Seems to be a simple programming question

beinganmeisfun · Feb 10, 2015

This is for a class project. Seems to be simple, but I feel I may be overthinking it.

My conveyor motor is controlled by two outputs.

O:0/2 turns the motor in the forward direction.

O:0/1 (relay) and O:0/2 turn the motor on in the revere direction.

Say I wanted to do this...

I:0/1 turns on O:0/2

I:0/2 turns on O:0/2 and O:0/1

How would this be written in Logix500 so that I can change directions?

Thanks for any and all help!!

jawolthuis · Feb 10, 2015

I:0/2----------------O:0/1

I:0/1----------------O:0/2
I:0/2----|

EDIT: Fixed caps...

James Mcquade · Feb 10, 2015

Welcome to the forum.

You have O:0/2 listed in your description as forward and reverse.

May I suggest the following.
1. Write down what you want to do. Review and edit if necessary.
2. Add I/o to your document.
3. Do the plc program, zip it, and attach to the forum.

we will be more than happy to look at your work and suggest any changes.

regards,
james

beinganmeisfun · Feb 10, 2015

That is correct.

O:0/2 runs the motor in the "forward" direction.

When O:0/2 AND O:0/1 (relay that reverses the polarity) are on, the motor runs in the "reverse" direction.

Unfortunetly, it must be wired this way.

The inputs used in my example are at random, just to help explain changing direction based on conditions.

Looks like jawolthius's logic would get the job done. I was thinking I would have to use a bit (B3:..) somehow.

beinganmeisfun · Feb 10, 2015

Thank you for your suggestions, James

bernie_carlton · Feb 10, 2015

Make sure that a change in direction does not happen too quickly. The motor needs to come to a halt before applying power for the other direction.

In applications I made sure enough time had passed before changing the reversing relay, either on or off. The run (O:0/2) would probably be capable of absorbing the turn off spike from the motor. The reversing (O:0/1) should only be changed when the motor is fully stopped.

Of course a very small motor, like for a small classroom tabletop project may not need that level of protection.

T Gibbs · Feb 10, 2015

I:0/1-------------o:0/2

i:0/2-------------o:0/2
____________|---o:0/1

jrwb4gbm · Feb 10, 2015

bernie_carlton said:
Make sure that a change in direction does not happen too quickly. The motor needs to come to a halt before applying power for the other direction.

In applications I made sure enough time had passed before changing the reversing relay, either on or off. The run (O:0/2) would probably be capable of absorbing the turn off spike from the motor. The reversing (O:0/1) should only be changed when the motor is fully stopped.

Of course a very small motor, like for a small classroom tabletop project may not need that level of protection.

I've written an example program in LogixPro based on your description. I will post it later but will wait for the OP to post their attempt first as James McQuade has requested.

Firejo · Feb 10, 2015

So my example uses inputs 1 and 2 and outputs 0 and 1. The principles are the same regardless of which inputs and outputs are used. What I like to do when working on something relatively simple is first break it down to binary (where applicable) and work from there. The inputs and outputs are really reflections of bits with each input represented by one bit in a word and each output the same. In this case all you need to do is take what is needed via the outputs, come up with the binary number (I.E. 0 1 0 = output 0 off, output 1 on, output 2 off), translate that to the decimal number and move that to the outputs when certain conditions are met (I.E. when input 1 and 2 are on send “3” to the outputs turning on outputs 0 and 1).

willxfmr · Feb 11, 2015

Firejo said:
So my example uses inputs 1 and 2 and outputs 0 and 1. The principles are the same regardless of which inputs and outputs are used. What I like to do when working on something relatively simple is first break it down to binary (where applicable) and work from there. The inputs and outputs are really reflections of bits with each input represented by one bit in a word and each output the same. In this case all you need to do is take what is needed via the outputs, come up with the binary number (I.E. 0 1 0 = output 0 off, output 1 on, output 2 off), translate that to the decimal number and move that to the outputs when certain conditions are met (I.E. when input 1 and 2 are on send “3” to the outputs turning on outputs 0 and 1).

The only problem with this method is that the maintenance people will hate you for using it. Why use moves and math when simple outputs will get it done and be easier to decipher?

rdrast · Feb 11, 2015

T Gibbs said:
I:0/1-------------o:0/2

i:0/2-------------o:0/2
____________|---o:0/1

NO.
Double outputs on O:0/2.
The only way O:0/2 can ever come on in this case is if I:0/2 is on. I:0/1 has no effect.

blkfalc4 · Feb 11, 2015

I'd also add a slight start dwell to O:0/2 so that there is no way for the motor to plug.

jrwb4gbm · Feb 11, 2015

Here is one method as described by bernie_carlton, see attached.

jrwb4gbm · Feb 11, 2015

Here is a bit more refined version than the one I posted in post #10, see attached.

T Gibbs · Feb 11, 2015

rdrast said:
NO.
Double outputs on O:0/2.
The only way O:0/2 can ever come on in this case is if I:0/2 is on. I:0/1 has no effect.

OOPS! Can't do that in RS Logix. I can do that in DS5 using an OR OUT.

Seems to be a simple programming question

beinganmeisfun

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jawolthuis

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James Mcquade

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beinganmeisfun

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beinganmeisfun

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bernie_carlton

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T Gibbs

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jrwb4gbm

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Firejo

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willxfmr

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blkfalc4

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T Gibbs

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