Solar powered outdoor weather sensor

To be independent of a plug socket for an outdoor weather sensor solar power looks a lot more promising than wind or water for power generation. 😉 Especially since simple solar panels for tinkering are available for little money in the meantime. Only shipping from China usually takes a couple of weeks.

Earlier this year I launched my personal outdoor weather sensor to collect weather data such as temperature, humidity and air pressure. So far this required a plug socket and a 5V power supply. For the future I plan to use a solar panel to load a rechargeable battery which will alternatively power the outdoor weather sensor. Well, at least, when outside temperatures allow. During wintertime the cold temperatures might shorten the life of the rechargeable battery. Therefore, in the cold season the 5V power supply can be used alternatively.

Components used

Outdoor weather sensor
5V solar panel
Lithium battery 3,7 V, 2500 mAh
Lithium battery charger
Step up power supply

Wiring

Starting from the solar panel the wires go to the input of the charger module. The charger is connected to the battery and the step up power supply. The output lines of the step up power supply are soldered to the outdoor weather sensor. The battery should be removable to switch easily to a conventional 5V power supply.

The following sketch roughly illustrates the setup:

sketch

Adjusting the Step Up power supply

The desired output voltage of the step up power supply is 5V in this case. It can be adjusted by turning the small screw while the outgoing lines of the charger modules are connected to a multimeter measuring the voltage.

Notes

To fully charge the rechargeable battery it should be very sunny! Charging takes a couple of hours depending on the size of the battery. Since it is a lithium battery the memory effect known from NiMh or NiCd rechargeable batteries can be neglected.

As soon as the outdoor weather sensor is powered by an electric 5V power supply the battery should be removed! (Mentioned just in case.)

Result

Summers sunlight is optimal for charging a lithium battery and driving the outdoor weather sensor. This works in parallel. Since the outdoor weather sensor will spend most of the time in deep sleep mode the battery should last a while! So far I did not measure how mich power is drawn by awaking the outdoor weather sensor from deep sleep, doing the measurements, sending the measured values via WiFi to the server and going back to sleep. Perhaps later…

Well, now it is time to find a weather-proof box for all of this!

 

 

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