diff --git a/esphome/__main__.py b/esphome/__main__.py
index 199b68a6f1..c48d49b9ac 100644
--- a/esphome/__main__.py
+++ b/esphome/__main__.py
@@ -127,7 +127,10 @@ def wrap_to_code(name, comp):
     def wrapped(conf):
         cg.add(cg.LineComment(u"{}:".format(name)))
         if comp.config_schema is not None:
-            cg.add(cg.LineComment(indent(yaml_util.dump(conf).decode('utf-8'))))
+            conf_str = yaml_util.dump(conf)
+            if IS_PY2:
+                conf_str = conf_str.decode('utf-8')
+            cg.add(cg.LineComment(indent(conf_str)))
         yield coro(conf)
 
     return wrapped
diff --git a/esphome/components/ntc/__init__.py b/esphome/components/ntc/__init__.py
new file mode 100644
index 0000000000..e69de29bb2
diff --git a/esphome/components/ntc/ntc.cpp b/esphome/components/ntc/ntc.cpp
new file mode 100644
index 0000000000..1b5c5182c7
--- /dev/null
+++ b/esphome/components/ntc/ntc.cpp
@@ -0,0 +1,31 @@
+#include "ntc.h"
+#include "esphome/core/log.h"
+
+namespace esphome {
+namespace ntc {
+
+static const char *TAG = "ntc";
+
+void NTC::setup() {
+  this->sensor_->add_on_state_callback([this](float value) { this->process_(value); });
+  if (this->sensor_->has_state())
+    this->process_(this->sensor_->state);
+}
+void NTC::dump_config() { LOG_SENSOR("", "NTC Sensor", this) }
+float NTC::get_setup_priority() const { return setup_priority::DATA; }
+void NTC::process_(float value) {
+  if (isnan(value)) {
+    this->publish_state(NAN);
+    return;
+  }
+
+  float lr = logf(value);
+  float v = this->a_ + this->b_ * lr + this->c_ * lr * lr * lr;
+  float temp = 1 / v - 273.15f;
+
+  ESP_LOGD(TAG, "'%s' - Temperature: %.1f°C", this->name_.c_str(), temp);
+  this->publish_state(temp);
+}
+
+}  // namespace ntc
+}  // namespace esphome
diff --git a/esphome/components/ntc/ntc.h b/esphome/components/ntc/ntc.h
new file mode 100644
index 0000000000..9d6b37412d
--- /dev/null
+++ b/esphome/components/ntc/ntc.h
@@ -0,0 +1,29 @@
+#pragma once
+
+#include "esphome/core/component.h"
+#include "esphome/components/sensor/sensor.h"
+
+namespace esphome {
+namespace ntc {
+
+class NTC : public Component, public sensor::Sensor {
+ public:
+  void set_sensor(Sensor *sensor) { sensor_ = sensor; }
+  void set_a(float a) { a_ = a; }
+  void set_b(float b) { b_ = b; }
+  void set_c(float c) { c_ = c; }
+  void setup() override;
+  void dump_config() override;
+  float get_setup_priority() const override;
+
+ protected:
+  void process_(float value);
+
+  sensor::Sensor *sensor_;
+  float a_;
+  float b_;
+  float c_;
+};
+
+}  // namespace ntc
+}  // namespace esphome
diff --git a/esphome/components/ntc/sensor.py b/esphome/components/ntc/sensor.py
new file mode 100644
index 0000000000..db7d7f9b99
--- /dev/null
+++ b/esphome/components/ntc/sensor.py
@@ -0,0 +1,120 @@
+# coding=utf-8
+from math import log
+
+import esphome.config_validation as cv
+import esphome.codegen as cg
+from esphome.components import sensor
+from esphome.const import UNIT_CELSIUS, ICON_THERMOMETER, CONF_SENSOR, CONF_TEMPERATURE, \
+    CONF_VALUE, CONF_CALIBRATION, CONF_ID
+
+ntc_ns = cg.esphome_ns.namespace('ntc')
+NTC = ntc_ns.class_('NTC', cg.Component, sensor.Sensor)
