Im working on replicating the work found on Ultrasonic Radar; Multi-Point. It bypasses the echo out on HC-SR04 and enables full analog output to Arduino ADC. The results are quite good but unlike the project described on the website, anything further than cca 20 cm is noise. Any ideas why?

used 4.6k ohm resistor 2x 4.7nF capacitors


What I get enter image description here

  • \$\begingroup\$ How long are you waiting between pulses for echos to dissipate? \$\endgroup\$
    – Trevor_G
    Commented May 16, 2017 at 15:16
  • \$\begingroup\$ From the Sketch, reading is done every 15ms. No change was done to OP code \$\endgroup\$
    – NccWarp9
    Commented May 16, 2017 at 15:22
  • \$\begingroup\$ I'd try experimenting with that to longer durations just to see. Results will vary depending on where you are. The size of the room and wall material can make a big difference to how long the sound takes to dissipate. \$\endgroup\$
    – Trevor_G
    Commented May 16, 2017 at 15:24
  • \$\begingroup\$ its large room, and tried changing the delays, no joy, still the same noise. \$\endgroup\$
    – NccWarp9
    Commented May 16, 2017 at 15:34
  • \$\begingroup\$ Then you are stuck with getting a stronger signal and reducing the sensitivity of the receiver. That and cleaning up the receiver to be less sensitive to electrical noise. \$\endgroup\$
    – Trevor_G
    Commented May 16, 2017 at 15:41


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