That is the direction I am going but this is the only tutorial I could find that used the NRF24L01+ radios to send data to Home Assistant. For now, I am just trying to get it to send accurate measurements and move to capacitive sensors as soon as I figure out how to send the data via NRF24L01+
Today I finished to fix failed soldering (too old solder paste made a mess ) on the "motherboard" of my air quality sensor.
It's based on ESP32, uses a charging IC with power path so it can run on batteries for around a day or stay plugged without destroying the battery, step down from USB/battery to get VCC, storage on I2C EEPROM, flash and/or µSD card (depending on use case), one SK6812 mini RGB led as indicator, a small 240*240 IPS LCD (backlight driven directly by ESP32 pin in high drive capability mode), a 3 way switch for basic user interface + footprint for PAJ7620 gesture recognition module, accelerometer and I2C IO expander to manage the 3 way switch and interrupts from sensor modules.
Sensor modules will be added on top, connected using an FPC connector. At the moment I made only one sensor PCB able to manage usual PM, CO2 and formaldehyde sensors. Only one sensor per sensor board where an attiny841 manages the UART sensor and convert it to I2C, it also manages the 5V step up to power the sensor.
On the main board I also added an NRF24 footprint so with the same PCB I will be able to make a gateway with integrated battery backup.
I'm pretty happy with the relatively well aligned components (no, I don't have OCD ) , too bad I had to unsolder, clean and re-solder each component as it now looks botched up. But at least everything (except a missing connection on µSD card, hence the blue wire) is working,
LCD test showing jpgs from SD card
@skywatch Agreed entirely on the supply quality for the Pi, but disagree with the "bonus" of throwing away the SD. Murphy's Law applies, a RO card allows you to revert to a spare OS card if the drive ever fails...
The Pi3 has 4xUSB2, the Pi4 uprated to 2xUSB2 + 2xUSB3, the data transfer limits of the Pi3 are lower, but still plenty fast.
PS - I recall some USB adapters for SSD could cause issues for the Pi, fairly sure it was on a video by the "Swiss guy"...
@zboblamont Thanks. FWIW, I first became aware of the issue from reading CREE datasheets. At some point CREE put out an advisory: https://www.cree.com/led-components/media/documents/XLamp_EyeSafety.pdf
Cree classifies its own XR-E royal blue LED's as RG-3 High Risk, which it defines as "Hazardous even for momentary exposure".
"To date, the testing shows that Cree’s blue and royal blue LED components (450-485 nm dominant wavelengths) pose a higher potential eye safety hazard than its white LED components. Other colors of LED components, such as green and red LED components, do not pose as significant of an eye safety risk. Regardless of LED color, Cree advises users to not look directly at any operating LED component. "
In the context of this thread, it's that last sentence that's tricky. I suppose for an indicator common sense suggests it's just plain safer to stick with a lower power LED and run it for a longer duration. So, the challenge will be to find high lumens/watt but at not too high absolute lumens.