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A project log for Wireless soil moisture sensor

NRF24L01 ATTINY85 work together to measure and broadcast soil moisture sensor data

andrey.malyshenkoandrey.malyshenko 06/06/2021 at 20:550 Comments

This project was on hold for the whole winter for simple reason - no flowers during winter where I live. Now I'm trying to resurrect that and move forward as much as time allows.

So first of all, I've dropped Tiny85 and got Tiny84 for few reasons

- Although it is possible (proved before) to communicate with NRF24 chip using 3 or 4 pins, to optimize battery usage it is much better to have all 5 pins to work with.

- First approach to use of-the-shelf moisture sensor turns out to be power hungry solution. Therefore I dropped 555-chip based sensor and added built-in on the board. Tiny84 will generate waveform just as well.

- Idea of the whole setup is that each module will report to master node (on the photo above). When it is not available It would be nice to have 'offline' kind of way to get information update. Hence 3 LEDs onboard  - red, yellowa and green. Their blinking should be a good clue of the actual sensor reading (when calibrated, clearly)

- First prototype of master node is prepared. Same NRF24 chip is there ("it is dead cheap" is the reason). But also WiFi connectivity added via mighty ESP8266. With possibility to switch to some ESP32 alternative in the future, It has 8 power MOSFET drivers to drive pumps, all individually adressable using onboard 74HC595 chip.

Having enough time I'd hope to make it work before winter comes :)

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