How to wire a 24V Actuator with reverse polarities across motor to PLC

MorphuisOGrady · Dec 1, 2011

Hi all,

I have an actuator which I need to control with an AB PLC. Its a 5 core actuator which a motor and limit switch.

To extend the arm I apply 24V across the motor. To retract I reverse the polarity across the motor. My question is how can I wire such to PLC output so I can control it?

What would the limit switch be used for in this case? Is it for positional feedback?

TConnolly · Dec 1, 2011

You'll need two DPDT interposing relays. To keep from accidentally crossing polarities and shorting things out use relay #1 to turn the motor on/off and relay #2 to control direction. Wire the normally open and normally closed contacts of relay #2 for opposite polarity. When relay #2 is off the motor polarity is forward. When relay #2 is on the motor polarity is backwards.





       Relay#1           Relay#2

Pos ----] [-----------+---]\[-----+----\

                      |           |     \

                      +---] [---+ |      \

                                | |       O Motor

                                | |      /

Neg ----] [-----------+---]\[---+-)-----/

                      |           |

                      +---] [-----+

iant · Dec 1, 2011

the Limit switch is used to stop the motor from over stroking and doing mechanical damage usually

MorphuisOGrady · Dec 1, 2011

Hi Guys,

Thanks for your help. I have 50 of these for the system and would really rather not going down the route of having to wire 2 extra realys per actuator. Is there any clever way of doing this without the relays, even if i use 2 PLC outputs?

bce123 · Dec 1, 2011

Is there any clever way of doing this without the relays

This would not be clever!
Best regards, Steve

iant · Dec 1, 2011

As Most PLC outputs have a common supply and you need to reverse the supply to the motor - there may be no alternative.
Some Actuators have a reversable status (3 wire)
A common and FWD = REV input

bce123 · Dec 1, 2011

you could use 1-4 pole relay and 2 or 3 outputs but that would notsave much wiring or space

bce123 · Dec 1, 2011

posting a wiring diag. would help to know 3 or 4 wire?

MorphuisOGrady · Dec 1, 2011

Hi,

OK perhaps this may not be the actuator to use. Its unfortunate because we were hoping to retro fit a PLC into current system which uses these.

This is basically just a linear actuator to control a locking mechanism. Do you know if its possible to get an actuator that can do the following:

1. -Pulse or maintained supply(24V)to extend.
-Another supply to do opposite. I.e if extended retract and .vice versa

2. -Pulse to extend 1 Output
- Pulse to retract 1 Output

Hope this makes sense. Its a simple system and I really dont want to add additional wiring

MorphuisOGrady · Dec 1, 2011

bce123 said:
posting a wiring diag. would help to know 3 or 4 wire?

Here is the specificiation of the actuator

iant · Dec 1, 2011

Can you post or let us know what the model / part no / MFG. of your actuators are please

brucechase · Dec 1, 2011

You could always use a relay output card on the AB PLC. You would need 4 outputs to do the same thing. The SLC line has a OW16 where the 1st 8 outputs have a common supply voltage and the 2nd out have a common supply voltage. You could use two outputs (0 and 1) for forward and 2 outputs (8 and 9) for reverse. Feed the common power for the 1st 8 outputs with +24 VDC and the second set of 8 outputs with -24 VDC.

This would allow you to get 4 actuators per 16 point card. You would then only need total OW16 cards to do what you want.

If it was me, I would use relays.

EDIT: Wow! There were a lot of posts in the time it took me to write my reply.

brucechase · Dec 1, 2011

MorphuisOGrady said:
Hi,

2. -Pulse to extend 1 Output
- Pulse to retract 1 Output

Hope this makes sense. Its a simple system and I really dont want to add additional wiring

Sounds like you need a pneumatic actuator. That way it could really be done with 1 output.

Off the subject - Can you let me know where you purchased these actuators? I've been looking for something exactly like this for a while and these look inexpensive.

MorphuisOGrady · Dec 1, 2011

I could accept using 2 outputs per actuator but not 4!. I would absolutely agree it makes sense to use relays. Might need to consider changing actuators

MorphuisOGrady · Dec 1, 2011

brucechase said:
Sounds like you need a pneumatic actuator. That way it could really be done with 1 output.

Off the subject - Can you let me know where you purchased these actuators? I've been looking for something exactly like this for a while and these look inexpensive.

Hi Bruce,

Pneumatics is not an option. Is there no electric alternative?

These actuators are very inexpensive and can be purchase from a company called AEW. We have 1000s of these in use around europe.

http://www.aeicomp.com

How to wire a 24V Actuator with reverse polarities across motor to PLC

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