Circuits & Schematics Light - 2

The circuit in Figure 1 is similar in principle to that of a previous Design Idea ( Reference 1 ) but offers improved, more reproducible performance. The output current is almost constant over an input-voltage range of 1.2 to 1.5 V and is ...

LED drivers have lots of features and require plenty of external components. When your application requires no PWM (pulse-width-modulated) dimming or controlled frequency operation, your primary concern may be that too much current could damage or ...

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 ...