Have you every wondered how much is the power consumption of these low cost room temperature humidity monitors?
Recently, I purchased this temperature humidity monitor for one of my experiments and measured the power consumption out of my interest.
This monitor has very low cost design with cheap temperature, humidity sensor, a small MCU/ASIC which senses the temperature/humidity and displays on the Segmented Glass LCD.
They have also given 3 buttons for configuration like you can select if you want to see min. values, max. values or average values, you can also set the real time clock, an extra feature they have provided.
Although, I did not like the quality of the instrument as it was showing 44 degree 🙂 when the room temperature was around 24 degrees.
I measure the average power consumption of this instrument as I wanted to see if these instruments could be improved in quality and can be made totally battery free.
It uses single 1.5V AAA cell.
I connected my Power Profiler Kit II from Nordic Semiconductor and quickly measured the power consumption.
This is what I got.
It consumes approx. 90uA @1.5V which is ~135uWatts power.
What could be improved:
With high quality T/H sensor from companies like Sensiron, Silabs, Texas Instruments, etc. , and segment glass display with a BLE MCU this instrument could be made very high-quality and with smartphone you can monitor or log readings easily.
Average current could be reduced significantly (~15 – 25uA) using various low power hardware and firmware strategies.
A small high efficient indoor solar panel (~50mm x 50mm) and PMIC, which could be used for charging the super capacitor which can supply power to the instrument and will not need any battery at all.
Ofcourse, price will increase but you will get a high quality product which needs zero maintenance.
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Hi Pallav, Thank you for this informative post. One suggestion: Using a solid-state micro-battery of 100 to 500µA.h (instead of a supercapacitor) would enable measuring the temperature and humidity much longer (and possibly to send beacons regularly by Bluetooth), even if there was not enough light or collected energy the days before Micro-batteries (like those of ITEN) are not only able to deliver power (for sensors and RF) but also to store the collected energy much longer than what a supercapacitor can do. They do behave like a small energy and power reserve that can be recharged at constant voltage (like a capacitor)