The board as it came out of the weather instrumentclick for a full size image The board as it came out of the weather instrument. Note that the DS18S20 had been previously removed. D2 on the schematic is not installed on the board. This part is a BAT54S and without it the only thing that will be powered if 5V is supplied externally is the DS18S20 temperature sensor. The anemometer and weather vane would still be powered parasitically.