[mythtv-users] Quiet fans

[Peter Loron]

On Oct 17, 2008, at 11:35 AM, Darrin wrote:
>
> On Fri, Oct 17, 2008 at 1:36 AM, Peter Loron  
> <peterl at standingwave.org> wrote:
>
> On Oct 15, 2008, at 5:04 PM, Yan Seiner wrote:
>
> >
> > On Wed, October 15, 2008 4:52 pm, Darrin wrote:
> >
> >> Nice.  If it were me, I'd complicate it a bit more and use an atmel
> >> avr
> >> tiny
> >> to do the same thing.  Then, you have the ability to reprogram it
> >> to your
> >> whims and no potentiometers are needed.  You could even change the
> >> ramp
> >> rate
> >> on the pwm to be completely non-linear for your specific needs. The
> >> ATtiny24
> >> could do the job, has an onboard temp sensor, built in PWM, and
> >> only costs
> >> $1.91 from digi-key.
> >
> > Any chance of doing a project page on this?  That could be cool.
> >
> > Even cooler (no pun intended) would be something with a termistor  
> on a
> > lead that could be stuffed into a hard drive caddy space.  :-)
> >
> > --Yan
> >
>
> Should be quite easy to put together...I've got some Arduino boards
> kicking around. I'd need to get a leaded temp sensor. Hmmm. I wonder
> how expensive it would be to get something together to read K-type
> thermocouples.
>
> -Pete
>
> I just ordered parts and picked up a Dallas DS18B20 digital  
> temperature sensor for less than $5 at Sparkfun electronics.  You  
> could probably call Dallas and get them to send you a sample if you  
> really want to do it on the cheap.  I got it mostly to figure out if  
> it would react any faster or better than the one already on the  
> ATtiny.
>
> Thermocouples would require some added interface circuitry (like the  
> LM741 op-amp) to get a usable signal.  The benefit is that they will  
> detect temperature changes more quickly than a packaged silicon  
> device would.   I'm sure there's plenty of example circuits already  
> out there on the web that would help if you decide to go this route.
>
> --Darrin

Oh, yeah. I just checked my inventory, and I've got temp sensors from  
Dallas/Maxim. Analog, and ST Micro in the parts bin. Guess my only  
excuse for not doing it now is lack of time.  :-)

Having the sensor on leads would be nice for checking the temp  
someplace the PCB won't fit. Should also be pretty easy to multiplex  
some sensors if you wanted multiple readings.

-Pete
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