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Small LED flashing circuits ( 73 ) :

  • Building lamps out of LEDs

    • Economical circuit drives white LEDs - this circuit provides a means of efficiently controlling LED current in a series-connected string     
    • LED driver delivers constant luminosity - . The output current is almost constant over an input-voltage range of 1.2 to 1.5V and is insensitive to variations of transistor gain.     
    • LED Headlamps - This article includes circuits of DC-DC LED drivers (click pics for bigger ones) step downs to run LEDs on less than Battery Volts, Boost for above.     
    • Ledilamppu - lamp built using LEDs, uses 4-8V DC, text in Finnish     
    • LED Mood Light - This circuit makes a nice lamp that is low power, runs cool, and has a long lifetime, based on LEDs and runs from 12V DC     
    • LED Torch - A white LED torch that consumes just 24 mW     
    • Light a white LED from half a cell - White LEDs are rapidly gaining popularity as sources of illumination, as in LCD backlights, but with forward voltages typically ranging from 3 to 5V, operating them from a single cell presents obvious difficulties. This design exploits the ultralow operating voltage of a single-gate Schmitt inverter based switching LED driver.     
    • Make a Joule Thief - In the November 1999 issue of EPE (Everyday Practical Electronics), a small and intriguing circuit was published in the Ingenuity Unlimited section by Z. Kaparnik. It was a very small implementation of a typical transformer feedback single transistor invertor. The transformer was a standard ferrite bead with two windings wound on it and the circuit was using the high voltage pulse generated when the transistor turns off to light an LED from a single 1.5V battery. This page has two variations on the original design to use the simple circuit in a useful manner.     
    • Single cell lights any LED - This circuit allows you to light any type of LED from a single cell whose voltage ranges from 1 to 1.5V. This range accommodates alkaline, carbon-zinc, NiCd, or NiMH single cells. The circuit's principal application is in LED-based flashlights, such as a red LED in an astronomer's flashlight, which doesn't interfere with night vision. White LEDs make handy general-purpose flashlights. You can use the circuit in Figure 1 with LEDs ranging from infrared (1.2V) to blue or white (3.5V).     
    • Special Lighting - experiments with white LEDs     
    • White-LED driver touts high efficiency     
    • White LED Flashlight     
       

  • Simple blinkers

  • Sequencer and chaser circuits

  • Multicolor LED controlling

    • Circuit efficiently switches bipolar LED - This article represents two methods to switch a bipolar, two-color LED using an SPDT mechanical switch or relay.     
    • Create secondary colors from multicolored LEDs - It is well-known that simultaneously mixing two primary-color light sources, such as red and green, creates a secondary color, such as yellow. This mixing process commonly occurs in tricolor LEDs. This Design Idea proposes a sequencing method to generate balanced secondary colors from bicolor, tricolor, and RGB LEDs, using only one LED's operating current.     
       

  • Misc circuits

    • 28 LED Clock Timer - programmable clock timer circuit that uses individual LEDs to indicate hours and minutes     
    • 8x8 LEDmatriisi - LED matrix circuit board     
    • A High Current Pulsed LED - Using this circuit will create a very sharp high current pulse to an LED at various Frequencies. With the values shown, and a 20 Volt supply, the Frequency is aproximately 10Khz and the current is about 525 mA.     
    • A linear Constant Current LED Lamp Dimmer - This simple Linear circuit provides continuously variable regulated current (~25-400mA) from a 4-6 Volt source.     
    • Circuit controls intensity of reflex optical sights - A popular category of aiming/pointing aids is the reflex, or "red-dot," sight. This system finds use in such diverse applications as astronomy, archery, and shooting. In the reflex sight, light from an internal source?typically a high-intensity red LED?reflects from a curved, transparent optical (reflex) element through which you view the target. The result of this geometry is that the image of the LED (the red dot) appears superimposed on the target image, thus indicating the point of aim. When you correctly adjust the aiming point of the telescope, bow, or gun, the target and LED images coincide. For best sight performance, the intensity of the red-dot light source must at least roughly match the illumination level of the target. This circuit adjust the LED intensity based on the target.     
    • Circuit drives mixed types and quantities of LEDs - Portable systems often use LEDs of different colors and in varying quantities of each color. Some examples are white for the display backlight, green for keypad illumination, and red for power. Typically, the LEDs derive power from at least two power supplies: one for "standard" LEDs (red and green) and one for white LEDs. (White LEDs exhibit a higher forward voltage.) This circuit mixes LEDs of different forward-bias requirements, yet keeps the loads reasonably well-balanced.     
    • Fading Red Eyes - can be used to slowly illuminate and fade a pair of red LEDs     
    • Fantastic Atom Expander - "exploding atom" effect using 98 LEDs     
    • LED dimmer uses only two lines - This circuit provides 32 steps of brightness control (from 0 to 100%) for a backlight or instrument panel, using just two general-purpose-microprocessor signals. Although the circuit shows the circuit driving white LEDs, the load could also be a dc motor or an incandescent lamp. The basis of the circuit is a modified Schmitt-trigger relaxation oscillator controlled by MAX5160 digital potentiometer.     
    • LED Lamp Dimmer - This circuit provides 32 steps of brightness control from 0 to 100% for a backlight or instrument panel using just two general purpose microprocessor signals. In addition, very little board space is required since only three SOT23's and a uMax package are used. Although the example circuit is driving white LED's, the load could also be a DC motor or an incandescent lamp.     
    • LED Mood Light - this LED circuit makes a nice lamp that is low power, runs cool, and has a long lifetime, operates from 12V, puts out a warm yellow shade of light, the color may be adjusted by changing the number of red or green LED strings     
    • Led Pilot Light - LED current is constant between 6 and 8 mA at 5 to 30Vdc     
    • Light Pollution Meter - LED brightness control circuit and a multimeter to compare light levels to LED level.     
    • McMurtrie's self powered flashing LED - circuit which uses a LED as solar panel to charge a capacitor which flashes a LED, the LED will blink when the circuit is placed in bright light     
    • Resources for Bike Light Builders     
    • Single FET controls LED array - White-LED backlights are gaining acceptance because they offer higher reliability and simpler drive circuitry than backlights based on CCFL (cold-cathode-fluorescent-lamp) and EL (electroluminescent) technology. This circuit shows a switch-mode boost design that regulates current instead of voltage and switching off individual LEDs or groups of LEDs is not a problem.     
    • Stroboscopic Tachometer using LED - use a LED, resistor and function generator to make a very small stroboscope     
    • Velleman MK103 Sound-to-Light Unit - This kit is a device that transforms sound into light.Sensitivity is adjustable, and when set at it?s maximum it is really very very sensitive, even the smallest whisper will make the four high-intensity LEDs glow bright red. This page has some theory of the kit operation.     
       

  • Other light projects

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