Control Cables

haythame78 · Feb 22, 2005

Hi

i am wondering if there is an amplification needed for the control signal when it is required to transmit control signals from and to the PLC for a distance of 6 meters using coaxial control cables.

sorry if this question is stupid

i will appreciate the help

Keeper523 · Feb 22, 2005

As long as there are not any noise issues no

Steve Etter · Feb 22, 2005

haythame78,

You really need more information.

Amplification requirements of a "Control Signal" would have to be based, in part, on the control signal voltage and amperage (source specifications), the impedence and length of the cable, and the requirements of the PLC.

Once you know all about the system requirements , do the math. It should become clear whether you need some sort of amplification.

Steve

rsdoran · Feb 22, 2005

I didnt understand the question.

6 meters is about 20 feet right?
What is meant by control signal?
Are you talking network/serial port type connection?

You did say coax cable but I have never seen or used coax for a control application.
What kind of connection is this?

6 meters shouldnt be a problem with any kind of connection...as was mentioned...there is no noise/interference that may get on the line.

Inquiring minds need to know!!!!!

haythame78 · Feb 22, 2005

hi again and thank you for all of ur replies

the control cables is to connect between the Servo Motor and the servo motor Drive.

i am talking about the feedback signal from the encoder the servo drive. i believe coax are used for such purposes(correct me if i am wrong)

the machine irrected in a rural areas in Africa where i guess there will be no interference or noise becoz there are no other electrical devices around apart from the generator generating the power for the machine there are even no mobile phone coverage (correct me if i am wrong)

what i know is that some of the coax cables have sheilding in them to protect against noise.

i hope these info will be of help to you.

bernie_carlton · Feb 22, 2005

The manufacturer of the servo drive itself would be the best source of information regarding cable length limitations or considerations.

Tmu · Feb 22, 2005

Coax from feedback sensor??

haythame78 said:
i am talking about the feedback signal from the encoder the servo drive. i believe coax are used for such purposes(correct me if i am wrong)

Is coaxial cable often used between feedback encoder and servo drive?

Sorry, I am from Finland but I have never seen nothing but different kind of serial paired? cables.

Maybe servo drives can be connected via coax-bus??

Tmu

Keeper523 · Feb 22, 2005

It greatly depends on the individual manufacturer however I have used several different makes without problems at the lengths your talking about.

Contr_Conn · Feb 22, 2005

You did say coax cable but I have never seen or used coax for a control application.

ControlNet is COAX
Modicon RIO is COAX

rsdoran · Feb 22, 2005

Encoder cable is usually shileded but an incremental encoder would need a multi-wire cable...depending on type how many wires would be needed.

An absolute encoder may have an interface which possibly could use coax but I wouldnt think so. Info on absolute encoders: http://www.patchn.com:/absolutencoder.html

The noise mentioned can be generated from AC wires that are run close to encoder (or network) wiring, attempt to run encoder wires separate from any AC (especially 3ph motor) wiring.

As was stated check with the Servo drive manufacturer on the proper wire to use and lengths, but I doubt 20 feet will be a problem.

LadderLogic · Feb 22, 2005

As an example: Yaskawa Sigma II series servos use serial communications between the motor encoder and the servo amp. The longest standard cable is 20 meters, although the manual says that up to 50 meters should be no problem.

It has to be really low-quality cable (poorly shielded, high capacitance etc.) or low-impedance circuitry (i.e. high-current) to worry about distortion or degrading of encoder pulses over the distance of 6 meters. I have seen systems where intermediate amplifiers were used for 10 m runs. It is not for nothing those were considered "overengineered" - especially considering that the amplifiers were custom-built PCBs...

haythame78 · Feb 23, 2005

thank you very much everyone

Control Cables

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