This robot is also in the Robot Contest for the age 12-18 category.
In this instructable I will write out the basic ideas which I used to make a wall following robot without any microcontroller. The robot in these instructions was originally used in the Trinity Firefighting contest , and was supposed to be the first robot (that I know of) to compete without a microcontroller. However it did not successfully blow out the candle.
Recently, my friend informed me of the 555 contest and encouraged me to enter the robot. However, I do not have time to remake the robot frame and whatnot, so I will give this instructable using the original frame with the firefighting parts removed. Also, I used some specific parts in this build like Vex motors, and I haven't tested if one can substitute in other continuous rotation servos and have the same effect. As a result of all this, I will not tell you how to replicate my robot, but instead give the ideas (and circuit) that its based on and leave it to you to determine the frame and parts to use in your build.
Also, this is my first instructable. I will update it or redo it with proper instructions if I have time later maybe.
Step 1: Materials
Parts I used:
-- 8" Aluminum circles
-- 3x Random erector set L channel
-- 3x Vex shafts
-- 6x Vex collars
-- some washers.
-- Vex screws of various sizes
-- 4x Vex motor mount spacer things
-- 6x Vex standoffs
-- 2x random bars with 5 holes
-- 2x Vex wheels
-- Vex omniwheel
-- 2x Vex motors
(you could just make it out of acrylic and regular continous rotation servos with some wheels and a caster)
-- Sharp IR GP2Y0D02YK (feel free to use any other Sharp IR sensor you feel appropriate)
-- LM 7805 Voltage regulator
-- 2x 330K resistors
-- 2x 104 (.1uf) capacitors
-- 1uF capacitor
-- 2.2uF capacitor
-- 741 Op amp
-- Diodes (I believe most kinds will work)
-- 2x 20k pot
-- 1000 uF capacitor (across power supply)
-- Vex Battery
-- alligator clips to connect battery with
-- Switch (to turn it on and off)
Step 2: Frame Overview
You do not need to make the elevated part like I did, because that was used to hold the fire extinguishing equipment.
Step 3: Electronics
Any analog Sharp IR distance sensor will do, but I used the long range one because it was more convenient for the firefighting competition. If your robot is smaller, you can use one with shorter range. However, you should consider the dead zone of the distance sensors when picking and mounting them. Try to keep about half the dead zone inside the robot frame, since it will allow you more range. However, if it runs into a wall, it might not recover. Once again, feel free to experiment.
In the picture there are a few resistors which I did not include in the parts list or schematic, because they do not add functionality.
Also, in the schematic, it doesn't show how to wire the IR sensor sensor. There are 3 wires on it. The red wire (power) goes to the 5V after the regulator., the yellow (signal) wire goes to the input of the Op amp buffer, and the black wire (ground) goes to ground.
There is also a 1000uF cap across the 5V supply.
Finally, the servo motors are powered by the unregulated voltage straight from the battery. If you are using different servos and a different battery, you may have to power them from the 5V supply if they are not rated for the voltage your battery provides. Regular servo wires have different colors then Vex servo wires, so it is up to you to wire them.
Step 4: Principles of Operation
For the video, I tuned it so that at when the IR distance sensor sees its max range it does a slow turn. This is done by tuning the circuit so that both wheels turn in the same direction at the max range, but one turns slower than the other.
Video: (does it work? If not: Link )