# #2) Digitrax - Boosters



## ED-RRR (Jun 4, 2015)

To [ fcwilt ]: 
Thanks for your feed back
in another subject matter in this forum..
This made me look much deeper into how boosters work..
I did my homework about "Boosters"..
Input power (Pin) = output power (Pout)

=============================================

"TRACK" (Scale) Voltage..
V-AC Output [N] = 12.V-AC 
V-AC Output [HO] = 15.V-AC
V-AC Output [O/G] = 20.V-AC

=============================================

Booster:

There are many different types of "boosters"
requiring dozens of calculations..
Digitrax boosters are also very old..

https://en.wikipedia.org/wiki/Boost_converter
A boost converter is sometimes called a step-up converter since it
“steps up” the source voltage.. 
Since power (P = VI) must be conserved, 
the output current is lower than the source current..

http://ecetutorials.com/electrical/buck-boost-converter-principle-
of-operation-applications/
By law of conservation of energy the input power has to be equal 
to output power (assuming no losses in the circuit)..
Input power (Pin) = output power (Pout)

Power (P) = Voltage (V) x Current (I) 

Caution:
Voltage power supply going into a Digitrax unit 
should not be "Less" voltage 
than the "required" track power supply..

Warning: (Maximum Input Amperage)
All Digitrax units can not exceed their rated capacity..

=============================================

"Minimum" Digitrax unit power supply input = 12.V-DC <-- "Revised" 
"Minimum" Digitrax unit power supply input = 15.V-DC 
"Maximum" Digitrax unit power supply input = 28.V-DC

"TRACK" (Scale) <-- Power Input.. <-- "Revised"
Digitrax power supply (Not Available)
[N] = 12.V-AC <-- 12.0V-DC Input (Same)
[HO] = 15.V-AC <-- 12.0V-DC Input (-3.V-DC) "Warning"
[O/G] = 20.V-AC <-- 12.0V-DC Input (-8.V-DC) "Warning" 

"TRACK" (Scale) <-- Power Input..
Digitrax power supply [PS514]
[N] = 12.V-AC <-- 15.0V-DC Input (+3.V-DC)
[HO] = 15.V-AC <-- 15.0V-DC Input (Same)
[O/G] = 20.V-AC <-- 15.0V-DC Input (-5.V-DC) "Warning" 

You can see why Digitrax went to "Minimum" of 15.V-DC Input..

"TRACK" (Scale) <-- Power Input..
Digitrax power supply [PS2012]
[N] = 12.V-AC <-- 13.8V-DC Input (+1.8V-DC)
[HO] = 15.V-AC <-- 18.0V-DC Input (+3.0V-DC)
[O/G] = 20.V-AC <-- 23.0V-DC Input (+3.0V-DC) 

=============================================

Calculations: 

Wattage = Volts x Amps (VA) 
Voltage = Watts / Amps 
Amperage = Watts / Volts

Power (P) = Voltage (V) x Current (I) 
Watts (W) = Voltage (V) x Current (I)

......


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## Cycleops (Dec 6, 2014)

You've obviously gone to a lot of trouble cutting and pasting but what does it all mean? In particular what does it mean to you and does it help people on here?


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## D&J Railroad (Oct 4, 2013)

I donno. I just plug my PS2012 into the command station or booster and run trains. Seem to all work out.
Now I do know a guy who gets very emotional about the European model railroaders and their true to form DCC and that Digitrax is actually not in compliance with DCC. For a perfect world environment, I guess I'm content with the performance of my Digitrax system. Some of my locos do drop their address on occasion, but with a fleet of over 60 DCC equiped locos, I suppose that isn't to bad.


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## JerryH (Nov 18, 2012)

Most perceived booster problems generally are insufficient power supply performance, voltage drops in the track wiring, and poor trackage (loose joiners & dirty rails).


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## CTValleyRR (Jul 26, 2014)

Cycleops said:


> You've obviously gone to a lot of trouble cutting and pasting but what does it all mean? In particular what does it mean to you and does it help people on here?


This may be an illustration of the details that Digitrax owners seem to enjoy digging into. For myself, my eyes glaze over trying to look at that stuff. I like my "so simple a caveman can do it" MRC system.


