PWM Proportional Driver and PLC

[jspann7]

Hi everyone,

I been searching through the forums and have not been able to find what I’m looking for.

I have a hydraulic proportional flow control valve which requires 12 VDC, 0.2 to 2.2 amps to operate.
I have a Micrologix 1400 B series which I want to use to control the flow of the hydraulic fluid by the flow control valve.
The applications engineer I was talking to told me I need a proportional driver to control the valve because the PLC is either 0-10V or 0-20 mA (not variable 12 VDC). I hence have an analogue module for the PLC so I can control the flow control valve.

My main issue is how the PLC connects to the proportional driver. I understand the solenoid in the flow valve is controlled by the current flowing through it, but the diagram of the proportional driver shows a DC power supply (power +, power -), a reference and another voltage which looks like it varies a 10k pot (potentiometer?).
I know the proportional driver is a PWM unit, so this must have something to do with it.

I have contacted the manufacturer for some information but have not received a reply.

I have attached documentation proportional driver. View attachment Proportion controller.pdf

The valve (p/n: EPFD-16-N-10-0-M-00) information can be found at: http://www.commandcontrols.com/40905/Products/Proportional-Valves/index.aspx

Please note that I am an undergraduate MECHANICAL engineer so am encountering a steep learning curve with this project.

If any one could shed some light as to how the proportional driver is wired up and therefore controlled by the PLC, I would very be appreciative.

Thanks,

Joel

 

[Peter Nachtwey]

I understand the solenoid in the flow valve is controlled by the current flowing through it, but the diagram of the proportional driver shows a DC power supply (power +, power -), a reference and another voltage which looks like it varies a 10k pot (potentiometer?).

The analog output common goes to terminal 4 and the control output itself goes to terminal 3. Your PLC analog output card replaces the 10K pot.

 

[jspann7]

The analog output common goes to terminal 4 and the control output itself goes to terminal 3. Your PLC analog output card replaces the 10K pot.

Thanks Peter,

A few last questions, just to clarify the wiring: I (i.e. the electricians) will wire the solenoid as shown, the common of the analogue output to terminal 4, and the control output to terminal 3; is a 12 VDC power source just connected to terminal 5? Is terminal 1 used at all? And is the output from my analogue module a PWM output?

Sorry for the additional questions, but this is the only way I'm going to learn.

Thanks in advance,

Joel

 

[BryanG]

Connections:
Solenoid between 6 & 7
12V supply between 4 & 5

Then you need a control signal from the PLC:
The 12V supply and your PLC analogue output have a common minus connection on terminal 4. Common connections from different power supplies can cause problems if they are grounded at different places. Your diagram doesn't showing any connection to GND and so you may well be OK.

The module control signal can either be 0 to 5V on terminal 2, or 0-20mA on terminal 1. You can select either output from your PLC and it will make no difference. The advantage to using the 0-20mA signal is that you can use the full range of the analogue output. If you use the 0-5V input but the analogue output is 0-10V you will only be able to use half scale.

 

[bernie_carlton]

You haven't mentioned the price model number of your Micrologix 1400 but some models (those with 4 letters following the L32) have analog output on the main unit.

 

[jspann7]

Bernie_carlton, MicroLogix 1400 L32BWA is what I am using; it does not have analogue outputs.

BryanG, thanks for the info; however I had already planned on using a 0-20mA signal. I worded my question incorrectly: in the PLC ladder logic, would I use some sort of PWM block to vary the output signal to the proportional controller?

Thanks for your responses.

Joel