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  • Re: solid state relay??

    From jeffj@jeffj@panix.com (Jeff Jonas) to comp.sys.raspberry-pi on Tue Aug 26 05:54:13 2025
    From Newsgroup: comp.sys.raspberry-pi

    The relays are switching DC at 12V, but the polarity is determined
    before the on/off relay. Most SS relays I've seen are triac-based for AC >only; one type would do DC, but not with the polarity changing (and at
    10x the cost anyway!).

    MOSFET based solid state relays
    handle DC or AC and shut off immediately
    whereas SCR or TRIAC turn off AC only at the zero crossing.

    see:
    https://www.ti.com/document-viewer/lit/html/SSZTB27
    --


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  • From Mike Scott@usenet.16@scottsonline.org.uk.invalid to comp.sys.raspberry-pi on Tue Aug 26 13:00:17 2025
    From Newsgroup: comp.sys.raspberry-pi

    On 26/08/2025 10:54, Jeff Jonas wrote:
    The relays are switching DC at 12V, but the polarity is determined
    before the on/off relay. Most SS relays I've seen are triac-based for AC
    only; one type would do DC, but not with the polarity changing (and at
    10x the cost anyway!).

    MOSFET based solid state relays
    handle DC or AC and shut off immediately
    whereas SCR or TRIAC turn off AC only at the zero crossing.

    see:
    https://www.ti.com/document-viewer/lit/html/SSZTB27


    Part of the issue is that I want the load and its psu electrically
    isolated from the control logic. Could probably be done with mosfets and optoisolators, but I've settled for an old-fashioned mechanical relay,
    at least for now. Thanks for the thought though.
    --
    Mike Scott
    Harlow, England
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  • From The Natural Philosopher@tnp@invalid.invalid to comp.sys.raspberry-pi on Tue Aug 26 13:07:25 2025
    From Newsgroup: comp.sys.raspberry-pi

    On 26/08/2025 10:54, Jeff Jonas wrote:
    The relays are switching DC at 12V, but the polarity is determined
    before the on/off relay. Most SS relays I've seen are triac-based for AC
    only; one type would do DC, but not with the polarity changing (and at
    10x the cost anyway!).

    MOSFET based solid state relays
    handle DC or AC and shut off immediately
    Can do. Most MOSFETS are unipolar

    whereas SCR or TRIAC turn off AC only at the zero crossing.

    Look up GTO thyristors

    see:
    https://www.ti.com/document-viewer/lit/html/SSZTB27

    --
    You can get much farther with a kind word and a gun than you can with a
    kind word alone.

    Al Capone



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