Correctly utilizing encoder with PLC

zblum said:
Again, I want EACH encoder pulse to shift the binary file.
Click to expand...

So essentially you're looking for the encoder's input/pulse to trigger an event. I don't know if the HSC would be the best option as they like to count, be reset, etc.

You might want to look into the User Interrupts in the EII function file. You can select an EII, give it a ladder file and input just like the HSC function file.
Every time that input triggers, that ladder will execute.
 
BlueAltezza said:
So essentially you're looking for the encoder's input/pulse to trigger an event. I don't know if the HSC would be the best option as they like to count, be reset, etc.

You might want to look into the User Interrupts in the EII function file. You can select an EII, give it a ladder file and input just like the HSC function file.
Every time that input triggers, that ladder will execute.
Click to expand...

And it can count at the same rate as the HSC?
 
BlueAltezza said:
Yeah- I don't know the exact speed off the top of my head, but I've seen an EII used with a 2.5kHz signal on Micrologix 1500's before.
Click to expand...

How do you increase a counter in your EII subroutine? Mine won't increase, presumably because there is no detected false-true transition. I just used an add function (+1) for the time being.

I was not able to do extensive testing (as our line was running), but I seem to be getting approximately the same results using the EII.
Could this be an electrical issue? I have to use pull-up resistors with this encoder. Would this introduce any additional "lag" into the response time of the encoder?
Could my resistor value be incorrect, keeping the pulses from occurring?
 
Last edited:
To verify your input you should be able to inch your conveyor/belt and see the input go on and off.


Did you add the UIE instruction anywhere in your logic to allow the interrupt?
Looks like the 1200 uses these:
Interrupt Types
Type 0
STI (bit 0)

Type 1
HSC 1 (bit 1)

Type 2
Event 3 (bit 2)

Type 3
Event 2 (bit 3)

Type 4
HSC 0 (bit 4)

Type 5
Event 1 (bit 5)

Type 6
Event 0 (bit 6)

So if you set up your EII:0 to work with your encoder input, put a UIE 6 instruction in your logic.
In the EII function file, I'd also set the Autostart and Event Interrupt Enabled to 1.
 
zblum said:
I am dealing with bottles that are irregularly spaced and conveyor speeds that are never exactly the same. I am not sure what you mean by using just the photoeye; I need some way to "store" bottle position data (on the conveyor, for up to 20 bottles at a time) that would not be thrown off by a sudden shift in conveyor speed. Hence, why I am not even trying to use timers.
Click to expand...



Inconsistent spacing and speed adds a level of complexity that is beyond me, so I'll just sit back and see what I can lean along with you.

Bubba.
 
BlueAltezza said:
To verify your input you should be able to inch your conveyor/belt and see the input go on and off.


Did you add the UIE instruction anywhere in your logic to allow the interrupt?
Looks like the 1200 uses these:
Interrupt Types
Type 0
STI (bit 0)

Type 1
HSC 1 (bit 1)

Type 2
Event 3 (bit 2)

Type 3
Event 2 (bit 3)

Type 4
HSC 0 (bit 4)

Type 5
Event 1 (bit 5)

Type 6
Event 0 (bit 6)

So if you set up your EII:0 to work with your encoder input, put a UIE 6 instruction in your logic.
In the EII function file, I'd also set the Autostart and Event Interrupt Enabled to 1.
Click to expand...

I guess I am also confused as far as the correct method of utilizing an interrupt. I thought when the EII is triggered, it immediately scans the ladder file that you assign it to during set-up.
Should I skip this altogether and just place the UIE command in the main ladder file?

And I know that I can verify the input by inching the conveyor; I have already done this. My question is whether or not the PLC is able to detect the change in voltage with the rapid pulsing. I know that my resistor was selected to drop the 24V down to 14V when the encoder is pulsing....it may need to be lower.
 
The EII will scan that ladder file when triggered, but the UIE instruction tells the PLC to allow that EII to operate.

I've put the UIE for my encoder EII function in the first scan, that way it enables it on startup and will always run. Try adding the UIE instruction in your first scan routine or main ladder and see if that helps.
 
BlueAltezza said:
The EII will scan that ladder file when triggered, but the UIE instruction tells the PLC to allow that EII to operate.

I've put the UIE for my encoder EII function in the first scan, that way it enables it on startup and will always run. Try adding the UIE instruction in your first scan routine or main ladder and see if that helps.
Click to expand...

Is this unnecessary if you set the UIE bit in the initial configuration for the EII?
 

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