Intelligent Solar Garden Light - Part 1

I bought a solar powered garden light. The solar panel charges the batteries and when it gets dark the lights (3x LEDs) turn on until it either gets lights again or the batteries run out.

It has a small amount of intelligence (turns on when dark off when light) but not enough! Time for some upgrades. :D

First, the batteries. The control box houses the batteries, which are three Ni-MH AA cells. They are 600mAh. (That's not a typo - six hundred). I swapped them out for three 1500mAh Ni-MH cells that I don't use anymore (because they are only 1500mAh).

Then I reverse engineered the circuit diagram for the electronics (nothing special there, two transistors, two resistors a switch and a diode).

I have a few ideas for sensors and transducers I want to add to the light, but I'll start by adding a microcontroller. Step forward the Arduino Wee made by SparkFun Electronics.

Step 1: Existing Circuit Diagram

When light is falling on the solar cell, transistor Q1 is turned on and connects the base of transistor Q2 to ground. This isolates the output of Q2 keeping the LED spotlights turned off. When it gets dark, Q1 is turned off, leaving the emitter isolated (floating). Assuming SW1 is turned on, the base of Q2 will be high due to R2. This will turn Q2 on and connect the emitter to ground. This completes the circuit for the LED spotlights and they turn on.

Comments

[alphaman1101]

You should probably use int for memory friendly..

[ax89]

What is the cost of this? Does this only turn on the lights slowly at dusk? To be honest, doesn't seem worth the bother because the cool factor would be gone after seeing it in action one or two times.

[ax89]

Okay, I found part 2 which added PIR. Does it significantly extend the battery life to give light for longer? Can't you add the PIR without the microcontroller? but that might reduce the geek cool factor though :(...

[ax89]

...excluding the battery upgrade, which is definitely a good one.

[wierd idiot]

nice work.

[sdallesasse]

Too cool! Currently learning about this type of subject in school this semester.