PLC Production Line Control

antjon1

Member
Join Date
Feb 2006
Location
Tennessee
Posts
29
OK, I've been trying to figure out on my own how I would setup a PLC control system for some of our production lines at work.
There are several converyors on the line, all hydraulically powered. Also, there is a mixing machine that pumps product onto the line. Another machine on the line uses hydraulics for its motors as well, but has flow control valves to control speed. Finally, there is a fryer on the line that is mostly hydraulic, but has a few AC motors attached to oil pumps. The heating is contolled by 2 TCUs, and uses electric heating (2 radiators). There are also 2 machines per line at the start of the line that are already conteolled by PLCs (a SLC 5/05). I figured that sol. valves could be put on the conveyors, and the fryer wouldn't be hard to convert. I would probably use a PanelView for the operator to control the line. My questions are:

1. How would you interface the line controller to the SLC in the first machine?

2. How could you keep the speed control on the other machine?


Like I said, I'm just trying to figure this out to satisfy my own curiosity. I'm not working on this project (there is no such project, actually), and honestly, I don't think that proposing hte idea to management would go anywhere.

Thanks!!
 
Antjon,

1. Machine motors are interfaced by using low-voltage control circuits. The control circuits can be 120 volts AC, or 24 volts DC or almost anything in between, but those two are very common in the US. The ZPLC controls (turns on and off) the control voltage, which in turn controls the motor "starters", which are specialized relays that have a low voltage mnagnetic coil and a higer-voltage switch that is activated by the coil.

2. PLCs can have analog output modules, which generally have either 4 to 20 miliamp current outputs or 0 to 10 volts DC outputs. THese outputs are sent to a flow control valve that has a transducer that converts the signal back to some usable function. There are many types of control valves. One type is air-operated and a 0-10 volt signal causes the air to move the valve from fully closed to fully open. Another type has a small electric motor (either AC or DC) and a control circuit that moves the valve from fully closed to fully open in response to an input signal.
 

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