Introduction Explanation of the circuit Price breakdown Construction notes Distribute kits Build time

http://www.nisk.k12.ny.us/iroquois/teched//Fall_Conference/battery_eater/battery_eater.htm

The Battery EaterGiving old batteries a new life

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http://www.nisk.k12.ny.us/iroquois/teched//Fall_Conference/battery_eater/battery_eater.htm

Joule Thief

EBC2N3904~ 0.3-1.5V10KΩ-Hand wound ferrite torroid

LDREBCEBC++47 uF47 uF2N39062N3906100 KΩ3 Volt LED3 Volt LED

LED Flasher

Battery Eater

• The Battery Eater is really two Circuits in one

The Joule Thief

• The Joule Thief uses a hand wound transformer to increase voltage

How it Works: Joule Thief

• Voltage flows through the left coil, the resistor limits current

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OFF

How it Works: Joule Thief

• The transistor turns on allowing a large current to flow through the right coil

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ON

How it Works: Joule Thief

• The current in the right coil induces a current in the left coil which opposes its existing current flow, shutting

off the transistor.E- E- E-

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OFF

How it Works: Joule Thief

• Current in the right coil cannot shut off immediately leading to a bump in voltage

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as the field in the left

coil breaks down

OFF

Small Voltage rise

Field breaks down

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How it Works: Joule Thief

• This process repeats, and the voltage rises

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OFF

Small Voltage rise

Field breaks down

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• Once the voltage reaches the breakdown voltage of the LED electricity can flow

How it Works: Joule Thief

E- E- E-E-

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OFF

Small Voltage rise

Field breaks down

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Turning the Joule Thief on

• Making the joule thief turn on at night and off in the morning adds just one extra component

EBC2N390410KΩ-Hand wound ferrite torroid

LDR3 Volt LED Single Cell(~ 0.3-1.5 )V

A voltage divider is created by the addition of the LDR keeping the transistor off when exposed to light

LED Flasher• Two PNP transistors act as switches to

turn on LEDsEBCEBC +9v++47 uF47 uF2N39062N390633KΩ100 KΩ

How it Works: LED Flasher

• Changing the resistor and capacitor will determine the LED flash rate

EBCEBC +9v++47 uF47 uF2N39062N390633KΩ100 KΩ

• An RC circuit triggers the transistors

Materials and Kit Cost

• 14 components, 1 single sided PCB

Kit Materials Quantity Part name Cost per unit Total cost per

kit Cheapest place to shop

2 Resistor 390KΩ $0.01 $0.02 www.jameco.com 1 Resistor 10KΩ $0.01 $0.02 www.jameco.com 2 High output LED $0.15 $0.30 http://www.goldmine-elec-products.com 2 Capacitor 47µF $0.02 $0.04 www.jameco.com 2 Battery Contacts $0.07 $0.14 http://www.allelectronics.com 1 Light Dependent Resistor

(CDS Cell) $0.60 $0.60 http://www.goldmine-elec-products.com

2 Transistor 2N3906 $0.049 $0.098 www.jameco.com

1 Transistor 2N3904 $0.045 $0.045 www.jameco.com

1 Toroidal Core $0.20 $0.20 http://www.goldmine-elec-products.com 28 gage stranded wire 30” www.jameco.com 1 Printed Circuit Board (PCB) $0.40 $0.40 http://www.kelvin.com

Total cost per kit: $1.86

PCB/Parts Layout