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Old 04-05-2019, 08:52 PM   #1
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Default Wiring a 10k pot for drive

I am building a panel for a chain conveyor with 3 powerflex 4 drives. Only 1 of 3 will the operator need control. I can wire the pot straight to the drive with no problem but I want to give the operator a read-out in the control station. I have a micrologix 1400 with an IF2OF2 card. My first thought would be to run the pot to the input of the card and use the 2 outputs to feed each the drive and the panel meter. However, I do not have a 10vdc power supply and the meter is 4-20ma loop powered. With the current configuration can someone offer a solution? I can get a 10-12vdc power supply if needed but want to see if itís possible without it first.
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Old 04-05-2019, 09:10 PM   #2
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You can't program it for a proportional 4-20ma. output signal? What about a different (compatible) panel meter? Different output card? Other than that, contact the manufacturer, AB.
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Old 04-05-2019, 09:28 PM   #3
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Over here, like Joe said, we'd also send 4-20mA to the drives analog input for speed control from the PLC.



Otherwise, we'd just use a 3 wire twisted shielded cable and remote mount the pot if you didn't need the PLC/HMI to know the speed reference.
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Old 04-05-2019, 09:31 PM   #4
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You can't program it for a proportional 4-20ma. output signal? What about a different (compatible) panel meter? Different output card? Other than that, contact the manufacturer, AB.
The drive is 0-10v and then pot will need a 0-10v so it would make sense to have 0-10vdc input meter. I wont need to scale and program. I guess i was just curious.
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Old 04-05-2019, 09:37 PM   #5
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Over here, like Joe said, we'd also send 4-20mA to the drives analog input for speed control from the PLC.
I'm not sure I understand what you're saying here. Im guessing you are referencing a different config of mfg's for your drives and output cards. Powerflex 4's from what I understand ONLY use 0-10vdc for its analog input which is provided on the drive.
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Old 04-05-2019, 09:41 PM   #6
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You can't program it for a proportional 4-20ma. output signal? What about a different (compatible) panel meter? Different output card? Other than that, contact the manufacturer, AB.
I just looked at the side of the card and it says the output ranges include 0-10vdc and 4-20mA, any info on that?
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Old 04-05-2019, 09:46 PM   #7
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I just looked at the side of the card and it says the output ranges include 0-10vdc and 4-20mA, any info on that?
I'd have to reference the manual, but sounds like you're on the right track. How are you at programming?
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Old 04-05-2019, 09:49 PM   #8
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I'd have to reference the manual, but sounds like you're on the right track. How are you at programming?
I can write ladder and scaling
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Old 04-05-2019, 10:07 PM   #9
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Originally Posted by TheDude_Abides View Post
I'm not sure I understand what you're saying here. Im guessing you are referencing a different config of mfg's for your drives and output cards. Powerflex 4's from what I understand ONLY use 0-10vdc for its analog input which is provided on the drive.

The manual will show which terminals accept 4-20mA analog current input signals.



I just happen to have a PF4 quick start guide near me, it's terminals 14 and 15.
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Old 04-05-2019, 10:11 PM   #10
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The manual will show which terminals accept 4-20mA analog current input signals.



I just happen to have a PF4 quick start guide near me, it's terminals 14 and 15.


THANKS!
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Old 04-05-2019, 10:13 PM   #11
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Problem #1 is that the PF4 is meant to be a very inexpensive drive, so it does not have a built-in analog output that you can use to tell how fast the motor is going. So the best you can do is to see what you have TOLD it to go at. Whether or not that reflects the actual speed is a matter of the motor performance.


You could use a better drive like the PF523, it has an analog output that can be 0-10V or whatever your meter needs, and you can scale that output to be a percent of the actual motor speed, not the signal you are giving it.


If you are stuck on the PF4s though, I have used these pots from Electro-Sensors that have their own built-in display that tells you the setting of the pot.


I liked them for what they are. They mount with one small hole through the panel that the wires pass through. They need power, but only use about 3mA so you could power it from the +24VDC terminal of the VFD (it can handle 100mA max.). You can make your own scale units, so for example I made mine 0-100 as in 0-100% speed.
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Old 04-05-2019, 10:40 PM   #12
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The manual will show which terminals accept 4-20mA analog current input signals.



I just happen to have a PF4 quick start guide near me, it's terminals 14 and 15.
So with that being said, could I not, in theory take the common to the pot and reutrn the output and ground to the PLC card?
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Old 04-06-2019, 12:17 PM   #13
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Just use 1 pot for the 3 drives. 12 to pot from 1 drive and other 2 wires to 13 and 14 on all drives. That's about as simple as you can go. I'd go a different route completely, but you sound like your wanting a cheap solution.

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Old 04-06-2019, 12:40 PM   #14
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Just use 1 pot for the 3 drives. 12 to pot from 1 drive and other 2 wires to 13 and 14 on all drives. That's about as simple as you can go. I'd go a different route completely, but you sound like your wanting a cheap solution.

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So here’s what I am wanting to do...

The operator only needs control of 1 of the drives. I have a pot in the control station for said drive. I want to be able to put a panel meter in the control station with a scaled reading of let’s say 0-100%. The panel meter is a 4-20ma loop powered device. I can’t just put it in series with the pot through the drive because I would like to scale the display. The if2of2 card on the ML1400 has a 0-10vdc or 4-20mA input AND output option that is set in the IO config of RSLogix500. The problem I am having currently is that I can feed the pot into the PLC and scale it but my outputs aren’t working. My input is 0-10vdc and I am wanting channel 0 to push 0-10vdc to the drive and channel 1 to push 4-20mA to the display. However, I am not getting anything on my outputs when I download. While monitoring the program the SCP is reading the input and the output is scaling it right, but the panel meter won’t so much as flicker on. I have checked the meter with a 4-20mA driver so I know it works....
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Old 04-06-2019, 07:27 PM   #15
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I figured it out. I just tied my SCP to an F8 bit instead of directly to the output channel on the card. Then F8 to the channel 0. Downloaded and the meters came on. Then I just had to play with the scaling on the meter.
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