• cpu cooler fan

    From john larkin@21:1/5 to All on Tue Nov 26 16:17:42 2024
    A cpu cooler has a 4-pin connector for the fan.

    Does anybody know if the fan will blow up if the connector is plugged
    in backwards?

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  • From bitrex@21:1/5 to john larkin on Wed Nov 27 00:35:09 2024
    On 11/26/2024 7:17 PM, john larkin wrote:
    A cpu cooler has a 4-pin connector for the fan.

    Does anybody know if the fan will blow up if the connector is plugged
    in backwards?



    I did a quick test on a spare fan...so if the pins are reversed we get
    +12 from the mobo to the RPM output signal from the fan, 12 volt input
    for the fan connected to the RPM signal input on the mobo, PWM output
    from the mobo to fan ground, and motherboard ground to PWM input on the fan.

    MOBO PWM OUT <--> FAN GND
    MOBO +12 OUT <---> FAN RPM OUT
    MOBO RPM IN <--> FAN +12 IN
    MOBO GND <--> FAN PWM IN

    I think Rpm in to fan +12 in is nothing, like connecting a high
    impedance digital input to the input of voltage regulator, maybe. For
    the +12 out to fan RPM out...all RPM outputs are open collector AFAIK so
    if the fan isn't powered and isn't spinning I don't think there's any
    harm there, I don't see any current flow when fan PWM in is grounded and
    I put +12 there, anyway.

    However reversing the PWM and GND pins looks to cause to a pretty good
    short, 85 mV at 10 mA current limit. The PWM drive is probably current
    limited, and/or the mobo may detect that and shut down I dunno.

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  • From Jasen Betts@21:1/5 to john larkin on Fri Nov 29 10:12:03 2024
    On 2024-11-27, john larkin <jl@glen--canyon.com> wrote:
    A cpu cooler has a 4-pin connector for the fan.

    Does anybody know if the fan will blow up if the connector is plugged
    in backwards?

    That would put 12V across the pwm input and pulse output, or are you
    also asking conerning other misalignments?

    They make these plugs with good alihnment features for a reason.

    --
    Jasen.
    🇺🇦 Слава Україні

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  • From john larkin@21:1/5 to usenet@revmaps.no-ip.org on Fri Nov 29 07:51:28 2024
    On Fri, 29 Nov 2024 10:12:03 -0000 (UTC), Jasen Betts <usenet@revmaps.no-ip.org> wrote:

    On 2024-11-27, john larkin <jl@glen--canyon.com> wrote:
    A cpu cooler has a 4-pin connector for the fan.

    Does anybody know if the fan will blow up if the connector is plugged
    in backwards?

    That would put 12V across the pwm input and pulse output, or are you
    also asking conerning other misalignments?

    They make these plugs with good alihnment features for a reason.

    Just backwards. I am testing CPU coolers and had to hack a power cable
    and connector and was wondering if fan makers considered this. Some
    are specific that swapping the 12 volt polarity will not damage the
    fan motor.

    We want to bolt a bunch of TO-220 resistors to a copper CPU cooler and
    mount all that on a PC board. Dynatron A41 looked fabulous, so I got a
    couple and tried to tap one for bolting the resistors down. I missed
    the tiny VC on the data sheet, which means Vapor Chamber. That became
    obvious when I started drilling.

    The Dynatron folks are great. The chat support people really know
    their stuff, and they are super reasonable about making specials.

    This is part of my resistor+inductor simulator dummy load project.

    Here's a similar gadget, but with a wimpier cooler:

    https://highlandtechnology.com/Product/P945

    I want to dump more watts next time. 300 would be great... I'm not
    cooling a CPU chip so could let things get very hot.

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  • From Jasen Betts@21:1/5 to john larkin on Fri Nov 29 20:18:59 2024
    On 2024-11-29, john larkin <JL@gct.com> wrote:
    On Fri, 29 Nov 2024 10:12:03 -0000 (UTC), Jasen Betts
    <usenet@revmaps.no-ip.org> wrote:

    On 2024-11-27, john larkin <jl@glen--canyon.com> wrote:
    A cpu cooler has a 4-pin connector for the fan.

    Does anybody know if the fan will blow up if the connector is plugged
    in backwards?

    That would put 12V across the pwm input and pulse output, or are you
    also asking conerning other misalignments?

    They make these plugs with good alihnment features for a reason.

    Just backwards. I am testing CPU coolers and had to hack a power cable
    and connector and was wondering if fan makers considered this. Some
    are specific that swapping the 12 volt polarity will not damage the
    fan motor.

    These started out as a 3 pin connector then they added an extra pin.
    reversing the 3 pin variant would likely damage the PC

    Pre-built extension cables are easily had.

    If you can't wait for the right part just use a 4x2 0.1" pitch pin
    header with two of the pins removed. Glue lined heatshrink or solder
    blobs, or other accesories on the two "key" pins are optional.

    --
    Jasen.
    🇺🇦 Слава Україні

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  • From Don@21:1/5 to bitrex on Sat Nov 30 04:03:57 2024
    bitrex wrote:
    john larkin wrote:
    A cpu cooler has a 4-pin connector for the fan.

    Does anybody know if the fan will blow up if the connector is plugged
    in backwards?



