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Topic Title: Using AB Micro830 to control servo valve and solenoid valve.
Topic Summary: How does the embedded and analog output work
Created On: 07 August 2012 07:15 PM
Status: Read Only
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 07 August 2012 07:15 PM
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Posts: 11
Joined: 23 July 2012

I am currently working on a thesis on programming a basic process tank, I need to control the servo valve and solenoid valve so that the water can reach the desired setpoint. However, I encounter some problems along the way. The solenoid valve requires a 24volt voltage to be switched on and the servo valve requires a 20mA current to be open. I wired the solenoid valve to one of the embedded output on the PLC and wired the servo valve on the analog output on the PLC.

My questions are
1) Would the embedded output of the PLC be strong enough to turn on the solenoid valve?
2) Where should I wire the solenoid valve onto? Com or O1, O2, O3 ?
3) How do you program the plc to output an analog value to the servo valve from the analog output?
4) Can someone please tell me what is the characteristic of the embedded i/o? EG, if I assign a Boolean "1" on the output what would happen to the com / output?

Thanks in advance =)
 08 August 2012 08:30 AM
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Joined: 25 February 2008

Without wishing to be patronising, you need a liitle hardware design .....

Find out current consumption of the solenoid valve and max. current capability of the PLC digital output.
Why do you regard the i/o as embedded ?
Does your servo vlave require 0-20ma or 4-20ma which is more common.
Does you PLC Analog o/p need a 'loop supply' or is it powered internally.

To program an analog value, the obvious instruction is PID, but does not have to be.
I in the past wrote an algorithm for penstock control which adapted to either digital or analog o/p, and could vary motor speed as example.

Trust this helps
 08 August 2012 08:40 AM
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Hi, I regard the i/o as embedded because its the digital output/input embedded on the plc. The servo need 4 - 20mA current. I can plug 2 plugin modules onto the AB Micro830, so I guess the analog o/p is powered internally.

I thought about using PID but its too complicated I will get into that later in the project. I just want to implement a simple bang bang control. What kind of variable/ block should I use to send out a 4-20mA current from analog output module of my Allen Bradley Micro830 PLC to an external device? I can't find the proper block and I don't know the variable. Is it an integer or real variable? Its not specified on the manual and there is not much sample program that I can look it. Thanks. Is there website where I can read about all this things? I can't find any resources thanks.

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