Illuminate LEDs with 1.5V Battery using Joule Thief Circuit

This is a circuit that can make an LED light up from a dead battery!

It works with white, blue and even ultraviolet LEDs and all you need is a battery that is almost empty at least 1.2V.

The cool thing is the LED can even light up with just a tiny bit of power left as low as 0.4V.

One can now use batteries which were previously believed to be worthless!

WARNING: Building circuits can be dangerous.

Only do this with adult supervision.

What is a Joule Thief Circuit:

A Joule Thief circuit is a simple voltage booster or step up converter circuit that is designed to efficiently extract the remaining energy from a low voltage power source.

The concept behind the joule thief is to use a minimal number of components to boost the voltage of a nearly depleted battery enabling the powering of low voltage devices even when the battery voltage is below the typical operating voltage of the device.

Circuit Diagram:

Parts List:

Formulas and Calculations:

Turns in Coil (N): N = 2 x 50 turns

Coil Wire Diameter (d): Wire diameter: 0.05 mm to 0.2 mm

Cross Sectional Area of Ferrite Core (A): A = 7 mm²

Operating Frequency (f): Operating frequency: -50 kHz

Construction of ferrite core:

Coil Winding:

Take a piece of ferrite core with an ring type torroidal cross section as shown above.

Wind the coil with 2 x 50 turns of thin super enameled copper wire.

Simultaneously wind both windings for efficiency.

Use a wire diameter in the range of 0.05 mm to 0.2 mm.

Core Assembly:

Once the coil has been wound around one of the ferrite cores use super glue to connect the cores together.

Ensure a strong connection.

Circuit Integration:

Connect the coil to the circuit of joule thief.

On the basis of a self oscillating inverter the joule thief circuit functions.

Operating Frequency Adjustment:

Adjust the circuit finely at a frequency of about 50 kHz.

Although it is not necessary this frequency acts as a benchmark for best results.

Capacitor Optional:

Although a capacitor is not necessary for the circuit to work but one can opt to add one.

Use the following formula for calculating the required capacitance:

C = 1 / (2πfZ)

where,

• Z is the impedance of the circuit.

Enclosure Integration:

Use a damaged flashlight to make the enclosure.

Remove the original miniature bulb and 2 AA batteries.

Place the constructed joule thief circuit in the space originally occupied by the second battery.

Source of Power:

Use a single cell battery with a voltage not more than 1.5 or 1.2 volts.

The supply voltage at which the LED starts emitting light should be 0.4V.

Voltage Considerations:

For LED diodes a voltage drop of around 3V is required.

To do this a boost converter is required.

Operating Frequency:

The joule thief circuit operates at a frequency of about 50 kHz although this is not an essential element.

Optional Capacitor:

A capacitor is added to the circuit even if it is not actually necessary.

But even without it the circuit operates effectively.

Safety Measures:

• Double check the connections before switching ON the power and always use high quality soldering procedures.
• Use components whose ratings for voltage and current match the design of the circuit.
• Following these precautions will allow anyone to use a 1.5V battery that appears to be dead with a Joule thief circuit to enjoy the LEDs continuous illumination.

Conclusion:

This Illuminate LEDs with 1.5V Battery using Joule Thief Circuit provides an clever solution for powering LEDs from 1.5V low voltage batteries that might be considered unusable for conventional devices.

The construction details described above ensure a basic process making it accessible for electronics fans and hobbyists.

References:

Joule thief

Joule Thief and its Applications