I want to light up a led with my hand heat by using a peltier cooler. how can I light up a led with 30 millivolt-0.1 volt with a joule thief? Should I connect more transistor in parallel or give more turns on toroid? I have made a joule thief which can light up a led with 0.7 volt.
how can I light up a led with 30 millivolt-0.1 volt with a joule thief?
A joule thief will not work below 0.6V to 0.7V. If you want to light an LED with 30mV you will need a supplementary battery/power source. There are energy harvesting chips that "say" they can energy harvest at 20 mV but they use a supplementary supply to get the process started then move their power control circuits to the "harvested" larger voltage.
Linear technology and Texas Instruments both have parts that will do this.