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  • MIC2841A Driven Solar Outdoor LED Light

  • Created: Sep 16, 2016

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An outdoor light provides illumination to a house. It offers a welcoming feeling to your house and also serves as a safety feature. With electricity costs constantly rising, it’s high time to consider an alternative source of energy to power these outdoor lights. In this reference design, a solar outdoor LED light is developed which utilizes an MIC2841A device. The MIC2841A is a very efficient LED driver that operates from 3V to 5.5V supply. It can drive four white LEDs with a typical dropout of 40mV at 20mA. The device also includes ultra fast PWM (200-500kHz) which can operate up to 1% duty cycle that can be used to dim the LED lights.

The design is composed of a transistorized charge controller circuit, a PIC18F2550 microcontroller, two V7805-1000R 5V switching regulators, five MIC2841A LED drivers, 20 CLA1B-WKW-XD0F0E33 white LEDs, an external 12V solar panel, and an external 12V rechargeable battery. The operation of the circuit depends if it is daytime or nighttime. During daytime, the circuit is focus on charging the battery. At nighttime, the circuit is focus on switching ON the LEDs. The PIC18F2550 microcontroller acts as the brain of the circuit. It monitors the transition between daytime and nighttime through its pin RA0 and decides what operation it executes. The voltage from the solar panel is the basis of the microcontroller if it is daytime or nighttime. When the PIC18F2550 detects a sufficient voltage, it will control the charge controller to charge the 12V battery. The PIC18F2550 controls the energy sent to the battery through transistors Q1 and Q2. When the battery is full, the microcontroller stops charging the battery. When the PIC18F2550 detects that the solar panel voltage is dropping, it starts to activate or switch ON the five MIC2841A LED drivers to turn ON the LEDs. The supply for the MIC2841A is controlled by the microcontroller through Q3 and Q4.

The supply for the microcontroller is taken from the battery. The V7805-1000R (U6) regulates the 12V level to 5V to power the PIC18F2550. The MIC2841A LED drivers supply is also regulated by a V7805-1000R regulator (U7). The microcontroller just disconnects the supply for the MIC2841A drivers through Q3 and Q4 if it detects that the battery level is very low. It senses the battery level through pin RA1. The PIC18F2550 initially provides a 100% duty cycle PWM signal to the MIC2841A LED drivers. When the battery level is starting to drop, the duty cycle is also reduced to save power. This MIC2841A driven solar outdoor LED light can be used to replace outdoor lights that is powered from an AC supply.