absolute encoder

lacruth · Aug 10, 2009

hi!
I need to install an absolut encoder, I have a slc 5/04, but I don't know what is the right input module I need to add in my chassis to read the encoder information.
Can anybody help me?!!!

kamenges · Aug 10, 2009

It depends on the encoder you are going to use. If it has a fieldbus output (DeviceNet, Profibus, etc) you will need the appropriate scanner card for that network. If you are going to do a parallel digital interface you will need an input module to match up with that. Alot depends on the encoder.

I currently have an application where I use an Encoder Products 725 series absolute encoder with parallel 12-bit Gray Code output. I run this into an Allen-Bradley Flex I/O 16-point DC input module and it works just fine. But my encoder is designed to put out the appropriate voltage level to drive that input card.

Keith

zankorel · Aug 10, 2009

Tell us what encoder you are planning to use, and then we can give advice.

lacruth · Aug 10, 2009

thanks a lot for the response
and i have not the part number for the encoder. all I know is 360 resol.9bit gray code and 10-26vdc npn open collector output.

kamenges · Aug 10, 2009

Just to confirm, is that emcoder output NPN or PNP?

If it is PNP you will need a 1746-IB16. If it is NPN you will need a 1746-IV16.

Keith

lacruth · Aug 11, 2009

It is NPN, so I will try with 1746-1v16

thank you

geoplc · Aug 11, 2009

In order to get the correct pulse counts at high speeds, you should use a 1746-HSCE2 high speed counter card. You will have to get the tech data for your encoder to determine if you will need pull up resistors, whether the outputs are pnp/npn, etc. (some encoders have internal resistors, some do not) You will need this info to impedance match your encoder to the card using the cards tech data compared to your encoder data sheet.

lacruth · Aug 11, 2009

But is really necesary to use a 1746-hsce2 if I have an absolute encoder and not an incremental encoder?

kamenges · Aug 11, 2009

Originally posted by geoplc:

In order to get the correct pulse counts at high speeds, you should use a 1746-HSCE2 high speed counter card.

From the original post:

Originally posted by lacruth:

I need to install an absolut encoder,...

And later:

Originally posted by lacruth:

all I know is 360 resol.9bit gray code and 10-26vdc npn open collector output.

A VHSC will not work with this style of encoder. It is a 9-bit absolute encoder. The VHCS is intended for incremental encoders.

Keith

bernie_carlton · Aug 11, 2009

I think geoplc in his own way is concerned about the toggling speed of the least significant bit. Compare that (ON for two counts then OFF for two counts) to the max speed of the input card and you program scan rate. You may come up with the calculation that every individual change may not be seen. But I don't see any way around it using an HSC card.

As long as your scan rate is much less than one full revolution then you'll have absolute information through that revolution. You can use the MSB as a 'revolution count' trigger for any higher counting.

lacruth · Aug 14, 2009

I just want to say thanks
everyone for your support
the machine is working great right now!!

absolute encoder

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