4 require 2 lamps per power zone feeders, thus 1156 lamps (27
watts) will be required and since both of these lamps will be in SERIES with
the load (short), they will reduce the short current to around 1 Amp and will
not glow at all, no visual warning (bummer!!!!). I don’t have a PM42, so
I cannot experiment here.
For
other system users, you must have a Digitrax system to program the PM42s and
PM4s, so this feature makes them unsuitable for power management if you have
other than a Digitrax DCC system.
Note:
The PM4s can be upgraded to PM42s with a kit from Digitrax due to
their slow response time and causing the booster to trip instead of the PM4.
Some previous history on
the Circuit Breaker problem. Some of the early emails, are included below,
about my initial problem and Mark Gurries technical explanation of the problem
with possible solutions. Makes for very interesting reading and how some things
get past the early setting of Standards by the NMRA. We, including
manufacturers, are all learning about DCC. Thanks a lot Mark.
Hi All
Back in July last year
while building a demonstration DCC module I came across this problem, more than
one Soundtraxx equipped loco in the same power district and my NCE EB3 circuit
breaker would not reset.
I looked on all the lists
and found on the Digitrax list that some modellers were having this problem. I
posted on the NCE, Soundtraxx and QSI list my test results and asked for some
help.
I looked up Tony's site and under his auto
reversers, that since has been updated, a statement about Sound Considerations
at: http://www.tonystrains.com/technews/dcc_autoreversers.htm
and it said that the
reverser had problems resetting with Soundtraxx locos in the same power
district.
Mark Gurries on the NCE
group suggested I wire a 12 volt lamp in parallel with my NCE EB3 and I
experimented with different wattage lamps and was able to get the results I
wanted with 5 - 10 watt lamps.
Tony's Power Shields,
Digitrax's PM42s and PM4s as well as the NCE EB3 were having the problems along
with some power boosters. I helped a couple of U.S. modellers who had fitted
TTX Power Shields, get their layouts running properly, but they were happy to
fit the "fix" if it meant be able to have normal trouble free sound
loco operation, One was a Digitrax user and the other was an NCE user.
Many modellers with BLIs
were very disappointed with the booster inability to reset after a short. I
have only Soundtraxx units and I have the problem.
I had the same problem when
I connected my EB3 directly to my Command station/booster track outputs and
only one piece of track on my work bench, so in my case nothing to do with my
layout and wiring.
I am on a few groups and
some people have reported it while others have said they have many BLIs and
don't have any problems. About August September last year, many modellers on
the QSI group voiced their frustration about this problem and I am sure that is
all DCC system are suffering the same problem.
The problem is that when a
booster or circuit breaker tries to reset when there is a short, it connects back
on line and if the high current that a short creates, is still present, it
disconnects again. This process is repeated every few seconds until the
booster/circuit breaker does not see a short. Now the problem is that when
there is a short with sound locos, their onboard capacitors discharge and when
the booster/circuit breaker is trying to reset after the short has been
removed, this "Inrush Current" to charge the capacitors is high and
depending on how many sound locos are in the same power district will determine
on how high a current and for how long. If the current values are higher than
the criteria of a sensed short, then the booster sees this as a short. It
cannot tell the difference between a short and a high inrush current sound
reset with a few sound locos.
For those that want a more
technical description and possible solutions, I have included Mark Gurries's
reply on the NCE group about the problem with Sound locos and booster/circuit
breaker resets.
Hope this helps.
Marcus.
Mark Gurries technical
explanation.
Top of page
-----Original Message-----From: Mark Gurries [mailto:gurriesm@comcast.net] Sent 28 July
2004
Subject: Re: [NCE-DCC] EB3 too slow to reset after
short
Sound equipped locomotives
have presented challenges to DCC that were not anticipated when the NMRA
specification were written. The problem is the amount of capacitance that
needs to be charged up to allow the sound electronics to function reliably with
various types of DC power that is NOT pure DC. The capacitor charge current is
a huge spike involving amp levels that far exceed the current capability of the
both boosters and Circuit breakers. But it does not take long to charge.
But every time you add another sound equipped engine, the problem grows
in size to a point it will become a major problem.
