Streetlights, emergency lights, and security lights must automatically turn on when it gets dark. You base the control circuit on the resistance of a photoresistor or another LDR (light-dependent resistor) that varies with light intensity. An ...
Many portable appliances and other products that must operate from a single cell are restricted to working at very low voltages. It is thus difficult to drive white LEDs that typically have a forward voltage of 3 to 5 V. The ability to flash the ...
Self-powered isolation amplifiers, which need no external isolated power supply, provide versatile and convenient interfaces in many applications that require galvanic isolation of the signal source. Examples of such applications include circuits ...
Whether you use them as indicators or to provide illumination, LEDs are hard to beat in efficiency, reliability, and cost. White LEDs are rapidly gaining popularity as sources of illumination, as in LCD backlights, but with forward voltages ...
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 ...