×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Maximum length of cable from digital output to solenoid valve

Maximum length of cable from digital output to solenoid valve

Maximum length of cable from digital output to solenoid valve

(OP)
I have an application where digital outputs from a PLC will be required to operate a solenoid valve in the field - 800m away(i.e., a cable length of 1600m between the PLC DO terminals).
The solenoid valve is rated 24V DC, 12W and will work upto 22V DC.I want to use a 1.5mm2 copper cable (say), which has a resistance of 13.14 ohm/km. The digital output card is rated for 24V DC (say). Will the valve operate at all?

Or, do I have to use a higher interrogation voltage and solenoid valve of a higher voltage rating?

I know this is all a simple problem involving Ohm's Law - but, somehow, I am not sure.

Will someone comment?

RE: Maximum length of cable from digital output to solenoid valve

bmsg

The simple answer to your question is no, the solenoid will not operate if it requires a minimum of 22v.  

The length of cable run is 800m (not 1600), you qoute the resistivity of 1.5mm cable as 13.14ohms, that means the 800m run will have a total resistance of 10.51ohms.  The rating of the solenoid is 12w @24v, that gives us a current of 500mA (0.5A). So applying ohms law, we get a volt drop of 5.255V, so the voltage at the solenoid end of the cable will be 18.745v.  You could adjust the power supply output to say 29-30v, then there will be enough voltage for the solenoid to operate.  check that your DO card in the PLC will accept this higher voltage at it's terminals first.

Paul

There are 10 types of people in this world....
Those that understand binary and those that don't!

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources