Electric OU: TKBloomer Hybrid Wireless Joule Thief
Here’s a demonstration of a wireless receiver coupled to a Joule Thief, with a supercapacitor energy reservoir, all in a small package. If you get bored, you may skip ahead to 11:00, but be sure to watch that last part.
The Green LED is simply hooked directly across the supercap, with no dropping resistor. There is a one-ohm resistor and a pushbutton switch across the supercap-LED which discharges the supercap through the resistor when the PB is pressed. This allows me to dump the stored energy in the cap and show the behaviour at various voltages without waiting all day — literally — for the Green LED to go out.
The Blue LED is the JT output. This JT circuit operates best at lower voltages. By the time the Green LED is completely out due to low voltage, the JT part is starting to see its preferred voltage range, so it brightens as the voltage drops further.
At the lowest end of the JT operating range, about 520 mV, the supercap can actually recover energy and _gain voltage_ while the Blue LED is still on.
The supercap is a 2.7V, 10 Farad unit, from an EBay store, cost about one dollar. The toriod is from a CFL, rewound with 8+8 turns of #27 (what else). The transistor is a BC337-25, and the base RC is 3.3k and 500pF. The whole thing probably cost about 3 dollars to make.
Not including the wireless transmitter part, of course.