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## ED-RRR (Jun 4, 2015)

*Efficiency !!*



Cycleops said:


> In particular what does it mean to you and does it help people on here?


Go ahead and operate your Digitrax units at a "much" less efficiency.. 
Go ahead and buy more Digitrax units..
Go ahead and buy more power supplies..
......


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## ED-RRR (Jun 4, 2015)

*Power to Spare:*



D&J Railroad said:


> I donno. I just plug my PS2012 into the command station or booster and run trains. Seem to all work out.
> .


The Digitrax PS2012:
I will be posting information regarding the [PS2012]..
If you are operating only (x2) 5.Amp Digitrax units in HO scale
you will have no "problems"..
......


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## ED-RRR (Jun 4, 2015)

*Booster Power [Input] = [output]*



JerryH said:


> Most perceived booster problems generally are insufficient power supply performance, voltage drops in the track wiring, and poor trackage (loose joiners & dirty rails).


Sorry:
In this "thread" I am only discussing that a Digitrax unit 
requires same/more Voltage than the required "track" voltage..
It has nothing to do with poor tracks or track wiring.. 
......


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## JerryH (Nov 18, 2012)

Somebody is really pissed at Digitrax.hwell:


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## ED-RRR (Jun 4, 2015)

CTValleyRR said:


> This may be an illustration of the details that Digitrax owners seem to enjoy digging into. For myself, my eyes glaze over trying to look at that stuff. I like my "so simple a caveman can do it" MRC system.


Nothing against [MRC]..

Are you using a [MRC] Power Supply Transformer - #0001414 ??
- Output 15.V-DC @ 3.5Amps 
......


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## higgsbosonman (Nov 17, 2014)

So are you complaining that Digitrax boosters require more voltage in than they output? I see that you've posted links to boost converters on wikipedia, but I don't see why that's important. Yeah, if you feed the system 12v DC and expect 15V out, then you'll have less amperage, but the Watts are pretty close to the same and if you feed something 24V at 5 Amps, then it should usually draw 10 amps at 12V (since it will be drawing around 120 watts in both cases). That's just fundamental electronics.

Our old lenz DCC system was exactly the same way, so it isn't just Digitrax. this is how they work. If they didn't, they couldn't cope with any power supply input other than 15V AC, and you better hope you've got a power supply that doesn't have voltage drop under load, or it's not going to be able to keep going.

It isn't that digitrax is less efficient; if you hook up a power meter to the box, it will be about the same Volt-amps on the input as the output (the difference will be neglegeble, but nothing is 100% efficient). If this wasn't the case, it would have to dump all that extra energy in the only way electronics know how; heat. and if you're thinking a Digitrax 8 amp booster being fed 24V and outputing 15V is dumping almost half the energy put into it as heat, you'd better have a fire extinguisher because it's going to catch fire because that would be almost 100 watts. in reality, they are only pulling around 4-5 amps at 24V at max load, and outputting 8 amps at 15V. Our boxes at our club are barely warm to the touch. For comparison, go grab a 100w light bulb, which is outputting around 90w of thermal energy.

Every DCC booster works this way. Don't single out one manufacturer.


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## feldon30 (Dec 30, 2012)

I've heard several valid complaints about Digitrax regarding configuration, programming, and various gremlins that make it tricky on large layouts with decoders from different providers. However I haven't found Digitrax to be particularly power-hungry or wasteful. For my 21 ft x 23 ft layout, I cannot imagine needing anything more than the 3 amps of my controller and 5 amps from my booster. That's 12-15 non-sound modern locos (250-400mA/ea) or 6-9 modern sound locos (800mA at load with sound) moving simultaneously.


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## D&J Railroad (Oct 4, 2013)

ED-RRR said:


> The Digitrax PS2012:
> I will be posting information regarding the [PS2012]..
> If you are operating only (x2) 5.Amp Digitrax units in HO scale
> you will have no "problems"..
> ......


Actually, I'm operating 1 DCS100 command station and 2 DB200 boosters on my PS2012.


