Circuits & Schematics Light - 2

Solid-state-lighting applications are quickly moving into the mainstream. Although they are more efficient, the LEDs that produce the low-cost light often require a complicated driver circuit. Testing the driver circuit using LEDs, although easy, ...

When coach cars of long-range trains comprised compartments for six to eight passengers, the passengers could choose either “white” or deep blue light. The blue light helped passengers sleep, even when they were not in full darkness. ...

You can build a self-oscillating H bridge by replacing the pullup collector resistors of a classical BJT (bipolar-junction-transistor) astable multivibrator with PNP BJTs (Figure 1). Because this circuit oscillates at supply voltages as low as 0.6 ...

The article describes an RGB incident light sensor that uses colored LEDs as narrow-spectrum photosensitive elements. In the process of prototyping the RGB sensor, LEDs from the available batches were tested. However, the best results are obtained ...

Lighting LEDs from a single 1.5 V cell poses a problem because their forward voltages are higher than the cell’s. The simplest way to light the LED is to use a step-up dc/dc converter. This Design Idea offers a simple and reliable alternative ...

If you face the challenge of adding a second, independently controlled light source to an existing ceiling lamp controlled by a wall switch, you may find that stringing a second power line is impossible. First, you can replace the wall switch by ...

A few years ago, manufacturers specified their white, but dim, LEDs for a maximum forward-current rating of 20 mA. Today's white LEDs deliver more light and thus must operate at ever-higher bias currents. Maintaining control of an LED's ...

Many LED drivers, using both charge pumps and inductors, are available to boost the 1.2 to 2.4 V available from single- and dual-cell NiMH (nickel-metal-hydride) batteries to the 3.6 V that white LEDs require. However, most of these circuits, such ...

The simple circuit in Figure 1, which can be powered with a 3.6 V nickel-cadmium rechargeable battery, lets you use an LED to detect light. The circuit consumes practically no quiescent power. Two LEDs act as photodiodes to detect and respond to ...

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 ...