Sharp GP2Y0D340K sensors - strangely sensitive to noise

[RiO]

I use Sharp GP2Y0D340K (12 in digital) sensors for my sumo Robot.
They seem to be giving false positive readings from time to time, which disrupts my robot operation.
It only happens when my motors are running.
I use Maxons 13017 and Pololu TRex Jr controller (Freescale 33887 based). Could that be electrical noise? Is there a way to fix it easily? Please give me advice.
Specifically I am interested in what noise-protection people use with these sensors.

[pomprocker]

these are very noisy sensors the solution is to put a capacitor on there somewhere...Search the forum.

[RiO]

I connected it exactly as in datasheet http://sharp-world.com/products/device/lineup/data/pdf/datasheet/gp2y0d340k_e.pdf
No I could not find anything about them in this forum. Maybe under different name?
Shall I attach a cap to the output leg? If yes - what size? Maybe RC filter?

[pomprocker]

Here this link talks about adding a cap on the power/gnd and on the signal

http://www.robotroom.com/DistanceSensor3.html

[Admin]

You didn't search hard enough

http://www.societyofrobots.com/sensors_sharpirrange.shtml
http://www.societyofrobots.com/robotforum/index.php?topic=2712.0
http://www.societyofrobots.com/axon/axon_FAQ.shtml#sharp_ir_reset

[RiO]

I reviewed these links and added the capacitors, but still have noise issues.
Would anyone have a solution specific to GP2Y0D340K?

[waltr]

Since you only experience a problem when the motors are running I suspect noise from the motors. Brushed DC motors are notorious for producing noise, brush contacts arc. So it would be best to kill the noise at the source.
Try putting a .001 uF ceramic disc cap on each motor terminal to the motor case.

[RiO]

waltr,
thank you for the suggestion, but I think that the motors can be ruled out. I tested the robot on a rack, with motors running, but wheels off the ground and had no single false positive  from the sensors.

[waltr]

Did you have any problems with the robot on the ground so that the motors are loaded? This would increase the motor current and make brush noise worse.

You did say you only get false positive readings when the motors are running. Right?

How is the power connected to the motor driver and the processor? Each should go directly to the battery.

[Pratheek]

I think your battery is not able to power both your processor and your motors. Try using a higher capacity battery (Li-ion or Li-poly) or uses two different batteries for your motor and your processor.

[Soeren]

Hi,

Did you have any problems with the robot on the ground so that the motors are loaded? This would increase the motor current and make brush noise worse.

I have to second that!
3 caps directly on the motor (from each terminal to the motor housing which should be grounded as well and one 10nF+ from terminal to terminal).
And separate wiring to each motor and the logic of course.

[galannthegreat]

I myself found that braiding the motor wires really helped aswell, it eliminated the noise issues on one of my 'bots.