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I suggest you use grain of rice bulbs instead of LEDs. The reason
is because GOR bulbs have insulated wire leads and LEDs don't. GOR
bulbs are simly easier to wire in confined spaces.

How to use GOR bulbs is covered in my web page at:



Digitrax has some installation notes for a decoder into your
locomotive at:



Digitrax has wiring of ditch lights at:



Note that they show using a 12V GOW bulb. You can definitely do
that. I'm just thinking you will want the smaller GOR bulb. Just
add the resistor specified on my web page or as they specify on
their web page. Also, the Digitrax web page tells you how to set up
the CVs.

Allan

Giles,

You definitely don't need to solder any wires to the guard rails
around the frog.

I'm not sure how Walthers makes their frogs. I get good electrical
continuity when I measure a new turnout. If you want to be safe, you
can solder a wire in a "U" shape and attach it to both frog rails -
the rails leaving the frog. That's what I have to do on my
Pilz/Tilleg turnouts.

Allan

Hi, I'm new to this, but I need to install ditch lights in Kato's
SD80MAC. I'd like to use LEDs, but will use GOW bulbs if need be. How
do I do that and how do I configure the decoder? I'm using the 163
decoder.

--- In WiringForDCC@..., "bobgrosh" <bobgrosh@h...>
wrote:

I knew I had worked on a page to explain transpondiing, and it had

to

be somewhere. Well I finally found it. Still needs to be cleaned

up,

but here it is.

ard

ware/default.htm

Maybe there is something on these two drawing that will help.

B0B

Bob,

OOPS. After including the rest of the link, I got the pages to show
up and thanks, I'll look them over when I can devote more time to it.

Thanks,
Mike

I have one and I found that the most important thing operationally is
to throw all 4 switches at the same time. That is all 4 crossed or
all 4 straight. This prevents any opportunities for funny thngs to
happen if a derailment should occur. There is no reason not to do
this either, you can only occupy one route at a time when crossing
over so crossing both ways makes no difference and you can't have one
route straight and one crossed.

Dale.


--- In WiringForDCC@..., "wirefordcc"
<wire4dcc_admin@c...> wrote:

The double cross is not as bad as it looks. If you study the color
diagrams, you will see that it is simply four turnouts connected
together. It is nothing more complicated than that. If you treat it
as four individual turnouts, all will go well.

Allan

The double cross is not as bad as it looks. If you study the color
diagrams, you will see that it is simply four turnouts connected
together. It is nothing more complicated than that. If you treat it
as four individual turnouts, all will go well.

Allan

I'm busy enhancing some DCC-friendly HO turnouts, following Allan Gartner's excellent
website. Has anyone had experience performing similar solder connections on the double
crossover? Some locos are hesitating on it but the darn thing looks pretty complicated, so
I'm hesitating too.

Giles Goodhead

Mike, You can't fool Mother Nature. 40v for 200nSec across a 100 ohm resistor 8,000 times/sec is only 3.2 micro-watts. You have something wrong with your set-up. Wrong value of C or shorted C or a polarity sensitive C or the resistor is somehow wired directly in parallel with the track. With your R-C networks installed you should NOT see any more voltage ringing at the track. The ringing IS gone...Right?

However, there IS a difference between temperature (as in Hot) and average heating power (as in watts). [A burning match may be hotter than the electric stove element, but does not have the heat energy to boil a pot of water.] The fine print on many resistor data sheets shows that a lowly 1/2 watt resistor may have a temmperature rise of 70C...thats 90C and too hot to hold on to with bare hands when the room temp is 20C. "Rated" operating temp may indeed be 100C. If you want it to run cooler, you need to increase the case size to add more surface radiating area. i.e. - a bigger watt rated resistor. But yeah, it should not get hot quickly, or begin to smoke. That's a good sign that there is something wrong.

