Problem with HSC

Hello to everyone.

I have a problem with a HSC.

I setted up the HSC 1 and i use it with a A/B rotary encoder with 500 PPR.

The counter seems to work because when i turn the encoder i get the counting value but i get the value only when i turn it by hand. When i increase the speed (by hand always) of the shaft i get no readings. The point is that the speed isn't that much to get over the 100khz on board input.

Thanks in advance.

Dear partner,

You must change the imput filter in PLC properties, In attachment you can see the options, if the filter is smaller you can get faster frequencies 

Best regards

Thanks for the answer.

I cannot try this at the moment because i am at home but that should fix the problem. 

Andrés_Ariza

Dear partner,

You must change the imput filter in PLC properties, In attachment you can see the options, if the filter is smaller you can get faster frequencies 

Best regards

 Thanks the counting works perfect. 

 I still got a problem with other instructions like a comparator i added to reset the HSC value. Any idea how to compare the value from HSC faster ? It seems like when it exceeds the number (on fast frequency) the comparator doesn't react. Tried to decrease the program cycle to 30 ms but still nothing. I'm doing something wrong here. any ideas?

William_B

 

 

 

 

 

 Thanks for the fast answer.

 I am new programmer and it's my first time working with HW interrupts. Able to upload a sample program ?

Thanks in advance.

Demendia

Thanks for the fast answer.

 I am new programmer and it's my first time working with HW interrupts. Able to upload a sample program ?

Sorry.. I will not offer you a sample program at this time.
I urge you to follow the directions.

A few notes:
* A hardware interrupt (like OB40) will call itself when the trigger occurs.
* A hardware interrupt runs almost like the other a FC / FB code blocks.
* A hardware interrupt should not have too much code.
* HSC_CTRL instruction should update RV to a new value, to ensure that a new CV = RV interrupt occurs.
* The HSC updates itself in the background, but reading the ID1000 (example) address gives the counter value when the PLC scan began. ID1000:P gives the best reading but is seldom helpful.

--------------------------------------------------------------
A practical note through an example....
An object moves along a conveyor. A sensor detects the object and a pneumatic gate pushes the object from the line. The sensor and gate is 5m apart, so the conveyor movement is measured with a encoder (HSC).

At slow speeds the pneumatic action is accurate but at faster speeds there is a problem.

There is a problem because..
a) the PLC cycle takes a while to process the trigger (reaching 5m)
b) the physical output is only updated at the end of the scan
c) the pneumatic coil + valve takes 30ms to react
d) the movement of pneumatic air in the pipes and movement of cylinder takes a further 80ms to move the object.

The point being.... always keep physics in the back of your mind when doing "higher" speed measurements and actions.

w

Thanks a lot.

Very helpfull post i will create a program to try it.

Demendia

Thanks a lot.

Very helpfull post i will create a program to try it.

(I was asked some questions about this post...)

Hi.

Please be careful when you compare the HSC counter to a value.
Remember that the HSC counter is ever changing and the [==] compare will not always capture the HSC at the target value.

I think it makes more sense to show with some coding (attached).
Note that the coding is an example only..
there are several other (and more accurate) ways to do the same task.

Helpful?
w

Demendia

Thanks a lot.

Very helpfull post i will create a program to try it.

I earlier made "mention" of the hardware interrupt.
Please find attached some (rough) step-by-step instructions.
The interrupt is useful when a task needs to be done without any delay.

.... in other words:
normal PLC operation is interrupted when a target is reached in this case.

Possibly more helpful to others that to you...
but please do look through it as there might be useful information.
w