mirror of
https://github.com/esphome/esphome-docs.git
synced 2024-08-31 00:19:54 +02:00
* add note for asynchronously update of adc * Move to section; add details; change ID name to match example config Co-authored-by: Otto Winter <otto@otto-winter.com>
129 lines
3.9 KiB
ReStructuredText
129 lines
3.9 KiB
ReStructuredText
NTC Sensor
|
|
==========
|
|
|
|
.. seo::
|
|
:description: Instructions for setting up NTC thermistor sensor in ESPHome
|
|
:image: ntc.jpg
|
|
|
|
The ``ntc`` platform is a helper sensor that allows you to convert resistance readings
|
|
from a NTC thermistor to temperature readings.
|
|
|
|
First, you need to get resistance readings from the sensor - you can set this up with the
|
|
:doc:`resistance <resistance>` and :doc:`adc <adc>` sensors.
|
|
|
|
This platform will then convert the resistance values to temperature readings.
|
|
It also requires calibration parameters for this conversion. There are two
|
|
ways of obtaining these values: By looking at the datasheet or manual calculation.
|
|
|
|
If you have the datasheet of the thermistor, you can look at its "B-constant" and
|
|
reference temperature/resistance. For example `this product <https://www.adafruit.com/product/372>`__
|
|
would have the following calibration configuration.
|
|
|
|
.. code-block:: yaml
|
|
|
|
# Example configuration entry
|
|
sensor:
|
|
- platform: ntc
|
|
# ...
|
|
calibration:
|
|
b_constant: 3950
|
|
reference_temperature: 25°C
|
|
reference_resistance: 10kOhm
|
|
|
|
If you don't have access to the datasheet or want to calculate these values yourself,
|
|
you have to first measure three resistance values at different temperatures.
|
|
Heat/cool the NTC to three different temperatures (best if temperatures are far apart)
|
|
and write down the resistance readings at those temperatures. Then enter these values in the
|
|
calibration parameter:
|
|
|
|
.. code-block:: yaml
|
|
|
|
# Example configuration entry
|
|
sensor:
|
|
- platform: ntc
|
|
# ...
|
|
calibration:
|
|
- 10.0kOhm -> 25°C
|
|
- 27.219kOhm -> 0°C
|
|
- 14.674kOhm -> 15°C
|
|
|
|
.. code-block:: yaml
|
|
|
|
# Example configuration entry
|
|
sensor:
|
|
- platform: ntc
|
|
sensor: resistance_sensor
|
|
calibration:
|
|
b_constant: 3950
|
|
reference_temperature: 25°C
|
|
reference_resistance: 10kOhm
|
|
name: NTC Temperature
|
|
|
|
# Example source sensors:
|
|
- platform: resistance
|
|
id: resistance_sensor
|
|
sensor: source_sensor
|
|
configuration: DOWNSTREAM
|
|
resistor: 5.6kOhm
|
|
name: Resistance Sensor
|
|
- platform: adc
|
|
id: source_sensor
|
|
pin: A0
|
|
|
|
Configuration variables:
|
|
------------------------
|
|
|
|
- **name** (**Required**, string): The name for the sensor.
|
|
- **sensor** (**Required**, :ref:`config-id`): The sensor to read the resistance values from
|
|
to convert to temperature readings.
|
|
- **calibration** (**Required**, float): The calibration parameters of the sensor - see above
|
|
for more details.
|
|
- **id** (*Optional*, :ref:`config-id`): Set the ID of this sensor for use in lambdas.
|
|
- All other options from :ref:`Sensor <config-sensor>`.
|
|
|
|
Self-Heating
|
|
------------
|
|
|
|
A constant voltage supply to the NTC sensor causes it to heat up and therefore creates unreliable temperature values.
|
|
So it's recommended to only supply the NTC sensor (and voltage divider) during the actual measurement.
|
|
More info `here <https://learn.adafruit.com/thermistor/using-a-thermistor#self-heating-3-22>`__.
|
|
|
|
To do this, replace the 3.3V side of the voltage divider with a connection to a GPIO pin. This GPIO pin will
|
|
be switched HIGH (3.3V) only during the measurement, thus preventing the sensor from heating up.
|
|
In the example below, the pin ``D0`` is the "top" side of the voltage divider:
|
|
|
|
.. code-block:: yaml
|
|
|
|
sensor:
|
|
# Same as before:
|
|
- platform: ntc
|
|
sensor: resistance_sensor
|
|
# ...
|
|
|
|
- platform: adc
|
|
pin: A0
|
|
id: source_sensor
|
|
# Added:
|
|
update_interval: never
|
|
|
|
switch:
|
|
- platform: gpio
|
|
pin: D0
|
|
id: ntc_vcc
|
|
|
|
interval:
|
|
- interval: 60s
|
|
then:
|
|
- switch.turn_on: ntc_vcc
|
|
- component.update: source_sensor
|
|
- switch.turn_off: ntc_vcc
|
|
|
|
See Also
|
|
--------
|
|
|
|
- :doc:`adc`
|
|
- :doc:`resistance`
|
|
- :ref:`sensor-filters`
|
|
- :apiref:`ntc/ntc.h`
|
|
- :ghedit:`Edit`
|