Need input: Programmable Limit Switch

[BobO]

Working on a PLS function for...um...something new we are working on. What do you typically use a PLS for and what are the parameters it requires...how many outs, how many steps, how fast, etc? Don't be bashful...

[DLTimmons]

You talking about what I always called a rotary cam limit switch? Like used on Punch presses.

[b_carlton]

Some have an advance/retard control based on the current speed adjustable for each output.

[BobO]

You talking about what I always called a rotary cam limit switch? Like used on Punch presses.

That is essentially what the implementation is in the CTRIO. Working on developing a hardware-based feature that would be very highspeed. Just need to know how people use these things and what the care-abouts are.

[deep6ixed]

Can someone please explain what a PLS is?  I'm a young pup in this game (32yo) and haven't seen one in use yet.  As far as I can read it works similar to a digital cam that most of our welding machines use and if that's the case then the feature we have on ours that really make the huge difference is the ability to advance / retard the timing of the cam by xx Milliseconds

Basically we have 14 "Lobes" on the digital cam that we can set the start / stop degrees on and every one of the positions has an ability to have a time offset positive or negative.  So you can have 100 MSEC after 145 degrees the signal come on and the signal go low at say 200 MSEC before 200 degrees, (all based on machine speed)

[rlp122]

That is a pretty good explanation of a PLS.

[BobO]

I can easily add an offset register.

[b_carlton]

The speed dependent time delays are needed when an actuating device (which takes a fixed amount of time to turn on) is actuated at the same physical point in the process. At higher speeds the actual effect takes pace too late. Thus a time delay, which is short or zero at high speeds, is greater at slower speeds. These are set individually by output.

The same effect can be done by changing the actuating point for the device (e.g. earlier on the cam at higher speeds).

[ATU]

What I have always seen is a cam advance based on a programmable rate offset; 1 degree per XXX RPM. For example if the cam angle is on at 100 degrees and off at 130 degrees, with a rate offset of 100 RPM, then at 100 rpm it advances the cam angles to 99 and 129. At 1000 rpm , its 90 and 120.
Typically, I use PLS functions on high speed stamping presses to verify material feed and line shaft driven automation.