I'm using a Matrix Orbital LCD but it can only provide 1A @12V (5V also available). I started searching for a circuit which could supply the fans, but with the 12V (or 5V) from the LCD as a signal. This way the lcd doesn't have to provide the power for the fans, but the psu has to do it.
I searched for amplifiers, opamps, etc. but haven't found anything useful.
Most circuits i've found use a variable resistor to control the speed of the fan.
I'm thinking of a transistor/mosfet circuit, but i don't know what type nor the other parts i need
in short:
needed :
variable 0-12V @3-4amps (for fans)
available:
fixed 12V (from PSU)
variable 5V and 12V from LCD (but low current)
thanks
Hekke