Attempting to make a co2 meter with batteries.
Posted:
Thu Mar 17, 2022 11:26 amby Oscar Fuentes
I am doing a project for college, in which I need an ESP-12E chip, a temp/hum sensor (SHT30) and the MHZ-19C CO2 sensor. I have it connected with 3 AAA batteries, but I can't get it to last more than 4h and 50min.
Could the problem be that when it enters deep sleep mode, the CO2 sensor continues to consume the same amount of energy?
Re: Attempting to make a co2 meter with batteries.
Posted:
Thu Mar 17, 2022 5:31 pmby btidey
The current draw of the sensor will certainly be a significant factor. I believe the MHZ-19C draws about 40mA, The SHT30 is very low power.
Normally one would power down sensors when entering deep sleep in between measurements if one wants to maximise battery life. That is tricky with the MHZ-19C as it has a 1 minute warm-up time before measurements are valid so unless you have a long interval between measurements (e.g. > 5 minutes) that is not going to be a viable strategy. Even if you can do that you will probably need to be a little clever like coming out of deep sleep to power up the sensor, sleep again for a minute then take the measurement, followed by powering down the sensor and enetering sleep again. Otherwise you will have a 1 minute of the ESP drawing its full current for every reading.
I would, however, have expected the AAA batteries to last about longer as assuming a typical capacity of around 900maH then your 5 hour life is equivalent to a current draw of around 140ma. That makes me suspect that your not getting into real deep sleep as the 80ma of the ESP + the sensor would be nearer to what your average current draw is.
First thing to check is with a current meter to see what current is being used. You should see one higher current when the ESP is active and then a lower one when it goes into deep sleep.