+
+CONF_B_CONSTANT = 'b_constant'
+CONF_REFERENCE_TEMPERATURE = 'reference_temperature'
+CONF_REFERENCE_RESISTANCE = 'reference_resistance'
+CONF_A = 'a'
+CONF_B = 'b'
+CONF_C = 'c'
+ZERO_POINT = 273.15
+
+
+def validate_calibration_parameter(value):
+    if isinstance(value, dict):
+        return cv.Schema({
+            cv.Required(CONF_TEMPERATURE): cv.float_,
+            cv.Required(CONF_VALUE): cv.float_,
+        })
+
+    value = cv.string(value)
+    parts = value.split('->')
+    if len(parts) != 2:
+        raise cv.Invalid(u"Calibration parameter must be of form 3000 -> 23°C")
+    voltage = cv.resistance(parts[0].strip())
+    temperature = cv.temperature(parts[1].strip())
+    return validate_calibration_parameter({
+        CONF_TEMPERATURE: temperature,
+        CONF_VALUE: voltage,
+    })
+
+
+def calc_steinhart_hart(value):
+    r1 = value[0][CONF_VALUE]
+    r2 = value[1][CONF_VALUE]
+    r3 = value[2][CONF_VALUE]
+    t1 = value[0][CONF_TEMPERATURE] + ZERO_POINT
+    t2 = value[1][CONF_TEMPERATURE] + ZERO_POINT
+    t3 = value[2][CONF_TEMPERATURE] + ZERO_POINT
+
+    l1 = log(r1)
+    l2 = log(r2)
+    l3 = log(r3)
+
+    y1 = 1/t1
+    y2 = 1/t2
+    y3 = 1/t3
+
+    g2 = (y2-y1)/(l2-l1)
+    g3 = (y3-y1)/(l3-l1)
+
+    c = (g3-g2)/(l3-l2) * 1/(l1+l2+l3)
+    b = g2 - c*(l1*l1 + l1*l2 + l2*l2)
+    a = y1 - (b + l1*l1*c) * l1
+    return a, b, c
+
+
+def calc_b(value):
+    beta = value[CONF_B_CONSTANT]
+    t0 = value[CONF_REFERENCE_TEMPERATURE] + ZERO_POINT
+    r0 = value[CONF_REFERENCE_RESISTANCE]
+
+    a = (1/t0) - (1/beta) * log(r0)
+    b = 1/beta
+    c = 0
+
+    return a, b, c
+
+
+def process_calibration(value):
+    if isinstance(value, dict):
+        value = cv.Schema({
+            cv.Required(CONF_B_CONSTANT): cv.float_,
+            cv.Required(CONF_REFERENCE_TEMPERATURE): cv.temperature,
+            cv.Required(CONF_REFERENCE_RESISTANCE): cv.resistance,
+        })(value)
+        a, b, c = calc_b(value)
+    elif isinstance(value, list):
+        if len(value) != 3:
+            raise cv.Invalid("Steinhart–Hart Calibration must consist of exactly three values")
+        value = cv.Schema([validate_calibration_parameter])(value)
+        a, b, c = calc_steinhart_hart(value)
+    else:
+        raise cv.Invalid("Calibration parameter accepts either a list for steinhart-hart "
+                         "calibration, or mapping for b-constant calibration, "
+                         "not {}".format(type(value)))
+
+    return {
+        CONF_A: a,
+        CONF_B: b,
+        CONF_C: c,
+    }
+
+
+CONFIG_SCHEMA = sensor.sensor_schema(UNIT_CELSIUS, ICON_THERMOMETER, 1).extend({
+    cv.GenerateID(): cv.declare_id(NTC),
+    cv.Required(CONF_SENSOR): cv.use_id(sensor.Sensor),
+    cv.Required(CONF_CALIBRATION): process_calibration,
+}).extend(cv.COMPONENT_SCHEMA)
+
+
+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_sensor(sens))
+    calib = config[CONF_CALIBRATION]
+    cg.add(var.set_a(calib[CONF_A]))
+    cg.add(var.set_b(calib[CONF_B]))
+    cg.add(var.set_c(calib[CONF_C]))
diff --git a/esphome/components/resistance/__init__.py b/esphome/components/resistance/__init__.py
new file mode 100644
