ok.
i'm building a control circuit to control the array of fans in my PC (i have 12 of the buggers - dont ask!). to control this lot i'm using a VB app ive already 80% coded (needs some tweeks which can only be done when hardware is available). device is to be powered from standard molex power pins (0v, 5v and 12v lines available). communication was to be using the parallel port, but using it serially (as i dont want to wire up so many wires), however i'm now thinking about USB, however i have no idea how to code for, or hardware required for USB. if anyone has any linkage, please fell free to post in this thead, even if it going sideways to this original post.
anyway.
i was thinking of putting some inteligence into the device, such as if no contact from the software after 30 seconds the device goes into "full protection" mode - all fans on 100%, but at the end of the day it doesnt need it - a bit overkilled, besides i have no abaility to program the device - writing the code no probem but i dont have time or money to make a programmer aswell
I have read up about PWM, but ive read in places this is not actually that good - can make fans have a "growling noise" and across 12 fans would be a nightmare esp. when playing doom3 LOL
my idea was first to have each fan connected to 2 relays, so i could put 0V, 5V 7V and 12V across each fan respectivley, but i want a little more control, so i want to use D/A'a to convert an 8 bit number to a voltage with a range from +5 to +12 (a 5V offset). my idea was to plug that voltage via some current buffering straight into the fans - hence my previous question.
if i havent answered what i was asked, sorry! atleast i may have cleared up what i'm doing
given the above project profile, what you tink i should do. do you think PWM is the best way to go, or can a current buffering device be applicable here?
B