Quadrature Encoder

[apbt.drewyoung]

I have a project with a quadrature encoder. I have a 570 HMI in a remote operator station and all of my PLC connections are in the main enclosure. I am using two IO-DI16 expansion modules, among other expansion modules. Can I use a high speed input from each unit two read the encoder?

[AlexUT]

Yes, you can use it in all configurable modes allowed by specification.

You have no way to reset counter like in snap-in module.

And it will be mapped only to MI.

BR.

[Simon]

With all due respect, I think Alex, you have misunderstood the question.

The IO-DI16 does not support quadrature encoder (Shaft Encoder) inputs. It is only a simple, single-channel, high-speed counter. None of the remote I/O modules support quadrature encoders. There is no way to link two remote high-speed counters to form a single quadrature encoder interface. The only option for quaradture counters is to use one of the inputs on the snap-in I/O, attached to the PLC. For remote encoders you could add a V130 as a remote I/O slave (via CAN, Ethernet or Serial), as all models of V130 suppost at least one Shaft Encoder input.

Editorial Note: The addition of quadrature inputs for remote I/O would be a welcome feature if Unitronics offered it. If a dedicated unit was designed, it should also support the marker pulse (Z) input.

[apbt.drewyoung]

So, are you saying I can't tie each channel to a high speed input and use ladder logic to create a quadrature encoder reader?

[Emil]

In general, you can connect both A & B signals of the encoder and perform the logic in Ladder. But I'mm in deep doubts if this will work with frequency more than 5 Hz.

If this is the case, we can discuss the logic.

[Joe Tauser]

If you're going to do the quadrature decoding in ladder logic then there's no need to use the high speed inputs. You can connect the encoder inputs to any two inputs and write logic to monitor both and see which one goes high first to determine direction.

Emil- if the scan time of the PLC is 10 ms or so then the shortest pulse you can catch is 20 ms, which translates to a frequency of 50 Hz; still pretty slow for an encoder of any resolution.

You really need to add a V200-18-E1B module to the back of the V570 to run the encoder to.

Joe T.

[cmarcus]

I like Simon's suggestion of an encoder expansion module! It would be nice to have the ability to handle 2 encoders simultaneously with (A,B,Z). I also wouldn't mind an encoder output module where you can take two PWM outputs and offset them to simulate A and B channels. Any shot we can get this on the development team's radar?

[Dave]

I also would like to see a dedicated encoder module....don't know if its possible, but with the abiltiy to accept various encoder signal types ( TTL line driver, open collector, etc.)