Add docs for CT Clamp (#256)

* Add docs for CT Clamp

* Fix title bar

* Fix reference

* 2 many changes

* Update docs for new configuration

* Compress index image

* Update for config changes

- Also remove 3.3V message, because if the user needs to calibrate anyway, then the 3.3V is also part of the calibration process.
- Use calibrate_linear instead of multiply, more user-friendly
- Update SEO image
-


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

components/sensor/ct_clamp.rst

@@ -0,0 +1,82 @@
+CT Clamp Current Sensor
+=======================
+
+.. seo::
+    :description: Instructions for setting up ct clamp sensors.
+    :image: ct_clamp.jpg
+
+The Current Transformer Clamp (``ct_clamp``) sensor allows you to hook up a CT Clamp to an analog
+voltage sensor (like the :doc:`ADC sensor <adc>`) and convert the readings to measured single phase AC current.
+
+First, you need to set up a voltage sensor source (:doc:`ADC sensor <adc>`, but for example also
+:doc:`ADS1115 <ads1115>`) and pass it to the CT clamp sensor with the ``sensor`` option.
+
+Please also see `this guide <https://learn.openenergymonitor.org/electricity-monitoring/ct-sensors/introduction>`__
+as an introduction to the working principle of CT clamp sensors and how to hook them up to your device.
+
+.. figure:: images/ct_clamp-ui.png
+    :align: center
+    :width: 80.0%
+
+.. code-block:: yaml
+
+    # Example configuration entry
+    sensor:
+      - platform: ct_clamp
+        sensor: adc_sensor
+        name: "Measured Current"
+        update_interval: 60s
+
+      # Example source sensor
+      - platform: adc
+        pin: A0
+        id: adc_sensor
+
+Configuration variables:
+------------------------
+
+- **name** (**Required**, string): The name of the sensor.
+- **sensor** (**Required**, :ref:`config-id`): The source sensor to measure voltage values from.
+- **sample_duration** (*Optional*, :ref:`config-time`): The time duration to sample the current clamp
+  with. Higher values can increase accuracy. Defaults to ``200ms`` which would be 10 whole cycles on a 50Hz system.
+- **update_interval** (*Optional*, :ref:`config-time`): The interval
+  to check the sensor. Defaults to ``60s``.
+- **id** (*Optional*, :ref:`config-id`): Manually specify the ID used for code generation.
+- All other options from :ref:`Sensor <config-sensor>`.
+
+Calibration
+-----------
+
+This sensor needs calibration to show correct values, for this you can use the
+:ref:`calibrate_linear <sensor-filter-calibrate_linear>` sensor filter. First, hook up a known
+current load like a lamp that uses a known amount of current.
+
+Then switch it on and see what value the CT clamp sensor reports. For example in the configuration below
+a 4.0 A device is showing a value of 0.1333 in the logs. Now go into your configuration file
+
+.. code-block:: yaml
+
+    # Example configuration entry
+    sensor:
+      - platform: ct_clamp
+        sensor: adc_sensor
+        name: "Measured Current"
+        update_interval: 60s
+        filters:
+          # Measured value of 0 maps to 0A
+          - 0 -> 0
+          # Known load: 4.0A
+          # Value shown in logs: 0.1333A
+          - 0.1333 -> 4.0
+
+Recompile and upload, now your CT clamp sensor is calibrated!
+
+See Also
+--------
+
+- `EMonLib <https://github.com/openenergymonitor/EmonLib>`__
+- `CT Clamp Guide <https://learn.openenergymonitor.org/electricity-monitoring/ct-sensors/introduction>`__
+- :doc:`adc`
+- :doc:`ads1115`
+- :apiref:`sensor/ct_clamp.h`
+- :ghedit:`Edit`

index.rst

@@ -99,6 +99,7 @@ Sensor Components
     BMP280, components/sensor/bmp280, bmp280.jpg
     CCS811, components/sensor/ccs811, ccs811.jpg
     CSE7766, components/sensor/cse7766, cse7766.svg
+    CT Clamp, components/sensor/ct_clamp, ct_clamp.jpg
     Dallas, components/sensor/dallas, dallas.jpg
     DHT, components/sensor/dht, dht.jpg
     DHT12, components/sensor/dht12, dht12.jpg