Help selecting thermistor

Discussion in 'General Electronics Chat' started by Nick Bacon, Jan 7, 2017.

  1. Nick Bacon

    Thread Starter Member

    Nov 7, 2016
    130
    2
    hi guys,

    I don't really understand thermistors so help required please.

    I need one to go between a line filter and a pcb mount SMPS. The max input voltage is 260 VAC. The SMPS is rated at 167mA

    The second application is again between line filter and SMPS but this time there are 2 x 420mA SMPS being fed by the line filter.

    Can someone please please me select the correct thermistor for both applications.
     
  2. #12

    Expert

    Nov 30, 2010
    18,076
    9,690
    Why do you think you need thermistors?
    Not just because nobody else does that, because nobody can select a thermistor for a purpose they don't know.
     
  3. Nick Bacon

    Thread Starter Member

    Nov 7, 2016
    130
    2
    Looking at the spec sheet for the SMPS the manufacture recommends using one for good EMC practice. The thing is I just don't understand the different resistance levels the come in and why it makes a difference.
     
  4. RichardO

    Late Member

    May 4, 2013
    2,273
    894
    #12 likes this.
  5. #12

    Expert

    Nov 30, 2010
    18,076
    9,690
    Can you give us a link to the datasheets? Or the model numbers? or the manufacturer's name? or why your product needs EMC compliance? or which EMC regulation you are trying to meet?
     
  6. Alec_t

    Expert

    Sep 17, 2013
    10,117
    2,468
    Do you mean "varistor"?
     
  7. Nick Bacon

    Thread Starter Member

    Nov 7, 2016
    130
    2
  8. Nick Bacon

    Thread Starter Member

    Nov 7, 2016
    130
    2
    The recommendation is a MOV after the fuse but before the filter and a thermistor between the filter and the SMPS.
     
  9. Nick Bacon

    Thread Starter Member

    Nov 7, 2016
    130
    2
  10. GopherT

    AAC Fanatic!

    Nov 23, 2012
    7,983
    6,786
    I like red ones.
     
  11. Nick Bacon

    Thread Starter Member

    Nov 7, 2016
    130
    2
    http://docs-europe.electrocomponents.com/webdocs/14ae/0900766b814ae925.pdf

    http://docs-europe.electrocomponents.com/webdocs/141c/0900766b8141c3ba.pdf

    The product need EMC compliance because in Europe CE marking is mandatory and EMC testing is part of that. It is an industrial water level sensor. The standard is EN61326-1
     
  12. #12

    Expert

    Nov 30, 2010
    18,076
    9,690
    Here are the part numbers. Now the mystery is, "Who makes them and who sells them?"
    External input NTC is recommended to use 12D-5;
    External input MOV is recommended to use S14K350
     
  13. Nick Bacon

    Thread Starter Member

    Nov 7, 2016
    130
    2
    I have seen the part numbers, the 12D-5 seems to only be available in China and the S14 is obsolete Epcos
     
  14. #12

    Expert

    Nov 30, 2010
    18,076
    9,690
    You knew the part numbers before you typed your first post?
    And it took us an hour to pry them out of you?

    I need to go work on something else now.
     
    GopherT likes this.
Loading...