ping sensor and acoustics

tehmoordar

Hi
I am facing a very unique problem.
the ping range sensor that I am using shows me square wave on oscope but as I switch on my motors I can see the different peaks emerging on Oscope and it increases with the speed or the noise of the motor.
I seprated the motor from the circuit put a 300uf capacitor and schottky diode in the circuit with motor and ran the motor in air. I again saw the ripples in Oscope with increase in speed of motor infact number of· square waves being generated in Oscope also increased.

Now I took the motor away from range sensor like 8-10 feet away where the sensor could not hear the noise of motor and amazingly range sensor worked and there was no ripple in the Oscope aswell. as I brought the motor closer to the circuit ripples started.

Now I am also assuming beside the RF , sound waves generated from motor is also effecting the capabilities of the range sensor.
How can I reduce these effects and sounds.
I am using DC motor( item # 1205· @· www.hobbyengineering.com)
Thanks

steve_b

You might try grounding the case of the motor.

By moving the motor away and the noise disappearing, you've determined that the noise is transfering up in to the power supply.

Run your motor in a shielded metal box....
What happens when you put the motor wires close to the sensor? Or is it just the motor that's causing it?!
Where, in relation to the sensor, is the motor when it causes problems?

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
·

Steve
http://ca.geocities.com/steve.brady@rogers.com/index.html
"Inside each and every one of us is our one, true authentic swing. Something we was born with. Something that's ours and ours alone. Something that can't be learned... something that's got to be remembered."

Chris Savage

Hello,

·· If you're getting acoustic interference, you could try re-positioning the PING so that it isn't likely to get echoes from the motor.· You could use a simple shroud.· If you can, please post a screenshot or two of your scope readings with the motor on.· Also, using the scope, can you confirm any noise on the power supply lines?

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Chris Savage
Parallax Tech Support
csavage@parallax.com

tehmoordar

hi,
finally I havve come to the conclusion that it is the emg being genearted by the motor which makes the ping sensor flicker more and send more frequent pulses than nomal see my two pics( attached) one is without motor oN· and other is with motor.
As motor speeeds up so will the rate of flickering of the sensor, which then will start missing the data and will start ahowing the range time to be one msec alternatively in basic stamp editor.
see attachment

steve_b

HAve you tried separate power supplies?
Shielding one or the other?

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
·

Steve
http://ca.geocities.com/steve.brady@rogers.com/index.html
"Inside each and every one of us is our one, true authentic swing. Something we was born with. Something that's ours and ours alone. Something that can't be learned... something that's got to be remembered."

tehmoordar

Hi,

see the attachment these ar e my two power supplies, and I have not shielded these,
though I have instead of these power supplies used 9V battery for Basicstamp and 3v battery for motorcontroller seprately but not shileded.

By shielded you mean I put these power supplies in some shielded box
thanks

tehmoordar

Hello,

A little success as I did few things I have changed the wires of power supply to shielded wires and I have also grounded the motor case -- this has helped me now atleast I can run the motor separately but as soon I assemble the upper portion of robot to lower portion like on top of each other then sensor again malfunctions--

If two pieces of robot are beside then they are ok and sensor too works fine.

Now I need to see either it is some frequency that is being generated by gear box itself is it the sound problem creating some vibrations--

How can I cut the sound coming from motor how can I cover it with some shroud what kind of shroud -- motors has very little space inside robot

I need you technical help

Thanks in advance

Forrest

You could try mounting the screws/nuts holding the PING sensor on vinyl grommets www.radioshack.com/product.asp?catalog%5Fname=CTLG&product%5Fid=64-3025