LED Flashlight circuit with MAX1811

Posted on Sep 25, 2012

White LEDs have a rated current at a voltage drop of about 3.3 to 3.4 V. It is ideal to be powered from the battery voltage which is slightly larger. Then there is the best energy used. In this I used a flashlight battery, Li-ion battery, which lasts the full brightness of the lamp lit for many hours. Circuit for power LEDs is described here , and I will not repeat its description. More interesting is the charger with the MAX1811 circuit. When designing a lamp for my past experiences like charging as simple as possible. No dedicated external charger that was lost just when it needed to charge the flashlight.

LED Flashlight circuit with MAX1811
Click here to download the full size of the above Circuit.

You just come on and join lamp standard AB cable to any USB port or cable to temporarily pull out just one unused device. The port is used only to power supply, no software support is not needed. Circuit MAX1811 is designed for charging Li-Ion USB in portable devices. Its great advantage is that, unless the input circuit voltage from the USB port does not consume practically no battery power and may be permanently connected to the battery. This greatly simplifies the connection. Circuit to charge one cell voltage of 4.1 or 4.2 V and a current of approximately 100 or 500 mA. Here is the connecting terminals 1 and 2 on the + selected voltage of 4.2 V and current of 500 mA. The stability of the circuit are required according to the manufacturer's quality capacitors C1 and C2. Datasheet for circuit, see eg http://www.maxim-ic.com/quick_view2.cfm/qv_pk/2536/ln/en . LED10 light when charging, but unfortunately only in the charging constant current phase. Reaches the battery voltage of 4.2 V, the LED goes out, even if the battery is still fully charged. This is unfortunate especially in older batteries, which due to increased internal resistance of the charging voltage reaches the final soon after the start of charging. Otherwise I do not have any reservations about charging circuit. The lamp I used protective circuit of the battery to the mobile phone. Protection circuit disconnects the battery at high voltage drops (it...

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