Using a Raspberry Pi distance sensor (ultrasonic sensor HC-SR04)

For many (outdoor) projects a distance measurement is necessary or advantageous. These small modules are available starting at 1-2 bucks and can measure the distance up to 4-5 meters by ultrasound and are suprisingly accurate. This tutorial shows the connection and control.



  • HC-SR04 Module (US / UK)
  • Resistors: 330Ω and 470Ω (US / UK)
  • Jumper wire (US / UK)


There are four pins on the ultrasound module that are connected to the Raspberry:

  • VCC to Pin 2 (VCC)
  • GND to Pin 6 (GND)
  • TRIG to Pin 12 (GPIO18)
  • connect the 330Ω resistor to ECHO.  On its end you connect it to Pin 18 (GPIO24) and through a 470Ω resistor you connect it also to Pin6 (GND).

We do this because the GPIO pins only tolerate maximal 3.3V. The connection to GND is to have a obvious signal on GPIO24. If no pulse is sent, the signal is 0 (through the connection with GND), else it is 1. If there would be no connection to GND, the input would be undefined if no signal is sent (randomly 0 or 1), so ambiguous.

Here is the structure as a circuit diagram:


Script for controlling

First of all, the Python GPIO library should be installed

To use the module, we create a new script

sudo nano

with the following content:

After that we run:

sudo python

So every second, the distance will be measured until the script is cancelled by pressing CTRL + C.
That‘s it. You can use it many fields, but who still want to measure larger distances would have to rely on laser measuring devices, which, however, are much more expensive.

40 Responses

  1. Thank you, I need this for a Magic Mirror. I want it to activate when someone is nearby, in front.
    I have experimented with PIR, I always seem to find them a bit random but this should be good.
    I found other examples of “how to do this”. This one, yours, worked immediately.

    OK, so it is not my solution and I need to do much more to make my exact application work but “Thank You” so much for this proof of concept.

  2. Thank you for making it so easy to get playing with this sensor.

    I only had 1k and 2.2k resistors available. Would that be the reason my measurements are off by about 1.7cm on the distances (0.5 – 2 meters) I tested?

    My understanding is that a higher resistor will merely pull the voltage even lower than the target 3.3V needed to make the echo response safe for the pi’s GPIO pins.

    Thanks again


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