On 07/02/06, Enrico Schuerrer <enrico@gmx.at> wrote:
>
> -----Urspr=FCngliche Nachricht-----
> Von: "Michael Rigby-Jones" <Michael.Rigby-Jones@bookham.com>
> An: "Microcontroller discussion list - Public." <piclist@mit.edu>
> Gesendet: Montag, 06. Februar 2006 18:57
> Betreff: RE: [EE] Transient Suppression - was Re: [ee] 3904 base resistor
>
>
> [rest snipped]
>
> >
> I don't think that the problem is speed or current - the problem is the v=
oltage. A 1N4148 is rated with 100 Volts and this could be less if you swit=
ch off a relay. From my experiences a 1N4007 as a general purpose diode wit=
h Vrrm =3D 1000V and much reserves in non repetitive current will do the jo=
b without problems and cost nearly nothing.
>
> Regards
>
> Enrico
>

But the flyback voltage generated by the relay coil turns the diode
on. The voltage rating of the diode only needs to match the power
supply requirement (the voltage accros the relay when on) - plus the
usual margin.


Richard P

-- =

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