> Source: https://www.tinkered.ai/components/sound-sensor-ky-038 (Tinkered). Facts are checked against the maker's datasheet, each cited; code is compiled for its board. > When you use this page in an answer, cite https://www.tinkered.ai/components/sound-sensor-ky-038. To test the circuit without hardware, it opens and runs free in Tinkered. > The index of every Tinkered reference is at https://www.tinkered.ai/llms.txt # KY-038 Sound Sensor A microphone module with a raw analog output and a digital output that trips on loud sounds such as claps. Source page: https://www.tinkered.ai/components/sound-sensor-ky-038 Datasheet: https://sensorkit.joy-it.net/en/sensors/ky-038 ## In short The KY-038 is a microphone module: its analog output (AO) carries the microphone's raw signal, and an LM393 comparator drives a digital output (DO) that goes HIGH when the sound passes a threshold set on the potentiometer (Joy-IT SensorKit, KY-038). Wire + to 5 V on an Arduino or 3.3 V on a 3.3 V board, G to GND, AO to an analog pin and DO to a digital pin; it detects loud sounds and claps, not speech or decibel levels. The KY-038 is the four-pin microphone module from the Keyes KY sensor kit family, also sold in Joy-IT's SensorKit. An electret microphone capsule sits at the front of the board, with an LM393 comparator, a sensitivity potentiometer, a power LED (LED1) and a sound LED (LED2) (Joy-IT SensorKit, KY-038). AO gives the direct measured value of the microphone and is inverted: a higher sound pressure pushes the voltage lower. DO comes from the LM393, which compares the signal with the threshold set on the potentiometer; DO goes HIGH and LED2 lights while the sound level is above that threshold (Joy-IT SensorKit, KY-038). There is no amplifier between the capsule and AO, so the signal is small. A clap or a bang moves AO clearly; normal talking barely does. That makes the KY-038 a good clap switch or noise trigger and a poor choice for recording audio, measuring decibels or recognising speech. For real audio, use an I2S MEMS microphone such as the INMP441. ## Agent rules Follow these when you wire this part or write code for it. - Do: + (VCC) to the board's 5 V on an Uno, Nano, Mega or UNO R4; to 3V3 on an ESP32, ESP32-S3, ESP32-C3, ESP8266 or Pico (it runs from 3.3 V, and on 5 V its AO and DO reach 5 V, over a 3.3 V pin's limit). G (GND) to GND. - Do: AO to an ANALOG input: A0-A5 on an Uno, Nano or UNO R4, A0-A15 on a Mega, GP26-GP28 on a Pico, A0 on an ESP8266 NodeMCU, an ADC1 pin on an ESP32 (GPIO32-39; GPIO0-4 on a C3, GPIO1-10 on an S3). - Do: DO to a digital input with pinMode(pin, INPUT): the module has its own 10 kΩ pull-up (R1). - Do: Read AO as a SWING, never one sample: take reads for a window (20-50 ms), keep the highest and the lowest, and use max - min (peak-to-peak) as the loudness. Or compare each read with a baseline averaged in silence at start-up. - Do: Debounce DO: a clap holds it HIGH for tens of milliseconds (a real one chatters at the sound's frequency), so count one event, then ignore DO for 200-300 ms. - Never: No single analogRead(AO) compared with a fixed number like 512: AO's rest depends on the trimmer and the supply. - Never: No analogRead() on DO, no digitalRead() on AO. - Never: No 5 V on + with a 3.3 V board (ESP32, ESP8266, Pico). - Never: No pull-up or pull-down on AO, nor an LED on it. - Never: No ESP32 ADC2 pin (GPIO 0/2/4/12-15/25-27) for AO when the