Intelligent Solar Garden Light - Part 1

Step 2 Add the Arduino

So, the Arduino Wee is a 3.3V device (the normal Arduino is 5V TTL). The battery is made of 3x 1.2V cells giving 3.6V total. The Wee can cope with the extra 0.3V. I connected the Wee to the positive power rail after the switch and to the negative rail on the battery compartment. Then I unsoldered R1 and connected digital pin 3 to the base of transistor Q1, and the analogue input A0 to the positive rail of the solar panel. The Wee can now control the LED spotlights and knows if it's light or dark.