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Jmri interface

vincent marino
 

Question. If I wind the interface wire around a 110 extension cord will the dcc signal be affected by the 110 current? 

Mark Gurries
 

Not sure what you mean by interface wire.

There are 3 classes or wires found in a layout.

1) Low Voltage Control/Communication Cables

2) Low voltage DCC Track or DC/AC cables that distribute layout power.

3)  High Voltage 120V/220V AC power cables.

In general it is bad to mix Class 1 with Class 2.  There is no hazardous power involved.  The only problem with mixing them is noise and communication problems.

You can bundle Class 1 cables in a loose group of its own and you can bundle Class 2 cable in a loose group of its own..

You cannot bundle a Class 3 cable with Class 2 or a Class 3.  When it comes to high voltage AC outlet power, I would not wrap it that cable with anything else.   The AC cable is a hazardous cable and should be protected from accidental contact with tools or anything else that one might use in wiring up a layout.  It should be run all by itself away from all other cables and given some mechanical protection thoughts as to its installation.


On Nov 22, 2018, at 11:12 AM, vincent marino <vmarino2009@...> wrote:

Question. If I wind the interface wire around a 110 extension cord will the dcc signal be affected by the 110 current? 

Best Regards,

Mark Gurries
Electrical Engineer
DCC Website & NMRA DCC Clinics: www.markgurries.com



General
 

Sounds to me like he is talking about the JRMI interface wire!


On 11/22/2018 9:34 PM, Mark Gurries wrote:
Not sure what you mean by interface wire.

There are 3 classes or wires found in a layout.

1) Low Voltage Control/Communication Cables

2) Low voltage DCC Track or DC/AC cables that distribute layout power.

3)  High Voltage 120V/220V AC power cables.

In general it is bad to mix Class 1 with Class 2.  There is no hazardous power involved.  The only problem with mixing them is noise and communication problems.

You can bundle Class 1 cables in a loose group of its own and you can bundle Class 2 cable in a loose group of its own..

You cannot bundle a Class 3 cable with Class 2 or a Class 3.  When it comes to high voltage AC outlet power, I would not wrap it that cable with anything else.   The AC cable is a hazardous cable and should be protected from accidental contact with tools or anything else that one might use in wiring up a layout.  It should be run all by itself away from all other cables and given some mechanical protection thoughts as to its installation.


On Nov 22, 2018, at 11:12 AM, vincent marino <vmarino2009@...> wrote:

Question. If I wind the interface wire around a 110 extension cord will the dcc signal be affected by the 110 current? 

Best Regards,

Mark Gurries
Electrical Engineer
DCC Website & NMRA DCC Clinics: www.markgurries.com



vincent marino
 

I have a nce / jmri interface. The laptop USB cord to the interface circles around a 110 extension cord about 4 times in a 4' distance.  I'm wondering if the computer signal to the interface will be affected by the 110 current? 


On Fri, Nov 23, 2018, 9:44 AM General <aj81504@... wrote:

Sounds to me like he is talking about the JRMI interface wire!


On 11/22/2018 9:34 PM, Mark Gurries wrote:
Not sure what you mean by interface wire.

There are 3 classes or wires found in a layout.

1) Low Voltage Control/Communication Cables

2) Low voltage DCC Track or DC/AC cables that distribute layout power.

3)  High Voltage 120V/220V AC power cables.

In general it is bad to mix Class 1 with Class 2.  There is no hazardous power involved.  The only problem with mixing them is noise and communication problems.

You can bundle Class 1 cables in a loose group of its own and you can bundle Class 2 cable in a loose group of its own..

You cannot bundle a Class 3 cable with Class 2 or a Class 3.  When it comes to high voltage AC outlet power, I would not wrap it that cable with anything else.   The AC cable is a hazardous cable and should be protected from accidental contact with tools or anything else that one might use in wiring up a layout.  It should be run all by itself away from all other cables and given some mechanical protection thoughts as to its installation.


On Nov 22, 2018, at 11:12 AM, vincent marino <vmarino2009@...> wrote:

Question. If I wind the interface wire around a 110 extension cord will the dcc signal be affected by the 110 current? 

Best Regards,

Mark Gurries
Electrical Engineer
DCC Website & NMRA DCC Clinics: www.markgurries.com



 

If you are using double insulated line cord designed for 110V then you don't have a safety issue.  The cable is safe in all circumstances.  The primary source of any noise that might have an effect on low level signals is actually coming from your DCC components.  If your system is legally compliant with FCC rules then there will not be anything on the AC wires that will mess with your low level signals (this may not be the case because enforcement is rare).   The ability of the AC signals to impart interference onto the low level signals is a function of proximity, how long the wires are in close proximity and whether the fields of the wires are aligned.  This is the reason that twisted wire is recommended and used CAT5 and other internet wires.  When you twist the wire the effect of alignment and proximity is essentially eliminated.

Your DCC track wiring is actually vastly more likely to effect adjacent low level signal wires than anything else.  This is because the track wiring is higher frequency, carrying significant currents and consists of more or less square wave signals.  The frequency content of a square wave is many times higher then the basic frequency of the signal.  The higher the frequency and the greater the power the more likely it is to couple to nearby cables.  A clean 60Hz signal won't get very far.   The audio noise we associate with 60Hz power is generally because of the fluorescent light fixtures connected to it.  The fluorescent load can broadcast high frequency noise that occurs at a 60Hz rate.  Hence we hear the 60Hz but not the much higher frequency noise that is broadcasting it into the air.

I hope I have kept the simple and concise enough to be understandable.  The mechanisms involved are very complex and are not at all easy to predict.  Small changes in the configuration of cables can have huge effects.

Ken Harstine
BSEE with 40 years of experience in various aspects of electronics including technician work early in my career and significant experience in getting new systems to comply with with FCC rules.