Induction voltage in control cable for digital signal and command for solenoid valve

Thread Starter

Abhishek singh_1497710510

Joined Jun 17, 2017
4
Actually I have a control cable of 19 core armored , run of approx 500 mtr , the cable carries digital signal and command for solenoid valve operation, control voltage is 110 v ac , The problem what I am facing is that I am getting induction voltage of 45 vac in all the cores even in spare cores also, so due to which I am getting false signal even though there is a stop command from plc, in field I have a controller for operation of bag filter , from where I take digital input to my IO through my control cable , so even though the bag filter is stopped I get the return signals from control cable due to induction voltage , PLZ give me solution to remove this induction voltage.
 

crutschow

Joined Mar 14, 2008
23,529
Some ways to reduce the effects of the offending voltage:
  • Reduce the line impedance by adding a low value load resistor to the lines with the induced voltage.
  • Add a capacitor from the lines to common to filter the line frequency.
  • Go to differential line drivers and receivers for the control lines to reject the common-mode induced noise (if you have enough spare lines).
 

Thread Starter

Abhishek singh_1497710510

Joined Jun 17, 2017
4
Some ways to reduce the effects of the offending voltage:
  • Reduce the line impedance by adding a low value load resistor to the lines with the induced voltage.
  • Add a capacitor from the lines to common to filter the line frequency.
  • Go to differential line drivers and receivers for the control lines to reject the common-mode induced noise (if you have enough spare lines).
Thanks a lot but can u give me some other alternative apart from this
 

MaxHeadRoom

Joined Jul 18, 2013
19,194
I use
Actually I have a control cable of 19 core armored , run of approx 500 mtr , the cable carries digital signal and command for solenoid valve operation, control voltage is 110 v ac , .
What is the nature of the armour around the cable, if running 120vac along with low level signal cables you need all twisted pairs with shield on each pair and over all shielding,
Also is your AC supply referenced to earth ground?
Max.
 

Reloadron

Joined Jan 15, 2015
4,591
That won't have any effect on the steady-state AC he is picking up.
Do a total redesign of the cables to separate the signals.
I agree and my bad as I read:
The problem what I am facing is that I am getting induction voltage of 45 vac in all the cores even in spare cores also,
I read into it as an inductive kick. That is obviously not the case and thanks for bringing it to my attention.

Ron
 

MaxHeadRoom

Joined Jul 18, 2013
19,194
Actually I have a control cable of 19 core armored , run of approx 500 mtr , the cable carries digital signal and command for solenoid valve operation, control voltage is 110 v ac , .
If this installation is above ground, I would look at either metallic conduit or Metallic Flexible conduit, ensure the power is twisted pair as well as the signal cables.
All pairs, both power and signal should have a shield.
This is has been done this way in industrial systems for decades.
Max.
 

Thread Starter

Abhishek singh_1497710510

Joined Jun 17, 2017
4
Thanks to all , for giving precious suggestions, but I would again keep my points so that there is no confusion,
The cable is armored, with no shielding, use for 110 vac signals both for DI & DO, the problem is that I am getting induction voltage in all cores of cable , what would be the easiest way to get rid of induction voltage.
 

LesJones

Joined Jan 8, 2017
2,361
You have given no information on the nature of the control signals. Are they signals directly from a microcontroller or similar ? Two suggestions.
One have logic level converters at each end of the cable so the signals on the cable are a much higher amplitude than the induced voltages. Using something like MC1488 / MC1489 RS232 level converters (Or there modern equivelents.) would give RS232 signal levels of up to +/- 15 volts. Adding resistors to ground at the receiving end would also help. (I am assuming that the signals alway originate at the same end of the cable. (Not like the data signal of I2C protocol.) Two modulate a high frequency signal with the data then you could add filters at the carrier frequency at the receiving end. (A bit like the SKY remote control extender system works by sending the signal down the antenna cable without interfering with the TV signal. I think they use abou 7 Mhz as the carrier frequency.)

Les.
 

Danko

Joined Nov 22, 2017
826
Replace 110 VAC control voltage with 110 (or maybe lower) DC control voltage.
No AC - no induction voltage - no problem.
Hope 110 VAC control line do not feed some transformers?
 

MaxHeadRoom

Joined Jul 18, 2013
19,194
The cable is armored, with no shielding, use for 110 vac signals both for DI & DO, the problem is that I am getting induction voltage in all cores of cable , what would be the easiest way to get rid of induction voltage.
You are using the wrong style cabling and method.
By armor, do you mean metallic sheath if not, one if the most important is equi-potential bonding, especially to earth of each end of the the equipment as well as OA shielding.
Making each end common to earth ground eliminates ground loops.
Ensure any current carrying conductors are twisted the whole length, this reduces or eliminates EMI.
Max.
 
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