Analog Output

DEAR SIR
ANALOG OUTPUT 0-10 VDC ITS FROM ANALOG OUTPUT DEVICE OF SIEMENS 7 200 AND MY PROJECT TO CONTROL PLASTICI NJECTION MACHINE AND IT HAVE PROPORTIONAL VALVE ONE FOR PRESSURE AND SECOND FOR FLOW SO EVERY MOTION IN MACHINE NEED SPEED AND PRESSURE SPESIALLY. SO PLC GIVE ME 0-10 VDC BUT THE VALVE WORK ON 0-24 VDC AND MAX 2 AMP. SO I NEED TO TREAT THIS VOLTAGE TO BE SITUBAL FOR LOAD ,

THANKS ALOT

Don't take this the wrong way, but first learn some punctuation.
It will make your posts easier to read.
As to the problem in hand.....
There used to be a device available from Radio Spares that could do this, it was a DC motor controller, but I can't seem to find it anymore. You could look for DC motor controllers from somewhere else, these could probably give you what you want.
Another method would be to use and ordinary 24V output from your PLC, run it through a high speed switch (optocoupler or transistor) and drive it from your PLC's built in PWM generator. Of course you will have to check to see if the PWM base frequency is high enough. And there is also the problem that not all PLCs have this function built in.

Hope this helps

Doug

Do a web search for "proportional amplifiers." You will find plenty of devices that will do exactly what you want.

The manufacturer of the valves you are using should also be able to point you in the right direction.

Kevin

Programming languages

Sir:
I am new to this very interesting and informative site
What are some of the common programming languages used for PLC's
I was under theimpression that companies such as Johnson

Programming languages

Sir:
I am new to this very interesting and informative site
What are some of the common programming languages used for PLC's
I was under theimpression that companies such as Johnson HAVE their
own language to prgramm their controllers Thanks

Not fast enough

The S7-200 is a very good PLC, but it is not fast enough to control the pressure transients that occur in an injection molding machine.

Even Siemens has special versions of S7-300s for their injection molding machine applications and these include special injection molding cards.

If it were possible to control an injection molding machine with a lone S7-200, Siemens would be selling S7-200s for injection molding applications right now.

Johnson control, Bristol Babcock, and other DCS (Distributed Control System) vendors do have proprietary languages. These are not truly PLCs, and their products have developed over the years to serve specific HVAC (Heating, Ventilating, and Air Conditioning) and process control markets. Some of them, particularly in newer models, support ladder logic, which is the most common programming system for PLCs.

Peter,

It really depends on the hydraulic circuit.

If the circuit uses a single valve for speed AND pressure (force) control, then you are correct in that most PLC's are not fast enough and/or lack the sophistication required for the mode change.

But if the hydraulic circuit is very elementary, meaning it uses a simple proportional valve for open loop speed control, and a simple proportional relief valve for open loop pressure control, then almost any PLC can be used. The PLC becomes a source of simple preset analog commands.

My gut feeling is that MNJO5 doesn't fully understand what he needs in the way of electrical hardware. He really needs to check with the valve manufacturer to determine what type of 'valve driver' electronics are required.

Greg Gauper said:

Peter,
But if the hydraulic circuit is very elementary, meaning it uses a simple proportional valve for open loop speed control, and a simple proportional relief valve for open loop pressure control, then almost any PLC can be used. The PLC becomes a source of simple preset analog commands.

Click to expand...

Yes, you know I know that. I don't consider a relief valve as being capable of pressure control, just pressure relief.