[TriEmbed] laptop fan motor control question

[Pete Soper]

You are about 99.999% likely to be right. 😀 I haven't looked at that third lead yet with a 'scope as I told John I would by email yesterday, but for my application I can use an old style thermostat to power both fan and pelletier devices on and off. I don't think I have to care about the .0001% chance this is some outlier design.I was mostly ignorant about these fans and how many flavors there are, not thinking right about the high resistance, not wanting to blow the thing up, conflicted about the third wire being tach or control, etc.As I shared with you, the last "weird motor" I encountered was from a server disc drive with just three windings in series.I didn't include yesterday that I learned in the hardest way imaginable how difficult it is to control such a motor without arranging to sense the back EMF the motor design requires. The summary is that it is a fool's errand. There are no Hall effect sensor(s) in that motor, in case somebody is tempted to 'splain this.  I spent an embarrassing number of days on that, against the hard stop in Edison mode and wishing I'd spent five minutes in Tesla mode earlier. By the time I realized I had to use a controller my time budget had been exhausted five fold and I never confirmed the Phillip's chip was the right part. Bought a stepper motor and got on with my life. 😀Thanks again, everybody. This was fun.PeteSent by my phone with an editing mind of its own
-------- Original message --------From: Brian via TriEmbed <triembed at triembed.org> Date: 2/3/21  10:42 AM  (GMT-05:00) To: triembed at triembed.org Subject: Re: [TriEmbed] laptop fan motor control question On 2/2/21 5:14 PM, Pete Soper via TriEmbed wrote:> Thanks, guys. The connections were red for positive, blue for ground and > brown for what I assume is the PWM input. That third wire is almost certainly[1] a tachometer OUTPUT, not an input.  It's there so that the motherboard can monitor fan speed. Modulating the speed would be accomplished by one of the several methods that other folks've mentioned.-B[1] - unless, ya know, it isn't.  :)
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