I'm using an attiny microprocessor that uses around 6mA plus another 3mA for the LED. It periodically runs a servo ( Tower 9G ) that according to a few source online draws 120 – 200 mA ( for around 6 seconds ). (200 x 6)/3600 gives me .33 mAh. If I add the two together, I get a draw of 10 mAh a day. Now lets say i had a tiny battery, something like this one. that has 100 mAh. If i then add a solar panel like this that is capable of providing 45 mA in peak sun, It sould ba able to provide more than ample power to keep the battery fully charged indefinely … are my calculations correct? or am I missing something?
Electronic – How to power an attiny from a solar panel
attinybatteriessolar cell
Related Solutions
Constant LED brightness means constant current, and constant current means a current limiter.
simulate this circuit – Schematic created using CircuitLab
Select R2 as (VD2 + VD3 - VbeQ1)/ID1. Don't be afraid to use a current slightly lower than the spec (i.e. 3 to 6mA).
Your units are confused. For reference: $$Power(W)=Voltage(V)*Current(A)$$ $$Battery~Capacity(Ah)=Current(A)*Time(h)$$ $$Energy(Wh)=Power(W)*Time(h)=Battery~Capacity(Ah)*Voltage(V)$$
For solar panel output,
- calculate total energy of one day
- divide 1 by minimum peak sun hours
- divide 2 by about 0.85
For battery capacity, you have to consider the day when there is no sun. Multiply 1 by longest no-sun period length.
Best Answer
You power budget looks ok. But the battery says:
and
The battery claims to have overvoltage protection, but it's not clear how that is achieved. It may overheat and catch fire....particulary as it says that
so-- don't burn your house down.