Picaxe solar power supply

[Kiwi Bruv]

Has anyone done this? Did a search but couldn't find anything.

I have an 18x transmitting temp and humidity measurements on the bench and have just come to design the power supply and thought why not go solar.

Can I just have a panel charging a small 9 or 12V re-chargable battery (through appropriate circuit)and the battery output controlled to 5V with the usual picaxe power supply as in the manual?

 

[Jeremy Leach]

This the sort of thing?...

<A href='http://www.siliconchip.com.au/cms/A_103238/article.html' Target=_Blank>External Web Link</a>

 

[BeanieBots]

That is pretty much all you need to do.
The things to watch out for are over-charging your battery and excessive cycling of the battery. A typical spec life for a re-chargeable battery is about 300 full cycles (1000 in practice) so if your design does close to a full charge/discharge every day, your battery will only be good for about 1 year. Go for a battery that is at least 10 times bigger than the project would normally need. This will help to iron out the problems that un-predictable levels of sunshine will cause.
Alternatively, you could start a whole new project in it's own right to control and monitor the charge/discharge.

A solar panel output looks very similar to a constant current source clamped with a zener diode. The current is proportional to the amount of light. The voltage does vary slightly but it is only significant when the light is so low that the current is not worth having anyway.