# G2 as Track side RC and DCC control



## RCE (Sep 14, 2009)

I am going to use the CVP G2 as a track side receiver for control of DC only engines and for DCC equipped engines.









I am leaving the capacitor out for now.


I am going to use ether a 16.8 v 2000 mha battery or a MRC 6200 power pack. 
After I get it up and running I will post pictures of the setup.

Here is a question though 
When I did some testing with a battery and the MRC this is what I found 


Battery out ......17.7
with bridge ......16.3
G2 DCC output..15.5
This looks right 


MRC 6200
MODE 1.out ......18.8
with bridge.......17.8
G2 DCC output..26.8
MODE 2 out......14.0
with bridge ......13.4
G2 output........19.6 
This doesn't look right 

Does anyone know why the voltage using the MRC is so wearied?
Do I need to use batteries only or is the reading with the MRC not right?
Any help would be appreciated 

Richard


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## Greg Elmassian (Jan 3, 2008)

Do not leave the capacitor out if using your MRC power pack, it has pulsating, unfiltered DC. 

The battery is fine w/o the cap. 

That cap is a little small to filter the MRC at higher currents, I would use twice the value. 

What RMS AC voltmeter did you use to measure the DCC output? 

If you do not have a true RMS AC voltmeter, then put a full wave bridge on the DCC output and measure as DC. 

You cannot measure DCC voltage directly with an inexpensive, non-RMS AC meter. 

Regards, Greg


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## Paul Burch (Jan 2, 2008)

It will work for DC but not DCC. The DCC output is low power meant to drive aux decoders.


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## Greg Elmassian (Jan 3, 2008)

I thought the spec said it would source 2 amps on the DCC output? 

Maybe small engines would work. 

Or a cheap DCC booster. 

Greg


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## Paul Burch (Jan 2, 2008)

Greg,
Actually the G2 is rated for a maximum of 3 amps on the DCC booster output. Thats going to limit what can be run quite a bit. It will be interesting to see if it works. That output was designed for sound and/or function decoders. I don't recall anyone trying this setup.


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## Greg Elmassian (Jan 3, 2008)

Yep, interested to see if the motor control commands come out this interface... you would think so because that is how the Phoenix sets the "speed" of the sounds. 

Regards, Greg


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## RCE (Sep 14, 2009)

The DCC output does control a motor decoder at least it works for me. 

I started over with my testing 
MRC 6200..........NTE 5314 Bridge rectifier..........4700uf 35v capacitor 
Output of MRC MODE 1............18.5 MODE 2............13.8 
Output through bridge no load ...Mode 1...18.1..MODE 2..13.4 Output through bridge and cap no load...MODE 1.. 28.9..MODE 2..21.5 Output through bridge and cap with load MODE 1..27.4 MODE 2 ..20.4

Output of Battery.......18.8 
through bridge........18.12 output through bridge and cap no load.....17.96 Output through bridge and cap with load.....17.4 
Looks looks I need to stay with batteries and not use the bridge or the cap. Any more thoughts about why the MRC has so weird readings? 
Richard


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## Greg Elmassian (Jan 3, 2008)

Richard, I'm a little confused on what you posted, and the spacing is way off. 

So, I downloaded the manual, mode 1 and mode 2 are different output voltages... mode 1 should be up to 18.5 volts, and mode II to 14v DC

Remember this is an inexpensive, unregulated, low power "transformer"..

your measurements of the output voltage from the 6200 match the specs...

Are you using DC or AC range on your meter to measure? 


Something is very funny... is the "output" in the second set of measurements from the G2? Or all these measurements on the 6200? 


Greg


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## RCE (Sep 14, 2009)

Greg 
I am using the DC range on the meter.I did not hook up the G2. Readings are from the 1. MRC DC output, 2. readings are after the bridge 3.Readings are after the bridge and cap 4. readings after bridge and cap at the load,which is a small motor.











Richard


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## Greg Elmassian (Jan 3, 2008)

OK, now it makes sense... 

You are now seeing the results of "pulsating" DC, just rectified from 60 Hz AC .... remember all the pictures I sent you?












So, the "full wave rectified" is what is coming from the 6200.

If you look at it, you would see that the voltage drops to zero 120 times a second.

so the AVERAGE of this looks like 18 volts DC, BUT when you filter it, it will look a lot higher, because the capacitor is trying to "fill in" the valleys...

That's why the filtered DC is a higher voltage...

The filter cannot fill in the valleys all the way, but it will significantly raise the voltage reading.

In the picture below, the red lines would be the output of the 6200, and the blue lines might be the voltage with a capacitor added.

(I am mis-using a picture intended for another purpose, so all you other electrical engineers, please don't jump me) 













You meter on DC measuring the Red lines would get a reading somewhere between zeron and the maximum voltage, actually about 0.707 times the peak voltage, but meters vary.

That's why measuring unfiltered, pulsating DC is tough... (and also trying to measure any waveform actually)

Hope this is clearing things up.


Greg


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## RCE (Sep 14, 2009)

Greg 
What power supply would you recommend in the range of 18 volt? 
Can't spend a lot for it SWMBO would do away with me. 
Richard


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## Greg Elmassian (Jan 3, 2008)

Richard, trying to read the voltage while a motor is connected and running will most likely give you somewhat erratic readings. 

The motor is a very complex load... You would do better to measure with a resistor connected. 

I can tell you that the output voltage can approach the peak voltage of the rectified ac... but a rule of thumb is that it will be about .7 of the peak AC...

so if your transformer is putting out 27 volts peak (what your meter will probably read), the equivalent DC when filtered may be about .7 of that... about 18.9 volts.


Take a look at this page: *http://www.electronics-t...trong>**

Look at the first schematic and waveform (ignore the fact of how it is wired, it is really pretty equivalent to your full wave bridge in your 6200)

Now look at the last picture and the forumula...

The problem in giving you a "straight" answer is that the output voltage depends on the current drawn... so as that varies, the equivalent DC also varies.

Sorry to make it so complicated, but this is why people often use regulated power supplies that have filtered output, then the voltage is as "smooth" and "stable" as a battery.

Complicating this is that the 6200 is a low current power supply, and from direct experience, the output voltage varies wildly according to the load as you get in the 2 amp territory.

Let's drop back a bit... what is your goal for the DCC output voltage to the rails? 

I would select that target, and then feed your system from batteries to test and measure on the rails using a bridge rectifier, a small capacitor (like 100 mfd) and a meter on the DC setting.

Once you know what input voltage you want, then I would look for an inexpensive regulated switching power supply in the voltage range you have determined.


But again, just test this out with battery power so you can try different input voltages.


I hope all this makes sense.... I'm trying to make it as clear as possible... you are asking good questions....

Greg 

 

*


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## RCE (Sep 14, 2009)

I have been using an Aristo track side T.E mounted in a box car.but I wanted something smaller and lighter installed in the engines. 
I purchased a CVP G2 decoder and a NCE G Wire cab. 
I installed 1Digitrax DH465 and a SFX004 sound bug in the center cab I used the speakers out of a broken pc monitor








After that I built a box and wired the G2.








Here is the diagram of the wiring








I know that the DCC output is only 3 amp and the voltage is what ever the battery is,I'm using a16.8 volt 2000 mha battery for now. 
I will buy a regulated power supply some day but for now the battery will do. 
I have installed 1 DH465 in 1 Annie and am waiting on another broken pc monitor. I have tested the installation on my in door test track and it works good. 
Richard


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## Greg Elmassian (Jan 3, 2008)

A very clever way of making an inexpensive DCC system, well done! 

Greg


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