Arduino Solar powered Weather Station help

[Loctar]

Hi,

First of all, I´m sorry if I have some english grammatical mistakes because it´s not my mother language but I can understand it perfectly.

I´m thinking on making a solar weather station with an Arduino. I´m been researching for the last weeks about solar energy and power consumption and I have a general idea and a big mess in my head XD

In the last year I have tried to learn as much as possible about basic electronics with many books but I still lack some basic knowledge.

The idea:

• Use a Raspberry Pi connected to Xively with a nrf24L01 antenna on it (DIY 433MHz Wireless Transmitter + Receiving Module Superregeneration - Free shipping - DealExtreme) as a receiver.
• Use a barebone Atmega328p at 8 mhz using low power mechanism as explained by Nick Gammon (Gammon Forum : Electronics : Microprocessors : Power saving techniques for microprocessors) to send weather information to the raspberry pi through another nrf24L01
• Power the arduino through a solar panel like the one in the following link (http://www.aliexpress.com/item/New-Retail-packaging-5V-6V-130mAh-165mAh-0-8W-Solar-Panel-Solar-cell-Solar-System-With/1339738242.html)
• Do not use any product from Adafruit nor similar shops because they are very expensive in my country $) and I can't find cheap distributors that could send the items without a huge fee =(. I love their products but I can't afford their cost. Sometimes I can find similar products but for the solar project, I have not been lucky.
• Take advantage of the previous problem to learn more about electronics.

About the solar circuit I have found many ideas. I have taken the main background knowledge from the awesome post of heliosoph (Solar arduino - heliosoph). Then I also got ideas from other webs:

• This looks like the simplest way: Simple Solar Circuits | Evil Mad Scientist Laboratories
  

• This also looks pretty simple but still seems like too simple: Solar Charger Tutorial – Part 3 | Voltaic Systems Blog

I have progress until the solar powered Atmega. I have learned how to change the bootloader and how to communicate the arduino with the raspberry. I'm a bit stuck with the charge regulator.

So, the main problems now are how to build the charge regulator for nicd batteries or lipo with basic components that I have access to (diodes, zener diodes, transistors, voltage regulators) and how to control the voltage to the microcontroller and the antenna with "low power consumption philosophy" (I suppose I have to avoid voltage regulators for this ). I have connected a voltage meter to xively and, in a very cloudy day of winter I have reached peaks of 5 volts and I have got an average of around 4,5v (enough to kill the antenna).

Ok, I'm sorry if the post has been a bit long but I'll share all the progress and knowledge adquired during the project to all

[jremington]

This nice project describes a solar-powered remote water tank monitor and the design principles for the charging system are clearly documented. The principles will be the same for a solar-powered remote weather station. The finished Arduino wireless water sensor | Lifeboat Farm

[Loctar]

Thank you for the link, is it interesting but, as the own blogger said " I’ve used a 10W solar top-up charger with a built in charge controller" So it doesn't fit my current needs.

I'm still working on a way to regulate power with minimum losses. I want to try an arrangement with a 470uf capacitor, a 2.7v zener diode and 2 panels rating 5.5v and 80-90mh in parallel.

Checking the maximum and minimum voltage requirements of the components I want to attach, I have a maximum voltage allowed of 3.6v (the nrf25L01 as extracted in it's datasheet) and a minimum voltage required of 3.3v (a humidity sensor).

I think that, every time the atmega wakes up it will consume about 80mh for few seconds before going to sleep again. So, the solution circuit I have think is the one that is attached. I suppose it has many mistakes but, as I said previously, I'm trying to learn.

Thanks in advance.