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This  Emergency lighting using white LEDs Circuit Diagram should be assembled only by experienced people and it is advisable to use a protection network, which can be a light bulb in series. For anyone who is thinking of making a system of emergency lighting and simple, this circuit is a cheap and functional output. The circuit is basically composed of a source AC / DC without a transformer, a charger, a system of automatic switching using a diode and a diode switch to change the brightness.  Emergency lighting using white LEDs Circuit Diagram List of Components R1 = 1M, ¼ Watt, 5% R2 = 10K, ¼ Watt, 5% R3 = 10 Ohms 1Watt All resistors are LED = 22 Ohms, ¼ Watt C1 = 205/400V, PPC C2 = 100uF, 25V Z1 = 9 V, 1 WATT T1 = BD 140 All diodes = 1N4007 BATTERY = 6 volts 4 AH LEDS = WHITE, HIGH EFFICIENCY, 5mm

This High Power LEDs up to 15 Amperes Circuit Diagram employs a simple scheme that limits the current flow to the LED, you can easily modify the circuit, and can change the power just replacing the value of R2. You can use a DC source of any tensions between 9V to 15V.Para powers or other LEDs just use the approximate formula: Current (I) = 0.8/R2 where I is the current specified by the LED manufacturer. Value of I this conductor is 10A. Use R2 = 0.8/Current formula (I) to determine R2. High Power LEDs up to 15 Amperes Circuit Diagram Parts List Q1 2N3055 or similar NPN transistor R1 1W 220ohms D1, D2 1N4001 silicon diode or rectifier See R2 power for each LED R2 for 1W LED 1W 2.7ohms R2 LED to 1.5 ohms 1W 3W 5W LED R2 to 0.6 ohms or 2 x parallel 1.2-ohms/1W

This project flashes eight LEDs in an apparently random manner. It uses a 4060 combined counter and display driver IC which is designed for driving 7-segment LED displays. 8 Random Flashing LEDs Circuit Diagram The sequence is not really random because seven of the LEDs would normally be the display segments, the eighth LED is driven by an output that is normally used for driving further counters. The table below shows the sequence for the LEDs. You can use less than eight LEDs if you wish and the table may help you decide which ones to use for your purpose. Source

Function LEDs emit light when an electric current passes through them. Connecting and soldering LEDs must be connected the correct way round, the diagram may be labelled   a   or   +   for anode and   k   or   -   for cathode (yes, it really is k, not c, for cathode!). The cathode is the short lead and there may be a slight flat on the body of round LEDs. If you can see inside the LED the cathode is the larger electrode (but this is not an official identification method). LEDs can be damaged by heat when soldering, but the risk is small unless you are very slow. No special precautions are needed for soldering most LEDs.  Testing an LED Never connect an LED directly to a battery or power supply!   It will be destroyed almost instantly because too much current will pass through and burn it out. LEDs must have a resistor in series to limit the current to a safe value, for quick testing purposes a 1k  resistor is suitable for most LEDs ...