re - The R-C network
The voltage spikes you see at the track without the R-C are created by the DCC booster attempting to rapidly change the polarity of voltage stored on rail capacitance when fed by wires with a significant amount of inductance. Using your example, the remote rail to rail capacitance and layout wiring inductance of the DCC bus form a resonant L-C with a 1/2 period of ~200 nano-seconds (0.2 uSec). Current must flow in to (or out of) the rail capacitance in order to flip rail voltage polarity. The faster you attempt to flip it (power FET switching speed inside the booster) the more peak current must flow to the rail capacitance. This causes higher and higher current and subsequent voltage ringing in the wiring-Rail L-C. You can calculate the energy content of the actual ringing which represents energy flowing back and forth between the L of the wiring and C of the track...only if you know the actual circuit values...But it is rather small. However, there is little or no energy absorbing damping to keep the L-C 'tank' circuit from voltage 'peaking' and ringing. Adding an external resistor to the L-C circuit will provide damping to the point where it limits the voltage peaking effects and doesn't ring any more. But we don't want to add series resistance as that would reduce power available to our locos on the track. A parallel resistor can be used, but it will also see the rms value of all the DCC track voltage as well and heat up accordingly (14.25 volts continuous, squared, divided by R ohms). A capacitor of the right value placed in series with a damping Resistor in parallel with the track will the reduce resistor dissipation if sized so that the cap will charge up to the full track voltage on each voltage transition but much more slowly than the ringing we are trying to suppress. [100 ohms X 0.1 uFD = 10 uSec, maximum DCC transition time is ~2uSec (I'm sure someone will correct me), NCE/Sys-1 boosters switch in ~0.6 uSec. Digitraxx boosters switch much more slowly and don't generate the ringing problem.]

In brief, current flows through the resistor only during the DCC voltage polarity transitions, about 4 X 8,000 times per second. And the 40 volt spikes aren't there when you connect the R-C, becauses the ringing energy of the track L-C (a much smaller value of C) is being damped and absorbed by the resistor. But whatever energy flows in and out of the external added capacitor must also flow through the series resistor, causing it to heat up. The extreme and easy to understand case is when you fully discharge a capacitor into a resistor. The entire energy content is 1/2 X C X V^2. If you discharge it only once, the energy content is so many joules or watt-seconds, all absorbed by the resistor (regardless of the ohms value of the resistor). If you do it repeatedly, multiply the watt-seconds of each event by the number of events per second to get the average watts being dissipated as heat in the resistor. But a resistor will heat up with current flow in either direction...so charging the capacitor up to a certain voltage will cause a series resistor to heat up with the same energy content as discharging it. When you apply the DCC square wave of voltage to the series R-C network and assume that the capacitor becomes fully charged up to the the appropriate DCC level (the peak voltage is gone on your scope traces, right? That's why we put in the R-C) the cap charges and discharges 2 times each per DCC cycle [0 to + to 0 to - to 0] So the resistor sees 1/2 X C X V^2 X 4 X the number of times per second (~8,000) watts. Notice that you don't want to make the external capacitor too large, as it does determine resistor watts.

An R-C network used in this manner is referred to as a "snubber".
You need to locate it out where the ringing to be suppressed is occurring...At the end of the DCC bus wires. [i.e.- Where the inductance of the wiring meets the capacitance of the track.] It does no good if placed at the booster terminals.

DonV

Hi Don,
In your calculation, you used 14 volts in your formula.
But I have 40 volts peak for 200ns.
It sounds like the power would be the .156 watts at nominal voltage, PLUS additional power when it has to pass the 40v peak.
I believe this is why the 0.5 watt resistor gets so hot.

No the cap is not shorted, (at least not all 40 of them).

Mike B

Sorry folks I goofed
Resistor dissipation of series R-C across DCC track bus is Pw = 1/2 X C X V^2 X ~8kHz X 4 (not 2)
So for a 0.1 uFD cap and 14.25V DCC, the resistor heat will be ~0.32 watts. Select a resistor at least 2X that value for long life. So use a 1 watt resistor with a 0.1 uFD cap.
Note that if you use a different value cap be sure to re-calculate the resistor watts!

DonV

Mike,
sounds like you have a shorted cap! [ the R & C ARE in series...Right? :-) ]
e^2/R = 1.5 watts for 130 ohm resistor directly on a 14V DCC bus
For cap & series resistor: resistor Pw = 1/2 X C X V^2 X ~8kHz X 2 or 0.156 watts for 0.1 uFD
DonV

Hi All,

I recently scoped the DCC signal at the far end of my booster districts and saw considerable ringing and excessive overshoot on the rising edges of our DCC signal.
After reading previous post on this subject and checking out the data on the below links, I decided to see what effect they had.
To see a learn more about blown decoders and long bus runs and a RC filter solution....

and

Well I must say I was stunned by the remarkable difference they made in cleaning up the overshoot and ringing.
I used a 330 ohm 1/2 Watt resistor in series with a 0.1uf 50V capacitor.
With this in place my Tony's DCC RR Volt ammeter no longer gave odd readings at the power district either, as it was now seeing a cleaner DCC wave form.

