Topics

DCC HO DC Question

Blair & Rasa
 

Hi
For those with a lot more experience. I keep reading comments about 13.8
VDC not being enough to power DCC systems for HO, because you "dont get
enough speed out of the locos". Now, when I think about it for not very
long, it seems to me that that implys running the units at full throttle and
being unsatisfied with performance. So what voltage DC is required to
achieve full performance? Yes, I realize that we have to assume a few
things, like the voltage drop to the farthest corner of the layout, etc.
etc, but ignoring those factors for a moment, what input voltage DC should
we strive for to get satisfactory DCC performance?

If 13.8 VDC is satisfactory as long as we aren't looking for slotcar
performance, then the next question becomes will a DCC system perform
satisfactorily from an automobile electrical system? With and without
alternator charging system, or only when the car is running?
12 VDC is the minimum input, right? Or is that optimistic?

I ask all of this because there is a significant chance I am going to want
to go off-grid in my next abode, and I expect 12 Volts will be part of my
life at that point.

Blair Smith

Jan Frelin <jan.frelin@...>
 

At 21:34 2005-07-11 -0400, Rasa and Blair Smith wrote:

Hi
For those with a lot more experience. I keep reading comments about 13.8
VDC not being enough to power DCC systems for HO, because you "dont get
enough speed out of the locos". Now, when I think about it for not very
long, it seems to me that that implys running the units at full throttle and
being unsatisfied with performance. So what voltage DC is required to
achieve full performance? Yes, I realize that we have to assume a few
things, like the voltage drop to the farthest corner of the layout, etc.
etc, but ignoring those factors for a moment, what input voltage DC should
we strive for to get satisfactory DCC performance?

1. The DCC systems I've encountered all required AC input. Have you found
one that runs on DC power?
2. Power is not the same as speed with DCC, the DCC signal is full power
all the time. However, more power in the signal allows more speed. I like
to aim for 14-15 volts on the tracks, which implies a similar amount of
input power.


If 13.8 VDC is satisfactory as long as we aren't looking for slotcar
performance, then the next question becomes will a DCC system perform
satisfactorily from an automobile electrical system? With and without
alternator charging system, or only when the car is running?
12 VDC is the minimum input, right? Or is that optimistic?

I ask all of this because there is a significant chance I am going to want
to go off-grid in my next abode, and I expect 12 Volts will be part of my
life at that point.
Like I wrote above, the systems I've found all require AC input. I was
going to say that you can always change the power source at a later time if
it doesn't work, but your situation kind of rules that out.
/Jan

Marcus Ammann
 

Hi Blair

You can power your DCC systems with DC.
NCE - 18 to 28 volts DC
Lenz - 15 to 18 Volts DC
Digitrax - 12 to 28 volts DC

DCC power at the track is produced from DC that is made from rectifying
the normal AC voltage from your transformer by a bridge rectifier in the
booster. Supplying the bridge rectifier with DC instead of AC will still
provide DC to the booster circuits. It just uses 2 diodes to pass the
DC, instead of the 4 that are used for rectifying the AC.

The bridge rectifier and the electronics that produce the DCC voltage
will require some "extra" volts. For example if you supply the DCC
system 12 volts from a car battery you will only at maximum get say 10
volts. All decoder will work on 10 volts DCC but top speed will
certainly be affected. Sound decoders will start dropping out at 9
volts.

So for a DCC system to provide the recommended HO voltage of 14.25
volts, it will require at least 16 to 18 volts DC.

So if you go off the "grid" and have to supply your system with DC then
I would check your system requirements. From the above if you were
operating either the NCE or Digitrax, you could supply them with two 12
volt batteries connected in series to give you 24 volts. You will have
to separate the batteries to charge them with a 14 volt car alternator.

Hope this helps

Marcus

-----Original Message-----
From: WiringForDCC@... [mailto:WiringForDCC@...]
On Behalf Of Rasa and Blair Smith
Sent: Tuesday, 12 July 2005 11:34 AM
To: WiringForDCC@...
Subject: [WiringForDCC] DCC HO DC Question

Hi
For those with a lot more experience. I keep reading comments about
13.8
VDC not being enough to power DCC systems for HO, because you "dont get
enough speed out of the locos". Now, when I think about it for not very
long, it seems to me that that implys running the units at full throttle
and
being unsatisfied with performance. So what voltage DC is required to
achieve full performance? Yes, I realize that we have to assume a few
things, like the voltage drop to the farthest corner of the layout, etc.
etc, but ignoring those factors for a moment, what input voltage DC
should
we strive for to get satisfactory DCC performance?

If 13.8 VDC is satisfactory as long as we aren't looking for slotcar
performance, then the next question becomes will a DCC system perform
satisfactorily from an automobile electrical system? With and without
alternator charging system, or only when the car is running?
12 VDC is the minimum input, right? Or is that optimistic?

