Here's my first prototype for a DIY binary fan controller:
DIY binary fan controller
The front plate is for an Antec P182 3.5" bay; they'll sell more, ordered by phone. I should have used a stepping bit, for a cleaner 1/4" cut for the toggle switch holes.
The circuit is simple: Each diode introduces a 0.75 V (or so) voltage drop. There are seven diodes in series; note that they alternate directions to facilitate twisting their leads together under the project board. The "yellow, green" toggle switch shorts one diode, the "green, red" toggle switch shorts two diodes, the "red, black" toggle switch shorts the remaining four diodes. So by entering a value in binary from the front panel, one can select eight different voltages, with 000 = 12 - 7*0.75 = 6.75 volts, and 111 = 12 volts.
It took me a while between conception and execution, to get over the idea that using binary toggles was affected. The idea is both simple and natural. My first friend to own his own computer, in 1977, had toggles in front. Perhaps all computers should, in remembrance of their ancestors.
I used 22 gauge solid wire, enough to carry the current of my eight fans, but 20 gauge would have been a fairer fight, twisting together with the very thick diode leads. The design badly needs strain relief for the yellow and black leads leaving the board. I tested the circuit with a separate power source (the test supply wire is to the right) before "going live".
Remember that solder is neither welding nor glue. A "solder free" design, using e.g. the terminal strips sold at RadioShack, could well be more robust than the connections I achieved by twisting and soldering. The longer the better, for the twisted leads under the board, and it takes a powerful soldering iron to contend with the thermal mass of pairs of these diode leads, to make a good solder joint.
For theory behind this and other designs, see Fan Noise Solutions.
DIY binary fan controller
The front plate is for an Antec P182 3.5" bay; they'll sell more, ordered by phone. I should have used a stepping bit, for a cleaner 1/4" cut for the toggle switch holes.
The circuit is simple: Each diode introduces a 0.75 V (or so) voltage drop. There are seven diodes in series; note that they alternate directions to facilitate twisting their leads together under the project board. The "yellow, green" toggle switch shorts one diode, the "green, red" toggle switch shorts two diodes, the "red, black" toggle switch shorts the remaining four diodes. So by entering a value in binary from the front panel, one can select eight different voltages, with 000 = 12 - 7*0.75 = 6.75 volts, and 111 = 12 volts.
It took me a while between conception and execution, to get over the idea that using binary toggles was affected. The idea is both simple and natural. My first friend to own his own computer, in 1977, had toggles in front. Perhaps all computers should, in remembrance of their ancestors.
I used 22 gauge solid wire, enough to carry the current of my eight fans, but 20 gauge would have been a fairer fight, twisting together with the very thick diode leads. The design badly needs strain relief for the yellow and black leads leaving the board. I tested the circuit with a separate power source (the test supply wire is to the right) before "going live".
Remember that solder is neither welding nor glue. A "solder free" design, using e.g. the terminal strips sold at RadioShack, could well be more robust than the connections I achieved by twisting and soldering. The longer the better, for the twisted leads under the board, and it takes a powerful soldering iron to contend with the thermal mass of pairs of these diode leads, to make a good solder joint.
For theory behind this and other designs, see Fan Noise Solutions.
