Hi all, I'm new to the forum and could really use some help. I learned a smattering of digital and analog electronics when I was a Physiologist but never used discrete components much - mainly simple A/D converters and op amp circuits. I haven't done anything much in electronics for 5 years but I'm getting drawn back in! Now of course I'm over my head, to be expected I suppose
Simple problem -> I have watercooled my computer and have 3 fans on the radiator. I'd like to control their speeds together by modifying their 12V DC voltage but fan controllers typically have too little curent to drive more than one fan. Computer fans effective voltage range is about 7-12 vDC, too low and they stall and you can simply monitor speed using the tach out (open collector 2x/ revolution) from one of the fans so no need for calibration, just need a way to modify the foltage but be able to provide a good 12 watts. (Is this called a voltage folower?)
Simple I thought, take the output from the fan controller and use that to drive a N-MOSFET (which I have never used before BTW). So I made the circuit:
Vcontroller -> Gate, +12VDC to Drain and Source to fan V+
well great, nice current but Vsource= Vout to fan max is about 9.5V with Vgate = fan controller output at about 12.1 VDC! So I'm dropping about 2.6 V across the drain to source??? I really need 12V to 7V as the total range. I don't need to put out voltages < 7V. Help me with a circuit design please, I'm over my head! TIA
Lyle
Simple problem -> I have watercooled my computer and have 3 fans on the radiator. I'd like to control their speeds together by modifying their 12V DC voltage but fan controllers typically have too little curent to drive more than one fan. Computer fans effective voltage range is about 7-12 vDC, too low and they stall and you can simply monitor speed using the tach out (open collector 2x/ revolution) from one of the fans so no need for calibration, just need a way to modify the foltage but be able to provide a good 12 watts. (Is this called a voltage folower?)
Simple I thought, take the output from the fan controller and use that to drive a N-MOSFET (which I have never used before BTW). So I made the circuit:
Vcontroller -> Gate, +12VDC to Drain and Source to fan V+
well great, nice current but Vsource= Vout to fan max is about 9.5V with Vgate = fan controller output at about 12.1 VDC! So I'm dropping about 2.6 V across the drain to source??? I really need 12V to 7V as the total range. I don't need to put out voltages < 7V. Help me with a circuit design please, I'm over my head! TIA
Lyle