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
DE
AD
ER
CE
LL
NEVERLAST
NE
VE
RR
EA
DY
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
E- E- E-E-
E-
E-
E-
E-
E-
E-
E-E-E-
E-
E-
E-
E-
OFF
How it Works: Joule Thief
• The transistor turns on allowing a large current to flow through the right coil
E- E- E-E-
E-
E-
E-
E-
E-
E-
E-E-E-
E-
E-
E-
E-
E-
E-
E-
E-
E-
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-
E-
E-
E-
E-
E-
E-
E-
E-E-E-
E-
E-
E-
E-
E-
E-
E-
E-
E-
OFF
How it Works: Joule Thief
• Current in the right coil cannot shut off immediately leading to a bump in voltage
E- E- E-E-
E-
E-
E-
E-
E-
E-
E-E-E-
E-
E-
E-
E-
E-
E-
E-
E-
E-
as the field in the left
coil breaks down
OFF
Small Voltage rise
Field breaks down
E-
E-
How it Works: Joule Thief
• This process repeats, and the voltage rises
E- E- E-E-
E-
E-
E-
E-
E-
E-
E-E-E-
E-
E-
E-
E-
E-
E-
E-
OFF
Small Voltage rise
Field breaks down
E-
E-E-
E-
E-
• Once the voltage reaches the breakdown voltage of the LED electricity can flow
How it Works: Joule Thief
E- E- E-E-
E-E-E-
E-
E-
E-
E-
E-
E-
OFF
Small Voltage rise
Field breaks down
E-
E-E-
E-
E-
E-
E-
E-
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