Source: https://mokxi.com/parts/hcsr04 Updated: 2026-09-27 Part # Ultrasonic ranger Pulse TRIG and time ECHO. The slider moves whatever it is looking at. or see every part - 4 pins - 1 property Drawn live by the editor's own code, at the size you see it. Reference ## Every one of its 4 pins Pin Role What it does VCC Input or output Supply, 4.5 V or more. TRIG Input Input; hold high 10 us or more to fire a ping. ECHO Output Push-pull output, high for the round-trip time. GND Input or output Ground. This part ## What it does The HC-SR04 measures distance with sound and reports it as time. Hold TRIG high for ten microseconds and the module fires a short burst of 40 kHz, then holds ECHO high for as long as the sound takes to reach the object and come back: about 58 microseconds for every centimeter of range. There is no bus, no register and no address, which is why it is the sensor every class starts with. Mokxi’s part keeps the datasheet’s timing, including the 460 microsecond wait before ECHO rises, the full 38 millisecond pulse when nothing is in range, and the rule that a new ping inside 60 milliseconds of the last is ignored. The speed of sound follows an air temperature you can set, so a sketch that divides by 58 drifts with the weather the way a real module does. The distance itself is a slider on the part, from 2 centimeters to 4 meters. How to use it ## How to use the HC-SR04 with an Arduino Wire VCC to 5 V, GND to GND, and TRIG and ECHO to two digital pins. To measure, hold TRIG high for 10 microseconds, time how long ECHO stays high with pulseIn(), and divide by 58 for centimeters. Give pulseIn() a timeout of about 38 milliseconds so an empty room does not stall the sketch, and leave at least 60 milliseconds between pings. Part pin Board pin VCC 5 V TRIG Pin 7 ECHO Pin 6 GND GND The same code runs on an ESP32 or a Pico. On real hardware those boards are not 5 V tolerant, so put a divider on ECHO. Click to open it in the editor This is the simulator itself, running here. Click anything to open it in the editor. Open this project in the editor Read the full tutorial One reading, in centimeters Reference ## The one property you can set Property Default What it means temperature 20 the air temperature in degrees Celsius, 20 by default. Sound travels at 331.3 + 0.606 T meters a second, so this is what sets the microseconds per centimeter: 6.04 per centimeter of round trip at freezing, the datasheet's round 5.8 at room temperature, 5.63 at 40 °C. How it is modeled ## What is true about the Ultrasonic ranger, here ### What is modeled The datasheet's own timing, including the awkward number every sketch divides by: ECHO rises 460 microseconds after the trigger ends and stays high for 58 microseconds per centimeter of range: the round trip at the speed of sound. With nothing in range it stays high for the full 38 ms timeout, and a sketch that does not expect that hangs for 38 ms on a reading. The 60 ms re-trigger cycle is real too: trigger it faster and the module ignores the request, because the last burst is still rattling around the room. ### Not modeled No beam angle or off-axis reflection. The slider is a single number, "how far away the thing in front of it is", not a scene to bounce sound around. No sound is simulated at all. The 40 kHz burst is never emitted; the part is a stopwatch that waits 460 microseconds and then holds ECHO high for the round trip at the speed of sound. That speed does come from the air temperature: the temperature property is degrees Celsius, 20 by default, and sound moves at 331.3 + 0.606 T meters a second, so a 1 m wall echoes for 6.04 ms at freezing and 5.63 ms at 40 °C. A sketch that divides by 58, as every sketch does, reads that wall as 104 cm in the cold and 97 cm in the heat, which is exactly what a real module does and why one never quite agrees with a tape measure. What is still missing is humidity and any drift: the temperature is a dial you set, not something that wanders. The reading has no error in it. Whatever the slider says comes back exactly, with no ±3 mm accuracy figure, no jitter between readings, no dead zone and no drop-outs from a soft or angled surface. Anything closer than 20 mm or further than 4000 mm reads as nothing in range rather than as a wrong number, which is what a real HC-SR04 does at the near end, and kinder than one at the far end. ECHO is a push-pull 5 V output with no rise time, and there is no supply current. From HC-SR04 ultrasonic sensor, in full. Projects ## See the Ultrasonic ranger in a project Shown here on: Arduino Uno R3 Learn ## Where it turns up in a lesson ### In a learn article - Arduino Ultrasonic Sensor (HC-SR04) Tutorial More parts ## The rest of the bench Every one of these is drawn and simulated the same way. Full-size breadboard A real 0.1 inch grid with the rails and the center channel, 63 columns wide. Jumper wires Drag from any pin or hole to any other. Corners snap, and you can drag them. Power A supply rail at the voltage you choose. Ground The other end of every circuit. LED Lights when current flows. Five colors, and the brightness is what your eye would see. Resistor Any value you like, with the color bands drawn to match. ESP32-C3-DevKitM-1 A RISC-V board that runs your firmware at 160 MHz on the real memory map. Pushbutton A 12 mm tactile switch. Hold it while the simulation runs. Raspberry Pi Pico The RP2040 board on our own Cortex-M0+ core. Pick a program and press Run. Raspberry Pi Pico W Raspberry Pi Pico W (RP2040). The same board and the same pinout as a Pico, with the CYW43439 on it. The WiFi is simulated (no radio, no real internet), and the on-board LED, which hangs off that chip rather than off GP25, is driven through the same path. Everything else is the Pico. STM32F411 Black Pill The Black Pill on our own Cortex-M4 core. Pick a program and press Run. BBC micro:bit V2 The nRF52833 board with its 5x5 LED matrix, buttons A and B and a speaker. Wire the rings to a breadboard. See every part ## Wire up the Ultrasonic ranger Open the editor and push it into the breadboard. It is free, and it runs on your own machine. Start building Open the editor