Sorry my poor english,
I connected my arduino board at power suppy of 4.8v and monitored the circuit with a multimeter. When the leds is off arduino provide 3,3v with leds off, when one led is on provide 3,0v, when two leds on provide 2,98v.... the temperature sensor going up about 3-4 ºC the leds is OFF or ON
This is independent of the power supply source, with USB connection success too.