Recently I acquired a Raspberry pi computer board to be used as a gateway for my sensor mote in our backyard that is monitoring the water temperature and water level of the fish pond. I also wanted the whole system to run off solar power, so I went and bought a 35 Watt solar panel and went about designing a power supply for the system.
The specifications of the power supply were that I wanted to be able to charge 3 smart phones and run my Raspberry pi all at the same time. To accomplish this, the power supply would need to be able to output 5V and supply about 2.5A of current. I decided to build a switching power supply instead of simply using a linear regulator because of its inefficiency (calculations suggest that about as much as 15Watts of power will be dissipated as heat).
The solar panel
Testing the circuit…
Here I was busy charging my phone while the raspberry pi was playing HD video on the TV, from the multimeter I could see the power supply was outputting 0.8A of current. So far its working fine, I just need to do more load testing and then put the components onto a board.
Then I would have my own solar power station which cost me like R400 to build and will last a long time 😀