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General Category => Maths, Geometry, Physics and others => Topic started by: praet531 on October 14, 2008, 01:36:47 AM

Title: Motor automation
Post by: praet531 on October 14, 2008, 01:36:47 AM
Hello

I am trying to make an automation with a 3-phase motor that will have 2 limit swiches and two buttons. When the operator press the start button, the motor will rotate right wise until limit switch 1 is actuated. Then it will stop and rotate left wise until limit switch 2 is actuated. Then it will rotate the other direction and so on. This will do until the stop button is pressed.

Can someone help me with this? What will i need? Do i need PLC? I have no idea to use them. Can i do it with relays?

Thank you for you help in advance.
Title: Re: Motor automation
Post by: kam on October 14, 2008, 17:08:37 PM
Aha. Now i get the point of your post How to stop a rotating motor (http://pcbheaven.com/forum/index.php/topic,498.0.html)...

The automation is very simple. You need to be sure first that the motor is stopped before switching rev.
You need 2 switches, S1 to start moving and S2 to stop it. You also need 2 limit switches that will stop the motor and then change the rev. These are the S3 and S4. The stop switch is normal closed and all other is normal open. Check the attached elektonik drawing for details.

TG1 is a toggle switch.
C1 and C2 will control the left and right rev. I hope you know how to wire those relays to change the rev.
C3 will control the break of the motor. I assume you will use a mechanical ABS break or similar.
T1 and T2 will have the breaking time. You must wisely adjust those timers in order to have a good breaking without too much time loss. Adjust them according to tests. I cannot give you a value but i can tell you that the higher the adjusted value, the more the breaking time will occur.

Select appropriate C1 and C2 relays according to your load and add some fuse before S2 for protection. 4-5 amps is far enough. Add the coil current drains and multiply by 1.2 to find the  appropriate fuse value.

BUT:
For this application i would highly recommend a PLC to be used if you know how to program it. it will be cheaper. A LOGO for example will cost you less than 100 euro (of course the C1 C2 and C3 relays must be added). Serafino could help you with the programming if he has time.

Hope i helped.