This has been an idea I have been kicking around for awhile. The OctoPROBER is a 8 channel, K-type thermocouple temperature logger. It has a micro SD card slot for logging data remotely. The USB connection can send log data directly to the PC.

Power is supplied via internal lithium 18650 3.7V cell and is charged over USB. The BQ24075RGTT is used to manage the charging of the lithium battery by using the outputs of the FT230X USB chip. I will cover this in more detail when I can verify my idea will work.

To prevent corruption of the SD card a soft power circuit is employed. A single optocoupled output is given to allow control of an external circuit.