Non-invasive graphing of energy usage

Wed, 01 Apr 2020 00:00:00 +0000

“If you can’t measure it, you can’t improve it.”

Reducing energy usage is hard if you can’t see it. Here’s a cheap way to graph home or office energy usage.

By reading data from the energy meter, one can get super accurate, real-time usage data.

I’ve used:

A smart home controller, Home Assistant
A graphing system, Grafana
A micro controller, esp8266, ~$5
An LDR sensor, $1

You need some familiarity with all of the above to set this up.

Here’s my energy meter:

It doesn’t matter which one you have, as long as it has a LED that blinks each X kWh used. I’ve written software for the esp8266 in MicroPython, called esp_energy_meter, that measures the time between each blink. It works great, and I’ve had it running for several locations for years. See the gitlab repo for more info on setup.

When you have this set up, you can combine it with real-time energy prices to get full control of your energy usage. And then it’s time to adjust your usage based on pricing. =)

VEML7700 in ESPHome

Sat, 29 Feb 2020 00:00:00 +0000

I have a VEML7700 digital light level sensor, which is not supported by ESPHome, but can be used as a custom i2c component. This is how:

# espnode.yaml

esphome:
...
includes:
    - veml7700_custom_sensor.h
libraries:
    - "https://github.com/adafruit/Adafruit_VEML7700"

sensor:
- platform: custom
    lambda: |-
    auto veml7700 = new VEML7700CustomSensor();
    App.register_component(veml7700);
    return {veml7700, veml7700->lux_sensor, veml7700->white_sensor, veml7700->als_sensor};
    sensors:
    - name: "VEML7700 Light" # Required dummy sensor
    - name: "VEML770 Lux"
        unit_of_measurement: Lux
        accuracy_decimals: 0
    - name: "VEML770 White"
        unit_of_measurement: raw
        accuracy_decimals: 0
    - name: "VEML770 ALS"
        unit_of_measurement: raw
        accuracy_decimals: 0

# veml7700_custom_sensor.h

#include "esphome.h"
#include "Adafruit_VEML7700.h"

// Requires this lib installed: $ platformio lib --global install "Adafruit BusIO"
// based on https://github.com/adafruit/Adafruit_VEML7700/blob/master/examples/veml7700_test/veml7700_test.ino


class VEML7700CustomSensor : public PollingComponent, public Sensor {
public:
Adafruit_VEML7700 veml = Adafruit_VEML7700();

Sensor *lux_sensor = new Sensor();
Sensor *white_sensor = new Sensor();
Sensor *als_sensor = new Sensor();

VEML7700CustomSensor() : PollingComponent(15000) {}
void setup() override {
    Wire.begin();
    veml.begin();
    veml.setGain(VEML7700_GAIN_1);
    veml.setIntegrationTime(VEML7700_IT_800MS);
    // veml.powerSaveEnable(true);
    // veml.setPowerSaveMode(VEML7700_POWERSAVE_MODE4);
    // veml.setLowThreshold(10000);
    // veml.setHighThreshold(20000);
    // veml.interruptEnable(true);
}

void update() override {
    float lux = veml.readLux();
    float white = veml.readWhite();
    float als = veml.readALS();
    ESP_LOGD("VEML7700", "The value of sensor lux is: %.0f", lux);
    ESP_LOGD("VEML7700", "The value of sensor white is: %.0f", white);
    ESP_LOGD("VEML7700", "The value of sensor ALS is: %.0f", als);
    lux_sensor->publish_state(lux);
    white_sensor->publish_state(white);
    als_sensor->publish_state(als);
}
};

Iot on falkp.no/blog

Non-invasive graphing of energy usage

VEML7700 in ESPHome

# espnode.yaml

# veml7700_custom_sensor.h