However......
I have found that the 130 ohm resistor is quite HOT.
Not warm, Hot!

In looking closer at the un-terminated DCC wave on the scope, I see that the nominal voltage is 14.5 peak, but the overshoot voltage is 35-40 volts peak for a duration of about 200 nanoseconds.
Lets see....
80v p-p / 130 ohm = 0.615 Amps
0.615 amps x 80v = 49 Watts !
However this should only be for the 200 nanosecond duration of the spike that the resistor would ever see this much power, so I never suspected that the temperature would rise so quickly for a small duty cycle.
I was surprised that the resistor got so hot.

I did an experiment to see what wattage resistor would not be hot to the touch.
Not having a 1 or 2 watt resistor handy, I put 4 of the 130 ohm 0.5 watt resistors in a series / parallel arrangement, which still measured 130 ohms.

With this I could feel some minor warmth from the individual four resistors, but nowhere near the heat off the 1/2 Watt resistor when it was the only one in series with the cap.

I suspect that I will have to search for a 2 watt resistor.

Has anyone else who has used this terminator noticed how much heat this circuit gives off?

Mike Beckemeier

I knew I had worked on a page to explain transpondiing, and it had to
be somewhere. Well I finally found it. Still needs to be cleaned up,
but here it is.



ware/default.htm

Maybe there is something on these two drawing that will help.

B0B

Mike
Possibility 1: You need a wire from the booster ground to pin 11.

Possibility 2: You need one detection section wired up and working.
Leave it connected, don't remove the wire and then connect up just
Transponding. The board needs the DCC track signal for Transponding
to work. My guess is that you probably have got detection working and
then just added the wires for Transponding, but I mention this just
in case.

Possibility 3: Each time you try something, reverse the a and b wires
at the booster. If it is not working, reverse the A and B wires right
at the command station/booster and try a second time. (I had a RX4
with the printed side backward from the others, maybe you got one
like that too.)

The direction the wire passes through the RX is important, as well as
which track feeder wire is connected to "A" on the booster. Each time
you try it, also swap the loco from end to end on the track. If a
loco transponds in one orientation but not the other, then you are
close to having it work, but still have a polarity issue as far as
the direction the wire travels through the RX1 or the polarity of the
booster output. When everything is connected right, a Transponding
car or loco will work regardless of orientation on the rails.

Just to confirm, the dt400 find key does indeed seem to be a good
check to see if Transponding is working. I have used it often.

One last thing if all the above still does not help. Plug your
throttle direct into the command station, connect the BDL directly to
the other loco net socket on the command station. (eliminate all
other devices from the LocoNet). Make sure the loco net cable is a
good cable, A Digitrax factory cable is a best choice. Check the
cable against the diagram in the big system manual and make sure the
colors and polarity match the diagram exactly! Mis-wired LocoNet
cables may work fine for most other devices, but will not work at all
with Transponding. Don't ask me why, I don't know why Transponding is
so picky about the LocoNet cable, must be another polarity issue.

If all of the above still does not help, then let me know. I'll hook
up my spare command station and a BDL and experiment. Perhaps some
good clear photos of your test setup could be posted or emailed. I
live in Florida. Planning a vacation? Maybe you could stop by and
bring your stuff.

B0B

Just a thought, You do not need to select the loco for detection, but
you do need to select it for transponding. Did you try to run the
loco on that short test track? If the loco is transponding the front
LED should have a slight flicker to it when the headlight is off.

B0B


Bob,

Apparently someone has gotten this system to work! Good!

The loco DID run forward and back on the test track; turning the
loco around, it worked the same way and the LED does flicker when
the headlight is off so according to what I've read, this does
indicate that transponding is turned on.
However, I get no loco address showing in the DT400 when I push
the 'FIND' button with the loco sitting on the test track.
Unless I missed something, this is the way to find a particular loco
sitting on a detection section, like track in a hidden area;
You select the address you want to locate then push the 'FIND'
button but no section is indicated in the DT400 display.
Digitrax gave me the answer 'o' the day: check your wiring.
I set up a terminal strip as shown in their manual.
I used #18 stranded wire from the terminal strip thru the RX4 on the
non-printed side, exiting the printed side and then soldered to pin
#1 on the connector that the BDL162 plugs in to. I loosely looped
the wire as shown in their instructions.
Should I have also soldered the wire to pin 'A' on the pin connector?
If I move the wire from the test track section to any of the other
pin connectors, the LT5 shows that detection is working in each
respective section.
So, according to what I've read, loco detection works fine but
transponding is not showing the address sitting in a detection
section.

