[vdr] Re: Mainboard for use with vdr

[Thomas Heiligenmann <thomas@heiligenmann.de>]

Dirk Wiebel wrote:
> 
> Hello Thomas,
> 
> > However a few resistors in the fans' supply lines could fix the Problem.
> 
> please don't do this. With usual resistors, your fan might not power on --
> especially if it gets older... Zener diodes (? English term required) will
> have the same slow-down effect with less problems. As far as I remember from
> my physics lessons, this is due to the "non-Ohm's-law-like" resistance
> behaviour of coils ("Spulen"), i.e. the motor of your fan, too. The
> interaction with usual resistors could cause problems with the necessity of
> more amperage during spin-up, which will be reduced by the resistor. AFAIK
> the Zener Diode reduces voltage, which is not such a big problem -- depends
> on the values, of course.
> 
> If any professional knows better I would be very interested in the facts, as
> this seems to be the last tiny bit of my school knowledge...
> 
> Regards,
> Dirk

resistors are of course the simplest (and most awful) solution. a
pulse-width-modulated power supply would be a more efficient and
professional solution - maybe temperature controlled too. should be not
a big problem for any ambitioned electronics student or engineer ;-)