How to configure the unmapped encoders without using MAX?

[sidda]

Dear Sir,

We are using the NI PCI-7352 Motion card. In this we need to use 2 encoders for each axis. One for feedback(mapped) and other one(unmapped) is for external purpose. How to configure the unmapped encoders without using MAX?

[jamrite]

Hello,

Generally, motion controllers only have one encoder input per axis. If you had a 4-axis controller (and were using only two axes) then  you could potentially use the unused encoder inputs for the second set of encoders.

Encoders themselves, have a fixed number of steps per revolution and standard output formats. The configuration options in MAX only let you specify how to read them. If you have the documentation for your encoder, you can use it to configure any piece of equiptment that reads the encoders.

Thank You,

Jaidev Amrite

Applications Engineer,

National Instruments

[sidda]

Dear Jaidev Sir,

As I have mentioned earlier we are trying to use 2 encoders for each axis (One as a feedback and other as an external input).

When I configure the unmapped encoder say encoder 3 using "enable encoder.flx"  function and trying to read the encoder by calling the "read encoder.flx" function(for encoder 1 and encoder 2 are already been assigned to axis 1 and axis 2 respectively), an error message is displayed stating "the encoder is disabled, Please enable the encoder".

Can you please help me out.Waiting for your reply.

Thanking You,

With kind regards,

Siddu

[jamrite]

Hi Siddu,

The PCI-7352 is a two axis controller and hence has only two encoder inputs. As I had mentioned before, you would need a four axis controller to have two encoders per axis.

Can you tell me why you need two encoders per axis? Unless they are different resolutions (steps per revolution), they are generating duplicate information.

-Jaidev

[sidda]

Dear Jaidev Sir,

Let me put it this way.

Can we use an incremental encoder individually without coupling it to the motor so that we can read this encoder for only reading the steps per revolution (or counts).Is it possible with the 7352 (2 axis controller).  

Thanking you,

With kind regards,

Siddu

[Jaidev]

Hi Siddu,

Yes, you can use the digital inputs on the card to read in the encoder inputs.

If you are using one encoder to complete the feedback loop, are you using the other to read in only the encoder counts per revolution?

If you are using the card in stepper mode then you can configure the controller to run in open loop mode but still read in the encoder data. Please let me know if this applies to you.

Jaidev

[sidda]

Hi Jaidev Sir,

Yes, you are exactly right Sir. We are using one encoder to complete the feedback loop and the other encoder to read in the encoder counts per revolution only.

But we are using the card in servo mode and configured the controller to run in closed loop mode. But we are already using the digital inputs on the card for some other purpose.

Still we tried reading the encoder counts per revolution using NI-6229 (Daqmx card).But could not succeed.

Thanking You,

With kind regards,

Siddu

[Jaidev]

Hi Siddu,

Have you tried using the Read Encoder.flx on the axes that are configured? Please look at the example "One-Axis Move with Position Monitor.vi". This example moves one axis through a fixed number of steps, gets position from the encoder and displays it on the front panel.

You can find the example in the Example Finder (Help>>Find Examples...) at

Hardware Input and Output>>Motion Control>>Straight Line Move

Please let me know if this was what you were trying to accomplish.

Jaidev