Most commercial LED flashlightsuse three AAA or AA batteriesin series that produce 4.5V. The batteriesthen drive four white LEDs that connectin parallel. These LEDs can workat voltages as low as 2.7V ...
This circuit uses two National Semiconductor LM3914 dot/bar-display-driver ICs to implement a two-digit, 0 to 5V LED voltmeter that mimics a subranging flash ADC. An LED bar graph comprising five LEDs ...