    I did a quick test on a spare fan...so if the pins are reversed we get
    +12 from the mobo to the RPM output signal from the fan, 12 volt input
    for the fan connected to the RPM signal input on the mobo, PWM output
    from the mobo to fan ground, and motherboard ground to PWM input on the fan.

    MOBO PWM OUT <--> FAN GND
    MOBO +12 OUT <---> FAN RPM OUT
    MOBO RPM IN <--> FAN +12 IN
    MOBO GND <--> FAN PWM IN

    I think Rpm in to fan +12 in is nothing, like connecting a high
    impedance digital input to the input of voltage regulator, maybe. For
    the +12 out to fan RPM out...all RPM outputs are open collector AFAIK so
    if the fan isn't powered and isn't spinning I don't think there's any
    harm there, I don't see any current flow when fan PWM in is grounded and
    I put +12 there, anyway.

    However reversing the PWM and GND pins looks to cause to a pretty good
    short, 85 mV at 10 mA current limit. The PWM drive is probably current limited, and/or the mobo may detect that and shut down I dunno.

    Figure 2 of an AD App Note shows a typical schematic for a circuit
    embedded in a 4-wire DC fan. The embedded circuit contains three
    N-channel JFETS, a Hall sensor, and a couple of resistors.

    It's a brain teaser to deduce reversal repercussions. When the Tach's temporarily disconnected the PWM periodically pinches all of the JFETs
    off. Someone smarter needs to untangle what happens when 12 VDC is
    re-connected to the Tach output.

    Why and How to Control Fan Speed for Cooling Electronic Equipment

    ... In addition to the power, ground, and tach signal, 4-wire fans
    have a PWM input, which is used to control the speed of the fan.
    Instead of switching the power to the entire fan on and off, only
    the power to the drive coils is switched, making the tach
    information available continuously. Switching the coils on and off
    generates some commutation noise. Driving the coils at rates
    greater than 20 kHz moves the noise outside of the audible range,
    so typical PWM fan-drive signals use a rather high frequency
    (>20 kHz). Another advantage of 4-wire fans is that the fan speed
    can be controlled at speeds as low as 10% of the fan’s full speed.
    Figure 2 shows the differences between 3-wire and 4-wire fan
    circuits. ...

    <https://www.analog.com/en/resources/analog-dialogue/articles/how-to-control-fan-speed.html>

    Danke,

    --
    Don, KB7RPU, https://www.qsl.net/kb7rpu
    There was a young lady named Bright Whose speed was far faster than light;
    She set out one day In a relative way And returned on the previous night.

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  • From Jan Panteltje@21:1/5 to g@crcomp.net on Sat Nov 30 07:24:43 2024
    On a sunny day (Sat, 30 Nov 2024 04:03:57 -0000 (UTC)) it happened "Don" <g@crcomp.net> wrote in <20241129a@crcomp.net>:

    bitrex wrote:
    john larkin wrote:
    A cpu cooler has a 4-pin connector for the fan.

    Does anybody know if the fan will blow up if the connector is plugged
    in backwards?



    I did a quick test on a spare fan...so if the pins are reversed we get
    +12 from the mobo to the RPM output signal from the fan, 12 volt input
    for the fan connected to the RPM signal input on the mobo, PWM output
    from the mobo to fan ground, and motherboard ground to PWM input on the fan. >>
    MOBO PWM OUT <--> FAN GND
    MOBO +12 OUT <---> FAN RPM OUT
    MOBO RPM IN <--> FAN +12 IN
    MOBO GND <--> FAN PWM IN

    I think Rpm in to fan +12 in is nothing, like connecting a high
    impedance digital input to the input of voltage regulator, maybe. For
    the +12 out to fan RPM out...all RPM outputs are open collector AFAIK so
    if the fan isn't powered and isn't spinning I don't think there's any
    harm there, I don't see any current flow when fan PWM in is grounded and
    I put +12 there, anyway.

    However reversing the PWM and GND pins looks to cause to a pretty good
    short, 85 mV at 10 mA current limit. The PWM drive is probably current
    limited, and/or the mobo may detect that and shut down I dunno.

    Figure 2 of an AD App Note shows a typical schematic for a circuit
    embedded in a 4-wire DC fan. The embedded circuit contains three
    N-channel JFETS, a Hall sensor, and a couple of resistors.

    It's a brain teaser to deduce reversal repercussions. When the Tach's >temporarily disconnected the PWM periodically pinches all of the JFETs
    off. Someone smarter needs to untangle what happens when 12 VDC is >re-connected to the Tach output.

    Why and How to Control Fan Speed for Cooling Electronic Equipment

    ... In addition to the power, ground, and tach signal, 4-wire fans
    have a PWM input, which is used to control the speed of the fan.
    Instead of switching the power to the entire fan on and off, only
    the power to the drive coils is switched, making the tach
    information available continuously. Switching the coils on and off
    generates some commutation noise. Driving the coils at rates
    greater than 20 kHz moves the noise outside of the audible range,
    so typical PWM fan-drive signals use a rather high frequency
    (>20 kHz). Another advantage of 4-wire fans is that the fan speed
    can be controlled at speeds as low as 10% of the fan’s full speed.
    Figure 2 shows the differences between 3-wire and 4-wire fan
    circuits. ...

    <https://www.analog.com/en/resources/analog-dialogue/articles/how-to-control-fan-speed.html>

    Nice, thank you!

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