DC vs DCC

You're asking the wrong question.

The "signal strength" has little to do with it. There IS no signal on analog DC, just voltage. Due to the nature of the DC control, a voltage drop due to poor / insufficient wiring will nopt usually be evident. It will only manifest as having to run your throttles at a higher setting, and (perhaps) heating of the wire to some extent, and locomotives seeming to change speed as they move from one block to another.

With DCC, there IS a signal, superimposed on the (constant) track voltage. That's how DCC works, by broadcasting that signal to all locomotives, which listen for commands directed specifically to their address and ignore all others.

In it's most basic form, if a layout works on analog DC, it's simply a matter of moving the bus and feeders from the analog source to the DCC source, and it will work seamlessly (with DCC equipped locomotives, of course). Adding in reverse loops and power districts tends to make things more complicated, but not significantly so in most cases. They basic principles are the same. There are some caveats...  like "Don't use Common Rail Wiring for DCC", but in it's most basic form, if it works on DC, it'll work on DCC.

Don't go to the extra work and expense of putting in multiple cabs to just test it though.... there's no reason to spend the extra time and money doing things that are completely redundant with digital control.

to amplify that

At the museum the layout is routinely switched from DC to DCC and back. As in almost every day. For the most part I can't tell the difference, although we don't have reverse loops. It is a lot more hassle to get the DC locos off the powered track when the switch to DCC happens, but of course that won't be your problem.

Rail joints

My setup is to add a feeder to every section of flex track and only soldered the joints on curves.

If your room is stable for temperature and humidity, hopefully you wont have alot of rail movement ( expand and contract ). Normally its best to leave the joiners unsoldered on straight to allow the rails to move.

Something you might keep a eye on.

As for DC / DCC, it should be OK, being careful and thinking thru things now will save headaches in the future. Now is also the time to isolate blocks if you ever plan on adding signals and need block detection. Easier to add insulated joints now than later. 

Voltage or Signal Strength

I guess that's were I was a little confused with my question. in other words DCC is putting a constant voltage on the track thats close to the max that an ordinary DC transformer puts on?
The decoder in the engine only looks at a portion of this total voltage?
 

What I am getting at is that I believe I have enough feeders on my track, and if its working in just DC mode, then it surely will work as good,...maybe better in DCC mode??

I guess that's were I was a

Yes. DCC puts a constant "high" voltage (as compared to a DC power pack) on the track, and superimposes a digital signal over it.

No. the DECODER "looks at" ALL the voltage. It passes on a PORTION of it to the motor, based on the throttle commands.

The handheld "throttle" would be more properly called a "throttle controller". The actual throttle device that regulates the speed of the locomotive (analogous to the rheostat in your DC throttle pack) is a digital device within the decoder.
 

fix this...

Fix this

"..locomotives seem to like the set up (only a few weak points that are likely some sort of dirty track)."

Voltage drop applies to DC and DCC.

At you far end of the layout if a DC loco slows down, the DCC loco will also slow down.

For example, let's imagine the DCC has a digital wave with amplitude of 15.  At full throttle, the decoder rectifies that signal and puts 15VDC to the motor.  If the voltage, digital wave, at the far end of layout is only 14, then the decoder can only supply 14VDC to the motor.

BEMF can account for voltage drop

i read about a "dirt" switch that put 50V but limited the current to overcome dirty track.  the higher DCC voltage may do something similar,

decoders that use BEMF to monitor speed can adjust the duty cycle of motor voltage to maintain the voltage to the motor, despite voltage drops until it reaches 100% duty cycle

Not superimposed

DCC does not superimpose a signal on DC or AC voltage.  That describes the old "carrier control" systems that predated DCC.  In DCC, the signal IS the voltage.  It's a square wave, pulse-width modulated signal that can be phase shifted to give a non-decoder engine more voltage in the plus or minus direction, causing its DC motor to turn one way or the other.

So the signal is a form of AC, but being square wave it suffers the same voltage drop issues as DC.  That's the simplified description. 

Scott Chatfield 

Good wiring

Good wiring has a soldered path from the bus to every section of rail, never relying on joiner tracks (except where absolutely necessary like on joiner tracks between modules if applicable).

Voltage drop isn't really the issue, it's signal integrity. Some layouts that were wired for DC did poorly with DCC due to a poor quality DCC signal reaching decoders.

Testing with DC doesn't guarantee it will work with DCC, but neither does testing with DCC, as it doesn't always fail immediately, and DCC requires even more robust wiring the more trains you have running, as packets are repeated less frequently. DC or DCC will pick up dead sections and dead shorts, which is really what you're looking for.

The way to as close to guarantee as possible reliable operation with DCC is to follow the rules of a 14 gauge or larger bus, 22 gauge or larger feeders, soldered path to every section of rail, no more than 6' to a feeder.

For someone with little to no

For someone with little to no electrical knowledge, "superimposed" is easier to understand than a detailed technical data dump. Close enough,

What DCC is

Except that a digital signal "superimposed" on voltage is the literal opposite of what DCC is. DCC is the data encoded into the power signal itself. This is very fundamental to what DCC is, along with being a unidirectional (unless you have Transponding or RailCom) signal.

