Spotted this thermal-controlled 80mm case fan in the local shop, £6 so I got one. Their site's a bit low on detail, so a few thoughts. Sensor comes on a 6" lead, fairly big disc thermistor. Fan had double 4-pin molex connectors, no speed wire. Came with 4 screws. Speed 1000rpm @ 23C, straight-line rise to about 2250rpm @ 40C, (1500rpm @ 30C) top speed 2500rpm @ 45-50C. Air flow at 2500rpm estimated at 33cfm, so at 23C its no more than 13cfm. Very quiet cold, but there's a faint fast clicking noise, most odd. A PWM effect? I'd hoped it would be good for a psu fan swap, but the flow is really too low to be much use, its like 7-volting a Panaflo L1A. I can't see much in the case that would get the fan up over 30C, unless I set it to cooling the hard drives with the sensor taped to the hottest. Antec are doing a case Smartfan, their 45cfm top speed flow looks more useful. As is the Papst 8012NGMLV.
Better idea. The thermistor is a TTC123, 120K @25C, B=4050. So R @ 20C=15k, R @ 50C = 4.2k. Cut the thermistor off, connect instead a 10K pot and 4k7 resistor in series, you've a PWM controller and fan for under £7.
