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Adj. Temp Sensor Answered

I am looking for a 12V adjustable tempurature sensor that will provide a trigger output when the temp exceeds the setting. Can anyone help ?

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Goodhart (author)2007-10-17

What kind of sensitivity are you speaking of, a degree, 10ths of a degree, 20 degrees etc? Should it be electro-mechanical like a bimetal thermostat or like Temp sensor ic analog or digital ?

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daveyandgolie (author)Goodhart2007-10-17

Looking for something with a digital display that reads in degrees (maybe with one decial point)

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user

You didn't mention digital display in your original post. I would suggest you buy a ready made digital thermometer with a temperature alarm function. These devices are very cheap now, and you can hack the alarm output if you need it to trigger something. Cheers, Pat. Pending

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user

. That sounds like the best idea, so far. I bought a Sharp SPC315 for ~20$US (at Wal-Mart) a while back. Came with a wireless sensor. Has all sorts of calendar/time/temp functions (even moon phase).

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user

Hi NachoMahma, seems ages since I bumped into you on a thread:)

Much of the cheap electronic stuff you can buy today is cheaper than the price of the individual parts. Consequently, there is little point in reinventing the wheel and building it yourself, as you wont be saving any money.

Cheers,

Pat. Pending

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Goodhart (author)Patrick Pending2007-10-18

Unless you just want to put something together for learning purposes ;-)

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Goodhart (author)daveyandgolie2007-10-17

Well, here is a National Semiconductor spec sheet: NSC White Paper

And here is an example of one of the products: LM335 Precision Temp Sensor

If you are interfacing to a PC, here is another option <link>

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Goodhart (author)Goodhart2007-10-17

True, a properly constructed thermistor circuit could work too.

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guyfrom7up (author)daveyandgolie2007-10-17

you could do what I said and use a volt meter and calibrate it

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guyfrom7up (author)2007-10-17

what you probably need is a microcntroller with an analog to digital converter, and a thermistor. Or an alternative aproach without a microcontroller would be using a thermistor, potentiometer, and a relay

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guyfrom7up (author)guyfrom7up2007-10-17

all you need to do this is take the thermistor, hook it up in series with the potentiometer, and have the relay branching out from the center (so it would be a voltage divider) supply the voltage divider with 12 volts and have a 5v relay that turns on and off 12 volts.

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user

There are quite a few problems with this idea e.g., the current necessary for turning on the relay would cause self-heating in the thermistor. Cheers, Pat. Pending

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daveyandgolie (author)guyfrom7up2007-10-17

Where can I get one? I'm new on here today...can I have someone make it for me ?

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guyfrom7up (author)daveyandgolie2007-10-17

do you have elecronic knowledge or are you a complete newbie (not to be mean, but just to know how much to explain)

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daveyandgolie (author)guyfrom7up2007-10-17

I'm a bit of a newbie, but I understand your explaination. I just don't have the tools or knowledge for small electronic projects.

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