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BRIGHT FLASH FROM FLAT BATTERY This is a Bright Flash From Flate Battery and 3v  White LED Flasher Project. This circuit can flash a white LED, on a provide from 2v to 6v and turn out a really bright flash. The circuit takes regarding 2mA and recent cells are often used. the 2 100u electros in parallel produce a much better flash when the availability is 6v. 3v WHITE LED FLASHER This will flash a white LED, on 3v provide and turn out a really bright flash. The circuit produces a voltage on top of 5v if the LED isn't in circuit however the LED limits the voltage to its characteristic voltage of three.2v to 3.6v.   The circuit takes regarding 2mA an is really a voltage-doubler (voltage incrementer) arrangement. Note the 10k charges the 100u. It doesn't illuminate the LED because the 100u is charging and also the voltage across it's invariably less than 3v. When the 2 transistors conduct, the collector of the BC557 rises to rail voltage and pulls the 100u HIGH. The negative ...

This circuit was designed as a warning flasher to alert road users to dangerous situations in the dark. Alternatively, it can act as a bicycle light (subject to traffic regulations and legislation). White LEDs only are recommended if the circuit is used as a bicycle front light (i.e. for road illumination) and red LEDs only when used as a tail light. During the day, the two 1.6-V solar cells charge the two AA batteries. In darkness, the solar cell voltage disappears and the batteries automatically power the circuit.  High-intensity LED Warning Flasher Circuit Diagram The flash frequency is about one per second and the LED on-time is about 330 ms. The duty cycle should enable the batteries to power the circuit over night. The circuit is composed of three parts. Under normal daylight conditions the batteries are charged through diode D4. In darkness, pnp transistor T1 is switched on, supplying battery current to the second part, a low-frequency oscillator comprising T2 and T3.The thi...

Circuit Diagram: Description Ordinary LED flashers turn the LED on and off abruptly, which can get a little irritating after a while. The circuit shown here is more gentle on the eyes: the light intensity changes very slowly and sinusoidally, helping to generate a relaxed mood. The circuit shows a phase-shift oscillator with an adjustable current source at its output. The circuit is capable of driving two LEDs in series without affecting the current. The frequency is set by three RC networks, each of which consists of a 100 µF capacitor and a 22 kO resistor. Operation is largely independent of supply voltage, and the average LED current is set at about 10 mA. The circuit adjusts the voltage across the emitter resistor so that it matches the base voltage of the first transistor (around 0.6 V). The phase shifting network gives rise to the oscillation around this average value. In the prototype of this circuit we used an ultra-bright red LED.  Author : Burkhard Kainka, Elektor Electro...

The LM3909 is an integrated circuit (IC) which will flash a light-emitting diode (LED). Using only two extra components and a battery, the circuit is cheap and has a very low current drain from a 1.5 V cell. The circuit can be used as a novelty flasher, an indicator for a dummy alarm bell box, or it could be attached to a torch so that it could be found easily in the dark! The simple circuit Assembly The circuit can be built on a small piece of Veroboard (the piece shown in Figure 2 measures 15 holes by 10 strips). Using such a board, follow these instructions. 1. Depending on how far away you want the LED from the circuit board, solder a length of insulated wire to each lead of the LED. Use different colours of insulation – say, red and black, connecting the red lead to the anode (a) lead (the longer one) of the LED, and the black one to the cathode (k). Figure 2 shows these leads. 2. Cut the copper tracks as shown in Figure 2, using a 3 mm (1⁄8 inch) diameter drill, rotated between t...

The basic 2 LED astable multivibrator flasher built by Mary. She chose to use 2 different colored LEDs and the red LED is clear when unlit. It is quite bright when lit compared to the yellow LED despite the fact that it only draws 0.5 mA more. The bread boarded test circuit was powered by a new 9 volt battery and was regulated by a L78L05 (in a TO-92 package as shown in the schematic). The 5 volt regulator was used to avoid exceeding the reverse breakdown voltage of the 2N3904. This topic will be discussed a little later on. 470 ohm current dropping resistors were chosen to keep the collector current draw less than 10 mA. The LEDS were bright enough to see well in dim lighting. You may change this resistor "R" value (lower R = brighter), but do not exceed the maximum current rating for the LED or transistor (this is more applicable to higher voltage multivibrators). You may also place 2 or more LEDs in series on each half of a multivibrator, however, the current dropping...