mo0K

hi cheers for your input, i do realy want a progressive change of speed proportional to the difference of the two thermisters though, could the difference in resistance adjust the pulse width modulation..? ???

hi'ya Alun.. i have two Delta 120mm 4000RPM 190CFM 3A fans for a 240mmx120mm rad in my watercooling system on my computer, they sound like a jet engine..!!, LOL, now i want the be able to set the base level the fans run at (with a POT) also i want two temperature sensors, i want one to monitor the room temp and the other to monitor the water temperature, now if they are the same temperature i want the fans to run at the set base level, but if the water temp goes up when compared the room temperature i want the fans to go up by say a volt a DegC (but would like adjustment on this really too), do you see..? i didn't want to pulse modulated circuit as i find brushless fans are modulated and if you run them on a modulated source the double modulation makes them noisier, but i now don't know if i want to waste power and make heat using transistors and it might be easier to get the control i want from a modulated circuit... what do you think.... cheers mo0K ;D

???, ,er.. i guess as i'm not getting any relpys, no one can help..?? if so and some one could help with just getting a POT to control a transistor that can handle 12v 3A (or a pair), or 12v 6A, if some one could tell me if the circuit below would do fine for a simple speed controler, and if so which components would do the job..? thanks.. although pulse modulation with a 555 could make it easier to set the V to degC, ?

or maybe i could use a

Hi, i have a circuit i am trying to design and although i fear you are asked the same questions about power supplys over and over i feel my problem has differences that i wouldn't just find, so hope it's ok to start another thread about power supplys. the brief, to run two 12v 3A 120mm fans from a PC 12v/5v ATX molex connector, the circuit would have two thermistors, one reads the room temp (T1) and the other reads coolant temperature (T2), there needs to be a POT to set the output when the thermistors match resistance, but if T2's temp goes up so will the voltage output (and another POT would set the amount of V per deg C),