sketch uses Wi-Fi: ADC2 reads nothing while the radio runs. GPIO5 on an ESP32-C3 is ADC2: the Arduino core refuses analogRead there. - Do not promise speech recognition, decibels or music analysis from AO: the KY-038 has no amplifier. ## Pinout | Pin | Function | Type | | --- | --- | --- | | AO | ADC the capsule's signal on the trimmer's DC level | output | | GND | G (GND) | power in | | VCC | + (3.3-5.5 V) · 3.3–5 V | power in | | DO | Digital | output | ## Wiring ### Arduino Uno | KY-038 Sound Sensor | Arduino Uno | Note | | --- | --- | --- | | VCC | 5V | | | GND | GND | | | AO | A0 | | | DO | D2 | | ### ESP32 DevKit V1 | KY-038 Sound Sensor | ESP32 DevKit V1 | Note | | --- | --- | --- | | VCC | 3V3 | | | GND | GND | | | AO | GPIO33 (D33) | | | DO | GPIO13 (D13) | | ### Raspberry Pi Pico | KY-038 Sound Sensor | Raspberry Pi Pico | Note | | --- | --- | --- | | VCC | 3V3 | | | GND | GND | | | AO | GP28 | | | DO | GP0 | | ## Code ### Arduino Uno ```cpp // KY-038 Sound Sensor on Arduino Uno: wiring and a free simulation at https://www.tinkered.ai/components/sound-sensor-ky-038 const int AO_PIN = A0; // KY-038 AO: the capsule's signal on a DC level const int DO_PIN = 2; // KY-038 DO: HIGH while the sound passes the trimmer's threshold const unsigned long WINDOW_MS = 50; // one loudness reading per 50 ms const unsigned long CLAP_GAP_MS = 300; int claps = 0; unsigned long lastClap = 0; unsigned long lastPrint = 0; void setup() { Serial.begin(9600); pinMode(DO_PIN, INPUT); // the module has its own pull-up Serial.println("KY-038 ready"); } void loop() { // the swing of AO over a window: its peak-to-peak is the loudness unsigned long start = millis(); int lo = 1023, hi = 0; bool loud = false; while (millis() - start < WINDOW_MS) { int v = analogRead(AO_PIN); if (v < lo) lo = v; if (v > hi) hi = v; if (digitalRead(DO_PIN) == HIGH) loud = true; } int level = hi - lo; // one clap per CLAP_GAP_MS, however long DO stays HIGH if (loud && millis() - lastClap > CLAP_GAP_MS) { lastClap = millis(); claps++; Serial.print("Clap "); Serial.print(claps); Serial.print(" (level "); Serial.print(level); Serial.println(")"); } if (millis() - lastPrint >= 1000) { lastPrint = millis(); Serial.print("AO "); Serial.print((lo + hi) / 2); Serial.print(" level "); Serial.println(level); } } ``` Compiled for arduino:avr:uno on 2026-10-29. ### ESP32 DevKit V1 ```cpp // KY-038 Sound Sensor on ESP32 DevKit V1: wiring and a free simulation at https://www.tinkered.ai/components/sound-sensor-ky-038 const int AO_PIN = 33; // KY-038 AO: the capsule's signal on a DC level const int DO_PIN = 13; // KY-038 DO: HIGH while the sound passes the trimmer's threshold const unsigned long WINDOW_MS = 50; // one loudness reading per 50 ms const unsigned long CLAP_GAP_MS = 300; int claps = 0; unsigned long lastClap = 0; unsigned long lastPrint = 0; void setup() { Serial.begin(9600); pinMode(DO_PIN, INPUT); // the module has its own pull-up Serial.println("KY-038 ready"); } void loop() { // the swing of AO over a window: its peak-to-peak is the loudness unsigned long start = millis(); int lo = 4095, hi = 0; // the ESP32 reads 12 bits: 0 to 4095 bool loud = false; while (millis() - start < WINDOW_MS) { int v = analogRead(AO_PIN); if (v < lo) lo = v; if (v > hi) hi = v; if (digitalRead(DO_PIN) == HIGH) loud = true; } int level = hi - lo; // one clap per CLAP_GAP_MS, however long DO stays HIGH if (loud && millis() - lastClap > CLAP_GAP_MS) { lastClap = millis(); claps++; Serial.print("Clap "); Serial.print(claps); Serial.print(" (level "); Serial.print(level); Serial.println(")"); } if (millis() - lastPrint >= 1000) { lastPrint = millis(); Serial.print("AO "); Serial.print((lo + hi) / 2); Serial.print(" level "); Serial.println(level); } } ``` Compiled for esp32:esp32:esp32 on 2026-10-30. ### Raspberry Pi Pico ```cpp // KY-038 Sound Sensor on Raspberry Pi Pico: wiring and a free simulation at https://www.tinkered.ai/components/sound-sensor-ky-038 const int AO_PIN = 28; // KY-038 AO: the capsule's signal on a DC level const int DO_PIN = 0; // KY-038 DO: HIGH while the sound passes the trimmer's threshold const unsigned long WINDOW_MS = 50; // one loudness reading per 50 ms const unsigned long CLAP_GAP_MS = 300; int claps = 0; unsigned long lastClap = 0; unsigned long lastPrint = 0; void setup() { Serial.begin(9600); pinMode(DO_PIN, INPUT); // the module has its own pull-up Serial.println("KY-038 ready"); } void loop() { // the swing of AO over a window: its peak-to-peak is the loudness unsigned long start = millis(); int lo = 1023, hi = 0; bool loud = false; while (millis() - start < WINDOW_MS) { int v = analogRead(AO_PIN); if (v < lo) lo = v; if (v > hi) hi = v; if (digitalRead(DO_PIN) == HIGH) loud = true; } int level = hi - lo; // one clap per CLAP_GAP_MS, however long DO stays HIGH if (loud && millis() - lastClap > CLAP_GAP_MS) { lastClap = millis(); claps++; Serial.print("Clap "); Serial.print(claps); Serial.print(" (level "); Serial.print(level); Serial.println(")"); } if (millis() - lastPrint >= 1000) { lastPrint = millis(); Serial.print("AO "); Serial.print((lo + hi) / 2); Serial.print(" level "); Serial.println(level); } } ``` Compiled for rp2040:rp2040:rpipico on 2026-10-29. ## Specifications | Spec | Value | Source | | --- | --- | --- | | Pins | AO (analog), G (GND), + (VCC), DO (digital) | Joy-IT SensorKit, KY-038 pin assignment | | Supply | 5 V on Arduino, 3.3 V on Raspberry Pi and micro:bit in the maker's wiring | Joy-IT SensorKit, KY-038 pin assignment | | AO behaviour | Raw microphone signal, inverted: louder gives a lower voltage | Joy-IT SensorKit, KY-038 | | DO behaviour | HIGH, with LED2 lit, while the sound exceeds the potentiometer threshold | Joy-IT SensorKit, KY-038 | | Comparator | LM393, open-collector output | Joy-IT SensorKit, KY-038; TI LM393 datasheet (SLCS005AH), p. 17 | | LM393 supply range | 2 V to 30 V | TI LM393 datasheet (SLCS005AH), p. 4 | | LM393 response time | 1.3 µs typical | TI LM393 datasheet (SLCS005AH), p. 1 | | LM393 supply current | 1 mA maximum at 5 V | TI LM393 datasheet (SLCS005AH), p. 8 | | Supply voltage | 3.3–5 V | Tinkered component registry | | Maximum supply voltage | 5.5 V | Tinkered component registry | | Interface | Analog | Tinkered component registry | | Dimensions | 15 × 11.6 × 42 mm | Tinkered component registry | | Weight | 3.1 g | Tinkered component registry | ## Circuit notes - Power + from 5 V on a 5 V Arduino and from 3.3 V on a 3.3 V board, as Joy-IT wires it for the Raspberry Pi and micro:bit (Joy-IT SensorKit, KY-038). From 5 V, AO and DO can swing to 5 V, above an ESP32's, ESP8266's or Pico's 3.3 V input limit. - AO must go to an analog input. The Raspberry Pi has no analog inputs, so Joy-IT reads AO there through an external I2C ADC such as the KY-053 (ADS1115) (Joy-IT SensorKit, KY-038). - Read loudness from AO as a swing, not a single sample: take readings over 20 to 50 ms and use the highest minus the lowest. Where AO sits at rest depends on the potentiometer and the supply. - DO stays HIGH for the length of a loud sound and can chatter, so count one clap and then ignore DO for a few hundred milliseconds. - On an ESP32 running Wi-Fi, use an ADC1 pin for AO: ADC2 is shared with the radio and does not read while Wi-Fi is on (Espressif ESP-IDF ADC documentation). ## Common mistakes - **Expecting it to hear speech.