First post: Tips for stabilizing HC-SR04 ultrasonic readings

[Danieldsouza]

Hi everyone, new to the forum! I’ve been working with the HC-SR04 ultrasonic sensor for a small robotics project and wanted to share a quick tip for anyone struggling with "jumpy" or inconsistent distance data.

While these sensors are great for the price, they often pick up noise from mechanical vibrations or power supply fluctuations. I found that adding a small 10µF capacitor across the VCC and GND pins right at the sensor helps significantly with stability. Also, if you are getting ghost readings, try implementing a simple median filter in your code rather than just taking a single pulse-in value.

I’ve spent some time looking into the timing requirements to avoid trigger overlaps. For those interested in the exact pulse duration and echo timing curves, I found this detailed datasheet helpful for calculating the speed of sound compensation based on ambient temperature:

Technical Reference: HC-SR04 Ultrasonic Sensor Datasheet

Looking forward to learning from the community here!

 

[AnalogKid]

Modules like this one have amazing capabilities for the price, but that low price comes at a cost. The on-board decoupling is barely adequate, just enough to get by most of the time. Better to treat the module like a medium-current opamp circuit:

1 - 0.1 uF ceramic cap with the shortest possible leads, as close as possible to the Vcc and GND pins.

1 - Larger value electrolytic cap in parallel, something in the10 uF to 47 uF range.

Wiring inductance is a real thing. App notes for the LM317 and 7805 3-terminal regulators are clear about needing an input capacitor if the component is more than 4" or 6" away from the main filter capacitor.

ak