Wednesday, December 30, 2015

FLL - Trash Trek: Ultrasonic vs. IR Sensor...

As you may know, sometimes the FLL field mat does not quite fit properly on the recommended tabletop. So, in this year’s rules it is stated that, “Slide and align it so that there is no gap between the South edge of the Mat and the South Border Wall, then center the Mat east-west, with equal gaps at left and right.”

With the mat flush against the South Border Wall, a team may be able to use an Ultrasonic or IR Sensor accurately to detect the South Border Wall. 

So, this became a test challenge for the members of the Brics~2~Bots Academy. Brandon assisted in the tests by designing a test robot, writing programs in NXT-G and EV3 to test the NXT Ultrasonic sensor (on an EV3 brick), EV3 Ultrasonic, and an EV3 IR Sensor. We made a chart to record the results.

Using:
EV3 brick and software, at Power Levels 20-75, measuring a stopping distance set at 10 centimeters.


Trials
NXT Ultrasonic
EV3 Ultrasonic
(less than or equall to)
EV3 IR Sensor -Proximity
(measure in Centimeters)
(equal to)
1
5.5 centimeters - 20 power 10 centimeters - 20 power 10 centimeters - 20 power
2
5.5 centimeters - 30 power 10 centimeters - 30 power 10 centimeters - 30 power
3
2.5 centimeters - 40 power 10 centimeters - 40 power 10 centimeters - 40 power
4
2.5 centimeters - 50 power 10 centimeters - 500 power 10 centimeters - 500 power
5
3.5 centimeters - 75 power 10 centimeters - 75 power 10 centimeters - 75 power





Conclusions:

NXT Ultrasonic - Seems to work with the EV3, but the response time is off. Measuring for 10 centimeters, it stops much closer and at different distances for the different power levels. See chart. This may be because the response time for the NXT Ultrasonic is slower than the EV3 sensor.

Ev3 Ultrasonic - AT powers 20-75 the EV3 stops accurately. Since the Ultrasonic senses a sound wave that is reflected out to the object; one might wonder, if surrounding sound would have an effect? Testing under noisy conditions didn’t seem to effect the performance of the EV3 Ultrasonic. However, at the  NYC FLL finals at the Javits Center, the noise level is so high that it might cause a problem for the Ultrasonic.

EV3 (IR) Inferred - Used in the Compare - Proximity mode measures in centimeters. AT powers 20-75 the EV3 stops accurately. Since it measures light waves it would not be affected by loud sounds that will be apparent at the NYC FLL finals at the Javits Center tournament.

Note: Power levels above 75 does not allow a long enough response time for the Ultrasonics and IR Sensor to detect an object (however, you could try to push it to 80).

Also, if there is a high level of noise at a tournament, the noise level "seems" to interfere with reading the distance accurately.

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