esp32/8266 signalk or mqtt?

[SCarns]

I made one for my holding tank using a capacitive sensor (used the MODA tank sensor from https://tankedge.com/accessories.html). I used SensESP, a voltage reducer (for reading the sensor), a 12volt to 5 volt buck converter (to power the board off of 12 volt) and a lot of trial and error to get it working. It lives in a water-proof case under my mattress next to the tank and connects to signalk via wifi.

Just upgraded it to the new SensESP, which took a few minutes, as I had to update the programming a bit, but it was even easier and cleaner than the first time. Once I figure out the concepts and stopped trying to "Over Program" the code, it all came together.

There is some calculations needed, but those are outside of SensESP. I add an extra SKPath so I can monitor the ADC read values (for empty & full), and then do the calculation for needed Mulitplier and Offset, which I can enter in the web set up for SensESP. I also use a long period for MovingAverage to help smooth out reading fluctuations. It's all done in a couple lines of code. Here's what I have:


//
// This application demonstrates core SensESP concepts in a very
// concise manner. You can build and upload the application as is
// and observe the value changes on the serial port monitor.
//
// You can use this source file as a basis for your own projects.
// Remove the parts that are not relevant to you, and add your own code
// for external hardware libraries.

#include "sensesp/sensors/analog_input.h"
#include "sensesp/sensors/sensor.h"
#include "sensesp/signalk/signalk_output.h"
#include <sensesp/transforms/linear.h>
#include <sensesp/transforms/moving_average.h>
#include "sensesp_app_builder.h"

using namespace sensesp;

reactesp::ReactESP app;

// The setup function performs one-time application initialization.
void setup() {
#ifndef SERIAL_DEBUG_DISABLED
  SetupSerialDebug(115200);
#endif

  // Construct the global SensESPApp() object
  SensESPAppBuilder builder;
  sensesp_app = (&builder)
                    // Set a custom hostname for the app.
                    ->set_hostname("New-SensESP")
                    ->set_wifi_manager_password("SensESP32")
                    // Optionally, hard-code the WiFi and Signal K server
                    // settings. This is normally not needed.
                    //->set_wifi("My WiFi SSID", "my_wifi_password")
                    //->set_sk_server("192.168.10.3", 80)
                    ->get_app();


  const char* sk_path0 = "tanks.blackWater.0.currentLevel";
  const char* sk_read0 = "tanks.blackWater.0.reading";
  
  const char* analog_in_config_path = "/blackWater/analogInput";
  const char* linear_config_path = "/blackWater/linear";
  const char* level_avg_samples = "/blackWater/average";
  
  uint8_t pin0 = 35;        // read pin for sensor "0"
  uint read_delay = 1000;    // read frequency
  const float multiplier = 0.00862517325816782;  // 100% divided by total range (high-low read)
  const float offset = -0.380027721306852;     // Offset to compensate for low-end
  float scale = 1.0;

  // Create a new Analog Input Sensor that reads an analog input pin0
  // and sends it to SignalK.
  auto* blackwater_read = new AnalogInput(
      pin0, read_delay, analog_in_config_path);

  blackwater_read->connect_to(new SKOutputFloat(sk_read0))
                 ->connect_to(new Linear(multiplier, offset, linear_config_path))  // adjust for vacuum reading
                 ->connect_to(new MovingAverage(120,scale, level_avg_samples))
                 ->connect_to(new SKOutputFloat(
                    sk_path0,              // Signal K path
                    new SKMetadata("ratio",   // Define output units
                            "Blackwater Tank Volume")  // Value description
      ))
         ->attach([blackwater_read]() {
    debugD("Analog input value: %f", blackwater_read->get());
  });
 

  // Start networking, SK server connections and other SensESP internals
  sensesp_app->start();
}

void loop() { app.tick(); }


_________

Works great.


I'm moving on to a vacuum switch on my fuel filters next with the idea I can monitor fuel suction and get an alarm when it's time to change filters or if there's water in the bowl.