This is as far as I've gotten so far because I want to be sure
transponding works as it should before laying all the track in my
yard and hidden areas.
Was wondering if any later info/manual was available on this.

Mike

--- In WiringForDCC@..., "mmogen2004" <n_meister@m...>
wrote:

Allan,

Mike Mogensen here perplexed as usual in Indy.

Was wondering if you or any member has had first hand experience
implementing transponding/detection using BDL162 and RX4.

I read all the info I could get before starting, both the manuals

that

came with the units and also Loy's DCC Encyclopedia.

I wired the BDL and RX4 up on a board and then applied the section

in

the RX4 manual (8.6) to test it on a piece of flex track using one
zone.
I used a loco with a DN163AO decoder, with CV61 set to 002 to

perform

the testing.

Detection works OK using the LT5 tester and the correct diodes

light

up to detect occupancy so am satified that detection works as it
should but I get no indication of transponding either in the BDL

162

or on the DT400 throttle using the FIND key.

I double checked all the wiring and OPS Switches on the BDL using

the

troubleshooting tips in both the manuals and the DCC Encyc and am
satisfied that all are correctly set; still no transponding.

Maybe the magic wand or secret incantation was omitted from the
packaging?

I know this can be a complicated subject but everything I read

doesn't

seem to indicate and impossible implemantation.

Thanks,
Mike

Just a thought, You do not need to select the loco for detection, but
you do need to select it for transponding. Did you try to run the
loco on that short test track? If the loco is transponding the front
LED should have a slight flicker to it when the headlight is off.

B0B

--- In WiringForDCC@..., "wirefordcc"
<wire4dcc_admin@c...> wrote:

I think the biggest problem with transponding is the cost. I'm not
saying Digitrax is overcharging (I'm sure others will :-), it's

just

that the shear number of transponders, detectors, and BDL16's you

need

adds up to a pile of money and time to install. It's not for

everyone.

One reason I switched from detection to Transponding was the cost.

Transponding if far more powerful than detection. That translates
into doing much more with far fewer components.
First of all, The TD4 Transponding function decoder is one of the
cheapest four function decoders out there. Put one in a caboose for
the lights, and Transponding didn't cost you a thing. I use Digitrax
decoders in my locos, so Transponding didn't cost anything there
either. When a train crosses a boundary between two Transponding
sections, software can track the location, speed and length of the
entire train. Ther is no absolute need to put a transponder in every
car.

Second. There is no real need to use the 16 detection sections on a
BDL 168. Divide the mainline into just three Transponding zones and
software can track the locations of a hundred locos and cabooses. You
can virtually set up 360 degrees ( virtual detection blocks ) on your
mainline with only three insulators and feeders. Software can activat
one or hundreds of signals based on the ocupancy of these virtual
blocks.

When I changed over my Garden railroad from block detection to
Transponding I removed literally 125 pounds of copper wire from the
garden along with 30 insulators, 60 resistors, 11 BD1's, and one of
the four BDL16 cards. Had I gone to Transponding first, instead of
trying to make detection work outdoors, I would have saved hours of
frustration and hundreds of dollars.

B0B

It sounds like you have your acceleration CV set too high. Set CV3 to
0. Your problem should go away. Once you are sure your problem is
gone, you can program CV3 to any value that gives you acceleration
that you like.

Allan

I think the biggest problem with transponding is the cost. I'm not
saying Digitrax is overcharging (I'm sure others will :-), it's just
that the shear number of transponders, detectors, and BDL16's you need
adds up to a pile of money and time to install. It's not for everyone.

--- In WiringForDCC@..., "mmogen2004" <n_meister@m...>

wrote:

Allan,

Mike Mogensen here perplexed as usual in Indy.

Was wondering if you or any member has had first hand experience
implementing transponding/detection using BDL162 and RX4.

I've been using it outdoors on my G scale layout for several years.
While detection using the BDL is a real pain outdoors, the
transponding is very reliable. I have more than 50 transponders
working.

One thing important to remember is that the size of the current pulse
is important when in districts consuming a lot of amps. The resistor
and capacitor on F0 are a must for high current users. I decreased
the resistor value by 1/3 to make sure it would work with the large
motors in my locos. Also, In "G" scale some manufactures have added
capacitors to some of their electronics that are directly across the
rails. They have to be removed or a limit resistor added.


B0B