index 0000000000..e69de29bb2
diff --git a/esphome/components/resistance/resistance_sensor.cpp b/esphome/components/resistance/resistance_sensor.cpp
new file mode 100644
index 0000000000..7c48bbbc08
--- /dev/null
+++ b/esphome/components/resistance/resistance_sensor.cpp
@@ -0,0 +1,42 @@
+#include "resistance_sensor.h"
+#include "esphome/core/log.h"
+
+namespace esphome {
+namespace resistance {
+
+static const char *TAG = "resistance";
+
+void ResistanceSensor::dump_config() {
+  LOG_SENSOR("", "Resistance Sensor", this);
+  ESP_LOGCONFIG(TAG, "  Configuration: %s", this->configuration_ == UPSTREAM ? "UPSTREAM" : "DOWNSTREAM");
+  ESP_LOGCONFIG(TAG, "  Resistor: %.2fΩ", this->resistor_);
+  ESP_LOGCONFIG(TAG, "  Reference Voltage: %.1fV", this->reference_voltage_);
+}
+void ResistanceSensor::process_(float value) {
+  if (isnan(value)) {
+    this->publish_state(NAN);
+    return;
+  }
+  float res = 0;
+  switch (this->configuration_) {
+    case UPSTREAM:
+      if (value == 0.0f)
+        res = NAN;
+      else
+        res = (this->reference_voltage_ - value) / value;
+      break;
+    case DOWNSTREAM:
+      if (value == this->reference_voltage_)
+        res = NAN;
+      else
+        res = value / (this->reference_voltage_ - value);
+      break;
+  }
+
+  res *= this->resistor_;
+  ESP_LOGD(TAG, "'%s' - Resistance %.1fΩ", this->name_.c_str(), res);
+  this->publish_state(res);
+}
+
+}  // namespace resistance
+}  // namespace esphome
diff --git a/esphome/components/resistance/resistance_sensor.h b/esphome/components/resistance/resistance_sensor.h
new file mode 100644
index 0000000000..b57f90b59c
--- /dev/null
+++ b/esphome/components/resistance/resistance_sensor.h
@@ -0,0 +1,38 @@
+#pragma once
+
+#include "esphome/core/component.h"
+#include "esphome/components/sensor/sensor.h"
+
+namespace esphome {
+namespace resistance {
+
+enum ResistanceConfiguration {
+  UPSTREAM,
+  DOWNSTREAM,
+};
+
+class ResistanceSensor : public Component, public sensor::Sensor {
+ public:
+  void set_sensor(Sensor *sensor) { sensor_ = sensor; }
+  void set_configuration(ResistanceConfiguration configuration) { configuration_ = configuration; }
+  void set_resistor(float resistor) { resistor_ = resistor; }
+  void set_reference_voltage(float reference_voltage) { reference_voltage_ = reference_voltage; }
+
+  void setup() override {
+    this->sensor_->add_on_state_callback([this](float value) { this->process_(value); });
+    if (this->sensor_->has_state())
+      this->process_(this->sensor_->state);
+  }
+  void dump_config() override;
+  float get_setup_priority() const override { return setup_priority::DATA; }
+
+ protected:
+  void process_(float value);
+  sensor::Sensor *sensor_;
+  ResistanceConfiguration configuration_;
+  float resistor_;
+  float reference_voltage_;
+};
+
+}  // namespace resistance
+}  // namespace esphome
diff --git a/esphome/components/resistance/sensor.py b/esphome/components/resistance/sensor.py
new file mode 100644
index 0000000000..fb245bcdf0
--- /dev/null
+++ b/esphome/components/resistance/sensor.py
@@ -0,0 +1,37 @@
+import esphome.codegen as cg
+import esphome.config_validation as cv
+from esphome.components import sensor
