External Sensor Ground

Cellular Boards RAK5010
1

I have an external sensor connected via some test points on the RAK5010 (SDA and SCL) and power from ground/VDD (1.8v). It’s working as expected.

The issue I have is that the sensor is drawing power 100% of the time and battery life is significantly lowered.

It’s a very simple sensor with the main SGP30 chip, a couple resistors and a cap.

I’m looking at redesigning the sensor to have switching transistor for power but before I do, can I used one of the I/O pins for Ground? That is set it as an Output, set it High to turn off the ground, then set Low to engage ground to drive the sensor?

If so, is there a better pin on the RAK5010 to use? IO1, IO2, IO3, IO4?

If not, then I’ll probably use one of those pins to drive a Transistor to engage power to my sensor but wanted to ask if there might be a solution already available on the RAK5010.

2

Hi @InlineTechnology ,

The heating element of SGP30 is causing the high current consumption. I will recommend to use an external transistor (should be mosfet) to power the sensor instead of using GPIO pin. It will consume around 48mA in measurement mode and not ideal for the GPIO. If you will use the header with the built-in logic level shifter in RAK5010, it wont be ideal as well since the max current of that chip is 50mA. It wont give you enough design margin. An external mosfet will surely make your design reliable. Btw SGP30 requires a certain period before you can get a reliable reading. Something to consider if you are turning it off.

3

Carl - thanks for the advice. We’ll go with a mosfet and redesign the sensor.