Pc controled fluid selector

[nanopoylos]

HI

I would like to construct a device wich will have a motor,20 inputs of fluids and an output.

The pc will have a programm to tell to the device wich fluid must be connected to the output each time and for how long.

The selector will be in circle shape , on the one side the inputs , in the center the motor , and to the other side the output.

The pc must know the position of the selector any time , and the pc must know when the selector is beeing "locked " to each output .
The pc must be able to tell the selector where to go toconnect the correct fluid to the output.

So, how should i do this?
Do i need a step motor?a servo?
How will the pc able to know the position of the selector?
What programm should i use? What language?
Some people told me about plc's , others for pic's , others for just rele's .
THNX

[MP]

You can control the motor directly from the PC. A stepper would be easy but you would need some type of feed back circuit to tell you where you really are. This could be opto switches, etc. The other choice would be a servo motor with the internal feed back which always knows the position. The part from the PC is a simple matter of sending pulses from the PC port to the motor. There is no reason to use a microcontroller or plc if you are using a PC to control this circuit. You should research motor control from a PC.

MP