I have had all MOC3XXX optos get destroyed by noisy AC lines, with the
exception of the 3051 & 3052's. Although the rated Viso is the same as the
MOC 3031 at 7500V, the actual detector voltage rating is about 200V higher
on these. I have it on advisement from the Fairchild App eng dept to only
use MOC305X chips in commercial environments, and the results have proved
true.
Chris

> -----Original Message-----
> From: pic microcontroller discussion list
> [mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of Vern Jones
> Sent: Tuesday, November 27, 2001 7:38 PM
> To: PICLIST@MITVMA.MIT.EDU
> Subject: Re: [EE]: favorite opto isolators?
>
>
> Spike through relays - Maybe yes, maybe no
>
> If relay spikes are with AC relays, use an MOC3031 with a good triac.
> The MOC3031 is a '0' point opto isolator trigger for Triacs.
>
> When using Relays and Solenoids, overkill is in order, if
> your load is 3
> to 5 amps, use a 20 - 30 Amp device, and place the flyback
> protection at
> the driver device, not at the load end. If a fast recovery diode is at
> the load, and there is any wire length at all, then the
> induced spike in
> the wiring can kill your driver as well. Make sure that your flyback
> diode is fast enough, and its current rating is sufficient to damp the
> flyback waveform, and place it at the driver.
>
> Vern
>
> "Peter L. Peres" wrote:
> >
> > > spike through relays
> >
> > You can buy relays with groundable armature. This acts as a
> shield between
> > the contacts and the coil. I don't have a type number for you...
> >
> > Anyway if the grounds are no laid properly then there is no
> need for the
> > strike to jump the coils, it can be induced or direct
> ground current that
> > does your circuit in.
> >
> > Peter
>
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