AB Micro850 Using 2080-MOT-HSC

[RGriffin]

Good day,
I have a micro 850 with a 2080-MOT-HSC that is being fed by two flowmeters, Schneider Electric using IMT31's as converters. They are sending pulse signals via D/D-. I currently have them wired to the HSC via A/A- and B/B-. I am not sure if I need to have 24VDC and 0VDC on the O/O- connections and if there is anything to connect to the Z terminals. The flowmeters are working but I am not getting anything through the HSCE_CFG or HSCE blocks in the logic. I am attaching my wiring and the code. Any help is greatly appreciated. The code is not complete. I stalled at the flowmeters.

 

[drbitboy]

I don't know if it makes a difference, but I tied my A- and B- to the -24VDC at the main power terminals. I was able to drive the 2080-MOT-HSC with the PWM/PTO outputs of a MicroLogix 1100 that its -24VDC connected to that same -24VDC.

Your code was not attached, but I remember the HSC instruction was a bit fiddly to get the right combinations of input parameters to get it to count. It also has to be configured in the main PLC tab ("Micro820"). There are plenty of youtubes; the one by @Tim Wilborne should get you going.

 

[RGriffin]

My flowmeters are passive if that matters so I have to source 24. Did you tie the 24 in with the wires from the source or connect those somewhere else? Should I run my signal wires to a couple of terminal blocks with power connected and then to the A and B positive? I am afraid of damaging the controller.

Trying to attach file again. The manual is unclear as to the input wiring.

 

[RGriffin]

I have added this to the logic , have a Schneider Electric flowmeter IMT31 converter using D/D- pulsed output going to the 2080-MOT-HSC. I have configured exactly as stated in the submission but it is not reading. I have flowmeter one D/D- connected to A+/A- and flowmeter 2 connected to B+/B- but they are not reading the signal input.

Am I missing a connection?

the pulse output is ‘passive’, or externally powered , meaning you must power the loop from the PLC

 

[Old Man]

You've got an OUTPUT on the last rung with NO VARIABLE, I don't think your program will even run.

 

[RGriffin]

As I stated, code is not complete, stalled at flowmeters. And not all code is provided due to proprietary and not relevant ant to support questions.

 

[drbitboy]

Caveat: I am a hobbyist and not an electronics tech, so you should think long and hard about what I write here.

That said, DC is fairly straightforward.

First of all, instead of using the HSC, you can check the HSC inputs directly in the PLC program using __IO_P1_DI_00/_01/_02 (A/B/C)to see if a +24VDC discrete signal is detected.

I was using the MicroLogix 1100 output to drive A+, so that setup was active i.e. MicroLogix provided the +24VDC.

I assume your passive IMT31A is wired summat like the examples in the image below, yes? The approach (on the left) in the IMT31A manual is essentially a voltage divider, with

• A- at 0V
• Fixed resistance between A- and A+
  • This could also be called a pull-down resistor, no?
• The IMT31A "resistor" between A+ and +24VDC
  • IMT31A's D- connected to A+
  • IMT31A's D connected to +24VDC

So A+ measures/detects the "divided" voltage between the "resistances" as the IMT31A's "resistance" varies between ~∞ and ~0.

This is Physics/EE 101/102, right?

The approach in the red box on the right is based on the A-B manual; the fixed-resistance R could also be called a pull-up resistor, no?

I am afraid of damaging the controller.

The A+ can take a +24VDC signal when A- is at 0V. The fixed-resistance resistors are a current limiters in both examples, but the 2080-MOT-HSC has an impedance of ~3.6kΩ, so I suspect the resistors in the image above are unnecessary; removing the resistors makes the circuits identical. I know I have tested the HSC by touching a bare wire from +24VDC on the Micro820 to A+ with no ill effect (maybe a small spark).

​