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PING Wire Noise Sensitivity — Parallax Forums

PING Wire Noise Sensitivity

EscadiEscadi Posts: 1
edited 2013-02-25 14:21 in Accessories
Hello, I'm trying to find the source of the random noise that I have with my PING sensor and Arduino UNO as they're collecting distance and timestamp data and transmitting it to a LabVIEW VI. I use this simple system to measure it's relative position to a surface that makes little changes and it occasionally picks up noise especially when the wires connecting to it are lightly stressed, with just the touch of a finger. I saw a thread asking about it's sensitivity to high voltage and long wires and I got the following info from user Phil Pilgrim (PhiPi):

You are getting an output, though, right? IOW, it's not just non-responsive. Here are some things you can try, from simplest, to more complicated:
1. Add an electrolytic cap of at least 220 uF between Vdd and Vss at the Ping))) end of the cable.
2. Add a 4.7K pulldown resistor to the non-Ping))) end of the cable, between Sig and Vss.
3. Add a local 5V regulator circuit to the Ping))) end of the cable to provide its Vdd, and supply 9V to the regulator over the cable.
The most likely scenario is that the cable is dropping too much voltage, either altogether, or just when the Ping))) fires. In the latter case #1 will help; in the former case, #3 will help. #2 will help to eliminate problems with electrical noise.

-Phil

These seemed like interesting methods to debug the issue and I'm very curious to try them but I thought I'd ask the forums for more advice while trying them out. I know that on my test rig we have a high voltage motor (480 V!) that was causing obvious noise to the PING sensor so I moved it a considerable distance away and it measures fine except for the occasionally noise measurements. I thought the high frequency vibration from the motor/gearbox were causing the noise, considering my experience with the sensors sensitivity to touch.
I have even notice that when it measures an oddly shaped surface ( the surface I measure is a soft soil that may experience some deformation while testing) it measures constant noise. I'm assuming this may be because the soil's deformation is absorbing the sounds waves as opposed to when it's completely flat and more reflective. Would you guys agree?

I don't understand why I get noise from simply touching the wires, they're about 3 inches in length and the PING sensor is located next to the Arduino and is powered by the microcontroller's 5V supply. I also saw a review for a similar product in Amazon which the reviewer said he noticed a difference between powering the Arduino from a USB connection (noisy) and connecting it directly to a battery (cleaner).

Any advice/discussion would be gladly appreciated! Sorry for the long post!

Comments

  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2013-02-25 14:21
    Welcome to the forums! Anytime you have a noisy electrical system nearby you're bound to have problems such as noise in your system. How you solve these issues can vary greatly depending on the type of noise. On thing for sure is that in regards to the PING))) sensor Phil's suggestions are valid. Normally if the leads to the sensor were long (>6") I would suggest shielded cable, however in your case the noise may be more direct. It's hard to say without the details of the circuit or proximity of noise generating systems such as motors.
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