Low cost thermostat for heatsink cooling fan?

Discussion in 'General Electronics Chat' started by DMahalko, Jun 27, 2012.

  1. DMahalko

    Thread Starter Senior Member

    Oct 5, 2008
    175
    14
    Is there anything cheaper for on/off fan setpoint temperature control than these snap-action bimetallic disc thermostats?

    http://www.newark.com/jsp/search/br...ap+action+thermostat&Ntx=mode+matchallpartial


    Maybe a single-chip IC in a TO-218/220 package that can be mounted on the heatsink to be monitored?

    I understand there may be AC/DC voltage and current limits of a thermal management fan controller IC, vs this mechanical switch.
     
  2. bountyhunter

    Well-Known Member

    Sep 7, 2009
    2,498
    507
    You can use a cheap 2N3904 glued to the heatsink as a temp sensor and a comparator and FET to turn on the FAN.
     
  3. DMahalko

    Thread Starter Senior Member

    Oct 5, 2008
    175
    14
    Thank you, you answered my question, though I guess I didn't write that clearly enough to ask what I really meant.


    What "drop-in" "readymade" "no design required" IC-based thermostat options are available that cost less than this bimetallic thermostat?

    For example with this thermostat there's nothing much to do except buy it, remove it from the shipping packaging, screw it down, and attach the fan wires.
     
  4. Bernard

    AAC Fanatic!

    Aug 7, 2008
    4,176
    397
    If you are happy with 65 deg. C, Thermal Switch, G14366, Electronic Goldmine, 3/ US $ .99. Made for battery packs.
    Sorry SW is NC-- shuts off fan if to hot.
     
    Last edited: Jun 28, 2012
  5. DMahalko

    Thread Starter Senior Member

    Oct 5, 2008
    175
    14
    Ah thank you, this has steered me in the right direction. Oftentimes to find something on the Internet, you need to know its proper technical name. Finding the correct descriptive name is often the biggest challenge.

    In this case "thermal switch" is the proper name for some 88 devices, just on Newark alone.


    http://www.newark.com/jsp/search/browse.jsp?N=422+201783+783&Ns=P_PRICE_NEWARK_US|0&locale=en_US&appliedparametrics=true&getResults=true&suppressRedirect=true&isRedirect=&originalQueryURL=/jsp/search/browse.jsp%3FN%3D422%2B201783%26No%3D0%26getResults%3Dtrue%26appliedparametrics%3Dtrue%26locale%3Den_US%26divisionLocale%3Den_US%26catalogId%3D%26skipManufacturer%3Dfalse%26skipParametricAttributeId%3D%26prevNValues%3D422%2B201783
     
  6. strantor

    AAC Fanatic!

    Oct 3, 2010
    4,302
    1,988
    Ironically, I just stumbled across this today.
     
  7. bountyhunter

    Well-Known Member

    Sep 7, 2009
    2,498
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    That article has some erroneous BS in it:

    1) For most electrical components (IC's, capacitors, transistors, etc) you don't just want to remove excess heat being made. In reality, the time-to-death of the components is directly related to operating temp.

    You would not want them freezing, but running at 40F (or 60F) definitely increases life compared to 80F. The only caveat is that cheap electrolytic caps have a thing called ESR (equiv series resistance) that goes up rapidly below about 30F. But, you are not going to "over cool" any component since the air the fan is blowing on it is room temperature.


    2) Adding series diodes to reduce voltage to a fan as "speed control" is a terrible way to do it. Most DC fans have built in IC speed control/current limit. Starving the voltage is a crappy way to reduce speed, it's running the fan closer to stall mode. Not a way I would run a DC fan since operating current may be going up as the IC tries to compensate and maintain nominal speed.
     
  8. strantor

    AAC Fanatic!

    Oct 3, 2010
    4,302
    1,988
    I guess I should have read the article before posting it.
    It didn't really interest me so I didn't read it, but the title seemed to suggest it was exactly what OP was looking for.
     
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