+from esphome.const import CONF_SENSOR, UNIT_OHM, ICON_FLASH, CONF_ID
+
+resistance_ns = cg.esphome_ns.namespace('resistance')
+ResistanceSensor = resistance_ns.class_('ResistanceSensor', cg.Component, sensor.Sensor)
+
+CONF_REFERENCE_VOLTAGE = 'reference_voltage'
+CONF_CONFIGURATION = 'configuration'
+CONF_RESISTOR = 'resistor'
+
+ResistanceConfiguration = resistance_ns.enum('ResistanceConfiguration')
+CONFIGURATIONS = {
+    'DOWNSTREAM': ResistanceConfiguration.DOWNSTREAM,
+    'UPSTREAM': ResistanceConfiguration.UPSTREAM,
+}
+
+CONFIG_SCHEMA = sensor.sensor_schema(UNIT_OHM, ICON_FLASH, 1).extend({
+    cv.GenerateID(): cv.declare_id(ResistanceSensor),
+    cv.Required(CONF_SENSOR): cv.use_id(sensor.Sensor),
+    cv.Required(CONF_CONFIGURATION): cv.enum(CONFIGURATIONS, upper=True),
+    cv.Required(CONF_RESISTOR): cv.resistance,
+    cv.Optional(CONF_REFERENCE_VOLTAGE, default='3.3V'): cv.voltage,
+}).extend(cv.COMPONENT_SCHEMA)
+
+
+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_sensor(sens))
+    cg.add(var.set_configuration(config[CONF_CONFIGURATION]))
+    cg.add(var.set_resistor(config[CONF_RESISTOR]))
+    cg.add(var.set_reference_voltage(config[CONF_REFERENCE_VOLTAGE]))
diff --git a/esphome/const.py b/esphome/const.py
index 98e1505ee0..92b23f602f 100644
--- a/esphome/const.py
+++ b/esphome/const.py
@@ -62,6 +62,7 @@ CONF_BUILD_PATH = 'build_path'
 CONF_BUSY_PIN = 'busy_pin'
 CONF_BUS_VOLTAGE = 'bus_voltage'
 CONF_CALIBRATE_LINEAR = 'calibrate_linear'
+CONF_CALIBRATION = 'calibration'
 CONF_CARRIER_DUTY_PERCENT = 'carrier_duty_percent'
 CONF_CARRIER_FREQUENCY = 'carrier_frequency'
 CONF_CHANGE_MODE_EVERY = 'change_mode_every'
diff --git a/esphome/platformio_api.py b/esphome/platformio_api.py
index cafb8ebaf4..adadab4109 100644
--- a/esphome/platformio_api.py
+++ b/esphome/platformio_api.py
@@ -19,12 +19,16 @@ def patch_structhash():
     # all issues
     from platformio.commands import run
     from platformio import util
+    try:
+        from platformio.util import get_project_dir
+    except ImportError:
+        from platformio.project.helpers import get_project_dir
     from os.path import join, isdir, getmtime, isfile
     from os import makedirs
 
     def patched_clean_build_dir(build_dir):
         structhash_file = join(build_dir, "structure.hash")
-        platformio_ini = join(util.get_project_dir(), "platformio.ini")
+        platformio_ini = join(get_project_dir(), "platformio.ini")
 
         # if project's config is modified
         if isdir(build_dir) and getmtime(platformio_ini) > getmtime(build_dir):
diff --git a/tests/test3.yaml b/tests/test3.yaml
index 85dc714173..1b75dac7b1 100644
--- a/tests/test3.yaml
+++ b/tests/test3.yaml
@@ -115,6 +115,20 @@ sensor:
       - calibrate_linear:
           - 0 -> 0
           - 100 -> 100
+  - platform: resistance
+    sensor: my_sensor
+    configuration: DOWNSTREAM
+    resistor: 10kΩ
+    reference_voltage: 3.3V
+    name: Resistance
+    id: resist
+  - platform: ntc
+    sensor: resist
+    name: NTC Sensor
+    calibration:
+      b_constant: 3950
+      reference_resistance: 10k
+      reference_temperature: 25°C
   - platform: tcs34725
     red_channel:
       name: Red Channel