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lm3909n-led-flasher

4 min read

Important Note

This entire repo was AI created - including all of the data within. The intent was to A) help me with my personal electronics inventory; and B) see how I could use AI to make that process a bit easier. DO NOT TRUST!

LM3909N - Low Voltage LED Flasher/Oscillator

Details

  • Location: Cabinet-3, Bin 33, Section A
  • Category: Logic ICs
  • Brand: National Semiconductor (vintage)
  • Part Number: LM3909N
  • Package: 8-DIP
  • Quantity: 1
  • Status: Available
  • Price Range: $5.00-15.00 (vintage/rare component)
  • Datasheet: LM3909 Datasheet
  • Product URL: https://www.ti.com/product/LM3909 (discontinued)

Description

The LM3909N is a vintage integrated circuit from National Semiconductor designed specifically as a low voltage LED flasher and oscillator. This remarkable IC can operate directly from a single 1.5V battery cell, making it ideal for simple battery-powered LED flashing applications. The IC integrates an oscillator and LED driver circuit that manages the charging and discharging cycles to drive LEDs in a pulsed manner, optimizing power consumption for extended battery life. This was a popular choice in vintage electronics projects due to its simplicity and ultra-low voltage operation.

Specifications

Electrical Characteristics

  • Operating Voltage: 1.5V ~ 12V (optimized for single cell operation)
  • Minimum Operating Voltage: 1.5V (single AA/AAA battery)
  • Supply Current: Very low (designed for long battery life)
  • LED Drive Current: Sufficient for standard LEDs
  • Flash Rate: Adjustable via external timing components
  • Operating Temperature: 0°C to +70°C (typical)

Physical Characteristics

  • Package: 8-pin DIP (Dual In-line Package)
  • Dimensions: 0.300” (7.62mm) width
  • Pin Pitch: 0.100” (2.54mm)
  • Vintage Component: Originally manufactured by National Semiconductor

Key Features

  • Ultra-low voltage operation (1.5V minimum)
  • Integrated oscillator and LED driver
  • Minimal external components required
  • Optimized for battery-powered applications
  • Adjustable flash rate with external R/C components
  • Classic vintage IC design

Pinout Diagram

    LM3909N 8-Pin DIP
    ┌─────────────┐
V+  │1          8│ LED+
C1  │2          7│ LED-
C2  │3          6│ R/C
GND │4          5│ R/C
    └─────────────┘

Pin Descriptions

PinNameDescription
1V+Positive power supply (1.5V-12V)
2C1Timing capacitor connection 1
3C2Timing capacitor connection 2
4GNDGround connection
5R/CResistor/Capacitor timing network
6R/CResistor/Capacitor timing network
7LED-LED cathode connection
8LED+LED anode connection

Applications

Common use cases for the LM3909N:

  • Battery-powered LED flashers and blinkers
  • Low voltage indicator lights
  • Emergency signaling devices
  • Toy electronics and novelty items
  • Educational electronics projects
  • Vintage electronics restoration
  • Ultra-low power warning indicators
  • Single-battery LED circuits

Circuit Examples

Basic LED Flasher (1.5V Battery)

1.5V Battery + ---- V+ (Pin 1)
1.5V Battery - ---- GND (Pin 4)
LED Anode ---- LED+ (Pin 8)
LED Cathode ---- LED- (Pin 7)
Timing Capacitor (100µF) between C1 (Pin 2) and C2 (Pin 3)
Optional timing resistor between R/C pins (5,6) for rate adjustment

Adjustable Flash Rate Circuit

V+ ---- 1.5V to 12V supply
GND ---- Ground
LED between LED+ and LED- pins
Timing capacitor (10µF-1000µF) between C1 and C2
Variable resistor (10kΩ-1MΩ) between R/C pins for rate control

Multiple LED Flasher

Standard LM3909N circuit with:
LED+ ---- Multiple LEDs in parallel (with current limiting)
Each LED with appropriate current limiting resistor
Common cathode connection to LED- pin

Technical Notes

Important considerations for the LM3909N:

  • Vintage Component: This IC is discontinued and may be difficult to source
  • Low Voltage Optimization: Specifically designed for 1.5V operation
  • Timing Components: Flash rate determined by external R/C values
  • LED Selection: Use standard LEDs with appropriate forward voltage
  • Battery Life: Optimized for maximum battery life in flashing applications
  • Heat Dissipation: Minimal heat generation due to pulsed operation

Flash Rate Calculation

The flash rate can be estimated using:

  • Capacitor Value: Larger capacitors = slower flash rate
  • Resistor Value: Larger resistors = slower flash rate
  • Typical Range: 0.1 Hz to 10 Hz depending on R/C values
  • Formula: Approximate period = R × C (where R is in ohms, C is in farads)

Tags

led-flasher, oscillator, low-voltage, vintage-ic, national-semiconductor, battery-operated cabinet-3 bin-33 status-available

Notes

The LM3909N is a fascinating vintage IC that represents elegant engineering from the era when battery-powered electronics required extreme efficiency. Having this component in your collection provides access to ultra-low voltage LED flashing capabilities that are difficult to achieve with modern ICs. It’s perfect for vintage electronics restoration projects, educational demonstrations of low-power design, and unique battery-powered LED applications. Since this IC is discontinued, it has become somewhat of a collector’s item among electronics enthusiasts. The ability to operate from a single 1.5V battery makes it invaluable for projects where power consumption is critical. This IC showcases how specialized components were designed to solve specific problems with minimal external circuitry.

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