I have created a PCB for a wireless sensor that uses USB or an LiPo battery for power, and that is guided by a switch. The USB is the for data purposes when loading a sketch. It hit me last night, that when the LiPo battery gets low, and I replace the battery back, the sensor will loose power. To fix this, I want to put in another switch to direct current between the LiPO (normal) and a cell battery (LiPo replacement). However, I need to make sure there is no interruption of power when i flick the switch from LiPo to button cell. How do I do this with a capacitor to have an uninterrupted power supply?
Thank you.