Prior to BLI, sound equipped
locomotives were few and quite a show item initially since it involved a lot a
work to install a sound system. (But what head turners the sound units
were!) Anyway, the problem existed but showed up at more of an annoyance
level issue.
When BLI came on the scene,
things changed quickly. Engines with sound became "Ready To
Run" along with good quality construction allowed people to acquire more
sound equipped engine faster than ever. Today most BLI customer come back
for more and having many sound equipped engines on the layout has now become
common place. Correspondingly, the problem is has now become a BIG issue.
Here is how the problem
happens.
Electronic based Circuit
breakers use Current Level and Time Duration to determined the difference
between a normal momentary short circuit (normal stuff rolling down the track)
versus a real short (caused by a
derailment) where the short
current can be sustained indefinitely.
Sound decoders have BIG
capacitors in them that are used to store power to keep the sound going
un-interrupted as the engine roles down the track make less than perfect
electrical power pickup at all times. These capacitors must be charged up
BEFORE the sound system will work. When they are first charged up, they
look like a short to booster or circuit breaker. The short circuit
current level fades quickly with time for it only momentary. The current
goes to zero when the cap is fully charged up.
If the capacitor current
fades fast enough below the short circuit trip level before the circuit break
decides it is time to kill power, then everything works like you expect.
No problem. If the current trip level is lowered or reduced, then the
exact same capacitor current will not fade fast enough to clear and the circuit
breaker will trip.
Adding more sound equipped
locomotives is the same as adding more capacitors in parallel. Depending
on your electronic circuit breakers setting and the peak current capability of
your booster, people will get various degrees of success and failure with
combinations of locomotives. The layout wiring also plays a part here
too. So there are lot of variables involved on the layout side.
What fails to function on layout A may work just fine on layout B.
Your light bulb solution
works because it adds resistance in series with the engines limiting the peak
current. The down side with the light bulb is that if you have a lot of
engines on the same section, the track voltage will drop a lot as the light
bulb starts to glow. The engines will not run well.
=============
Technical Discussion and discussion of possible
solution at the Manufacture's end...
The amount of capacitance to put into a sound
decoder will have a minimum and maximum requirement.
The minimum capacitance dictated
for the circuit are typically concerns that are covered by the datasheet of the
parts involved or an engineers experience with the circuits involved. But
all of these specifications assume the power is clean and un-interrupted (
Soundtraxx discovered with
the DSD that there was not enough capacitance to make all the customers
happy. Yet the size of the decoder was a big concern since not every
would have the space to fit a large capacitor if it was factory
installed. Although they never updated the DSD design (now that Tsunami
DSD is to replace it), the did address it with the DSX by allowing one to
optionally add extra capacitance. There is a technical note about how to
do just this on the Soundtraxx website. Since decoder size is a Soundtraxx
feature, having enough capacitance is a tough issue to address. I think the DSX
approach is good idea that they should keep in the Tsunami product when it
comes out.
QSI, which does the sound
for BLI and Lionel and perhaps others, has the luxury of making decoders that
are specifically design to fit in space provided by the locomotive from the day
the locomotive design was started. Since the sound unit is guaranteed to fit,
size is less of an issue and unlike Soundtraxx, can use less expensive and
bulkier components. Their boards reflect just that design and
thinking. They are huge compared to Soundtraxx boards.
From an electrical standpoint, there are two parameters
that determine the effective short circuit current level and durations.
1) The circuit
impedance. Using Ohms law, V = I x R and re-writing it to I = V/R we can
see that there is a direct relationship between the current, track voltage and
circuit resistance. If the resistance goes down, the current goes
up. The resistance is all the resistance in the complete loop of current
flow from the booster to the track to the sound board through the cap back out
all the way back to the booster. Typically this resistance is less than 2 ohms
and typical track voltage is 14.5V. So the maximum current is really
limited by what the booster will provide. So clearly every time the cap
charges up, we WILL hit the booster current limit.
Part of that resistance is
the resistance inside the cap which is called ESR or Equivalent Series
Resistance. Its resistance value can be high relative to the layout
wiring resistance. High performance caps will have low ESR and cheap caps
will have high ESR. Low ESR will result in High peak Current
Flow into the cap. High ESR will reduce or limit the peak current to a
lower value. So the choice of cap can also effect the peak current value.
