Embedded Gardening, Part 2 - Picking Parts


The next step was to pick some parts.

I have to admit, I'm a bit of a hardware fiend.  And if a part is less than $10, I'll often buy a couple.. just in case!  In case of what?, yeah, well, occasionally I'll find I have a part from a previous project that works out.  But mostly they just hide in different little carboard boxes in their little Mylar bags, almost but not quite organized enough to be where I look for them.  In this case I did have a success.  The level shifters were needed and I was able to find them.  So there, they do ACTUALLY get used sometimes!

So now, on to what is needed to make the watering thingy.

The Brains...


I wanted to keep it small and am really loving the ease and flexibility of MicroPython. 

Some of the smaller SoC's that I like are Espressif ESP8266 based devices.

I generally use NodeMCU type dev boards.  You can get them for between $0.79 and $3 these days.  Shipping is usually the deciding cost if you need under 100 in under 100 days.

The one I got for this was a WeMos D1 Mini clone.


Some specs:
  • Microcontroller ESP-8266EX
  • Operating Voltage 3.3 V
  • Digital I/O Pins 11
  • Analog Input Pins 1(Max input: 3.2V)
  • Clock Speed 80MHz/160MHz
  • Flash 4M bytes
  • Length 34.2mm
  • Width 25.6mm
  • 11 digital input/output pins, all pins have interrupt/pwm/I2C/one-wire supported(except for D0)
  • 1 analog input(3.2V max input)
  • Micro USB connection
  • Compatible with Arduino
  • Compatible with nodemcu
  • Support OTA wireless uploading
  • 11 x I/O pins,1 x ADC pin
And the stats for the ESP8266 itself are:
  • Memory:
    • 32 KiB instruction RAM
    • 32 KiB instruction cache RAM
    • 80 KiB user-data RAM
    • 16 KiB ETS system-data RAM

With that as the thinker, here are the other parts:


Sensors...

Temperature, Humidity, Pressure Sensor - BME280 (I2C)



Light Intensity Sensor - BH1750FVI (I2C)


Capacitive Soil Moisture Sensors - EK1940 (Analog)




















Flow Sensor - DIGITEN G1/2 (Digital 5V)











Control...

12v Solenoid Valve - AQT15SP

Relay for Valve - COM22639P



Signal Handling...


8 x ADC - MCP3008  (For reading up to 8x soil moisture sensors)



Voltage Level Shifter - BSS138 (The flow sensor is 5v)



And it turns out I ran out of GPIOs, so I needed an expander to be able to read the flow sensor.  More on that later...

I2C 8 Port I/O Expander - MCP23008











Power Conversion...

DC-DC Buck Converter - MP1584EN (Convert main 12v to 5v for the board + 5v peripherals) 



12v AC Adapter - DUNZHITECH






Connectors...

I made the very unfortunate mistake of trying to learn how to crimp my own connectors with a "cheap" kit.  
Long story short, it was a disaster...

Qibaok Crimping Tool Kit 







The next installment will go over the prototyping with solderless protoboard and will include some pictures.



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