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You have to give the power supply everytime you are using it. As far as I remember it was 3.3 V device so you have to level convert the 5v source to 3.3 v ...there are tons videos on this topic on YouTube.
MQTT+NODE-RED+ESP8266View Instructable »
Guide to ESP8266 for Beginners
Guide to ESP8266 for NewbiesView Instructable »