4-20ma speed control with Micro1400

[mdprice55]

Just getting started with programming and playing around a bit with some equipment we have here at work.

Here is what I have:

Banner Ultrasonic Sensor w/ analog output
Micrologix1400 w/ 1762-IF2OF2 module
Conveyor controller (proprietary) with a 4-20ma speed control input

Here is what I am trying to do:

Control the speed of the conveyor dependent upon the level of product in the conveyor.

So far I have used an SCP instruction to scale the signal from the sensor. I can now tell how much product (in inches) is in my conveyor.

Question is: How do I translate the incoming signal from the sensor, to an outgoing 4-20ma signal to the speed controller?

I am looking for a few nudges in the right direction.

 

[iant]

the speed controller, MFG?, can be set so the 4~20 mA signal tells the drive to operate between the variable that are set in the drive.
The level is then calculated in the program
use the SCP instruction for the output say 0~100% 1" = 10%
3" = 100% for an example

 

[iant]

just a side note
know you use feet and inches
If you use Millimeters (25.4 mm / inch) all the calculations are decimal
the visual scale can be kept in Inches

 

[Lancie1]

How do I translate the incoming signal from the sensor, to an outgoing 4-20ma signal to the speed controller?

Take the same incoming signal (that you already scaled to display inches of product on conveyor) and send it to a PLC PID block instruction (that will have a Setpoint Input in Inches where you set the desired product depth on the conveyor), then pass the PID Control Variable output on to your proprietary conveyor controller, by scaling the PID output with another SCP and sending it to a PLC 4-20mA analog output for your proprietary conveyor controller.

That assumes that your proprietary conveyor controller does not have a built-in Setpoint input and PID output (you didn't say- top secret I suppose). If it does, then simply pass the 4-20 mA raw signal through to the controller by either hard-wiring it in series with the PLC input, or passing it through the PLC to an analog output.