RE: Buzzing relays? Anyone help?

["Rodney Hall" <rmh@xxxxxxxxxx>]

Lee,

You *won't* get fireworks with a diode - it lets through half the AC
waveform and not pure DC. There may be a case for two diodes back to back
to
prevent back emf damage, but I have not experienced that with the relays I
used (more than 10 years in service in my central heating and I haven't
burned down yet!). The relays I used were ex WD skeleton (not plug-in)
relays and are quite happy with this arrangement. Others may not, which is
why I originally said *try*. However, you will not get sparks!

Your relays may be different, in which case, an alternative which I have
also used is to insert a 1 watt resistor instead of a diode. You'll need to
try a few values, but around 330 ohms would be a good start. This will
reduce the current through the coil enough to stop the leakage current
making the relay buzz. The leakage is due to switching by triacs, which is
what I use in my (home brew) heating controller and also caused my relays
to
buzz. Not any more.

Hope this helps

Rodney

> -----Original Message-----
> From: LeeUKHA [mailto:mailinglists@xxxxxxx]
> Sent: Sunday, January 23, 2005 12:11 AM
> To: ukha_d@xxxxxxx
> Subject: Re: [ukha_d] Buzzing relays? Anyone help?
>
>
> So it'll work great  or  I'll have fireworks and burn the
> house down???
>
> Anyone care to comment?
>
> Lee :
>
>
> Rodney Hall wrote:
>
> > Yes, 1N4004 should do the job. I have them on my mains relays.
> >
> > --
> > Rodney Hall
> > Dum spiro spero
> > While I breathe, I hope
> >
>
>
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