Thursday, April 1, 2010

lm3909 led flasher

lm3909 led flasher

LM3909 LED Flasher Oscillator

General Description

The LM3909 is a monolithic oscillator specifically designedto flash Light Emitting Diodes By using the timing capacitor

for voltage boost it delivers pulses of 2 or more volts to the LED while operating on a supply of 1 5V or less The circuit is inherently self-starting and requires addition of only a battery and capacitor to function as an LED flasher

Packaged in an 8-lead plastic mini-DIP the LM3909 will operate over the extended consumer temperature range of b25 C to a70 C It has been optimized for low power drain and operation from weak batteries so that continuous operation life exceeds that expected from battery rating

Application is made simple by inclusion of internal timing resistors and an internal LED current limit resistor As shown in the first two application circuits the timing resistors supplied are optimized for nominal flashing rates and minimum power drain at 1 5V and 3V

Timing capacitors will generally be of the electrolytic type and a small 3V rated part will be suitable for any LED flasher

using a supply up to 6V However when picking flash rates it should be remembered that some electrolytics have very broad capacitance tolerances for example b20% to a100%


Y Operation over one year from one C size flashlight cell

Y Bright high current LED pulse

Y Minimum external parts

Y Low cost

Y Low voltage operation from just over 1V to 5V

Y Low current drain averages under 0 5 mA during
battery life

Y Powerful as an oscillator directly drives an 8X speaker

Y Wide temperature range


Y Finding flashlights in the dark or locating boat mooring

Y Sales and advertising gimmicks

Y Emergency locators for instance on fire extinguishers

Y Toys and novelties

Y Electronic applications such as trigger and sawtooth

Y Siren for toy fire engine (combined oscillator speaker driver)

Y Warning indicators powered by 1 4V to 200V

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