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DanielCV
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Joined: 10/05/2011
Location: Cape Verde
Posts: 19

Posted: 03:04pm 23 May 2011

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Hello,

Can somebody help me what would I need to measure temperature with a KTY84-130 ?
http://www.nxp.com/documents/data_sheet/KTY84_SER.pdf
I have built it into a stator of my windgenerator in order to measure the temp.
I would like to do a very simple circuit for it.

Thanks for help!
DanielEdited by DanielCV 2011-05-25

powerednut

Senior Member

Joined: 09/12/2009
Location: Australia
Posts: 221

Posted: 12:00am 24 May 2011

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Unless your happy with "ballpark" figures I wouldn't bother. That device has a best case error of + or - 4.9 Degrees C (at 100C. Anything other than 100C it gets worse than that). I could be reading the datasheet wrong, so you might want to check that yourself.

I'd be inclined to either stick a cheapy multimeter on the sensor and measure the resitance directly (the device changes resistance with temperature).

Alternatively you could use a simple op amp circuit, with the KTY84-130 in place of the lower resistor of a resistive divider. The junction would then be one of the inputs to the op amp. That way you can either scale the output voltage and feed it to a voltmeter of some kind, or you can compare it to a reference voltage and trigger something (like a beeper to alert you to a problem, or a mosfet to switch on an additional load dump).

You could also use the resistive divider route and provide the input to the ADC on a little microcontroller (arduino or just an avr (e.g ATtiny85) or a pic or whatever). Then its just a software issue to convert the voltage to a temperature and drive whatever outputs you want.

If you want to go the op amp route take a look at the op-amp battery charger circuit that gets discussed a few times on this forum. From memory the op-amp portion uses a resistive divider to measure the voltage across a battery and switch a transistor (mosfet?) on or off. Thats pretty much what you want to do. Just pay attention to the max current requirements of the sensor.

I suspect you'll find a simple diode (1n4148) would provide a similiar level of accuracy for temperature sensing. try googling it.

Tinker

Guru

Joined: 07/11/2007
Location: Australia
Posts: 1904

Posted: 01:57pm 24 May 2011

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I assume the aim of checking the temperature is finding out when the stator gets too hot and putting on the brakes?
If so why not use a simple temperature sensing switch? These are quite cheap and come in either high temperature off or on contacts. You pick the switching point to suit. A neat feature is they self reset once things have cooled down.
You can switch around 10A so it should be fine to activate brakes.

Klaus

DanielCV
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Joined: 10/05/2011
Location: Cape Verde
Posts: 19

Posted: 05:35pm 25 May 2011

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Thankyou for your very helpful answers !!

Best regards,
Daniel

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