This isn't a question so much as an answer (for once).
I've known for a long time that Dell fans had an internal speed control, based primarily off a green or blue blob (almost certainly a cheap thermistor) that's in the airflow of every single Dell fan since basically Day One.
I've never really investigated that green blob. I've known two things about it... one, it's a temperature sensor of some sort; and two, it is The Thing Of Electronic Damnation Which Makes Dell Fans Not Work In Regular PCs. A pity indeed on the second one -- Dell fans are fast as shit when they get going. But they always seem to behave the same -- spin up fast for ~5sec and then quiet down to almost nothing.
Today I dragged out two fans. One, a Datech fan from one of several systems (it's Dell's P/N 7G538, for two Optiplex models, four Dimensions, and a trio of Precisions) and the other, a Minebea/NMB blower that happens to be from a P4 Optiplex (the matching heatsink is marked 7P182) although that particular heatsink and fan is a VERY popular item in SFF P4 Dells...
I didn't care about wrecking the Datech fan, I've got at least five more just like it but I've only the one NMB blower so I wanted to test my theory on the Datech first. What theory? Having looked up thermistors on Wiki I had a vague idea of how they work -- just enough to get an idea. Seems that, generally speaking, as a thermistor gets hotter, it conducts electricity more easily. So: short the two bare leads on the green (or blue) blob and the fan should spin up enough to levitate off the desk (OK, I exaggerate, but only slightly!).
I took the wires off the weird shit Dell connector for the Datech fan, leaving the pins intact. Then I shoved the red and black wires into a spare drive-testing "molex power supply" that I'd received courtesy of eBay some time ago. (Alas, it's one of the new ones that's 2a per rail rather than 2.5a per rail. Oh well.) Plug in the supply and the fan cuts on. Put a flathead screwdriver across the two leads for the green (in this case) blob, and HOLY SHIT THAT'S SOME FUKKIN' WIND COME OUT THAT FAN. Same thing happened with the NMB blower. You could blow moon dust to Earth with this thing. Dell makes some serious fans!
Lazy ass that I am I came up with a nifty trick for solderlessly joining the two wires as well. In the NMB blower, the thermistor is on a little pair of wires, and the leads do a 90deg angle into a spot where the blower rotor isn't. This is under a bit of black paper tape. So: peel back the tape, wiggle the blue (this time) blob out and cut it off, bend the leftover leads straight, and as it turns out they're about the size of pin header pins, so I stuck 'em into a spare CD drive jumper and added a generous helping of electrical tape. Since I didn't need it, I cut off the white RPM line from the cable as well.
For once I'm not bothering with pix, it's just a Dell blower fan with a couple extra lumps of electrical tape
Now I have a blower that's "strong like bull" for next summer's exercise walks. Trouble is it's got a 1.34a rating on it I'll figure a portable power source out later... I think I've got plenty of time for that indeed.
Anyone else with a spare Dell fan or three, who comes across this -- now you know how to harness the power in these fans for yourself Have fun but be safe...
I've known for a long time that Dell fans had an internal speed control, based primarily off a green or blue blob (almost certainly a cheap thermistor) that's in the airflow of every single Dell fan since basically Day One.
I've never really investigated that green blob. I've known two things about it... one, it's a temperature sensor of some sort; and two, it is The Thing Of Electronic Damnation Which Makes Dell Fans Not Work In Regular PCs. A pity indeed on the second one -- Dell fans are fast as shit when they get going. But they always seem to behave the same -- spin up fast for ~5sec and then quiet down to almost nothing.
Today I dragged out two fans. One, a Datech fan from one of several systems (it's Dell's P/N 7G538, for two Optiplex models, four Dimensions, and a trio of Precisions) and the other, a Minebea/NMB blower that happens to be from a P4 Optiplex (the matching heatsink is marked 7P182) although that particular heatsink and fan is a VERY popular item in SFF P4 Dells...
I didn't care about wrecking the Datech fan, I've got at least five more just like it but I've only the one NMB blower so I wanted to test my theory on the Datech first. What theory? Having looked up thermistors on Wiki I had a vague idea of how they work -- just enough to get an idea. Seems that, generally speaking, as a thermistor gets hotter, it conducts electricity more easily. So: short the two bare leads on the green (or blue) blob and the fan should spin up enough to levitate off the desk (OK, I exaggerate, but only slightly!).
I took the wires off the weird shit Dell connector for the Datech fan, leaving the pins intact. Then I shoved the red and black wires into a spare drive-testing "molex power supply" that I'd received courtesy of eBay some time ago. (Alas, it's one of the new ones that's 2a per rail rather than 2.5a per rail. Oh well.) Plug in the supply and the fan cuts on. Put a flathead screwdriver across the two leads for the green (in this case) blob, and HOLY SHIT THAT'S SOME FUKKIN' WIND COME OUT THAT FAN. Same thing happened with the NMB blower. You could blow moon dust to Earth with this thing. Dell makes some serious fans!
Lazy ass that I am I came up with a nifty trick for solderlessly joining the two wires as well. In the NMB blower, the thermistor is on a little pair of wires, and the leads do a 90deg angle into a spot where the blower rotor isn't. This is under a bit of black paper tape. So: peel back the tape, wiggle the blue (this time) blob out and cut it off, bend the leftover leads straight, and as it turns out they're about the size of pin header pins, so I stuck 'em into a spare CD drive jumper and added a generous helping of electrical tape. Since I didn't need it, I cut off the white RPM line from the cable as well.
For once I'm not bothering with pix, it's just a Dell blower fan with a couple extra lumps of electrical tape
Now I have a blower that's "strong like bull" for next summer's exercise walks. Trouble is it's got a 1.34a rating on it I'll figure a portable power source out later... I think I've got plenty of time for that indeed.
Anyone else with a spare Dell fan or three, who comes across this -- now you know how to harness the power in these fans for yourself Have fun but be safe...