2) The capacitance value of
the capacitor(s). Simply put, the more capacitance you have, the more
energy you can store. Its a bigger rechargeable battery so to speak! That also
means if the current available to charge up the cap is limited, the longer in
time it will take to charge up to full.
So the worse thing to have
is a low ESR cap with high capacitance. It will draw high current and
sustain that high current for a long time. Just what the Circuit Breaker is
looking for to shutdown. For a given size, cheaper caps will have higher
ESR and Store less energy. So there are cost versus Size versus
performance tradeoffs that must be made. The total capacitor solution
will then vary with the application requirements.
The thing that bothers me
is that there is a simple solution the high current cap charge inrush
current. First install the minimum capacitance needed by the parts on the
board. Then add the extra big capacitance for intermittent power holdup
in parallel with the small cap but with a circuit change. Put a
combination diode + resistor in series with the big cap with the diode in
parallel with the resistor. The Resistor will limit the peak current or
power to a safe level when charging up that is well below any trip limit.
The diode allows the cap to bypass the current limiting resistor and provide
full power to keep the sound unit running when power is momentarily lost.
It cheap, small and simple to do. I hope the Soundtraxx Tsunami has that
or fixes the problem some other way.
If the NMRA DCC body was to
do something, it would be to define a inrush current profile that all booster
and circuit breakers must pass and to recommend the circuit in question be
designed to minimize the inrush current below this inrush current profile as
best as possible.
Hope this helps.
Mark Gurries
Hi All.
Since I posted the below
message about slow response times of EB3 I have done some experiments.
With CV 49 set at 10 (100 mSecs), system works ok only if one sound equipped
loco is in power zone, but with two locos in same zone, double headed or second
in a siding but still powered, the EB3 does not reset within a reasonable time.
Changing CV 49 to 11 to 14
still no good. With CV 49 set to 15 (150 mSecs) when there is a short in the
zone then all three status lights start flashing and after a few seconds, command
station trips. This is not a desirable result.
If I increase current trip
limit to 3 Amps then sometimes ok. Put 3 sound equipped locos in zone - no
good, if I increase to trip limit to 4 Amps still won't reset in
reasonable time of what I would expect say within 5 - 10 seconds. See results
below.
These are my test results.
My sound locos in all tests, all have Soundtraxx DSD100LCs. I don't have any
BLI locos. I have wired up EB3 off the layout and on my bench with no other
track connected and away from any other track wiring and using only one channel
at a time.
Trip current 2 amps
1 sound loco = OK
2 sound locos = reset
sometimes after at least 1 minute
Trip current 3 amps
2 sound locos = reset 5 to
40 secs and 50% greater than 1 minute
Trip current 4 amps
2 sound locos =
resets after 5 - 10 seconds most of the time 3 sound locos = never resets in
less than a minute
Above tests done on circuit
breakers 1 & 2 and CV 49 and 50 set at 10(100msecs)
These results are not good
since I have 9 sound equipped locos and if I am running 2 consisted sound
equipped locos and I am in a zone where there is one other sound equipped loco
parked, then EB3 will not reset in less than a minute and that is only when I
have set current trip to 4 amps. If I am running 1 sound loco and have a short
in a zone where there are 2 sound locos parked like in a yard, the EB3 will not
reset in less than a minute.
If this is normal operation
of EB3 then I will go back to running with automotive tail lights as power district
protection control, but I think the EB3 should work better than this. I
reviewed all NCE Yahoo Group messages and there has been no reported problems
with EB3 except one with "EB3 Jitters".
With above results I had
divided my layout into 3 zones with EB3 and even if I had 6 zones (2 EB3s), I
would have problems.
Today I searched on Tony's
Trains http://www.tonystrains.com/technews/dcc_autoreversers.htm
and found this about his Power Shield Circuit Breakers and under
"Soundtraxx Considerations" it says you cannot expect the Power
Shield to reset with 3 or more Soundtraxx locos in one zone. These are the
results I am getting with my EB3 and that is only when current trip is set to 4
amps.