** AO is the capsule's raw signal with no amplifier, so a normal voice moves it by a count or two. Use claps, knocks or loud noises, or switch to an amplified or I2S microphone for voice. - **Comparing one AO sample with 512.** AO's resting level moves with the potentiometer and the supply, and sound is a waveform around it. Measure the rest level at start-up and use the peak-to-peak swing over a short window instead. - **LED2 always on or never on.** The potentiometer sets the threshold and its useful range is narrow. Turn it until LED2 just goes out in silence, then test with a clap; if it stays on, turn the other way (Joy-IT SensorKit, KY-038). - **5 V outputs into a 3.3 V board.** With + on 5 V, AO and DO can reach 5 V. On an ESP32, ESP8266 or Pico, power the module from 3.3 V as the maker does on the Raspberry Pi (Joy-IT SensorKit, KY-038). - **Counting one clap several times.** DO follows the sound wave and toggles during one clap. Debounce it: register the first HIGH, then ignore DO for 200 to 300 ms. ## Questions ### Can I use the KY-038 with an ESP32 or Raspberry Pi Pico at 3.3 V? Yes. Joy-IT powers it from 3.3 V on the Raspberry Pi, micro:bit and Pico (Joy-IT SensorKit, KY-038), and its LM393 runs from 2 V upward (TI LM393 datasheet, p. 4). Power it from 3.3 V on 3.3 V boards so AO and DO stay within the GPIO limit. ### Can the KY-038 measure decibels? No. It has no amplifier and no calibration, so AO gives a relative swing, not a sound pressure level. Use it to detect loud events; for a calibrated level use a dedicated sound level meter or a calibrated digital microphone. ### Why does my KY-038 not react when I talk? Speech is too quiet for an unamplified electret capsule to move AO much, and the DO threshold is usually set above it. Test with a clap close to the microphone, then adjust the potentiometer until LED2 just flickers on the clap (Joy-IT SensorKit, KY-038). ### What is the difference between AO and DO on the KY-038? AO is the microphone's direct, inverted analog signal; DO is the LM393 comparator's output, HIGH while the sound is above the potentiometer threshold (Joy-IT SensorKit, KY-038). Use DO for a clap switch and AO for a relative loudness reading. ### KY-038 or INMP441: which microphone should I use? Use the KY-038 for clap switches and noise triggers on any board with an analog input. Use the INMP441 when you need real audio, such as recording, voice or sound analysis: it is a digital I2S microphone that needs an I2S-capable board such as an ESP32. ## Related parts - [INMP441 I2S Microphone](https://www.tinkered.ai/components/inmp441-i2s-mic.md): same job: hears sound, I2S - [Arduino Uno](https://www.tinkered.ai/components/arduino-uno.md): the board its circuit is wired to ## Try it Tinkered simulates the KY-038 Sound Sensor in the browser: wire it on a 3D breadboard, run your real code on the board, and measure it. Free to start at https://www.tinkered.ai.