Voltage controller?

[Daniel Houlton]

rr wrote:
> 
> Dan,
> 
> If you wanted to convert the 5v MAP to a 12v signal, relative, use an
> op-amp. Just use an amp with a gain of 2.4 (12 / 5). Use this in the
> non-inverting configuration. The only problem with this is head-room,
> most amps won't go to the plus rail.
> 
> A better approach might be PWM. Look in the 'incoming' directory for
> the files: PWM2.gif  and PWM2.txt (not sure of the exact case).
> 

Thanks, I just found that on the ftp site this morning.  I think that'll
do what I want.  I got on the ERL site to do some more checking.  They
say the pump is controlled by varying frequency and duration of the controlling
pulse.  In the specs for the pump, they list an Input voltage of around 14V,
Input current of 8A, and a control input of 0-12V @ 5mA(digital).  This 
would be a PWM signal right?  Does the voltage in this case of the control
input matter?  Since the motor has a seperate power source wouldn't a particular
pulse frequency @ say 4V have the same result as the same pulse @ 8, 10 or
12V?

thanks
--Dan