LED Circuits

LOW BATTERY VOLTAGE FLASHER (9) (undervol)
This circuit is designed to monitor two alkaline cells (3v) that from the battery often used in portable electronic equipment. It use an inexpensive IC from Panasonic that is connected to an efficient LED flashing circuit. When the battery voltage drops below a certain point the circuit flashes the LED. In the off state the circuit draws only 1uA, while in the active flashing state it draws 20uA. Published in EDN, Jan 2, 1997

FLASHING LED POWER INDICATOR DRAWS LOW CURRENT (18) (3vledfs1)
This circuit flashes a power indicator LED to keep the average current low.

1.5V LED FLASHER VERSION A (23) (ac14fls)
Many published circuits that flash LEDs need 3 volts or more. This circuit uses only a single inexpensive C-MOS IC and flashes the LED for a full year on a single 1.5 volt AA alkaline battery cell. The circuit uses a charge pump technique to provide the LED the needed voltage.

1.5V LED FLASHER VERSION B (24) (1vled3)
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 1.5 volt 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.

2 LINE TELEPHONE LINE STATUS INDICATOR (46) (2phostat)
Many home businesses use multiple phone lines. This circuit gives you a visual indication when a line is in operation. The two AA battery cells should provide enough power for about one year of operation. The circuit is line polarity insensitive...

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