I ask all of this because there is a significant chance I am going to
want
to go off-grid in my next abode, and I expect 12 Volts will be part of
my
life at that point.

Blair Smith




http://www.WiringForDCC.com
Yahoo! Groups Links






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Blair & Rasa
 

Marcus
Yes, we know that the input may be AC or DC, and that regardless of that
input signal, in at least the Digitrax case, the input is rectified. Yes,
we know that any system that produces AC from DC from AC is going to need
what we generally refer to as "headroom". Digitrax specs 12 to 28 as input
DC, what I am more or less questioning is whether 13.8, or even 12, provided
sufficient voltage "at the track" for satisfactory operation. The latter is
a very subjective consideration, so I guess the upshot is I should just try
it.

The double battery suggestion is a fine one; I'll need yet a third, I guess,
for all the PS12 and other electronics. Alternatively, I guess an inverter
might be a better idea, with the layout wired for 110 VAC. Then I won't
need to make these decisions at all, off-the-shelf equipment will suffice.
Thanks
Blair

-----Original Message-----
From: WiringForDCC@... [mailto:WiringForDCC@...]On
Behalf Of Marcus Ammann
Sent: July 12, 2005 04:45
To: WiringForDCC@...
Subject: RE: [WiringForDCC] DCC HO DC Question


Hi Blair

You can power your DCC systems with DC.
NCE - 18 to 28 volts DC
Lenz - 15 to 18 Volts DC
Digitrax - 12 to 28 volts DC

DCC power at the track is produced from DC that is made from rectifying
the normal AC voltage from your transformer by a bridge rectifier in the
booster. Supplying the bridge rectifier with DC instead of AC will still
provide DC to the booster circuits. It just uses 2 diodes to pass the
DC, instead of the 4 that are used for rectifying the AC.

The bridge rectifier and the electronics that produce the DCC voltage
will require some "extra" volts. For example if you supply the DCC
system 12 volts from a car battery you will only at maximum get say 10
volts. All decoder will work on 10 volts DCC but top speed will
certainly be affected. Sound decoders will start dropping out at 9
volts.

So for a DCC system to provide the recommended HO voltage of 14.25
volts, it will require at least 16 to 18 volts DC.

So if you go off the "grid" and have to supply your system with DC then
I would check your system requirements. From the above if you were
operating either the NCE or Digitrax, you could supply them with two 12
volt batteries connected in series to give you 24 volts. You will have
to separate the batteries to charge them with a 14 volt car alternator.

Hope this helps

Marcus



-----Original Message-----
From: WiringForDCC@... [mailto:WiringForDCC@...]
On Behalf Of Rasa and Blair Smith
Sent: Tuesday, 12 July 2005 11:34 AM
To: WiringForDCC@...
Subject: [WiringForDCC] DCC HO DC Question

Hi
For those with a lot more experience. I keep reading comments about
13.8
VDC not being enough to power DCC systems for HO, because you "dont get
enough speed out of the locos". Now, when I think about it for not very
long, it seems to me that that implys running the units at full throttle
and
being unsatisfied with performance. So what voltage DC is required to
achieve full performance? Yes, I realize that we have to assume a few
things, like the voltage drop to the farthest corner of the layout, etc.
etc, but ignoring those factors for a moment, what input voltage DC
should
we strive for to get satisfactory DCC performance?

If 13.8 VDC is satisfactory as long as we aren't looking for slotcar
performance, then the next question becomes will a DCC system perform
satisfactorily from an automobile electrical system? With and without
alternator charging system, or only when the car is running?
12 VDC is the minimum input, right? Or is that optimistic?

I ask all of this because there is a significant chance I am going to
want
to go off-grid in my next abode, and I expect 12 Volts will be part of
my
life at that point.

Blair Smith




http://www.WiringForDCC.com
Yahoo! Groups Links






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http://www.WiringForDCC.com
Yahoo! Groups Links

Blair & Rasa
 

Jan

1. The DCC systems I've encountered all required AC input. Have you found
one that runs on DC power?
Digitrax. AC or DC input. They specifically did not put the wall-mains
input section into the DCS100. I suspect that was because of a) simplicity
of not having to certify that high-voltage front end, and b) not having to
have different front ends for different power regions.

2. Power is not the same as speed with DCC, the DCC signal is full power
all the time. However, more power in the signal allows more speed. I like
to aim for 14-15 volts on the tracks, which implies a similar amount of
input power.
Nope. Power is not at issue, as power is the product of Volts and Amps. My
concern here is strictly the peak voltage available to the Digitrax circuit
producing the DCC waveform. To have 14-15 volts at the track, your DC
source must have that voltage PLUS whatever headroom the switching circuits
require.

