Toggle bit

[markn]

Hi Folks, I've been trying to figure out how to use one input to toggle an output on then off. Initial state with table in start position would allow clamp, table travels away from limit switch, cycles, and returns to limit switch and releases clamp. Thanks

[Crossbow]

Depends on the PLC. In the FX it's called ALT. In the Q it's called FF. Check the programming manual for the PLC type you are using.

[markn]

Hi Crossbow, Thanks for the reply, so basically the comands ALT or FF are related to a Flip-Flop? Mark

[speakerman]

Hey Mark; Here's a thought: I would suggest that you use more than just the limit switch toggling to decide to release a clamp, because when the switch starts to age and wobbles, it would release the clamp during whatever cycle the table had moved the part being clamped into. I must assume that if you're clamping it, it will either fly around, or at the very least be spoiled. You can use the table output direction in conjunction with the switch changing state to decide whether to clamp, or to release. You control the table output already, so that has some backchecks in it, and this would work in manual or auto. If you have a 'cycle complete' bit for whatever is happening to the piece, that would be useful as well - just bypass that bit to unclamp when in manual, and the operator will appreciate it. The worst that would likely happen with this code is that the clamp could release while the piece was being moved back to the start position, and not while it's being worked on by whatever you've clamped it for. Then you also wouldn't need a discreet command, but rather the direction of the table determines the toggle. Hope you find this useful, speakerman.

[markn]

Hi Speakerman, Thanks for the reply, I like the control bit-manual operation idea. I,ll try to expand upon what I am trying to achieve. We have an old double mitre saw which has its own hardwired PLC. To operate the saw as it is presently functioning, the operator places the piece upon the table and presses a foot pedal to begin the cut cycle, the saw then clamps the piece and the saw cycles through the cut, returns to the home position and releases the clamp. We would like to use the existing PLC logic to operate the saw, however, we want to add in an anti tie down feature, so that the exisitng foot pedal would operate the clamp only. Upon clamping the piece, the operator would have to insert his finger of each hand into a Banner OSB sensor to start the cut cycle. I,ve worked out the logic for the anti-tie down feature, but I am having trouble with the logic to replace the exisitng footpedal_start_cycle. My thought was to use the existing signal that the foot_pedal switch now sends to the machines' existing PLC. Something like this: Saw down; (signal from exisitng limit switch) O K to clamp Clamp ;signal from foot switch Start cut cycle ;signal from anti-tie down to existing foot switch input Regards

[speakerman]

Hey markn; I am not certain what an anti-tie down feature is, but I'll take a shot at the description... It appears you would like to have the clamping of the piece not initiate the cut cycle, but rather the hands activating the photoeyes would start it - for safety, I assume. So that action, combined with the piece being clamped, will initiate the cut cycle and the piece will proceed into the saw. The cut cycle will complete, and the existing logic will run the piece out to the starting limit switch again, and you'd like the clamp to release automatically at that point. Then the operator will take that one out and put another in, hit the foot switch, put hands in the photoeye area... and so on. Is that close? I have a few questions so I can be of more help: Are you using the photoeyes to confirm the operator is not reaching into the saw area during a cut cycle? Is there an auto/manual mode for this, or is it a single, manually initiated cycle? Is the foot switch able to interrupt the logic and stop or mess up a cut if it's hit mid-process? Do you want it be able to stop the process for safety reasons? What stops a cycle now, if something goes wrong? This is a simple sounding move, and I would guess the priority is safety for the person feeding the saw, and a smooth, sensible work flow. Once I have a better understanding of the desired workflow, and the switches in the area and their functions, I can give you a code example to spark some ideas. Have a good one, speakerman. Edited March 18, 2008 by speakerman

[markn]

Hi Speakerman, You've got the basic idead, however the saw travels and the workpiece is stationary, optionally the workpiece is bored for dowels after being sawn. I,ve actually got the limit switch to toggle an output using the ALT command. I've setup a FX1s-10mr on a bench and am testing my logic as I go. I' using the ALT command in conjunction with a P input and a F input when the saw returns to home position. I,m outputing to a M relay and I think I'll use that as a control bit as well as a control to release the clamp. One thing that I am having a problem figuring out is to insure that the M relay is in the proper phase upon starting the Machine and FX1s. The way the anti_tiedown works, is that the operator must operator must activate both controls within an aloted time, in our case about 500 milliseconds, and it is set up so that the operator must maintain contact inorder for the machine to cycle. There is also an onboard emergency circuit that returns everthing to home position and brakes the saw rotation upon activation. If I can figure out how I will post the code that i have started. Thanks

[speakerman]

If you go to that trouble, markn, I'll do my best to help you. Nothing sounds too difficult, and I can see that you want this to be a safe as possible - which is something I believe strongly in. In another thread I was able to save my GX-Developer file as a new project, delete the extra stuff, then zip that folder and post it. If that's the programming software you're using it should be no problem. I'm here until Thursday, then traveling until next week, so I'll keep an eye out for your code. Cheers, speakerman.