Analog output logic

stevespra · Apr 15, 2008

I have a micrologix 1100 and need to control the speed setting to a VFD with a 1762-OF4 output card. I can't seem to get anything to transfer to the output address. I am using a scale w/parameters with the input source set as the HMI and the destination source set as the output addrsss. However, nothing seems to work. Any ideas?

curlyandshemp · Apr 15, 2008

stevespra said:
I have a micrologix 1100 and need to control the speed setting to a VFD with a 1762-OF4 output card. I can't seem to get anything to transfer to the output address. I am using a scale w/parameters with the input source set as the HMI and the destination source set as the output addrsss. However, nothing seems to work. Any ideas?

Have you configured the output from the I/O configuration?

Kev77 · Apr 15, 2008

What is your min and max and what is your scaled min and max? Is the rung true? If this is a new subroutine, is it enabled?

stevespra · Apr 15, 2008

Yes. If I am online with the laptop and just enter a number to the output, it will change speed on the drive. So it seems that the output is configured right (4-20) and wired right to the drive. I just can't get the number to the output to change any other way, like from the HMI. Thanks

stevespra · Apr 15, 2008

The input min is 0 and the input max is 3474 (motor rpm). The scaled min max is 0 and 32767. The rung is true and it is not a subroutine. Thanks

Kev77 · Apr 15, 2008

What hmi are you using? If it is a Panelview +, you can't brouse for tags unless you have the correct version installed. I ran into the same type of problem with a PVP 600 and a ML1100 over ethernet. I had to hand enter the tags because I couldn't brouse for them. My problem was the tag address was Mixer_1 on the buttons and was Mixer[space]1 in Linx enterprise. "Mixer[space]1" ended up being "Mixer1" Make sure the tag information is set up correctly and Linx enterprise is set up correctly. Can you brouse for tags?

stevespra · Apr 15, 2008

The HMI is a automation direct c-more 8" touch panel. It is using AB DF1 Micrologix protocol. I have tried using integers and floating points, which work fine for displaying the analog inputs but this is the first time I have tried controlling the speed with one of these.

Kev77 · Apr 15, 2008

Can you make a digital button on your screen and tie it to a bit? If you can't get the bit to change state, you have a comm setup problem

ndzied1 · Apr 15, 2008

Is your SCP instruction in a part of the program that is being scanned? If it is not in LAD2, you must have a JSR to the proper ladder file somewhere that will get called.

stevespra · Apr 16, 2008

The scp ladder is in the same program. I made it just like the analog inputs that I am using. Does the ML1100 support analog output?

Mickey · Apr 16, 2008

stevespra said:
The scp ladder is in the same program. I made it just like the analog inputs that I am using. Does the ML1100 support analog output?

HMMM?. You said in post#4 that the output worked, yes the ML1100 supports analog outputs. It sounds like the problem is with your HMI not writing the speeed value to the ML1100.If you can post you ML1100's code (.rss file, zip it then post) then someone can that a look. Also tell us the data file address the HMI is writing to (i.e. N7:0 or ?)

Electrically_Bound · Apr 18, 2008

I think you are trying to troubleshoot too many things at once. Forget about the HMI and see if you can simply get an ouput by "plugging in" some number.

Also check to see which device sources the 4-20 loop. Only one device can supply power to the 4-20 loop.

olman_plc · Apr 18, 2008

Hello.

I need one analog_output of 0 to 20Vdc, for compact_Logix.
Do you have some solutions??.

thanks and best regards.

robertmee · Apr 18, 2008

olman_plc said:
Hello.

I need one analog_output of 0 to 20Vdc, for compact_Logix.
Do you have some solutions??.

thanks and best regards.

I would use a 0-10VDC analog output and an external signal transducer that accepts 0-10VDC in and sends 0-20VDC out. Something like a Weidmuller Wave TTA.

Another approach and one I've never tried and may not work (hopefully someone will chime in yay or nay) is to take two ISOLATED 0-10VDC outputs and tie them in series for a combined voltage of 0-20VDC.

rdrast · Apr 18, 2008

robertmee said:
I would use a 0-10VDC analog output and an external signal transducer that accepts 0-10VDC in and sends 0-20VDC out.

Another approach and one I've never tried and may not work (hopefully someone will chime in yay or nay) is to take two ISOLATED 0-10VDC outputs and tie them in series for a combined voltage of 0-20VDC.

[Thread Hijack Response] I'd vote Option 1, though, if you have a very high impedance 0-20VDC load, it might be possible to generate by using a 0-20mA output into a 1K resistor.

For the ORIGINAL POSTER, and the ORIGINAL PROBLEM... You aren't trying to write drirectly from the HMI to the Analog Module output word, are you? You seriously need to write to either an internal register in the PLC before the SCP.

Analog output logic

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