Valentine Heart -  18 LEDs flash at three different rates and you can use these to create an eye-catching Valentine Heart for that special person! A template for the heart shape can be downloaded. The circuit is kept simple (and low cost) by using the 4060B IC which is a counter and oscillator (clock) in one package. The circuit requires a 9V supply, such as a PP3 battery. . .  [Designed by John Hewes]

Various LED Blinker Circuits -  The circuit uses independent timers to flash two light emitting diodes. Any time that light emitting diode D1 is lit__light emitting diode D2 will be switched off. Light emitting diode D3 is on if both D1 and D2 are offCircuit for model railroad trains. . . .  [from Rob Paisley's Model Train web site]

Versatile LED Display -  This circuit uses an erasable programmable read only memory (EPROM) to display various light patterns on LEDs. Since bicolour LEDs (comprising green and red LEDs) have been used, display is possible in three colours (green, red and amber). . . .  [© EFY Enterprises Pvt. Ltd. All rights reserved]

Version A of 1.5v LED Flasher -  To squeeze even more energy from a alkaline battery cell, this circuit adds two transistors to a circuit similar to the above design to boost the efficiency. A small 1.5volt alkaline N cell should flash the LED for a full year. It too uses a "charge pump" technique to provide a LED the needed voltage . . . [Circuit by David A. Johnson P.E.,  06/03/00]

Video Design Idea:  LED senses and displays ambient light intensity -  09/05/07  EDN Design Idea   Explains how an LED can double as a photosensor and a visual indicator of ambient-light intensity. . .  [by Dhananjay V Gadre of India's Netaji Subhas Institute of Technology]

Voltage boost and buck circuits using Atmel AVR Tiny13V for driving a white LED -  . . .  [by Steven Weber, KD1JV]

Voltage Monitor for a 9v Battery -  Nine voltage batteries are used in a wide variety of electronic devices. But, you often don’t know when it is time to change the battery until the device stops operating. The hobby circuit below provides a visual indication when the battery needs to be . . . [Hobby Circuit designed by David A. Johnson P.E.,  07/09/06]

Voltage to Frequency Converter + 1us LED Pulse Driver -  This circuit receives the signal from the above Amplifier and launches powerful 1uS infrared light pulses from a low cost LED that are frequency modulated by the audio information. The 10KHz center frequency of the pulse stream is low enough so a standard . . . [Circuit by Dave Johnson P.E.,  03/22/99]

Voltage-to-current converter drives white LEDs -  06/27/02  EDN Design Idea   Reset generator uses "fleapower" = You sometimes need to drive a white LED from one 1. 5V battery. Unfortunately, the forward voltage of a white LED is 3 to 4V. So, you would need a DC/DC converter to drive the LED from one battery. . .  [by Susanne Nell, Breitenfurt, Austria]

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