??? tip "This feature is included only in tasmota-sensors binary"
When [compiling your build](Compile-your-build) add the following to `user_config_override.h`:
```c++
#ifndef USE_SR04
#define USE_SR04 // Add support for HC-SR04 ultrasonic devices (+1k code)
#define SR04_MAX_SENSOR_DISTANCE 500 // Set sensor max detection distance #endif
```
HC-SR04 (HC-SR04P and JSN-SR04T) is an ultrasonic ranging sensor. Provides 2cm to 300cm of non-contact measurement functionality with a ranging accuracy that can reach up to 3mm. Each HC-SR04 module includes an ultrasonic transmitter, a receiver and a control circuit. See HC-SR04 Ultrasonic Sensor for more information.
Buy example:
The US-100 can also be use as a HC-SR04 if you remove the jumper at the back (check Adafruit documentation).
| HC-SR04 | ESP |
|---|---|
| Vcc | 5V |
| GND | GND |
| Trig | GPIOx |
| Echo use voltage divider! |
GPIOy |
The HC-SR04 operates at 5V and therefore the echo signal will be 5V as well. Connecting the echo pin via a voltage divider (see schematic) will divide the 5V to 3.3V, which is the operating voltage of an ESP8266.
There is a variant of the HC-SR04, called HC-SR04P. It mainly operates at 3.3V and then it doesn't need the voltage divider but you will notice a range drop of about 1 meter.
In the Configuration -> Configure Module page assign:
- GPIOx to
SR04 Tri (69) - GPIOy to
SR04 Ech (70)
After a reboot webUI displays the HC-SR04 distance.
Sensor sends a tele/%topic%/SENSOR JSON response:
{"Time":"2019-01-01T22:42:35","SR04":{"Distance":16.754}}