Help a COMPLETE NOVICE if you would.

Disclaimer: I browsed the forums and must say this is far outside of my knowledge in every facet. I work in Exhibit Design and have no real programming knowlege. I draw 3D models and do renderings and CNC/Shop plans.


My problem:

I have built a mockup of a clients body scanning machine that has two light bars that scan up and down. LEDs on down, off on up. IT is built as two separate drives due to the shape of it and the fact that it has to break down, ship, and be assembled by union trade show labor.

Under advice of others I used a PLC to make this happen using (what is called in the program) A flicker command on a timer controlled a relay to reverse the polarity of my motors thus giving me the up and down scan motion. Same control used for the LEDs.

The probelm is the two drives eventually got to the point where they were binding at the top causing a lound groaning under the strain(not be mention being bad for my motor and all)

I am installing limit switches at the top and the bottom to stop the motors and have gotten way out of my leage as far as trying to program this. The switches i bought are some bumper switches. The seem like they should work. Would a diferent type of switch be better?

Here is what I am trying to do. (if i am way off let me know)

Assuming light bar starts traveling up. LEDs off.

When Limit Switch 1 is hit stop Motor 1.
When Limit Switch 2 is hit stop Motor 2 then reverse motor direction of Motors 1 and 2 and start Motor 1 and 2

Light bar travels down. LEDs on.

When Limit Switch 1 is hit stop Motor 1.
When Limit Switch 2 is hit stop Motor 2 then reverse motor direction of Motors 1 and 2 and start Motor 1 and 2

Thats it. Thats what I am trying to program and have gotten completely lost.

I am using a Mitsubishi Alpha 2 PLC with is computer interface software.

Any help is greatly appreciated. Even if its a complete rewire and different design.


Thanks

Any chance of a sketch ? - I can't envisage your system from your description so far.

how about a picture



image shows the two light bars coming down on.

It looks like you have two totally independant light bars and motors - is that correct ?

Your description of the limit switches confuses me - limit switch 1 appears to be hit by motor 1 going up and going down.

Probable a switch on the moving part?

Check your switch's after contact is made - the drive is disabled and direction changed, but then the switch is still activated.

You'll probably need to disregard the limit switch for awhile during change of direction,
Try using a timer or implement aditional limit switches at both ends of travel.



Nice display!

1. Are the switches wired so as to interrupt the power to each motor as well as providing a signal to the PLC?

2. Is it possible that the drives have reached a physical stop just before engaging the switches?

3. You may have to provide a time delay after the second switch is hit before beginning the reversing and restarting process.

L D[AR2 said:

It looks like you have two totally independant light bars and motors - is that correct ?

Your description of the limit switches confuses me - limit switch 1 appears to be hit by motor 1 going up and going down.

Click to expand...

Revised:

Assuming light bar starts traveling up. LEDs off.

When Limit Switch 1 is hit stop Motor 1.
When Limit Switch 2 is hit stop Motor 2 then reverse motor direction of Motors 1 and 2 and start Motor 1 and 2

Light bar travels down. LEDs on.

When Limit Switch 3 is hit stop Motor 1.
When Limit Switch 4 is hit stop Motor 2 then reverse motor direction of Motors 1 and 2 and start Motor 1 and 2

bernie_carlton said:

1. Are the switches wired so as to interrupt the power to each motor as well as providing a signal to the PLC?

2. Is it possible that the drives have reached a physical stop just before engaging the switches?

3. You may have to provide a time delay after the second switch is hit before beginning the reversing and restarting process.

Click to expand...

I havent wired it yet, but yes, it was my intention to have the switches cut power to the motor.

I am actually a bit confused as to how i wire the switches into the PLC so that it can recognize when they are tripped. I would think that once they both were tripped, a time delay (as you mentioned in 3.) could be used to trigger the reverse direction and start the motors.

If thats close then I am unsure how I relate that in the programming.

Just a little more clarification:
In the photo it looks like there are 2 totally independent light bars is separate enclosures. Does motor 1 control light bar 1 and motor 2 control light bar 2? These could be treated as totally independent of each other. Program 1 and then once satisfied, copy for the other. Unless you want both to move in a synchronised fashion, keep control programming separate.

How did you control stop and reverse action prior to adding limit switches?

What starts the up-down process? Is there a start button and then the bar goes up and down on it's own until stopped or does it require a start prior to each up-down cycle?

gmferg said:

Just a little more clarification:
In the photo it looks like there are 2 totally independent light bars is separate enclosures. Does motor 1 control light bar 1 and motor 2 control light bar 2? These could be treated as totally independent of each other. Program 1 and then once satisfied, copy for the other. Unless you want both to move in a synchronised fashion, keep control programming separate.

How did you control stop and reverse action prior to adding limit switches?

What starts the up-down process? Is there a start button and then the bar goes up and down on it's own until stopped or does it require a start prior to each up-down cycle?

Click to expand...

They are indeed two independent systems running simultaneously.

I controlled the stop by cheating. Hence the binding and the noise. It was an unfortunate thing to have to do, but it wasnt until day 4 of 5 that the noise began to happen so it worked out well for the most part.

There is a switch that lights up the whole program. It runs continuously until it is switched off.