Well this maybe a stupid question but I have a dl 350 pc from automation direct and having a brain **** on a program. We are building a machine that moves in and out and we are only using 1 limit switch for both movements. How would I write a simple program to make that work so u can move forward to the limit then move in reverse till u tripped the limit agian?
This maybe a stupid question?
- Thread starter BDL273
- Start date
TConnolly
Lifetime Supporting Member
Use a flip flop or toggle. Search the forum for flip flop, there are dozens of ways to make them.
Also, One of our forum members, Doug_P has an animated avatar that shows a simple flip flop that will work with most PLCs.
This flip flop can be programmed on pretty much all PLCs. It should work just fine on the DL 350. In Doug's animated avatar your limit switch would be P. T is your direction bit.
Also, One of our forum members, Doug_P has an animated avatar that shows a simple flip flop that will work with most PLCs.
This flip flop can be programmed on pretty much all PLCs. It should work just fine on the DL 350. In Doug's animated avatar your limit switch would be P. T is your direction bit.
Last edited:
bernie_carlton
Lifetime Supporting Member + Moderator
Can it move beyond the limit switch? Or is the physical setup such that if it isn't on the limit switch it is somewhere between the limits?
Does the limit switch directly kill power to the movement also? In other words, if you are on the limit switch can you move off of it?
What type of limit switch is it?
Does the limit switch directly kill power to the movement also? In other words, if you are on the limit switch can you move off of it?
What type of limit switch is it?
it can move beyond the limits but it has another saftey switch to stop it from running off the tracks if its not on the limit it is between the limit its just a roller limit switch with no or nc contact it sends an input to the plc and it opens the contactor if the motor
TConnolly
Lifetime Supporting Member
I pictured something like this when suggesting a flip flop. Each time the leading or trailing dog hits the limit switch roller the direction bit will change state. Use the direction bit to control the actuator direction.
MOVED COMPONENT
Actuator +--------------------+
+--------------+ | |
| |--------| |
+--------------+ | |
| |
+-+----------------+-+
| | | |
+-+ 0 +-+
DOG | DOG
+-+
| |
+-+ LIMIT SWITCH
bernie_carlton
Lifetime Supporting Member + Moderator
The problem is, on startup you may not know which was you moved to get to the limit switch. Assuming you jog it the wrong way you will hit the safety which stops all movement. Can you not spare another input? If the limit is a lever arm style limit switch can you get one with seperate CW and CCW actuating contacts?
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