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Level-shifter/isolator; opinions? — Parallax Forums

Level-shifter/isolator; opinions?

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  • Yep, Mouser lists 1860 matches for digital isolators and there are other ones that also have their own isolated power supply built-in as well. Remember that opto-isolator inputs are powered by the signal itself, not so with digital isolators.
  • kwinnkwinn Posts: 8,697
    Mickster wrote: »

    Perhaps, but electrical noise could be a problem. A spectrometer I serviced would intermittently start to analyze a sample when not being used. Turned out a bad fluorescent light ballast was putting out enough noise to trigger it. That unit had transformer coupled isolators while most of them used optoisolators. Don't recall any optoisolated units ever having a similar problem.

    BTW, spell check gave me a chuckle this morning. Marked "isolators" as incorrect and suggested "idolators, violators, legislators, collators, dilators" as substitutes.
  • kwinn wrote: »
    Mickster wrote: »

    Perhaps, but electrical noise could be a problem. A spectrometer I serviced would intermittently start to analyze a sample when not being used. Turned out a bad fluorescent light ballast was putting out enough noise to trigger it. That unit had transformer coupled isolators while most of them used optoisolators. Don't recall any optoisolated units ever having a similar problem.

    BTW, spell check gave me a chuckle this morning. Marked "isolators" as incorrect and suggested "idolators, violators, legislators, collators, dilators" as substitutes.

    Glad I asked. My application requires close proximity to very large AC Vector drives.

  • I've used the ADUM2250 for i2c isolation for water quality instrumentation with both the Stamp and then with the Prop. Then switched the design to the Silicon Labs SI8600. Among other factors (lower cost, smaller package) it claims a "best in class" noise immunity, but it is not clear what means of coupling they use. The ADUM parts do claim high immunity from magnetic fields, so I'm intrigued by Kwinn's comparison in that particular situation.
  • pjvpjv Posts: 1,903
    Hi,

    I have been happy with the bi-directional ADuM family, and in particular like the isolated power supply they provide.

    Cheers,

    Peter (pjv)
  • kwinnkwinn Posts: 8,697
    I've used the ADUM2250 for i2c isolation for water quality instrumentation with both the Stamp and then with the Prop. Then switched the design to the Silicon Labs SI8600. Among other factors (lower cost, smaller package) it claims a "best in class" noise immunity, but it is not clear what means of coupling they use. The ADUM parts do claim high immunity from magnetic fields, so I'm intrigued by Kwinn's comparison in that particular situation.

    From what I see on the data sheets the ADUM part appears to be magnetically coupled The SI8600 is RF coupled, but it is not clear whether that is done inductively or by capacitance.

    In the case of the spectrometer I suspect the problem was caused by the RF generated by the failing ballast coming in to the spectrometer via the power lines. Both the light and spectrometer were powered from a panel in the adjoining room.
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