KY-013 Analog Temperature Sensor Module
The KY-013 is an analog temperature sensor module utilizing an NTC thermistor. It provides temperature measurements in the range of -55°C to +125°C with an accuracy of ±0.5°C. Suitable for various temperature monitoring applications.
KY-013 pinout
The KY-013 is a 3-pin analog temperature sensor module with NTC thermistor:
| Pin | Type | Description | Notes |
|---|---|---|---|
| Pin (-) | Power | Ground connection | |
| Pin (middle) | Power | Power supply | 3.3V to 5V |
| Pin (S) | Communication | Analog signal output | Voltage varies with temperature |
Interface: Analog output (voltage divider)
Sensor: NTC thermistor (negative temperature coefficient)
Range: -55°C to +125°C
Accuracy: ±0.5°C (typical)
Power: 3.3V to 5V operation
Operation: Resistance decreases as temperature increases
Wiring the KY-013 to ESP32
To interface the KY-013 with an ESP32 for analog temperature reading:
| KY-013 pin | ESP32 pin | Purpose |
|---|---|---|
| Pin (-) | GND | Ground |
| Pin (middle) | 3.3V or 5V | Power supply |
| Pin (S) | GPIO36 | Analog input (ADC pin) |
ADC Pins: Use GPIO32-39 for analog input on ESP32
Voltage: 3.3V recommended for ESP32 ADC range
Conversion: Requires Steinhart-Hart equation for accurate temperature
Filtering: Software averaging recommended for stable readings
KY-013 code examples
#include <math.h>
int sensorPin = 36; // Analog input (GPIO36 / ADC1_CH0, matches the wiring above)
void setup() {
Serial.begin(115200);
}
void loop() {
int rawValue = analogRead(sensorPin);
// ESP32 ADC: 12-bit (0-4095) at 3.3V reference
double voltage = rawValue * (3.3 / 4095.0);
double resistance = (3.3 - voltage) * 10000 / voltage; // 10k series resistor
// NTC thermistor: B = 3950, R0 = 10k at 25 C (298.15 K)
double temperature = 1 / (log(resistance / 10000) / 3950 + 1 / 298.15) - 273.15;
Serial.print("Temperature: ");
Serial.print(temperature);
Serial.println(" C");
delay(1000);
}The analog value is read on GPIO36 (ADC1) and converted using the ESP32's 12-bit range: voltage = raw * 3.3 / 4095. From the voltage the sketch derives the thermistor's resistance in the 10k voltage divider and applies the Beta equation (B = 3950, 10k at 25 C) to get the temperature. Analog readings on the ESP32 are noticeably noisier than on an Arduino Uno - average several readings for a steadier value.
#include <stdio.h>
#include <math.h>
#include "freertos/FreeRTOS.h"
#include "freertos/task.h"
#include "driver/adc.h"
#define ADC_CHANNEL ADC1_CHANNEL_0 // GPIO36
void app_main(void) {
adc1_config_width(ADC_WIDTH_BIT_12);
adc1_config_channel_atten(ADC_CHANNEL, ADC_ATTEN_DB_11);
while (1) {
int raw = adc1_get_raw(ADC_CHANNEL);
double voltage = raw * (3.3 / 4095.0);
double resistance = (3.3 - voltage) * 10000 / voltage;
double temperature = 1 / (log(resistance / 10000) / 3950 + 1 / 298.15) - 273.15;
printf("Temperature: %.2f °C\n", temperature);
vTaskDelay(pdMS_TO_TICKS(1000));
}
}This ESP-IDF code configures ADC1 on GPIO36 to read the analog signal from the KY-013 sensor. It calculates the temperature using the Steinhart-Hart equation and prints the result in Celsius every second.
sensor:
- platform: ntc
sensor: resistance_sensor
name: "KY-013 Temperature Sensor"
calibration:
b_constant: 3950
reference_temperature: 25°C
reference_resistance: 10kΩ
- platform: adc
pin: GPIO36
id: resistance_sensor
update_interval: 1sThis ESPHome configuration sets up the KY-013 temperature sensor using an NTC thermistor on GPIO36. The resistance is measured via ADC, and the temperature is calculated using the Steinhart-Hart equation with a B-constant of 3950.
[env:esp32]
platform = espressif32
board = esp32dev
framework = arduino#include <Arduino.h>
#include <math.h>
#define SENSOR_PIN 36 // Analog input pin
void setup() {
Serial.begin(115200);
}
void loop() {
int rawValue = analogRead(SENSOR_PIN);
double voltage = rawValue * (3.3 / 4095.0);
double resistance = (3.3 - voltage) * 10000 / voltage;
double temperature = 1 / (log(resistance / 10000) / 3950 + 1 / 298.15) - 273.15;
Serial.printf("Temperature: %.2f °C\n", temperature);
delay(1000);
}This PlatformIO code configures the KY-013 temperature sensor on GPIO36. It reads the analog value, converts it to voltage, calculates the resistance, and then determines the temperature using the Steinhart-Hart equation.
import machine
import time
import math
SENSOR_PIN = 36 # ADC input pin
adc = machine.ADC(machine.Pin(SENSOR_PIN))
adc.atten(machine.ADC.ATTN_11DB) # Full range 0-3.3V
def get_temperature():
raw = adc.read()
voltage = raw * (3.3 / 4095.0)
resistance = (3.3 - voltage) * 10000 / voltage
temperature = 1 / (math.log(resistance / 10000) / 3950 + 1 / 298.15) - 273.15
return temperature
while True:
print("Temperature:", round(get_temperature(), 2), "°C")
time.sleep(1)This MicroPython script reads the KY-013 sensor using ADC on GPIO36. It converts the voltage to resistance and then calculates the temperature using the Steinhart-Hart equation. The temperature is printed to the console every second.
KY-013 specifications
About the KY-013
The KY-013 is a bare 10 kOhm NTC thermistor wired into a voltage divider with a fixed resistor, so it reports temperature indirectly: as the thermistor heats up its resistance drops, and the divider’s output voltage shifts accordingly. Turning that voltage into a Celsius number takes real math on your side - the beta equation (a beta of 3950 K around the 25 degC/10 kOhm reference point is the commonly cited value for this style of module) or the fuller Steinhart-Hart formula - since there’s no chip on board doing that conversion for you.
That also means the accuracy quoted on cheap KY-013 listings is optimistic for what you actually get without individually calibrating each unit; component tolerances on the thermistor and the divider resistor both feed straight into the error. For a reading that’s accurate out of the box with no math required, a digital sensor like the DS18B20 - which the similarly-numbered KY-001 module is itself built around - or the SHT40 reports calibrated temperature directly over the wire. Wire the analog output to one of the ESP32’s ADC1 pins (GPIO32-39); the ADC2 pins share hardware with Wi-Fi and are best avoided for analog reads.
KY-013 troubleshooting
Incorrect Temperature Readings
›
Issue: The sensor outputs inaccurate or fluctuating temperature values.
Solutions:
- Ensure stable power supply to the sensor.
- Verify correct wiring connections, especially the analog signal pin.
- Implement proper analog signal filtering in the code to reduce noise.
No Output from Sensor
›
Issue: The sensor provides no data or constant values.
Solutions:
- Check for loose or incorrect connections.
- Confirm that the analog input pin on the microcontroller is functioning correctly.
- Test the sensor with a known temperature source to validate its operation.
Where to buy the KY-013
Resources
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