Cx-programmer instruction or method to detect sensor fault

[janner_10]

Omron supports differentiated inputs so the simple answer is a counter with a preset of 2 or 3. The clutch output would be used to trigger the counter and an on or off transition of the sensor would be used to reset the counter. If the counter reaches the preset then the sensor has failed.

This. Nice and simple.

 

[parky]

@Janner: totally agree

 

[Bobobodopalus]

thanks for all the input guys, i also agree that mendonsy's solution is as simple as i could hope for

 

[Bobobodopalus]

I would expect that even if a can is there you will get transitions as the cans are gapped by the star wheel, how do you determine cans there.
So, you need to see a gap or how can you tell if it is working ? the problem then becomes if there is a missing can what do you do ? do you alarm & stop just because 1 can was missed, or do you wait for at least 5 or six cans in that case, there are no cans or the sensor is not detecting cans ?.
I have worked on fillers, generally the speed is quite high above a few thousand cans a minute, however, some of the larger cans may be in the hundreds, scan time can then become a problem, answer use high speed interrupts.
The ones I worked on relied on sensors on the can infeed system to check if cans are present & runout routines to bypass can in place checking, we also had to do something with glass bottles, there were sensors to detect broken bottles, if so, a wash jet was used to clear the broken glass before it was filled, this was to reduce waste product so was tracked into the filler star wheel.

just for some more info, this is an aerosol packaging machine, the fillers only operate around 55 cans per min, we use a clutch to get every little drop of speed out of the index as it would take a moment to ramp up and down the motor.
no cans being present is not a problem as the machine checks if there is a can in pocket, if there isnt it just inhibits the heads over that empty pocket, we would still cause an alarm if this was a consecutive issue but wont affect the machines running.
there would be an issue if there was no can but the sensor says there was one however, there would be probably quite alot of spillage before it was noticed

 

[parky]

Yes at that speed I can understand what you are trying to do, perhaps that information would have been more relevant to the posts if included at the start.
Definitely go with the counter idea, it's simple & as you have an index with the clutch will work well.