I guess the upshot is, "try it", and see whether I get acceptable
performance.
Thanks
Blair

Marcus Ammann
 

Hi Blair

Further more on your question about 13.8 or 12 volts.

My NCE system outputs 13.8. I have an ammeter fitted fulltime that uses
a bridge rectifier in series with one track feeder so the voltage at the
output of the ammeter is 12.4 and I use 21 watt lamps for power division
which further drops the voltage to the track.

For a test, I consisted 4 sound equipped locos two Soundtraxx and two
Loksound, and run all with lights on and drawing .6 Amp and with the 21
watt lamp just starting to glow. The track voltage was 10.3 volts. Sound
decoders were all operating with sound. The Soundtraxx units on a
previous test for using 12 volt lamps for power division, do start to
play up at about 9 volts.

Operating with 12 volts DCC at the track, allows successful operation.
Obviously the top speed will be reduced at this voltage but all locos
were working.

Some operators on my NCE group have lowered the track voltage to 12
volts and have said that some problems they were experiencing, have
disappeared.

Hope this answers your question.

Marcus

-----Original Message-----
From: WiringForDCC@... [mailto:WiringForDCC@...]
On Behalf Of Rasa and Blair Smith
Sent: Tuesday, 12 July 2005 8:27 PM
To: WiringForDCC@...
Subject: RE: [WiringForDCC] DCC HO DC Question

Marcus
Yes, we know that the input may be AC or DC, and that regardless of that
input signal, in at least the Digitrax case, the input is rectified.
Yes,
we know that any system that produces AC from DC from AC is going to
need
what we generally refer to as "headroom". Digitrax specs 12 to 28 as
input
DC, what I am more or less questioning is whether 13.8, or even 12,
provided
sufficient voltage "at the track" for satisfactory operation. The
latter is
a very subjective consideration, so I guess the upshot is I should just
try
it.

The double battery suggestion is a fine one; I'll need yet a third, I
guess,
for all the PS12 and other electronics. Alternatively, I guess an
inverter
might be a better idea, with the layout wired for 110 VAC. Then I won't
need to make these decisions at all, off-the-shelf equipment will
suffice.
Thanks
Blair


-----Original Message-----
From: WiringForDCC@...
[mailto:WiringForDCC@...]On
Behalf Of Marcus Ammann
Sent: July 12, 2005 04:45
To: WiringForDCC@...
Subject: RE: [WiringForDCC] DCC HO DC Question


Hi Blair

You can power your DCC systems with DC.
NCE - 18 to 28 volts DC
Lenz - 15 to 18 Volts DC
Digitrax - 12 to 28 volts DC

DCC power at the track is produced from DC that is made from rectifying
the normal AC voltage from your transformer by a bridge rectifier in the
booster. Supplying the bridge rectifier with DC instead of AC will still
provide DC to the booster circuits. It just uses 2 diodes to pass the
DC, instead of the 4 that are used for rectifying the AC.

The bridge rectifier and the electronics that produce the DCC voltage
will require some "extra" volts. For example if you supply the DCC
system 12 volts from a car battery you will only at maximum get say 10
volts. All decoder will work on 10 volts DCC but top speed will
certainly be affected. Sound decoders will start dropping out at 9
volts.

So for a DCC system to provide the recommended HO voltage of 14.25
volts, it will require at least 16 to 18 volts DC.

So if you go off the "grid" and have to supply your system with DC then
I would check your system requirements. From the above if you were
operating either the NCE or Digitrax, you could supply them with two 12
volt batteries connected in series to give you 24 volts. You will have
to separate the batteries to charge them with a 14 volt car alternator.

Hope this helps

Marcus



-----Original Message-----
From: WiringForDCC@... [mailto:WiringForDCC@...]
On Behalf Of Rasa and Blair Smith
Sent: Tuesday, 12 July 2005 11:34 AM
To: WiringForDCC@...
Subject: [WiringForDCC] DCC HO DC Question

Hi
For those with a lot more experience. I keep reading comments about
13.8
VDC not being enough to power DCC systems for HO, because you "dont get
enough speed out of the locos". Now, when I think about it for not very
long, it seems to me that that implys running the units at full throttle
and
being unsatisfied with performance. So what voltage DC is required to
achieve full performance? Yes, I realize that we have to assume a few
things, like the voltage drop to the farthest corner of the layout, etc.
etc, but ignoring those factors for a moment, what input voltage DC
should
we strive for to get satisfactory DCC performance?

If 13.8 VDC is satisfactory as long as we aren't looking for slotcar
performance, then the next question becomes will a DCC system perform
satisfactorily from an automobile electrical system? With and without
alternator charging system, or only when the car is running?
12 VDC is the minimum input, right? Or is that optimistic?

