user71866: I am making a temperature sensor that can go in a freezer and I am trying to figure out what the best method is.
My research has taken me all over the place an I can't seem to find a straight answer. Some sites recommend using LiFePo4, while others say absolutely not, because it needs to be regulated.
One question I have is: could I use more voltage, say 6V from a series of batteries and connect it to the 5V pin since it is regulated, or is it better to go with an external regulator for the 3.3V pin with less voltage?

user14095: Since it is a freezer (operating temperature unknown) I am assuming it is connected to the mains why not do the same with the electronics. This will save you a lot work and time and when you find out it will not work in a  Faraday cage as stated by timemage.  Leave the sensor wire long enough to mount the electronics outside just in case. Also consider packaging, it will be cold, possibly below the operating range of some of the components requiring you to keep them warm (above minimum temperature). I would assume your freezer like ours has moisture concerns as ice will form when opened then removed by a defrost cycle. You will also have to protect for that. Then there is the operating temperature range of the batteries, are they capable of operating at your freezer temperatures. I would suggest you redefine your problem before starting the design, this process saves me a lot of grief.

71866: <p>I am making a temperature sensor that can go in a freezer and I am trying to figure out what the best method is.</p>
<p>My research has taken me all over the place an I can't seem to find a straight answer. Some sites recommend using LiFePo4, while others say absolutely not, because it needs to be regulated.</p>
<p>One question I have is: could I use more voltage, say 6V from a series of batteries and connect it to the 5V pin since it is regulated, or is it better to go with an external regulator for the 3.3V pin with less voltage?</p>
 14095: <p>Since it is a freezer (operating temperature unknown) I am assuming it is connected to the mains why not do the same with the electronics. This will save you a lot work and time and when you find out it will not work in a  Faraday cage as stated by timemage.  Leave the sensor wire long enough to mount the electronics outside just in case. Also consider packaging, it will be cold, possibly below the operating range of some of the components requiring you to keep them warm (above minimum temperature). I would assume your freezer like ours has moisture concerns as ice will form when opened then removed by a defrost cycle. You will also have to protect for that. Then there is the operating temperature range of the batteries, are they capable of operating at your freezer temperatures. I would suggest you redefine your problem before starting the design, this process saves me a lot of grief.</p>
