On-board 3.3V regulator and accompanying circuitry.

The main benefit to using the on-board regulator is that is has a higher

maximum voltage rating than the regulator located on the Photon. As stated

in the Photon datasheet, if power is supplied directly to the VIN pin on the

Photon, the voltage should be regulated between 3.6VDC and 5.5VDC. In

contrast, the MIC5219 regulator is rated for 2.5VDC to 12VDC, as per its

datasheet. Being able to power this system at 12V is handy for solar-

powered weather stations.

However, if you would rather have the alternative power source route power

through the regulator on the Photon (for lower current consumption during

sleep perhaps), simply cut the trace on the Power Select jumper (between

the VREG and RAW pads), and add a blob of solder between RAW and

P_VIN (Photon VIN) pads. Just be sure to not exceed voltages of 5.5-6V

once this alteration has been made.

Warning! Never power the Photon/Shield through both the micro USB

connector and the barrel jack or screw terminal at the same time! If

you need both connected for whatever reason (programming in DFU

mode over USB while powered via the barrel jack, for example), you’ll

need to cut the trace on the 3.3V Disable jumper, pictured below.

Only cut this trace is you have not altered the Power Select jumper

On-Board Sensors

The weather shield comes with two on-board sensors. Together, these two

sensors can give you a lot of information about the environmental

conditions around you or your project.

Si7021 or HTU21D Humidity and Temperature Sensor

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