I ask all of this because there is a significant chance I am going to
want
to go off-grid in my next abode, and I expect 12 Volts will be part of
my
life at that point.

Blair Smith




http://www.WiringForDCC.com
Yahoo! Groups Links






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Yahoo! Groups Links










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Mark Gurries
 

Jan

1. The DCC systems I've encountered all required AC input. Have you
found
one that runs on DC power?
Disclaimer: Consult with the DCC products manufacture for both DC and AC
capability before attempting to do anything.

Being familiar with DCC system internals in general (common circuits
shared by all), if a DCC system can take a low voltage AC input (less
than 30V), it will still work with a DC input.

A bridge rectifier converts AC power to DC power by "untangling" the
constant voltage reversal AC power present such that the voltage becomes
steady with one fixed polarity. If you present DC power to the input
designed for AC, all the bridge rectifier does is make sure the input DC
polarity will be matched to the required polarity inside the DCC system.

A less scientific way of stating this another way:

Think of the external DC power as being AC power source that suddenly
"Froze" at one polarity forever. The bridge rectifier does not care
what the polarity is at any given time because it job by definition is
to "on the fly" correct the polarity to match what is required inside.
So if the AC freezes, so does the rectifier in one rectification mode.
Hence the DC passes right through the rectifier to DC again.

This "capability" is limited to DCC products as far as my discussion
applies. Do not assume that above applies to every device especially
devices that run from 110/220VAC! See disclaimer.

Best Regards,

Mark Gurries
Linear Technology
Power Supply & Battery Charger Applications Engineer/Manager
---------------------------------------------------------
Model Railroad Club and NMRA DCC presentations are at:
http://www.siliconvalleylines.com/index.html
--------------------------------------------------------
Audio Enthusiast (Love SAE equipment)
http://members.ebay.com/aboutme/gurriesm/
----------------------------------------------------------

Blair & Rasa
 

Mark,
Yes, this is true- most AC consumer products do NOT fare well on DC.
Effectively, Digitrax, and perhaps others, appear to have "built in"
protection against DC reversal, a common source of damage for many other
product lines; for example, when you go out and buy a replacement 3rd party
wall wart that has -9V on the center of the connector, instead of +9V, and
your precious calculator calculates it's last. Anyway, the built in
protection of a bridge rectifier is nice, but it "costs" you in terms of
voltage overhead. When users complain of their DCS100 units overheating,
that rectifier is one (but only one) of the contributors to that
overheating.

We're on the same wavelength, as I'm EE technologist. I asked my question
intending to get feedback on operational satisfaction at 12VDC input from
people who would be cognizant of the issues, not to find out about DCC
system inputs - but I'm sure this is all interesting to others, as well.
And your explanation is, as usual, succinct.

Thanks
Blair

Jan Frelin <jan.frelin@...>
 

I was clearly wrong! I've always used AC power for my Lenz boosters, but
checking the documentation I note they too allow DC power.
/Jan

At 14:15 2005-07-12 -0700, Mark Gurries wrote:

Jan

1. The DCC systems I've encountered all required AC input. Have you
found
one that runs on DC power?
Disclaimer: Consult with the DCC products manufacture for both DC and AC
capability before attempting to do anything.

Being familiar with DCC system internals in general (common circuits
shared by all), if a DCC system can take a low voltage AC input (less
than 30V), it will still work with a DC input.

A bridge rectifier converts AC power to DC power by "untangling" the
constant voltage reversal AC power present such that the voltage becomes
steady with one fixed polarity. If you present DC power to the input
designed for AC, all the bridge rectifier does is make sure the input DC
polarity will be matched to the required polarity inside the DCC system.

A less scientific way of stating this another way:

Think of the external DC power as being AC power source that suddenly
"Froze" at one polarity forever. The bridge rectifier does not care
what the polarity is at any given time because it job by definition is
to "on the fly" correct the polarity to match what is required inside.
So if the AC freezes, so does the rectifier in one rectification mode.
Hence the DC passes right through the rectifier to DC again.

This "capability" is limited to DCC products as far as my discussion
applies. Do not assume that above applies to every device especially
devices that run from 110/220VAC! See disclaimer.

Best Regards,

Mark Gurries
Linear Technology
Power Supply & Battery Charger Applications Engineer/Manager
---------------------------------------------------------
Model Railroad Club and NMRA DCC presentations are at:
<http://www.siliconvalleylines.com/index.html>http://www.siliconvalleylines.com/index.html
--------------------------------------------------------
Audio Enthusiast (Love SAE equipment)
<http://members.ebay.com/aboutme/gurriesm/>http://members.ebay.com/aboutme/gurriesm/
----------------------------------------------------------


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