Re: Detectig fan failure - modes of failude

From: B (no_spam_at_no.com)
Date: 09/15/04 

Date: Wed, 15 Sep 2004 19:08:45 +0100

By NTC you mean using a termsistor in the airflow and moitor the temprature
rise if it stops overheating?
This is the most reliable method as this will actually monitor the desired
thing - airflow.

If (very very unlikely) all the blades broke the motor will still turn but
there will be no airflow.

Thanks
Darren

"Spehro Pefhany" <speffSNIP@interlogDOTyou.knowwhat> wrote in message
news:q9ngk01f9t1c9bjhnieddl12ghdv6e4ke8@4ax.com...
> On Wed, 15 Sep 2004 08:02:02 -0700, the renowned Jim Thompson
> <thegreatone@example.com> wrote:
>
> >On Wed, 15 Sep 2004 13:02:49 GMT, Spehro Pefhany
> ><speffSNIP@interlogDOTyou.knowwhat> wrote:
> >
> >>On Wed, 15 Sep 2004 15:00:02 +0200, the renowned "SioL"
> >><Sio_spam_L@same.net> wrote:
> >>
> >>>I'm designing a device with two convenient solder pads on the PCB
> >>>providing LC filtered power to the fan to. This will be a smallish 1W
> >>>12V fan, with only two connections (those are cheaper and I can't get
> >>>the 3-pin version of 40x40x20 easily).
> >>>
> >>>It occurred to me that it might be great to have failure detection. Now
> >>>it'd be easy if these were the 3-pin fans, but they're not. I wonder
whether
> >>>someone has some experience on modes of failure. Does it consistently
> >>>draw more current, no current or should I watch for some AC ripple on
> >>>supply line during normal operation, I'd expect there would be some and
> >>>it'd stop if the fan stopped rotating.
> >>
> >>Yes, that will work. It might be patented however.
> >>
> >>>I'll possibly settle for a NTC if everything else fails, but I have
some
> >>>PCB real-estate left for other solutions.
> >>>
> >>>SioL
> >>
> >>
> >>
> >>Best regards,
> >>Spehro Pefhany
> >
> >They have horrible current ripple, so bad that I once designed a
> >quick-fix circuit to fill-in the ripple, because the ripple was
> >disturbing a nearby CRT in a piece of OmniComp/GenRad portable gear.
>
> No capacitors inside them. ;-)
>
> >Did someone actually patent looking at the ripple ?:-)
> >
> > ...Jim Thompson
>
> Seems kinda obvious. I had a vague notion M*x*m did, but I've never
> had a reason to delve into it further. More expensive fans can have
> tacho output or locked rotor output, of course. Here's one of M*x*m's
> chips:
>
> http://pdfserv.maxim-ic.com/en/ds/MAX6684.pdf
>
> Best regards,
> Spehro Pefhany
> --
> "it's the network..." "The Journey is the reward"
> speff@interlog.com Info for manufacturers:
http://www.trexon.com
> Embedded software/hardware/analog Info for designers:
http://www.speff.com

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