BRX BX-04DA-2B Scalling Issue

[DavidS]

BRX BX-04DA-2B
When I set the Scaling in the module configuration:Enable Scaling, Analog Output 1: 0-10VDC, RY1 Min = 0, RY1 Max = 100, WY1 Min 2V, WY1 Max 10V.
We use this configuration to drive 2-10VDC valve motors all the time with Click PLC's
WY1 Min 2V, will not store, it always comes back as 0V.
Running Do-More 2.7.4
OS 2.7.5
Booter 1.0.7
FPGA 1.12
Hardware 6A 3A
BX-DM1E-M-D

Thanks
David

[BobO]

The built in scale uses RYn as the engineering units. WYn is being overwritten by the scaling function.

[DavidS]

So to properly use the scaling, I think I am missing something.
0%-100% is the output of my PID, that I would like to send as a 2V to 10V output signal to my valve. Valve is closed at 2V, and full open at 10V
My understanding was RYn as my engineering unit in %, would be scaled to 2V to 10V in the WYn DC output.
Can you provide some more insight, on how to accomplish what I would like to accomplish.
Thanks
David

[franji1]

Does your PID instruction have .Output scaling enabled or disabled?  If enabled, what are its scaling parameters (Min/Max/To)?
If disabled, do you have a MOVE instruction or a COPY instruction that is copying the .Output REAL structure member of your PID structure to your RY REAL engineering unit analog output register?

[BobO]

Eng unit of scale should be 0.0 to 100.0
Raw should be 6553 to 32767

Since you are using this with PID, you can just put the WY into the PID scale output. No need to use the channel scale in the module config.

[DavidS]

Thanks for the help as we learn the differences between the Brx and the Click, as we do the migration over to Brx. In the Click, we just need to have 0-100 is to 2V to 10V on the 0-10V output module.
We have all the scaling off in the PID. Before we send the PID.Output to RYn, we take some intermediate steps to see if there is a min or max output selected by the user that we clamp to and then move our internal value to RYn.
Thanks for the help. Will be at the site in a day or so, to verify all is good with a meter.

[BobO]

Thanks for the help as we learn the differences between the Brx and the Click, as we do the migration over to Brx. In the Click, we just need to have 0-100 is to 2V to 10V on the 0-10V output module.
We have all the scaling off in the PID. Before we send the PID.Output to RYn, we take some intermediate steps to see if there is a min or max output selected by the user that we clamp to and then move our internal value to RYn.
Thanks for the help. Will be at the site in a day or so, to verify all is good with a meter.

You can do exactly what you did in Click with what I entered in the picture. It sounds like you are doing more than that, but it doesn't need to be more complicated unless you need it.

[DavidS]

I am trying to do the scaling in the BX-04DA-2B, not in the PID.
I tried to set the configuration up in the BX-04 as you suggested with 0%-100% is 6553 to 32767 as 'count', instead of using the Volts output option with 2V to 10V as the scaled range. I still get 0V to 10V on the output terminal of the BX-04.

The reason I do not scale in the PID is that it is not the final say in what the output will be. We provide the user the ability to limit the range of the output (clamp), by setting a min% and max% values. PID.output is moved into a variable called internal_out, we then take internal_out and pass it through a Clamp, where the user defined min% and max% are applied. We then take the output of Clamp which is expressed in % from 0 to 100 which we then pass to RYn, and expect the output to go from 2V to 10V based on the value between 0% & 100% as output from Clamp.

In the click we just pass the 0-100% to the output module and it scales it 2-10V. The scaling takes place just when the value is going out the door, and all our working variables are 0-100% internally. Scaling at the PID output then means any user input that in input in the form of % into the clamp, will need to be scaled to match the PID, which can lead to more errors.

Thanks
David

[DavidS]

Work around fix....
I turned off the scaling for the channel that I needed to output 2-10VDC in the BX-04DA.
We have a task that sends all our internal output values to the ports, this way we can delay outputs at start up, until everything is stable. At this point in the program we added a 'SCALE' that takes the 0-100% input and scales it to 6553 to 32767, and sends the output of SCALE to WYn.
Just wondering why the scale in the BX-04DA-2B doesn't do the same?
Thanks
David

[RBPLC]

Work around fix....

Just wondering why the scale in the BX-04DA-2B doesn't do the same?

If you're coming over from using a Click, there shouldn't be a "work around". The two controllers aren't programmed in the same way because the BRX is exponentially more capable than the Click. The philosophy with PID in the BRX is a "tinker toy" approach where individual items/functions are broken out into individual commands so that the end user can pick and choose what they want to use in order to set up a process exactly how they desire it to be. There are discussions on this forum concerning this software design philosophy. I wouldn't take the approach of programming the BRX like you normally would have the Click. For example, you could use several rungs, a few timers and several bits in the BRX to make a flasher, but why would you when you can just use the FLASHER command.   

[BobO]

Work around fix....
I turned off the scaling for the channel that I needed to output 2-10VDC in the BX-04DA.
We have a task that sends all our internal output values to the ports, this way we can delay outputs at start up, until everything is stable. At this point in the program we added a 'SCALE' that takes the 0-100% input and scales it to 6553 to 32767, and sends the output of SCALE to WYn.
Just wondering why the scale in the BX-04DA-2B doesn't do the same?
Thanks
David

Minor point, but the module isn't doing the scale, the PLC is. And yes, the module config based scale should be capable of exactly the same result as the SCALE instruction. If it isn't, it might be a bug. The PID output scale should likewise be able to give you the same result.

[BobO]

I checked both a BX-08DA-2B and BX-08DA-3 and the driver's scale behavior appears to work as I would expect. I didn't have the -2B looped to anything, but the -3 was, and is what you see in the picture. I configured the scale as RYn = 0.0-100.0 and WYn = 2.0-10.0VDC (6553-32767) and I see 1.997VDC coming back in the BX-08AD-3 it is attached to.

[DavidS]

That is exactly how I tried to set up the 2B and when I try to set the Min to 2V it came back with a value of 0 when I reviewed the setting. It would not take, and just be back to 0 again.
I will try again when back at the site.
Even setting the scale from Volts to Count, and setting the Min Count to 6553, it took the count and was stored, but when I sent 0%, the voltage was 0V and not 2V.
Using the SCALE at the rung where I send the value to the output, works perfectly, just how you set it up 0-100/2-10
Strange.....
Thanks for the follow up.

[BobO]

Was it in RUN mode? Gotta be in RUN mode.

[DavidS]

Just stopped by the site, and tried every permutation of terminal, run, program... and nothing will allow the entered value in the WY1 Min of 2.0 to be stored and retained...