Power Booster Recycles Dead Battery

This power booster recycles a 'dead' battery to power a 1.8 volt red LED light. It's mainly made from recycled parts. The inspiration came after building an 'Everything is OK alarm' which used the same principle - a rapidly collapsing magnetic field inducing a power boost to a LED Circuit. As a bonus, it's sure to make for a splendid minimalist Christmas tree.

Supplies

1.8 volt red LED

'Dead' 1.5 volt AAA battery

Small 1.5 volt buzzer

Windings from a burnt out toy motor

Bamboo skewer sticks

Tools:

Soldering iron

Hot glue gun

New Vs 'Dead' AAA Batteries

When a 1.5 volt battery is new it will probably have more than 1.5 volts in it. As the battery is used the voltage will decrease until the voltage is not enough to run the application ( E.g. a red LED) and will be called 'dead' . But a Dead battery still has some power remaining in it - just not enough voltage. The trick is to use some of that remaining power to increase the voltage in a circuit. The trade off being there will be a reduction in current.

How to Increase the Voltage

A wire connected to a battery has a magnetic field around it, as can be seen if a compass is held close by. When the wire is disconnected from the battery, the magnetic field collapses and in doing so induces a current into the wire for a split second.
If a LED is connected across the battery which doesn't have enough volts to power it, no current flows and the LED doesn't shine.
But if you combine both circuits you can get a boost to the LED circuit from the induced current as the wire from the first circuit is disconnected from the battery and the LED will flicker. Then if the first circuit can be rapidly turned on and off the LED is likely to appear to be constantly on, maybe with a flicker here and there.
This project attempts to test this using the winding from a broken toy motor to create the first circuit and a small buzzer to create a switch which rapidly turns the circuit off and on. The aim being to have a LED glow constantly from a recycled 'dead' battery.

Testing the Theory

A 1.8 volt red LED was connected across a battery with 1.2 volts remaining, as expected it didn't light the LED.

Another wire was then connected from the battery to the windings from the dismantled toy motor (to increase the magnetic field in the wire) and then to the battery to complete the circuit. When the wire was disconnected from the battery the LED flickered on. A previous project using a beer can also demonstrated this phonomime

Next the buzzer, with its cover removed, was added to the setup. The buzzer (surprisingly) would run off the 1.2 volts from the battery and was set buzzing away. Another wire was connected between buzzer body and battery so when the wire from the windings circuit touched it, the windings circuit is completed and a magnetic field created. By holding the wire from the windings circuit just above the vibrating buzzer 'striker', the windings circuit was rapidly turned on and off (building and collapsing its magnetic field) and by doing so caused the LED Circuit to have enough volts for the LED to appear to be constantly on.

Assembly (Part 1)

Connect a switch to a battery holder. A soldiering iron and hot glue gun assisted with this.
Make a small pyramid above the battery holder using 4 bamboo skewer sticks secured with hot glue.
Soldier on a 1.8 volt red LED at the top of the mini Christmas tree.
Test the LED glows with a new battery (1.6 volts)
Test the LED doesn't glow with a dead battery (1.2 volts)

Completed Assembly

Add in the buzzer circuit, along with a switch.
Add in the windings circuit - to touch the striker of the buzzer a little copper foil was added.
Insert a dead battery (1.2 volt) with the buzzer circuit turned switch off - the LED will not glow but when the buzzer circuit is switched on the Red LED lights up.

Practical Application

The same principle explained and tested in this project is used in the small garden lights you are likely to be familiar with. In them a transistor is used as the rapid switch and a small choke winding (looks like a resistor) to create and collapse the magnetic field so a 3 volt LED can be lite up from a 1.2 volt battery.