Skip to main content

Hi All; I am working on a bit of a variable output power supply, and I would like to be able to automatically vary the cooling fan speed for the heat sink. The fan will be a standard computer type; maybe 60 x 60 x 10; less than 2 watts, 12vdc, two wire device. I have seen several types of temp sensors that bolt onto a heat sink, and sends information which is used to vary the fan speed, likely through a PWM type circuit.

But I am wondering if there might be some simple inline device with a resistance of maybe 60-80 ohms at room temp; decreasing to zero or close at around 180-200 F? Anyone know of anything that works like this, and how I could find the right one? 

Thanks for any help, Rod

 

Last edited by Rod Stewart
Original Post

Replies sorted oldest to newest

An automobile radiator mounted sensor delivers power (grnd)  to the fan  at X°(some are variable) About the size of a quarter x 3/8"?.

So a two speed setting depends a lot on motor variable speed ability; but...

Use 60-80ohms feeding the fan outright. Once at X° the thermo delivers full power downstream of the 60-80ohm; (at the fan bridging over the 60-80ohm ....or over other voltage reduction method 🤔

In other words; pos. thermos may work too if the circuit can be done "2spd".(or 3sp 4sp, etc) (yep-Thermistors , they come in MANY forms, probes to board mount)

 

???

Tom, those are also "bang-bang' control of the circuit creating the high temperature, not the fan.  They turn off when the limit temperature is reached, and are restored when the temperature drops sufficiently below their rated temperature.  With these, the fan would be turned off when the item got hot, not exactly the desired operation!

KSD-9700 Series Thermal Protector

Attachments

Files (1)

Thanks for all the ideas so far.  I searched on ebay and found a line of KSD301/302 temp switches. 301's are normally closed whereas 302's are normally open. They are available in 5 deg C increments from 40C to 160C.

So I plan to order a couple of 302's each, at 40C and 50C. They are simple inline hookup, 10 Amp rated, surface mount, with spade lug connectors, and only about a buck each. Perfect for what I need. Simple on-off switching, but that should be fine as grj suggested.

KSD302 NO Switch 40-160 C

Thanks all, Rod

Attachments

Images (1)
  • KSD302 NO Switch 40-160 C
Last edited by Rod Stewart
gunrunnerjohn posted:

Tom, those are also "bang-bang' control of the circuit creating the high temperature, not the fan.  They turn off when the limit temperature is reached, and are restored when the temperature drops sufficiently below their rated temperature.  With these, the fan would be turned off when the item got hot, not exactly the desired operation!

KSD-9700 Series Thermal Protector

Hmmm... You are exactly right. That datasheet is not what I was thinking they did. 

I was looking around at this stuff on ebay yesterday. Must have either gotten my devices mixed up or mis-understood the translation to English in the descriptions?  

But wait, here's what I was going by, ebay item 183364095688 says they come in either N.C. (break on temp rise) or N.O. (make on temp rise).  Some of the ads list them as available in either configuration from a drop down selection when ordering.

Last edited by rtr12

Add Reply

Post

OGR Publishing, Inc., 1310 Eastside Centre Ct, Suite 6, Mountain Home, AR 72653
800-980-OGRR (6477)
www.ogaugerr.com

×
×
×
×
Link copied to your clipboard.
×
×