I want to use Ultrasonic module HC-SR04 as ranging sensor but my MCU board is approx 80 ft away from the place where I have to put the US module.

These are its pin-outs and descriptions:

HC-SR04 Module back and front

Pin out descriptions

Timing diagram

My ranging is from 1 ft (min) to 6 ft (max) and accuracy is +-1 inch (2-3 cm).

Is it possible to run the 4 wires (Vcc, Trig, Echo, Gnd) directly from my MCU board to the US module 80 ft away?

  • \$\begingroup\$ Of course it is possible to use long wires, but it is quite likely it will not work as intended. If it works depends among other things on the (resistive, capacitive and inductive) specs of the cable and the driving capability of the Ultrasonic module and MCU board, etc \$\endgroup\$ – Huisman Jun 24 '19 at 10:52
  • \$\begingroup\$ How it the distance being determined? Difference in time between start of the trigger signal to the end of echo signal? With long cables, you defenitely won't see these infinite rising and falling edges from the Timing Diagram picture anymore: where does the trigger signal start and where does the echo signal end? \$\endgroup\$ – Huisman Jun 24 '19 at 10:58
  • 1
    \$\begingroup\$ If this MCU board is not expensive, I would buy a second and place it close to the Ultrasonic module and do the communication between the MCU's using a robust communication protocol. \$\endgroup\$ – Huisman Jun 24 '19 at 10:59
  • \$\begingroup\$ If I use RS232 drivers at both ends at the MCU and US module will that make my signal edges sharp? Unfortunately I cannot put a second MCU in the design.. I have to work out a way without that. \$\endgroup\$ – alt-rose Jun 24 '19 at 11:14
  • \$\begingroup\$ I can't tell, I've hardly no experience with (low-level) RS232 \$\endgroup\$ – Huisman Jun 24 '19 at 12:29

More cable == more inductance and capacitance == more phase delay

Common way to design for long cables

  1. Twisted wire
  2. use a signal driver
  3. Shielded cable
  • \$\begingroup\$ Twisting which cables? \$\endgroup\$ – Huisman Jun 24 '19 at 11:10
  • \$\begingroup\$ If I use CAT5 ethernet cable which has twisted pairs will that work? \$\endgroup\$ – alt-rose Jun 24 '19 at 11:12
  • \$\begingroup\$ you should first try with CAT5 ethernet cable and see result if you are not getting good result than you need to connect some kind of signal booster or amplifier \$\endgroup\$ – Jay Vadoliya Jun 24 '19 at 11:25
  • \$\begingroup\$ @Huisman Twisting wire will help in reduce noise \$\endgroup\$ – Jay Vadoliya Jun 24 '19 at 11:26
  • \$\begingroup\$ @JayVadoliya In general twisting cables can help reduce radiation and the susceptibility to EMI. But it will increase slew rate ass well, so, in this case, twisting cables might worsen it as well. \$\endgroup\$ – Huisman Jun 24 '19 at 12:15

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.