Multiple distance sensor question

VEX IQ General Discussion IQ Technical Discussion
1

My 11 year old son has been having a grand time with a Vex IQ Super Kit. He has the idea of using a second distance sensor to allow him to follow an object. Will multiple distance sensors on the same side of the robot interfere with each other?

Thanks!
Wayne Johnson

2

teresajude,

That is a great question!

I created a program that simply displayed the distance measurement of 2 distance sensors to the VEX IQ Brain, then I placed the two sensors side by side pointing up toward the ceiling, but with one of them a couple inches higher. Then, when I hovered over them with a book a few inches above the upper one, the values bounced around a lot AND a lot of the time the 2 values were nearly same. If there was no interference they should have been ~50 mm (2 inches) different.

I also tested the same setup where I had 1 pointed to the ceiling and the other pointed to the side wall (90 degrees off from each other). Then with a block at the intersection and with its faces perpendicular to the beams, the distance measurements did not seem to be confused by each other. However with a cylinder (coffee mug) at the intersection there were inaccurate results.

So… based on this testing, I say: YES. 2 ultrasonic distance sensors DO INDEED interfere with each other, and therefore: if they are nearly inline with each other, or if the sound waves can bounce off a rounded object to cross to the other sensor; you can expect to have incorrect results due to that interference.

Paul

3

Paul:

When you had the 2 sensors next to each other with about a 2" displacement, was the value they were indicating correct for either sensor, or was it the average of the correct readings?

Thanks for the response. It doesn’t sound like the concept as stated would work with that hardware.

Thanks!
Wayne Johnson

4

Wayne,

The values jumped around, sometimes they where the longer distance, sometimes the shorter, and sometimes neither.

Paul

5

Paul:

Thanks! That is about what I suspected. It was getting two conflicting values and trying to average them (with bizarre results). We discovered that the distance sensor we had got damaged, so the one new one on order will again be the only one in the house.

Wayne