12VDC thermostat switch?
 

Anyone know where I can get an adjustable 12V thermosensor switch? I have several applications in development that could use this. I need 1 to sense air intake temps and be able to send a signal (+ or -) to a relay when a set temp is reached.

I need another to sense the temperature in the cabin of the car. I have been searching google and some other sites, but no luck so far.

any ideas? btw, I have no idea what section to put this in.

thanks.

I would look for the word thermocouple.
By defenition a thermocuple returns a voltage based on the temperature, it's a variable resitor or Pot, by the way it operates, in that there are some where current goes up as temp increases, to a fixed point. But in most Voltage decreeases (Resistance increases) across the range of the thermocouple, as temperature increases. Once yout know the voltage that corresponds to the value you want to take action, pick a relay that sits slightly above that value and then pick a resistor to bring it to exactly that vlaue so the switch toggles exactly at your predefined value. To add adjustability add another rotray pot (Potentiometer) instead of a fixed resitor, and dial in a resistance untill you hear the relay click.
That way you can later adjust this to compensate for tuning purposes or other enviromental conditions, or age of the thermocouple.

They come in multiple flavors, some, for extreme temperature ranges. An EGT is nothing more than an example of this at the High end of extreme.

Im not smart enough to understand what all that means, but damn it sounds impressive....

I was kinda hoping for a linky for a switch. I know someone has to know where..Im just a googling it.

BTW, thank you very much for that write up, im just looking for something a little more simple :)

Is a Manufraturer
http://www.omega.com/toc_asp/section...ture&section=a

Okay a relay is nothing more than a switch, that is operated by a low amperager (danger/battery draw) cuircuit, that throws the switch for a High Amperager (danger/draw) cruircuit. Provided there is enough Voltage to energise the magnet to throw the switch.

Simpler.... Switch something else on as long as the first thing has enough voltage.

Finding what that "Enough Voltage" is depends on the Thermocouple. If your thermocouple is 0-1000 degrees @ 0-12v for simplicity, then it stands to reason that if the thermocouple reads 500 degrees the voltage should be 6v, and a 12v relay would not activate. Yet a 6v relay would. But could also overheat, should you send it 12v @ 0 degrees. So be carefull, and maybe test this whole thing with a car battery before you install it.

And there's another problem, you'll need an inverter, since @ 0 degrees the 6v relay will be "On" and at 750 degrees the 6v relay will be off, while you probhably want the opposite where the relay is off untill a certain temp is exceeded. You might be better off buying a cuircuit that allready has this fuctionality, as part of the termocouple.

This might be more usefull.

Search for Thermoswitch resulted in:

http://www.gaumer.com/ProductFilter....nwal17000therm

thanks, im gonna check out your link. I found this:

http://www.rparts.com/Catalog/Major_...s/controls.asp

Its a 12 VDC adjustable thermostat. It looks pretty cool.

get an LM34 temp sensor, an LM2940 voltage regulator, a pot, and an LM2903 comparator and put them together.

yea i'll have to do that after I design my fully scailable, multi tiered client server internet application using a variety of enterprise tools.

uh yeah. its really pretty simple if you just read a little bit. stop making smartass comments and playing dumb and maybe you could acomplish something. i gave you all the pieces for making a nice adjustable pre calibrated accurate to 1 degree temp switch.

I dont doubt it. How bout I give you all software api's and languages to write my next application and see how well you do it?

I asked for a Switch to BUY, not to build. Im not an electrician and I can afford to buy one complete.

I think I found it anyway. thanks for your input, someday maybe i'll put the pieces together after im done with my field trip to the electric company.

can you share what your cooking up? Id like to get in on the ground floor ;)

after I run my a/c for about 20 minutes or so I get frost building up on my vents and my car starts to look like a walk in freezer (the white frozen air) so I want a switch to regulate the compressor.

wow i envy you...your a/c blows cold

I re-wired the A/C system and dont use the stupid stock wiring anymore. it gets too cold actually.

you must have circumvented some sort of temp regulation cuircuit....

I dont know what I did but it feels like a freezer in my car.