Powerful LED Flashlight circuit

  
Presented circuit is very simple. With more sampling, I refrained from using the converter and lamp designed for powering three NiCd or NiMH batteries. Because the voltage difference between the battery and the LED is very small, this arrangement is paradoxically more effective than using the drive. If the battery voltage of 3.9 V (battery is discharged from about 10%) and the LED voltage 3.5 V, the electrical energy used by 90%, while the efficiency drive from PE 2 / 2000 is in the best case 80%. Remains to choose how to control the current through LEDs.
Powerful LED Flashlight circuit - schematic

Originally I wanted to stabilize the current circuit, which panned the LED current in a small series resistor Insertion and by deviations from the reference voltage and turning a blind opened the MOSFET. From this project, I eventually withdrew because of this relatively complex circuit would provide little improvement over the simple transistor circuit, which I eventually used. In Figure A current is flowing eight white LEDs, depending on supply voltage. The first curve shows the LED current, depending on the voltage without any current limitation. It's actually voltampere LED characteristics. The figure shows that the characteristics of the knee is not sharp. Diode really begins to shine it at a voltage of about 2.8 V. In the second case, the current limited resistor with resistance 2.7 ohms, and the third transistor with a resistor to the base - see Figure 2 . Most of the components on a printed circuit board according to Figure 4 and 5 . Outside the plate is only switch S2, which placed it as needed or replace R2 and drop the link. We create the behavior cut into boards for S1. LEDs are soldered to the board stops. Solder pads should be possible Can we shorten the time soldering LEDs to a strict minimum. Instead of engaging temporarily R1 trimmer resistance 5 kOhm resistance (up to 8 LEDs), more preferably in series with a resistor 1 kOhm. The board is designed so that more skilled at it-yourselfer can riveted...



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