Switching between 3 power sources using a microcontroller

Question

I am doing a project in which I use 230V mains to charge a battery. If mains power is down, I have to use solar power for charging; and if the solar power is not good I have to switch to the diesel generated power. I have to do this using a microcontroller. Also, I should display the the source with which the battery is being sourced on a lcd display. How do I do this?

Answer 1

Required:

• method to measure voltage and current of each source
• method to switch between sources

Mains monitoring can be done by measuring only voltage. To do this, I suggest you read How to connect 230V 50Hz to arduino analog input. Solar monitoring solutions can range from a simple current sense resistor to maximum power point trackers. It's up to you whether or not you need a generator monitor -- perhaps a simple "is it on?" indicator. A switch solution depends entirely on the power requirements. For moderate to low power, I suggest you read Interfacing microcontroller and mains via a relay; high power will need more buffering. Each of the mentioned sources produce different types of electricity, so you need circuitry to address this, like a Xantrex power hub or other AC-DC & DC-DC converters. Interfacing with an LCD is a different issue altogether, so start a new question with a specific LCD in mind and read Serial Enabled LCD.

Answer 2

o-------------+--- >| ---- + ---------- power output
              |            |
3 sources     |            |
o---------+---|--- >| ---- + 
          |   |            |
          |   |            |
o-----+---|---|--- >| -----/
      |   |   |
      |   |   |
      measure here (digital inputs with proper resistors)

beter use Schottky diodes