Introduction: 10 Year LED Flasher + PC Board
This LED flasher circuit will run for 10 years on a single 1.5v AA alkaline cell.
I have also included a PC-board. You can download it in PDF format here: PCB download . You will also find a component placement guide. Such long cell life is achieved by limiting average current drain to an initial value of 50uA(0.05mA) .
Teachers! Did you use this instructable in your classroom?
Add a Teacher Note to share how you incorporated it into your lesson.
Step 1: PC-board and Component Placement Guide
Step 2: Circuit Diagram & Component List
IC1: CD4001 (cmos quad NOR gates)
Q1: 2N4401 (NPN transistor)
C1: 100nF (0.1uF) ceramic capacitor
C2: 1nF (0.001uF) ceramic capacitor
C3: 10uF x 12v tantalum capacitor
R1: 4M7 resistor
R2: 2M2 resistor
R3: 4k7 resistor
LED: ultra-high efficiency LED (available current is very low)
T: 1/2" toroidal ferrite core & 2 meters (6 ft) of 24AWG (0.5 mm) enameled wire
BAT: 1.5 alkaline AA cell. (battery holder optional)
Step 3: Circuit Operation Details
Step 4: Making the Transformer
You can salvage the ferrite core from an old PC motherboard or power supply. Polarity of windings is important; if LED doesn't light when shorting header pins invert one of the windings.
Step 5: Measuring the Current Drain
Current drain should be around 50uA (0.05mA) when cell is new. You can adjust the current adjusting value of R2.