readme.md

AcreLink Node

• Designed for a sleep current around 6 to 7 uA.
• ESP32
• RFM95 Lora Module
• 868MHz PCB antenna, can be cut off and replaced by an SMA connector
• AA size lithium battery driven: (LS14500 Lithium-Thionyl-Chlorid or LifePo4 possible)
• Boost converter to supply sensors with stable 5V. Can be switched off for low current sleep mode
• External connector for Onewire, analog inputs and I2C including ESD protection with very low current TVS diodes
• Sensing battery voltage. Can be disabled for low sleep current
• Red led for signaling activity
• SPI header for external connection.
• Mechanical switch to select battery of external power supply
• Separate removable pcb section with wide range power supply 5 - 25V, USB-C connector and USB-UART adapter for programming
• Enableable current measurement at GND level with 1 Ohm Resistor and low pass filtering.
• Switchable Onewire power, data and datapullup, I2C power and pull ups.

3D Preview

Pin Mapping ESP32

• AnalogInput1 : PIN13 GPIO14 ADC2_CH6
• Analog Bat : PIN16 GPIO13 ADC2_CH4
• AnalogInput2 : PIN11 GPIO26 ADC2_CH9
• I2C SDA : PIN33 GPIO21
• I2C SCL : PIN36 GPIO22
• UART2_RX : PIN27 GPIO16
• UART2_TX : PIN28 GPIO17
• 5V Buck EN : PIN12 GPIO27
• LED_Signal : PIN9 GPIO33
• RFM_MISO : PIN31 GPIO19
• RFM_MOSI : PIN37 GPIO23
• RFM_SCK : PIN30 GPIO18
• RFM_CS : PIN29 GPIO5
• RFM_RST : PIN23 GPIO15
• RFM_IRQ/DIO0 : PIN26 GPIO4
• RFM_DIO1 : PIN8 GPIO32

Links

• Antenna Design: https://github.com/cernohorsky/LoRa-Node
• Selected soil sensor: https://de.aliexpress.com/item/1005001411485735.html?gatewayAdapt=glo2deu&spm=a2g0o.9042311.0.0.27424c4dQoBMf8 Supplyvoltage 3.6V - 30V. Two analog outputs 0 to 2 V for soil temperature and soil humidity. ~5mA current consumption at 4V

Oher Links for reference

• https://www.metergroup.com/de/environment/produkte/teros-21/

• https://www.metergroup.com/de/environment/produkte/teros-10/

• https://www.metergroup.com/de/environment/

• https://de.aliexpress.com/item/32750933038.html?spm=a2g0o.productlist.0.0.62fa2b2dD94RVC&algo_pvid=56dd73b6-6484-4bd3-be9a-3d29279feaf3&algo_expid=56dd73b6-6484-4bd3-be9a-3d29279feaf3-32&btsid=2100bddb16056484973607092e316c&ws_ab_test=searchweb0_0,searchweb201602_,searchweb201603_

• https://de.aliexpress.com/store/915786

• https://www.ugt-online.de/produkte/bodenkunde/bodenfeuchtetemperaturleitfaehigkeit/sm150t/

• https://www.delta-t.co.uk/product/sm150t/

• https://de.aliexpress.com/item/32793236869.html?spm=a2g0s.8937460.0.0.3a672e0eRfM3vv

• Usefull for pin mapping: https://www.electroniclinic.com/esp32-wroom-32d-pinout-features-and-specifications/

• https://github.com/matthijskooijman/arduino-lmic#dio-pins Lora requires at least DIO0 and DIO1

• https://jackgruber.github.io/2020-04-13-ESP32-DeepSleep-and-LoraWAN-OTAA-join/ Deep sleep lorawan

• SPI SD-Card header //https://www.sparkfun.com/products/544

• DC-DC Alternative: TP6841S6

TODOs (next hw version)

• Cutout around USB-C ?
• Connectionpoint GNG-Current Measurement
• Alternative battery with more capacity: LS14500(2.6Ah), LS17500(3.6Ah) , LS26500(7.7Ah) ? Solder directly to pcb without holder: LS [14,17,26]500CNA, TADIRAN SL360P ?
• Change to Keystone 1015. Slightly longer but feel mechanically more robust.