How long are you hoping to have the thing running from a set of batteries ?Is space / weight an issue ?The 9V battery is a poor choise for powering the Arduino. It will not last long.Depending on how often the heater is on it too will drain the 4 AA batteries pretty fast i think.
The absolutely best 9V batteries have around 500mAh of juice, if memory does not fail me.
thank you for the reply, but I'm looking to remove the 9V and run off just the 4xAAs.
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