Wall Following Robot Using 555 Timer

EDIT: 
 This robot is also in the Robot Contest for the age 12-18 category.

Foreward:
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

The robot uses only a single IR distance sensor, two continuous rotation servo motors and a 556 (or 2x555) circuit for its main operation. However, you also need a frame, wheels, batteries and all kinds of miscellaneous stuff to make it work. All that is up to you. The parts I used are what I had on hand at the time and are not necessarily optimal for this project. I will tell you the parts I used, but you can use what you like as long the principles remain the same.

Parts I used:

- Frame:
-- 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)

- Electronics:
-- Sharp IR GP2Y0D02YK (feel free to use any other Sharp IR sensor you feel appropriate)
-- LM556
-- 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
-- Breadboard
-- Switch (to turn it on and off)

Comments

[Ptr_V_2]

Nice ible, nicely written, innovative and detailed.

[HarveyH44]

I think there is a slight flaw in your schematic. The signal from the IR receiver goes to the opamp, the output of the opamp, feeds both halves of the 556. Both motors should basically do the same thing, only difference would be from variance in part tolerances. The trim pots should cover that. This bot, doesn't exactly move in a straight line, does it?

I have watch the video, I use FireFox, which doesn't like YouTube for some reason...

[hasn0life]

I tried to explain this in the last section. The motors do the same thing, but because one of them is upside down, it moves backwards, so the robot wants to turn. You have to bias the motors using the trimpots so that they both move forward when the distance sensor sees a certain distance.

The robot can move in a straight line if its following a straight wall and you calibrate it in a specific way. In my video I adjusted it to do wide turns because I didn't have much time to tune it. It can actually run even better than that and not do the twitching in the video.