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## mopac (Feb 24, 2011)

Glad to hear that Ken. I have a DCS200 and a DB200 and a PS2012, so I should
be fine. I have not really used them yet. Only the DCS and a few pieces of track.
Plans are for 80 some feet of around the wall layout. 2 separate railroads each
with double mains. Decent size yard that they will share. Probably would not happen
in real life but it will on my layout. UP and BNSF run very close to each other near my
house.

Sorry but I don't understand the rest of this thread. Way over my head. I am with Ken.
Plug them in, wire them up, and run trains. I don't think I need to know all that other
crap. That's not even fun. Sorry.


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## fcwilt (Sep 27, 2013)

What you see is the very much simplified drawing showing the essential function of a booster.

See here for a discussion of DCC power:

http://www.dccwiki.com/DCC_Power

As you can see the DCC signal is either at the max positive voltage OR the max negative voltage.

So now to the drawing. While a real booster doesn't use mechanical switches as drawn, it performs the same basic function.

The 4 switches can only be in one of two possible states if the booster is to perform the desired function.

With the 4 switches in "state one" the "DC Power In +" is connected to "DCC OUT A" and "DC Power IN -" is connected to "DCC OUT B".

With the 4 switches in "state two" the "DC Power In +" is connected to "DCC OUT B" and "DC Power IN -" is connected to "DCC OUT A".

There is obviously a bunch of circuitry that is not drawn that controls the state of these 4 switches but to summarize the circuitry takes an input signal from the DCC command station 
and changes the state of the switches, as needed, so that the waveform from the outputs is a replica of the waveform from the DCC command station, but "boosted" in power.

Now imagine for a minute the there is a small voltage drop across each one of those switches, say 1/2 volt each.

At any given moment there are 2 switches between the "DC Power In" and the "DCC OUT".

So if we have 12 volts in, we will only get 11 volts out: 12 - (1/2 + 1/2) = 11.

Now, in the real world, the "switches" are often FET transistors and they do exhibit a voltage drop across them when they are "closed".

Also there are one or two other things in the circuity, between the "DC Power In" and the "DCC OUT", which also exhibit a voltage drop.

The bottom line is that with real world designs there is always going to be a loss of voltage from power in to track power out.

Not an indication of a bad design, just the realities of the way FET transistors, etc behave.

So now that I have further complicated things - have a great day!


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## ED-RRR (Jun 4, 2015)

*Reply*



JerryH said:


> Somebody is really pissed at Digitrax.hwell:


I do not know where you get the intention that I dislike Digitrax..
This thread is "only" intended to show Digitrax Boosters function..

How to improve the performance..

......


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## ED-RRR (Jun 4, 2015)

*Thanks Again*

To [ fcwilt ]: 
Thanks for your assistance showing more detail..
Greatly appreciated..:smilie_daumenpos:

I tried to keep it simple but it still backfired..
I have been on and off with model railroading (Digitrax) since (2001)..
It seems that giving actual Digitrax information is received as an attack,
rather than assistance..

......


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## ED-RRR (Jun 4, 2015)

*PS2012 Power Supply*



D&J Railroad said:


> Actually, I'm operating 1 DCS100 command station and 2 DB200 boosters on my PS2012.


Very important question..
What "scale" are you using ??

The ‘N’ setting configures the supply to output 13.8 volts at 20 amps max.
The ‘HO’ setting configures the supply to output 18 volts at 15 amps max.
The ‘G’ setting configures the supply to output 23 volts at 12 amps max.
......


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## mopac (Feb 24, 2011)

No attack. I just don't know or understand it. I am ok with that.


The ‘N’ setting configures the supply to output 13.8 volts at 20 amps max.
The ‘HO’ setting configures the supply to output 18 volts at 15 amps max.
The ‘G’ setting configures the supply to output 23 volts at 12 amps max.

This is a lot of variance. Volts and amps. Let me ask this. Isn't the power
supply only putting out what is being drawn up to the stated max? Lets say
you are running 2 trains and only drawing around 1 amp from a 5 amp booster.
Isn't the power supply and booster just idling along? With plenty of reserve.

Ken's railroad is HO.