So it seems that those of
us that run sound equipped locos, then we can only have at best 2 Soundtraxx
equipped locos in one zone for Electronic Circuit breakers to work. This can be
with single sound loco operating train and one parked in siding or anywhere
else. What happens at a yard or roundhouse? I guess I will have to go back to
either light globes or as some have been doing when locos not used are parked
and track turned OFF, sounds like going back to crude "block
control". I thought this is why I am using DCC to get away from control
panels.
I wonder what all of you
with sound locos have done when operating in power zones protected by EB3 or
Power Shields to overcome this problem.
Please let me know.
Marcus
----- Original Message ----- From: "Marcus
Ammann" mammann@optusnet.com.au
To: NCE-DCC@yahoogroups.com Sent: Monday,
July 19, 2004 4:58 PM
Subject: [NCE-DCC] EB3 too slow to reset after
short
Hi All
Just wired in an EB3 for
power district protection instead of using 12V 18W automotive tail lamp and the
time for the EB3 to reset after tripping out for a short (status light
flashing) can be 5 secs to 1 minute and sometimes longer. Have set CV 49, 50
and 51 to other than 100 m secs and no difference. If set to 300 m secs then
Booster switches out. This would be normal. Have tried on 2 of the 3 circuit
breakers. Trouble seems to be with a sound loco with a DSD100LC decoder. Seems
to work okay with a non sound loco. If this is normal, I'm disappointed ‘cause
I running a few sound locos.
Am building a demonstration
module for a clinic I'm doing on DCC to show how good DCC works.
Has anyone experienced this
or do I have a faulty unit. May go back to tail lights, everything worked ok
but I thought I should go the EB3 way.
Marcus
Rex Beistle’s reply
Below is a message from Rex Beistle replying to Craig’s problems that he was having with a PM42
not resetting with his Walthers lighted passenger coaches. This is the
same inrush current problem that is happening with sound locos.
---
In digitrax@yahoogroups.com,
"Craig" <craigb@p...> wrote:
snip
Any start up limiting needs work every time the power
is turned on or if there is a momentary short at a turnout, causing the PM42 to
trip, the problem starts all over. Once the PM42 trips, it waits and then
turns the power back on, when this cycle starts, it just keeps
"clicking" off and on.
>
snip
Craig
Perhaps a simple addition to the PM42 could help. I am
not a great proponent of the light bulb as a do all/cure all, but maybe in this
case it could be used to advantage.
Lets
presume that you are using section 1 of the PM42. Pins 4&D are the rail A
input and pin E is the track output A. Likewise pins 7&H are the rail B
input and pin F is the track output B. The input connects to the common
terminal of a relay and the track output connects to a normally closed terminal
on the same relay. If there is no short, the relay is closed and the input is
connected to the output. In case of a short (or power on inrush current
problem) the relay is energized (picked) and the current from the booster is
interrupted.
If a lamp is connected from pins 4&D to pin E, and
another lamp from pins 7&H to pin F, then the lamps will be in the circuit
during a short. The lamps may pass enough current to bring the lighted cars (or
Soundtraxx decoder) up to some intermediate voltage level while the PM42 is
timing out to retry. When the time out occurs, the lamps would be taken out of
the circuit and full voltage would pass through the relay on the PM42. Some
fiddling with the lamp selection may be necessary - one might start with the industry
number 1156 or something similar rated at 12 volts and perhaps a couple
amperes. I have had cold lamps cause DB200 boosters to shut down when placed
directly across the output terminals. Putting lamps across the PM42 would put
them in series with the layout and would not be the same as putting them across
the booster output.
Initial power on would result in an overload and the
PM42 would say 'short' putting the lamps in series with the booster output.
Hopefully the lamps would pass enough current to 'charge up' the layout power
district and equipment so that when the PM42 times out and retries all will be
OK. This little scheme would come into play each time the PM42 said
"short." Remember to keep the lamps away from things that cannot handle
the heat! I do not want to read about fires or other damages or any kind of
injury.
A cheap and dirty 'soft start' that just might work.
Give it a try, what you have is not meeting your
needs.
Rex
Longmont
NMRA 17832
The Denver HO Model Railroad Club, located at
The Colorado Railroad Museum in Golden,
visit us at http://www.crrm.org
visit the NMRA at http://www.nmra.org