LED emergency light circuit diagram

This LED lamp circuit uses high-brightness white LED with a reflector. The lamp pole is made of a metal spiral tube, which can be bent and turned to adjust the angle of the lamp head. The lamp holder is equipped with a push-button switch. It is compact, practical and easy to carry. Figure 1 is its circuit diagram.

When the battery voltage is 4.38V, the working current is measured to be about 150mA, and the voltage drop on the LED is 3.2V. In order to effectively extend the battery life, the author decided to connect a small-value current-limiting resistor in series behind the button switch K. After repeated tests, When using a 2.7Ω resistor, the current drops to 120mA, and the brightness does not change significantly. If you think the battery is expensive, you can also use 220V AC mains power. This requires a suitable power adapter. It is recommended to use a discarded mobile phone battery charger at home. Since mobile phone charger plugs come in many different shapes, you need to use a mono in advance. After modifying the headphone plug, the charger I found has an output voltage of 6.28V. The circuit schematic diagram after the modification is shown in Figure 2, and the measured operating current is about 138mA.