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## mopac (Feb 24, 2011)

Here is my thinking in getting 8 amp command station and booster.
5 amp units would probably serve me but I could see getting near the
max and I had heard the units can produce plenty of heat. I know heat
and electronics aren't good partners. I got the 8 amps so they don't have
to work so hard and would have less heat. Right or wrong? 8 amp units
were only 20 some dollars more than 5 amp units.


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## johnfl68 (Feb 1, 2015)

Yes, but with Ohms Law, the Power is almost exactly the same for each scale voltage:

'N' 13.8V 20A = 276 Watts
'HO' 18V 15A = 270 Watts
'G' 23V 12A = 276 Watts

The scale voltages are loosely based on what people have been using for those scales over the years. Even the NMRA standards are vague on precise recommended voltage for each scale size.


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## fcwilt (Sep 27, 2013)

mopac said:


> No attack. I just don't know or understand it. I am ok with that.
> 
> 
> The ‘N’ setting configures the supply to output 13.8 volts at 20 amps max.
> ...


The power supply in question is a "constant voltage" unit. That means the output voltage (barring an overload) stays constant as the load varies.

No load - no current. 

As the load increases the output current will increase in proportion to the load.

Assume the HO setting of 18 VDC.

With an 18 ohm load the output current will be 1 amp (I = E/R).

With an 9 ohm load the output current will be 2 amps.

And so forth.

What happens with the load is so much that the max output current would be exceeded?

That depends upon the design of the power supply. 

I haven't read up on this unit but one of several things may happen. The output voltage may start to drop trying to keep the output current at the max. A fuse/circuit breaker may open. The unit may overheat and go up in smoke. That would be fun. 

But, you are correct, just because a power supply is rated at, in this case 15 amps, doesn't mean it forces 15 amps into the load.


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## fcwilt (Sep 27, 2013)

mopac said:


> Here is my thinking in getting 8 amp command station and booster.
> 5 amp units would probably serve me but I could see getting near the
> max and I had heard the units can produce plenty of heat. I know heat
> and electronics aren't good partners. I got the 8 amps so they don't have
> ...


Basically correct assuming the 8 amp unit has been designed with more robust components, better heat dissipation, etc.

On the other hand if the only difference is, say, a internal setting that changes the overload current setting from 5 to 8 amps - then a 5 amp unit with a 5 amp load and a 8 amp unit with a 5 amp load would both be working just as "hard".

Given the small price difference I'm rather surprised they don't just drop the 5 amp unit. 

I've got both a DCS-100 and a DCS-200. I need to open them up and see if there are really any differences. 

They both, at least superficially, look the same.


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## mopac (Feb 24, 2011)

Basically correct assuming the 8 amp unit has been designed with more robust components, better heat dissipation, etc.

On the other hand if the only difference is, say, a internal setting that changes the overload current setting from 5 to 8 amps - then a 5 amp unit with a 5 amp load and a 8 amp unit with a 5 amp load would both be working just as "hard".

I never thought of this and don't know the answer. I hope the components are more robust.
I did purchase 2 PM42s to cut the power down. I have heard 8amps will weld the
wheels to the track (or at least pit the wheels) in the event of a derail and a short.
I guess a short would draw the max amps. Not good.


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## fcwilt (Sep 27, 2013)

mopac said:


> I guess a short would draw the max amps. Not good.


If the command station is working correctly and the wiring to the track is of adequate capacity, a short on the track should cause the command station to shutdown, protecting things, until the short is removed.

You can determine this by putting a metal object (a coin, specifically a quarter, is often suggested) to see if the command station does indeed shutdown.

You should make this test at various places on your layout.


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## ED-RRR (Jun 4, 2015)

*Another Correction Required*



johnfl68 said:


> The scale voltages are loosely based on what people have been using for those scales over the years.
> Even the NMRA standards are vague on precise recommended voltage for each scale size.


NATIONAL MODEL RAILROAD ASSOCIATION Page 1
http://www.nmra.org/sites/default/files/standards/sandrp/pdf/s-9.1_electrical_standards_2006.pdf
50 C: Power Transmission and Voltage Limits for Transmitting Power
through the Rails

Mark Gurries: (Voltage)
https://sites.google.com/site/markgurries/home/technical-discussions/boosters/nmra-track-voltages
Read this article..
Large Scale = 16VDC + 2V => 18V DCC.
HO & O = 12VDC + 2V => 14V DCC. 
N Scale = 10VDC + 2V => 12V DCC.
......


