Let's Make Robots!

SpurtBot, Shadow Runner


This post will document a new SpurtBot design. This design integrates a mini breadboard and can be set up as a no-solder project for kids by pre-soldering wires to the motor. I plan to make take advantage of the solderless breadboard to make several variations, which I will document on other robot pages.

Edit: I have posted detailed build instructions and a materials list over on Instructables. The video also provides a walk through of the build.

Behavior

The Shadow Runner will run from shadows. That is, it will drive forward in normal lighting conditions, but if you cover its light sensor with your hand or it runs into shadow, it will reverse and turn. In many cases, this will remove the robot from shadow and it will start to drive forward again. A disadvantage of this simple robot is that if it drives too far into shadow, it will just spin in circles on one wheel.

Circuit

 

When the photo resistor sees light, the robot will drive forward. Both left and right motors are receiving 9V via the normally closed contact of the relay. 
When the photo resistor is in shadow, its resistance increases dramatically, and the voltage divider formed with the potentiometer now increased the voltage at the input of the Darlington transistor array, turning it on. This activates the relay.
Now the left motor will get ground on its + lead, and 9V on its - lead, reversing the motor.
The right motor's - lead is hard wired to ground from the battery. Since the + lead of the right motor is now also getting ground, the right motor will stop.
This combination causes a stop, backup and turn maneuver. If this maneuver removes the shadow from the photo resistor, it will revert the relay to its normal position, and both motors will drive forward again. If the robot stays in shadow, it will spin in circles with the right motor stopped and the left in reverse.

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Kind of waiting for the next project to take off and I wanted to show some support and enthusiasm for Andrew's (Ignoblegnome's) effort.  Let's just say that if a yutz like me can whip this together in a half hour, it won't be too much of a challenge for 10-year-olds ;-)  In any case, I breadboarded up one version, put it on the R.A.D. platform and it worked as described even with a few minor modifications:

 

http://youtu.be/AyIo_A_FCYA

 

The only things I did differently were to use 2n4401s in the Darlington Array and a fixed 4.7kΩ resistor for voltage division (I didn't have any 4-5kΩ varistors,) which makes it a little sticky as you can see.  I ended up using the flashlight as a "remote control."  

Then I got curious, and decided since I had more photo-resistors hanging around than potentiometers that I would try voltage division using those.  That was interesting too:

http://youtu.be/5-DKsy87lWc

If you guys do offer this as a kit, might I suggest including both options?  It certainly makes it more fun for me!

This is a great idea, though!

Glad you liked the circuit, and thanks for the feedback on the kit too.

I had some of the same behavior displayed in your videos with my prototype. A room with a good deal of ambient light may work better for you. The reason I wanted to integrate a potentiometer was to adjust for various lighting conditions.

I figured that was the case and saw the wisdom therein. I tried the circuit with a 10k pot but that was probably about twice what you'd want for useful sensitivity adjustment and couldn't get it to trigger. I guarantee if I had a better selection of trimmers I'd have done it right! Still, I like Chris's insights on the matter-decision making, basics of electronics/mechanics, etc. Definitely a great start here robot for younger types. If a no-solder kitof this caliber had been available for under $20 when I was 12, my life might have taken a very different track. But then I probably wouldn't be getting the joy out of it that I get now... Okay, enough philosophy. The point is, GREAT PROJECT!

I have created a monster...

First off, Andrew --All jokes aside, the 'stash works (100%) and you are truly pulling it off. Keep it. 

Now, back on track:
This really is a great project. It is a real-life robot, making "decisions" and altering its actions. All this with a circuit that can be dead-bugged, proto'ed, breaded, PCB'ed or paper-pattern-pcb'ed. Simply put, it is hard to make a true robot for less than 10 bucks. It makes me really happy to see this guy being refined (you have been doing this for a while now). Once it is all "tightened up", it will make a fantastic kit or Instructable. I would love to see this guy cleanly kitted and in a shop (mine or otherwise) --If it could be done for $20 retail, it would be an incredible starter project for a lot of folks. 

I hope you're serious, because I would definitely love to work with you on something like that.

I plan to make an instructable. Actually, I plan to make several instructables. I have at least three varieties designed on the same base.

  1. Line follower
  2. Light follower
  3. Shadow avoider

I need to document the build for the children's robot exhibit I'm doing on April 21st. From that, it's a cinch to build an Instructable and put together a video supporting it.

Give him a break, Chris.  He looks like Frank Zappa!  Cool project.  The kind of thing I could never get to work when I was a kid trying this.

Ha ha. Thanks  for coming to my defense.

Though, I admit I do look like some reject from a 70's porn video.

Video?

Video and much more info coming soon. Soon-ish, anyway.

This is gonna be my next project for me and my brother as I introduce him to robotics!

Also, you could easily pass for any of the village people with the 'stash (sorry, Chris started it) :P