Add CT Clamp component (#559)

* Add CT Clamp component

* Update lint

* Some more fixes

* Make updates to work as an analog sensor consumer

* Remove unused imports
Update lint suggestions

* Move setup_priority to header

* Remove unused calibration value

* Remove Unique ID

- Will be auto generated

* Update to use loop and not slow down main loop


Co-authored-by: Otto Winter <otto@otto-winter.com>

esphome/components/ct_clamp/ct_clamp_sensor.cpp

@@ -0,0 +1,67 @@
+#include "ct_clamp_sensor.h"
+
+#include "esphome/core/log.h"
+#include <cmath>
+
+namespace esphome {
+namespace ct_clamp {
+
+static const char *TAG = "ct_clamp";
+
+void CTClampSensor::dump_config() {
+  LOG_SENSOR("", "CT Clamp Sensor", this);
+  ESP_LOGCONFIG(TAG, "  Sample Duration: %.2fs", this->sample_duration_ / 1e3f);
+  LOG_UPDATE_INTERVAL(this);
+}
+
+void CTClampSensor::update() {
+  // Update only starts the sampling phase, in loop() the actual sampling is happening.
+
+  // Request a high loop() execution interval during sampling phase.
+  this->high_freq_.start();
+
+  // Set timeout for ending sampling phase
+  this->set_timeout("read", this->sample_duration_, [this]() {
+    this->is_sampling_ = false;
+    this->high_freq_.stop();
+
+    if (this->num_samples_ == 0) {
+      // Shouldn't happen, but let's not crash if it does.
+      this->publish_state(NAN);
+      return;
+    }
+
+    float raw = this->sample_sum_ / this->num_samples_;
+    float irms = std::sqrt(raw);
+    ESP_LOGD(TAG, "'%s' - Raw Value: %.2fA", this->name_.c_str(), irms);
+    this->publish_state(irms);
+  });
+
+  // Set sampling values
+  this->is_sampling_ = true;
+  this->num_samples_ = 0;
+  this->sample_sum_ = 0.0f;
+}
+
+void CTClampSensor::loop() {
+  if (!this->is_sampling_)
+    return;
+
+  // Perform a single sample
+  float value = this->source_->sample();
+
+  // Adjust DC offset via low pass filter (exponential moving average)
+  const float alpha = 0.001f;
+  this->offset_ = this->offset_ * (1 - alpha) + value * alpha;
+
+  // Filtered value centered around the mid-point (0V)
+  float filtered = value - this->offset_;
+
+  // IRMS is sqrt(∑v_i²)
+  float sq = filtered * filtered;
+  this->sample_sum_ += sq;
+  this->num_samples_++;
+}
+
+}  // namespace ct_clamp
+}  // namespace esphome

esphome/components/ct_clamp/ct_clamp_sensor.h

@@ -0,0 +1,46 @@
+#pragma once
+
+#include "esphome/core/component.h"
+#include "esphome/core/esphal.h"
+#include "esphome/components/sensor/sensor.h"
+#include "esphome/components/voltage_sampler/voltage_sampler.h"
+
+namespace esphome {
+namespace ct_clamp {
+
+class CTClampSensor : public sensor::Sensor, public PollingComponent {
+ public:
+  void update() override;
+  void loop() override;
+  void dump_config() override;
+  float get_setup_priority() const override { return setup_priority::DATA; }
+
+  void set_sample_duration(uint32_t sample_duration) { sample_duration_ = sample_duration; }
+  void set_source(voltage_sampler::VoltageSampler *source) { source_ = source; }
+
+ protected:
+  /// High Frequency loop() requester used during sampling phase.
+  HighFrequencyLoopRequester high_freq_;
+
+  /// Duration in ms of the sampling phase.
+  uint32_t sample_duration_;
+  /// The sampling source to read values from.
+  voltage_sampler::VoltageSampler *source_;
+
+  /** The DC offset of the circuit.
+   *
+   * Diagram: https://learn.openenergymonitor.org/electricity-monitoring/ct-sensors/interface-with-arduino
+   *
+   * This is automatically calculated with an exponential moving average/digital low pass filter.
+   *
+   * 0.5 is a good initial approximation to start with for most ESP8266 setups.
+   */
+  float offset_ = 0.5f;
+
+  float sample_sum_ = 0.0f;
+  uint32_t num_samples_ = 0;
+  bool is_sampling_ = false;
+};
+
+}  // namespace ct_clamp
+}  // namespace esphome

esphome/components/ct_clamp/sensor.py

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+import esphome.codegen as cg
+import esphome.config_validation as cv
+from esphome.components import sensor, voltage_sampler
+from esphome.const import CONF_SENSOR, CONF_ID, ICON_FLASH, UNIT_AMPERE
+
+AUTO_LOAD = ['voltage_sampler']
+
+CONF_SAMPLE_DURATION = 'sample_duration'
+
+ct_clamp_ns = cg.esphome_ns.namespace('ct_clamp')
+CTClampSensor = ct_clamp_ns.class_('CTClampSensor', sensor.Sensor, cg.PollingComponent)
+
+CONFIG_SCHEMA = sensor.sensor_schema(UNIT_AMPERE, ICON_FLASH, 2).extend({
+    cv.GenerateID(): cv.declare_id(CTClampSensor),
+    cv.Required(CONF_SENSOR): cv.use_id(voltage_sampler.VoltageSampler),
+    cv.Optional(CONF_SAMPLE_DURATION, default='200ms'): cv.positive_time_period_milliseconds,
+}).extend(cv.polling_component_schema('60s'))
+
+
+def to_code(config):
+    var = cg.new_Pvariable(config[CONF_ID])
+    yield cg.register_component(var, config)
+    yield sensor.register_sensor(var, config)
+
+    sens = yield cg.get_variable(config[CONF_SENSOR])
+    cg.add(var.set_source(sens))
+    cg.add(var.set_sample_duration(config[CONF_SAMPLE_DURATION]))