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## ED-RRR (Jun 4, 2015)

*Calculated Require Amperage*

[fcwilt] has replied with some excellent answers :smilie_daumenpos:

There are always so many variables..
This location may help..

Mark Gurries: (Amperage)
http://atsf93.qstation.org/Wiring.pdf
Read this article..
Go to page 15
......


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## ED-RRR (Jun 4, 2015)

*Booster Voltage [Output] --> Testing*

(private e-mail received) (friend of Mark Gurries)

To Ed; (ED-RRR)
I am a electric engineer and many decades ago
designed power supplies..
Some boosters such as Digitrax still have
"inefficient" analog power regulators.. 

From (Censored)..
He has a very large club HO model train layout 
using over (x10) Digitrax [DCC] units..

=============================================

[DCC] power systems are very complex..
- Required track "Voltage" to operate [DCC] Locomotives
- Required "Voltage" for [DCC] decoders to operate "correctly" 

Special Notes:
Required "Voltage"..
Not total "Wattage".. 
Not total "Amperage"..
No matter how you use "Ohms" Law
the required "Track Voltage" remains the same..

As per N.M.R.A. (Track Voltage) 
[N] = 12.V
[HO] = 14.V 
[O/G] = 18.V

Special Note:
The N.M.R.A. [DCC] track voltage
also applies to N.M.R.A. [DCC] decoders..

=============================================

Question:
Is your Digitrax Booster [Output] to the track
at the correct required "Voltage"..

As per N.M.R.A. (Track Voltage) 
[N] = 12.V
[HO] = 14.V 
[O/G] = 18.V

Procedures: (Testing Booster)
- Power up the booster
- Send power to the track
- LED "Track Status" is "On"
- Use a multimeter to check "Track" V-AC
- Measure across terminals "Rail A" and "Rail B"

=============================================

[DB200+]
DB200+.pdf (2008)
1.9.1 Track Voltage Adjustment
The actual track "voltage" supplied by the DB200+ 
can be adjusted..
(Read complete article)..

[DCS100]
SuperChiefXtra_2.pdf (2014)
7.8.1 Track Voltage Adjustment
The actual track "voltage" supplied by the DCS100
can be adjusted.. 
(Read complete article)..

Special Notes:
Input power (Pin) = output power (Pout)
You can "Not" increase the "track voltage" [Output]
if the Digitrax unit receives "Less" voltage [Input].. 
Also take in account from [fcwilt] calculations :smilie_daumenpos:
of a "Voltage" drop.. 

=============================================

I highly recommend this [DCC] checking meter..
Tonys Train Xchange
http://tonystrains.com/

RRampMeter (All In One)
http://tonystrains.com/shop/?s=RRampMeter
- [DCC] Meter
- V-AC
- Amps

Use the RRampMeter as a "manual" location meter
checking volt/amp meter readings..
Add the RRampMeter as a "checking" volt/amp meter
to each individual Digitrax Booster..
......


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## fcwilt (Sep 27, 2013)

ED-RRR said:


> (private e-mail received) (friend of Mark Gurries)
> 
> Some boosters such as Digitrax still have "inefficient" analog power regulators..


Just in the interest of accuracy boosters, in general, do not have "analog power regulators" (except for powering the control circuitry) nor, for that matter, do they attempt to regulate the output.

By their nature there is little between the input power and the track. Usually, at any given instant, a couple of FET (transistors) and one/two current sensing resistors (< 1/2 ohm) are all that are in the way.

The voltage drop across the FETs doesn't vary much with the load on the booster.

The voltage drop across the current sensing resistors DOES vary with load - otherwise they couldn't be used for sensing an overload. One design I looked at had a pair of 0.05 ohm resistors. At 5 amps load the drop across these would be 1/2 volt. 

So given the relatively low loss from input to output there is really no great motive to design a booster to provide a perfectly constant voltage out.

I am not aware of any boosters that regulate the output BUT if anyone knows of such I would much appreciate them posting that information here.

Always interested in adding more stuff to my brain. 

Thanks


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