I am enjoying this thread. I was not familiar with the need for pulse-stretching to accommodate tach sensor power. Fascinating. This seems like a great time to share my favorite app note about reducing acoustic noise when using PWM to control a BLDC fan. I found it when I was controlling a large fan that sounded awful under PWM control.
*Suppressing Acoustic Noise in PWM Fan Speed Control Systems* https://ww1.microchip.com/downloads/en/AppNotes/00771b.pdf Shane On Tue, Feb 2, 2021 at 6:25 PM Brian via TriEmbed <[email protected]> wrote: > I store my paste at room temperature. I like to live dangerously! (I > also don't have room in my house for another refrigerator, regardless of > size...) > > That said, I recently bought some fresh paste...although my old stuff > (and I mean old...several years of room-temp storage) still reflows, I > was amazed by how many fewer bridge problems cropped up with the fresh > stuff. My workflow had been stencil, place, reflow, clean up several > bridges on all four sides of TQFPs...with fresh paste, there was almost > no cleanup to be done. > > I still store at room temp, though. XD > > As an aside, I've been thinking about switching to a low-temp > tin-bismuth alloy, but I hear even the tiniest bit of lead will really > attack and weaken that stuff, and I can't guarantee there aren't some > atoms of lead still clinging to my iron.. > > -B > > 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. It spins up with 5V just fine > > and I feel silly about the high resistance measurement. The fan cools a > > pair of heat pipes from two IC sites side by side and the whole thing is > > copper. The IC sites have faint markings but I can just make out "attach > > Peltier devices here". After only eight years I may be able to store my > > solder paste in something smaller than a dorm fridge. :-) > > > > -Pete > > > > On 2/2/21 2:34 PM, Brian via TriEmbed wrote: > >> On 2/2/21 1:15 PM, Pete Soper via TriEmbed wrote: > >>> The DC resistance between any two pins with any polarity is much > >>> higher than I would have expected: thousands of ohms. > >>> > >> > >> Others have already mentioned: > >> - It's probably a brushless motor > >> - Three wires are probably power, ground, and tachometer > >> > >> The reason you see an unexpectedly high resistance across the power > >> leads is because there are active electronics inside the thing to > >> commutate the brushless motor. You're not measuring a motor winding. > >> > >> I say if you have a red and black wire, hook that up to +5 VDC and see > >> if she spins. > >> > >> -B > >> > >> _______________________________________________ > >> Triangle, NC Embedded Computing mailing list > >> > >> To post message: [email protected] > >> List info: > >> http://mail.triembed.org/mailman/listinfo/triembed_triembed.org > >> TriEmbed web site: http://TriEmbed.org > >> To unsubscribe, click link and send a blank message: > >> mailto:[email protected]?subject=unsubscribe > >> > > > > _______________________________________________ > > Triangle, NC Embedded Computing mailing list > > > > To post message: [email protected] > > List info: > http://mail.triembed.org/mailman/listinfo/triembed_triembed.org > > TriEmbed web site: http://TriEmbed.org > > To unsubscribe, click link and send a blank message: > > mailto:[email protected]?subject=unsubscribe > > > > > _______________________________________________ > Triangle, NC Embedded Computing mailing list > > To post message: [email protected] > List info: http://mail.triembed.org/mailman/listinfo/triembed_triembed.org > TriEmbed web site: http://TriEmbed.org > To unsubscribe, click link and send a blank message: mailto: > [email protected]?subject=unsubscribe > > -- [image: photo] *Shane D Trent* Patent Agent 919-348-0061 | [email protected] ShaneTrent.com | Skype: skype:shane.trent1 <#SignatureSanitizer_SafeHtmlFilter_> Raleigh, North Carolina <http://www.linkedin.com/in/shanetrent> <http://twitter.com/sdtrent> Create your own email signature <https://www.wisestamp.com/create-own-signature/?utm_source=promotion&utm_medium=signature&utm_campaign=create_your_own&srcid=>
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