Currently dealing with the PLC and electrical circuit construction of SMEMA 1.2 standard. Wonder anyone heard of this b4?

This is what I am doing -> 2 machines A and B has a conveyor in between. The conveyor has 2 sensors on both end. The conveyor is controlled by an electrical circuit consist of relays and PLC to move the circuit board from SMT machine A to SMT machine B. Therefore we need to deal with some logic programing of the conveyor mechanism.

Now let us look at the PLC aspect of this thing :

- Circuit board transfer occurs when Machine A (sensor A) has board available (detected - contact closed), and machine B (sensor B) is not busy.

- Signals can occur anytime, but board transfer does not occur until both contacts r closed

- The "Board is available signal" from machine A will remain closed until board left machine A

- Ready signal remain close until board arrive mahcine B

- Board transfer cannot occur until each signal opens for 50ms.

My initial PLC ladder diagram is this :


---lA invert \l---------------------(counter1)----l

---lBl------------------------------(counter2)----l

---lcounter 1 - 50msl--------lcounter 2 - 50msl------------( condition 2)----l

---lAl--------lB invert\l------------( condition 1)----l

---lAl---------------------(restart counter 1)--------l

---lB invert\l---------------------(restart counter 2)----l

--lcondition 1l--------lcondition 2l-------(motor)-------l

--lBl-------(stop motor\)----l

--lstop motor\l----------(off condition 1\)----l

--lstop motor\l----------( off condition 2\)----l

--end--



*motor is used to move the converyor track to allow board transfer.

Can anyone help me on this PLC part?

And yea, hardware part is weird to, because I dont think I actually need relay on this. Just plug the sensor wire into PLC should be done isn;t it?

 

So what are you asking?Do you want a ladder diagram or want hardware help?

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I just cant come up with a good one!

 

both. Any idea?