Homemade white light LED flashlight with adjustable brightness

Homemade white light LED flashlight with adjustable brightness

I have made several LED flashlights by referring to the circuits in some magazines. Although their circuits are simple and easy to make, the brightness is not easy to adjust. Some circuits can only light up a 5mm white LED, and some circuits require an input voltage higher than 0.8V to work properly. So I made an LED flashlight. The circuit is shown in the attached figure. It uses a self-excited oscillation working mode. It can be started with an input voltage of 0.6V. It can use a 1.5V battery to light up three 5mm white LEDs in series. Because the operating frequency of this circuit is about 1.4MHz, the circuit efficiency is relatively high and it is very energy-saving.

Component selection: Q1 uses 9014 or 2N2222, D1 uses a fast rectifier diode, C1 and C3 use general 22uF/16V electrolytic capacitors. If you don't have them, you can remove them from old home appliances. C2 uses ceramic capacitors or other capacitors with low leakage. The production of inductor L is a bit difficult. Readers with conditions can directly buy finished products in the electronics market, and then modify them slightly according to the parameters shown in the figure. You can also find an I-shaped magnetic core with a height and width of 8mm×6mm and an inner diameter of 3mm, and use 0.2mm diameter enameled wire to wind 88T in the forward direction. The inductance value is about 200uH. When winding, mark the starting end with the label A and the ending end with the label B. After winding, put a heat shrink tube on the magnetic core for insulation, and then use φ0.2mm enameled wire to wind 10T in the same way, and mark the starting and ending ends with the labels C and D respectively. R1 uses a general adjustable resistor.

Key points: The circuit is soldered on a breadboard. Connect the circuit and adjust the adjustable resistor to the middle value (5Ω), then use a 1.5V battery to power the circuit. If the LED does not light up, please confirm whether the phase of the inductor is wrong. If the phase is correct, it may be that the voltage after the boost is not high enough and the LED does not light up. At this time, just fine-tune R1 until the LED lights up. The brightness of the LED is adjusted by R1. You can also increase the number of LEDs in series to increase the brightness. Of course, the input voltage should also be increased accordingly, but it is best not to exceed 5V. It is best to use all LEDs in series to ensure that the current flowing through each LED is the same, so that their brightness is the same. Finally, find a flashlight shell to fix the circuit and the battery, and a beautiful LED flashlight is ready.