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by
Dennis Clark
Another month, and more interesting questions have
come my way. I will skip the traditional New Years
Resolutions, because, well, it’s February and I forgot to
make them last month. I do resolve to make a totally new
robot this year, so we’ll see how that works out. This is a
quiet time in the robot room — no imminent competitions,
except that SparkFun will be having another AUV
competition in a couple of months! Ahhhh!
Ahem ... let’s move on and get to the questions for
this month.
Q. I am Vikram from India. I am a higher secondary school student. I have been reading SERVO Magazine right from 2004 and I am a great fan of
your column. I have built many robots to follow lines with
PID control. For the last six months, I have been trying to
build a Micromouse robot for the Singapore Robot Games’
Micromouse JC and open. I built a robot using Pololu 50:1
micro metal gear motors, a Pololu wheel and encoder set,
and three Sharp GP2D120 IR range sensors. The Sharp
sensors are really reliable and I was able to implement PID
control successfully. However, the response time of these
sensors is about 40 milliseconds. My robot is really fast and
it travels about 4-5 cms in that time. So, I was not able to
make turns easily and my robot crashed in the initial search
run itself. I was informed that Pico Mouse will be
conducted instead of Micromouse from the next year in the
Singapore Robotic Games.
Now, I finally come to my question: Which is the best
analog wall sensor for Micromouse and Pico Mouse?
1. Sharp sensors are reliable, immune to external light
and the reflectivity of the object, but they have slow
response time, have a 4 cm minimum range, and are big in
size — too large for Pico Mouse. Is there any way that I can
hack these sensors to respond faster?
2. Ordinary IR sensors (Tx and Rx) are affected by wall
color, reflectivity, and external disturbances. (I have painted
my walls with white paint and there is a slight difference in
reflectivity of each wall.) How can I make better, more
reliable IR sensors?
Could you please help me with these problems which I
have been trying to solve for the last six months? Your
answer will really help me to compete in the Micromouse
event in IITs and the Pico Mouse event in SRG.
— B. Vikram
A. Oh my gosh, Vikram! That is quite the question! I’ll try to answer all of your questions, so bear with me. I’ll answer by number. That way, I can keep myself
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