Beckhoff KL5111 incremental encoder program

[[email protected]]

hello

could anyone tell me how to set up the KL5111 module on the Beckhoff plc to display a speed value from an encoder.

I believer the KL5111 will only accept an incremental encoder signal

if someone has some sample program or some explanation on how to do it, it would be a great help.

thanks in advance

 

[shooter]

the kl5111 is only a counter, so your counts/ time gives speed.

 

[[email protected]]

Ok i see, so it is a HSC module then? i suppose essentially for an incremental encoder you are only measuring pulses

http://www.beckhoff.com/english.asp?bus_terminal/kl5111.htm

is there any sample program that would give you a speed output from the card?. the encoder would give you so many pulses per revolution. how would i program the Beckhoff PLC to give me an RPM value for so many pulses per rev?

thanks

 

[JoanM]

Speed = space / time

Then you need the desired units, but at the end you need to:

r_rpmVar := ((r_last_read_pulses-r_previous_read_pulses)*r_pulses_to_revolution_factor)/r_milliseconds_between_reads;
r_previous_read_pulses := r_last_read_pulses;

Notes:
There are plenty of methods to read time and they depend on the kind of controller you have.
One that will work in all the controllers would be to use a TON and reading the ET output field (this would be the r_milliseconds_between_reads in the function).
Probably you won't need to make this calculation in each plc cycle step.
Be aware that the pulses counter can overflow, this would give you a bad calculation.
Also you should think about 0 values (divide by 0).

What I would recommend is to create a function block to deal with all those details.

Hope this helps.

 

[[email protected]]

hello joan,

do you know of any sample program that would show me how it would work?

i have a program that i am using however i think it is designed for an absolute encoder. i can send it on if you think you could put me right

i am not entirely sure where i connect the pulses into the KL5111 card. in the attached image could anyone tell me where i map the actual signals form the encoder?

thanks

 

[LadderLogic]

Did you look here: http://download.beckhoff.com/download/Document/BusTermi/BusTermi/KL5111en.pdf ?

It is not the frendliest documentation (Beckhoff's never is) but something may be gleaned from it.

 

[[email protected]]

hello, yes thanks, yes i found this document some time ago and thought i was sorted. however i am still not clear.

i did notice the "feature register" part and this is why i wondered must you activate the KL5111 or something like that. but to be honest i am not even sure where the feature register is?

when i tap a wire into terminal A i get a "1" appearing on the program. if i increase the rate at which i tap the wire off the A terminal i still only get "1". (i am trying to simulate a stream of pulses by doing this).

this indicates to me that the KL5111 is reading the pulses however the program i have dose not totalise the pulses or give a frequency of the pulse rate.

i am just not sure how i would go about getting a program that will read the pulse train from the encoder and give an RPM output.....

 

[LadderLogic]

I am not sure you can make the module count by just "tapping" one of the inputs. This is a quadrature encoder input module, not just a counter; it must have a proper quadrature signal (i.e. two pulse trains with phase offset 90 degrees) detected on both A and B channels in order to count.

 

[shooter]

use %IW25 as i can see on the screen.
so counterinput AT %IW25 :WORD; in the global VAR list or use nEncodercount.inputs.standard.test as on the screen.(easier to get with F2 when asking for a variable.)
check if Control register is set proper.
module can be used in several different ways.

 

[[email protected]]

can anyone suggest a suitable encoder for the KL5111 module?

ideally i would like an Avago Technologies encoder as the fitting on the back of my motor is of this type. however these are 5V supply. I think i will run into common ground problems with this as my card puts out a 24V supply.

i was thinking more about it and am wondering now if the KL5111 measures frequency, therefore in PLC control would you get some large number like 17000Hz