Temperature sensor?

[BANE]

Hello, I was just testing out my dual H-bridge and its getting pretty hot (not dangerously hot) , not because of overload or anything, its just its nature .  So I have two micro fans that I'd like to install from radio shack that i want to use.  I want to make a circult that has a temperature sensor so I can ether turn on the fans from my microcontroller or the H-bridge gets to hot (H-bridge takes priority )

Does anyone have a cheap temp sensor or an idea how to hack a digital out/inside environment sensor from walmart?  I all ready have the one from walmart and it runs on two AAA batteries.

Any Ideas?

Bane

[BANE]

I like this one
http://www.sparkfun.com/commerce/product_info.php?products_id=8257
However, after looking at the price, i'm beginning to look into hacking

Bane

[bulkhead]

Try digikey:

http://datasheets.maxim-ic.com/en/ds/DS1621.pdf $4.61

[pomprocker]

I like the parallax sensors.

http://www.parallax.com/Store/Sensors/TemperatureHumidity/tabid/174/List/0/CategoryID/49/Level/a/Default.aspx?SortField=ProductName,ProductName

[BANE]

thanks, can a make my own temperature probe from digikey?   Is the reading device called a "Thermistor"?  I have a digikey catalog that has a bunch of them

BWT temperature between 50 to 300 F, or how ever high a L298 can get

Bane

[bulkhead]

You can get this Parallax sensor off digikey for less: http://www.parallax.com/Store/Sensors/TemperatureHumidity/tabid/174/CategoryID/49/List/0/Level/a/ProductID/84/Default.aspx?SortField=ProductName%2cProductName although it doesn't have a temperature "probe" that you can put on something you want to measure in particular (a)lthough you might be able to get away with letting the IC itself contact the h-bridge's heat sink.  These sensors have a digital output.  Some (I think the one I linked before) you can even program a temperature threshold so that it will switch something on if the temperature exceeds it (no need for a microcontroller).

If you want to build your own, just get a thermistor (resistance varies as a function of temperature) and an ADC to read the value, although this would require a microcontroller.

[Luco]

Maxim DS18B20 Temperature Sensor

Its free, they give samples 
Also if you are using Codevision compiler for AVR they provide functions so its very easy to use.
Few month ago I got 2 of those sensors, external clocks, memory chips, and 2 iButtons.

[BANE]

dumb question ; you have the pay for shipping for free samples right?  Also, do you have the register or something with the vendor?

Bane

[Admin]

I'd just run the fan continuously - much easier than dealing with a sensor (or paying for it, too).

But if you want to save power or keep noise low or something, just command it to turn on only when your motor is turned on.

you have the pay for shipping for free samples right?

usually no

Also, do you have the register or something with the vendor?

Usually yes. And they've called me occasionally, too.

[BANE]

sweet , I just requested one and i got an e-mail saying its already shipping   Its really hard not to be greedy though .  Heres something, it requires that you list what company your with...... well i'm not ordering for the company i work for so i just put "none"..........   Does anybody check this or does a computer handle everything?

Bane

[Luco]

I think its automatic unless you are trying to sample expensive parts, then it says someone has to approve it.