Superimposed literally means "laid on top of"

So in terms of DCC vs DC, saying the DCC is superimposed on the DC signal gives a completely wrong picture.  DCC waveforms go from 0V to their max DC voltage in virtually a square wave, and the pulsetrains are decoded as digital words by the controllers (Digital Command Control).  If they were superimposed on a DC speed control method, it would be more like the older pulsed DC controllers of the 1970s and 1980s such as the MRC Tech and Tech2 power packs, where the pulses were there to overcome the tendency of 3 or 5 pole motors to cog at low DC voltages and provided short pulses of higher voltage to do so.  Those pulses diminished as the DC voltage increased and the cogging diminished, if I recall correctly, and affected every locomotive within the powered block of track.  

Janet N.

Command Control

DCC track power is a pure binary waveform, either on or off. It is not "superimposed" on a constant voltage.

Older systems used "high" frequency carriers, like audio tones, modulated onto a constant voltage. 

An early "digital" system, Digitrack, used pulses riding on top of a constant voltage to send instructions to a receiver. That idea would live on in the form of CTC-16.

returning to original question

DCC signal stronger than DC?

Brian,

They are different animals.  DCC is ~14 volts with the signal encoded as pulse widths.  DC is simply variable voltage from zero to ~18 or so.  The term 'stronger signal' is a misnomer in this case.

And yes, if it works well with DC it should work as well with DCC, provided you have adequate feeders.  Non DCC friendly turnouts are the biggest concern.

DC vs. DCC

As was answered previously.  

NO.  BECAUSE THERE IS NO SIGNAL IN DC. IT"S JUST VOLTAGE.

As was answered previously.  

Generally if it is wired properly for DC it will work fine for DCC. 

The caveat is that things like auto reversers, detection circuits and some circuit breakers are designed for either DC or DCC and may not work in one or the other.  For example, auto reversers generally won't work in DC.

I guess my wording of this

I guess my wording of this question is just not proper. Maybe instead of signal strength I should have said voltage strength?

What I am getting at is voltage sent to the track in a DCC system is more than with a DC signal,...so if my present wiring is working on DC, it should work as good if not better on DCC??

Two of my concerns would be 1) do I have enough feeder wires?, and 2) are any of those feeder wires too long?
( I have some feeders wires in my helix structure that are as long as 36",...#22 gauge solid conductor)

Voltage

It's really not about voltage, it's about signal integrity and ability to safely detect shorts.

1. There should always be a soldered path from the bus to every rail

2. NS rail should not carry the power more than 6' tops (I only allow it to carry 3')

If you follow those two rules, you'll have enough feeders.

There is a whole chart on feeder wires and short detection on WiringForDCC.com, but 36" is really pushing it. Best practice is to limit 22ga feeders to 1'. Just run the bus up the middle of the helix and tap feeders off of that... they should be under 6" in that case.

DC vs DCC wiring

i think only time will tell.    as others have suggested, having a "soldered path" to each rail will prevent corrosion from affecting performance over time.

in general, if your loco performs well using DC and 36" feeders, it should perform just as well, if not better with DCC.

but there is a difference between DC using constant voltage vs PWM.   both provide an average DC voltage to the rails, but PWM can overcome " stiction".    and DCC decoders have this added benefit since they use PWM to control the motors,

PWM

What is PWM?

AlexW Just run the bus up the

Not quite understanding what you are saying there.

Here you will see my arrangement,...   
https://forum.mrhmag.com/post/multiple-staging-areas-access-to-them-perhaps-subloop-in-the-helix-12209513

I don't have enough room to put a lot on feeder-to-buss wire connectors between the backside of the helix tracks and that outer wall material.

And i didn't want to put all that wiring out 'proud' to the inner radius of the helix tracks.   I'm reserving those 'face edges' of the helix roadbeds for a stringing-line safety barrier I have in mind.

"What is PWM?"

Pulse Width Modulation

instead of providing a constant DC voltage to a device (e.g. motor),  full voltage can be applied for a fraction of the time, %, the  duty cycle.    the average voltage is that % of full voltage.

PWM is more efficient in terms of wasted power and much easier to implement electronically.   because its so efficient, even smaller devices can drive larger loads.    a decoder outputs the PWM signal and external mosfets on the decoder are used in an H-bridge to drive the motor.     the processors used in decoders have PWM circuits built-in

as mentioned, the sharp application of torque when full voltage is applied to the motor overcomes stiction resulting in better starting and low speed performance.

Mearsured Voltage on helix tracks

Obviously I don't have a DCC multimeter,...but I did take my ordinary DC meter and measured my voltage at various spots on my helix tracks. All the measurements seem to indicate I was getting the full voltage to those tracks that my DC transformer was putting out.

I would hope that the 2 side-by-side helix tracks would also receive full signal for 2 engines running on the helix concurrently?

loaded voltage

a voltage drop is due to the resistance of the wire.   it would be better to measure with a load across the tracks.   could use a low current 12V bulb