[M91 Ladder Proofing]

I've got two portions of a project that are similar. One operates correctly and the other goes through the timing logic, but no output is fired. I'm not certain if I'm using the MB improperly or if there is some protocol I'm missusing. Can I send the ladder to someone or insert it here, somehow, for someone to review?

[timer or loop?]

I was under the assumption that U90 was under the visilogic group since my cd has both names on it. Got it now! thanks.

[timer or loop?]

The default timer, type TD, has contacts that close when it times out and they stay closed until power is removed from the timer or it is reset with an -® coil referenced to the timer's address.

I would look at the timed pulse for this application, type TE. This timer closes it's contact immediately for the preset amount of time, and then goes off until power is removed from the timer. If the timer is re-triggered while it is "busy", it will not restart. Set the timer's preset for the amount of time you want to debounce the limit switch input, and trigger the timer with that input. Then use the timer's contact in your program.

Look at the Help topic Timers(T) for a good explanation of all the timer types and how they work.

Joe T.

I don't see a TD or TE in the M91 timer list. This simple PLC must not have the full list of functions.

[timer or loop?]

What I'm trying to accomplish is have the PLC ignore any possible backlash from a limit switch. I1 is CW triggering from the limit switch and I2 is CCW triggering from the limit switch. It is possible as this switch gets worn that it can hit the CCW contacts after rebounding from the CW direction and it can do the opposite (hit the CW contacts after rebounding from the CCW direction). So I'm just trying to build a timer to ignore opposite inputs for the short time the limit switch arm returns to center neutral.

It appears to me that Phil's first example will accomplish this??

What I'm still a little fuzzy on is the duration that the timer coil remains latched after the delay has timed out. Are the contacts on the respective timer closed for one scan after the time out or are the contacts latched until the timer is reset again?

[timer or loop?]

I'm extremely new to ladder logic and I've run into a problem with my first program. For safety sake, I need to ignore input "1" while input "2" is high and then do the opposite, ignore input "2" while input "1" is high. Both situations need only occur for 500ms, then look for the opposite input again. I can make a timer to ignore one input, but my second timer disables the process from functioning. Thanks in advance for any help.