SparkFun Electronics Forum

I am wanting to build a heated temperature controlled pouch. I'm needing a heated pouch that is able to reach and maintain temperatures of 98°F-102°F for 6 to 8hrs with a 5v-12v power supply.

You need to know
1) The temperature on the outside of the pouch as well as on the inside
2) The heat transfer coefficient of the material (how well it insulates)
3) Newton's cooling law: https://physics.stackexchange.com/quest ... ferent-tem
4) Apply Newton's law to figure out how much energy it will take
5) From the above, you will know the electrical energy needed
6) Now you know the power requirements, you need a temperature controller. You can buy those cheaply off the shelf: http://www.ebay.com/bhp/temperature-switch