[SI-LIST] Re: Audio And Fan Circuits interference
- From: steve weir <weirsp@xxxxxxxxxx>
- To: brahim@xxxxxxxxxxxx, si-list@xxxxxxxxxxxxx
- Date: Thu, 13 Feb 2003 10:40:08 -0800
Brahim,
Almost all motor circuits produce large current spikes. Fans typically use
brushless motors, which don't generate commutator arcing, but which use
switch-mode operation, and usually the cheapest recovery diodes the mfg.
can get. The usual fix is a pi filter using either C-R-C, or C-L-C. If
you care to use one of X2Y's parts for the capacitor, then you can probably
get away with just an R-C filter, or even just the parallel C, depending on
your wiring.
A typical fan motor drive commutates between 1KHz and 20KHz, so the
capacitor values can be relatively large. A fast transient suppressor can
also help, but you will still most likely need the passive filter.
Regards,
Steve.
At 06:53 AM 2/13/2003 -0800, Brahim Koudssi wrote:
>Hello,
>
>I have designed a board that consists of an audio circuit and a fan
>controller circuit.
>When the fan is running it induces audible noise in the audio circuit, I
>can hear in the speakers the fan spinning.
>Can anyone please address the following questions:
>
>1. How's the fan audible noise getting into the audio?
>2. How can I get rid of this interference?
>
>Thanks,
>Brahim
>
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