USB LED Notifier Based on ATtiny45

Overview

The project uses the ATtiny45 to connect to eh USB port in order to create a LED notifier that can be attached to the EeePC.

Explanation

The schematic shows the pin 8 of ATtiny45 being connected to the USB port via V+ requiring 3.3V or thereabouts to be run. Two diodes are used in order to take the 5V of the USB port and bring it down to the correct voltage. Around 0.7V voltage drop is obtained when power passes through a diode. This proves a simple way of getting the correct voltage by using two diodes in series while avoiding the use of voltage regulators in the circuit.

The D+ and D- signal lines of USB port gets connected with the pins 7 & 5. The current is limited by the 68R resistors while the line to pin 5 is pulled up by the 1.8k resistor. Although a single RGB LED has pins for the 3 inputs, three LEDs were used wherein pins 6, 3, and 2 are connected to the Red, Green, and Blue outputs to the LED.

The best placement of LED is at the top edge of the screen.