Proportional valve control card

[Moustafa Elsherief]

Hello every body

I have old machine using some of very old proportional valves.....

one of these valves control card is damaged and no one can repaire

I want to use the machine PLC "S7-300" to control the valve instead of the card....

where the valve max current 800mA and AO can deliver 4-20mA

could anybody suggest any kind of amplifier or idea?
B.R

 

[Tom Jenkins]

Assumng this is electric and not pneumatic:

In the past I have encountered occasions where analog valve control wasn't working for various reasons. I have bypassed the positioner card by disconnecting the wiring between the card output relays and the contactor that moves the motor. Then I connected discrete outputs from my PLC directly to the valve motor contactor. You just keep jogging the valve motor until you get the process variable or valve position you are looking for.

 

[moggie]

http://www.highcountrytek.com/products/dr/drf.htm

 

[MasterBlaster]

Assumng this is electric and not pneumatic:

In the past I have encountered occasions where analog valve control wasn't working for various reasons. I have bypassed the positioner card by disconnecting the wiring between the card output relays and the contactor that moves the motor. Then I connected discrete outputs from my PLC directly to the valve motor contactor. You just keep jogging the valve motor until you get the process variable or valve position you are looking for.

+1 for this. In addition to working well, it eliminates a potential point of failure (the built-in card).

 

[shooter]

as it is probably a magnetic valve on 24 Volt, i have made a controller for this with an arduino and a FET.
Just to keep the cost low.
there are commercial valvedrivers available.