I have just created a circuit diagram for the Lightbix.

It features 3 schottky diodes for the solar panel to charge the battery and battery to run when solar panel voltage is reduced from shade.

It DOES NOT yet contain any smart charging. So the battery and solar panel volts have to match. I'd like to use the microcontroller to handle the smart charging since it's there.

I have a continuous servo in there because it might be cheaper than a stepper + driver. I forgot to add a MOSFET for the power supply and have the arduino hooked dirctly up the the servo.

I have wired the ESP8266 according to an instructable but I suspect I misunderstood their intention.

I have added to "snap action switches" as limit switches. These will be on either side of the topmost blind.

I have also shown the optical sensor, I feel I probably need a resistor. I don't want to filter the input with an RC circuit as the arduino should be able to average the samples over time.

Total build cost without case is around $30 now.

The servo is the most expensive component at $14.

I could reduce battery needs if I knew how to make a proper boost circuit...or buck?

Solar panel may be over/underpowered. No way to guess at that, I have to make a working circuit, build it, then test it. Luckily, building at hackerspace should be no problem.