▓Kick Start Feature ▓
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Kick Start Add-On
As we all learned, majority of pwm fans out there normally can not be stopped (0 rpm) even at lowest pot adjusment (lowest duty cycle setting), but there are few rare breed that has this special capability that is made by the manufacturer like the sanyo denki 9SG1212P1G01.
Now, the problem is when this kind of fan was adjusted to very low speed, like at very near their stopping point, if the controller and the fan went thru power cycle off and then on again, the fan will not start spinning at that particular low adjustment point anymore. This behaviour is normal and expected since the energy level required to start spinning the impeller is much higher than the energy level in maintaining that preset slow speed. Fyi, this kind of characteristic is acknowledged and clearly documented in the standard technical specification of pwm fan at formfactor.org.
Usually in this situation, the owner must manually turn the pot slightly higher than before to start the spinning, and turn back to that slow speed setting again if he needs it spins at that slow speed again as before. This is quite annoying and also at certain situation like the fan is installed at cpu heatsink and the owner didn't notice it, the cpu might get overheated.
So here this "Kick Start" feature really helps, once implemented, when the controller is powered on for the 1st time, it will hit at max duty cycle (100% or 98% depends on which version) for few seconds. This effectively will make the fan rotates at max speed during that initial kick start period, once it ended, the fan impeller at this stage already gained the spinning inertia that enough to be slowed down to the low speed set by the pot before it was turned off.
This feature doesn't hurt too if you're owner of pwm fan that can not be stopped at 0 rpm, just look at it as a nice sound indicator that your fan is still capable of screaming for few seconds if they're those high speed screamer when you powered on the rig for the 1st time.
Btw, this kick start behaviour is also implemented at most server cooling pwm fan, if you watch closely when the server was powered on, during the post period, the server will crank up the fan at max speed for few seconds, usually this is needed for the internal initial diagnostic routine to sense if the fan is still capable of reaching certain speed.
PS: The kick start period can be adjusted as you wish, read the foot note at the pic.
At this new changes, you only need 6 additional dirt cheap components, and a single change in the existing connection at the RESET1 or RST pin from positive line (dotted line) to the new section in the blue shaded area.
If you don't want this feature implemented permanently, you can use a double poles switch to switch the connection at the RESET1/RST pin to postive line like original connection to disable it, or to the new section to enable it, as simple as that.
Thats all, hope this helps.