If you're like me, you've dreamed of being a dolphin - smoothly gliding through the water. Using your echo-location abilities to detect tasty fish treats. Until genetic modifications catches up with our desires, we'll just have to make do with these handy HC-SR04 and US100 Ultrasonic Sonar Distance Sensors and a pair of flippers.

These ubiquitous sensors are really common in robotics projects, but they can also be used for automation, interactive art and motion sensing. They work at about 2cm to 400cm away, but we think 10cm-250cm will get you the best results. 

The HC-SR04 sensors are fast, fairly easy to use, and low cost. They do require powering from 5V for best results: connect GND (ground) and VCC to 5V power. While the Trig signal can be 3V or 5V, the 'return' Echo signal is 5V logic. For that reason, we include two 10K resistors, use these as a divider to convert the 5V logic level to a safe 2.5V that you can ready with your 3V device.

The US-100 is very similar to the popular HC-SR04 ultrasonic sensors, and even looks the same, but has a few extra tricks

  • This sensor can run from 3-5V so you don't need any logic level shifters or dividers. Just power from whatever your microcontroller provides
  • You can use in "HC-SR04" mode or in "Serial UART" mode.

When the jumper on the back is removed, it acts like an HC-SR04 with a trigger and echo pin. When the jumper is in place, you use 9600 baud UART to communicate with the sensor. In UART mode, send 0x55 and read back two bytes (16 bit value) that is mm distance, or 0x50 to read the temperature in degrees C. Handy if you want to use with a computer and a USB-serial converter, or some other device that can't do the special timing needed for the HC-SR04 trigger/echo.

This guide was first published on Dec 04, 2019. It was last updated on Dec 04, 2019. This page (Overview) was last updated on Jan 26, 2020.