Tank Bot

Let's Make Robots Robots
1

 

I just started with robotics a few months ago, I started with the boe-bot and basic stamp2. A good learning platform, but I quickly found it's limitations.

So I went for the propeller, and fitted the MSR1 robot control board to the boe-bot chassis, with wheel encoders, HMC3652 compass, easybluetooth module, and ping sensor. My goal was to teach the boe bot to navigate around the living room, using dead reckoning, compass directions, and corrections made with the ping at each waypoint. And overall, it worked very well. Just enter the X and Y coordinates, and it will go there (more or less).

I wanted to build a robot that could actually do something usefull, like pickup a beer bottle, and take to the bin, and sit it down along side. This could only be achieved if the robot can determine where it is with good accuracy, probably less than 5mm.

I found the ping sensor to be very accurate and repeatable, within 1mm usually. The compass is little tricker, very jittery, I fixed most of the problem using an averaging program I wrote, but it also gives different reading at different points of the room, up to 45 degrees from one side to the other, possible due to EMF ??

Anyhow, I bought the 1/16th scale Heng -Long tank, which shoots BBS and makes smoke too, which was fun, but it seems so pointless when it can't think on its own, so within half hour of un-wrapping it, I had it in pieces, and starting moving my robot bits onto it.

 

The Boe-Bot chassis, with compass (attached to drinking straw), easybluetooth, ping, propeller, and wheel encoders.

 

 

The tank, with all non-esential bits removed.

 

The Propeller MSR1 RObot board fitted into the tank frame, with compass, easybluetooth, ping, and wheel encoders.

 

 

 

Wheel encoders are original boe-bot ones, just slapped together temporarily, I have some smaller ones on order

which I will fit inside the geaboxes. I hate waiting for parts !!!

 

 

Navigtes around the house using waypoints and ping corrections.

  • Actuators / output devices: DC Motors
  • Control method: autonomous
  • CPU: Parallax Propeller
  • Power source: 7.2V
  • Programming language: Spin
  • Sensors / input devices: wheel encoders, compass, PING
  • Target environment: indoors
This is a companion discussion topic for the original entry at https://community.robotshop.com/robots/show/tank-bot
2

Looks like a great base to

Looks like a great base to build on!! Hope to do the same later on :slight_smile:

Are those threads metal or hard plastic ??

3

Hey Vince, the treads are

Hey Vince, the treads are hard plastic, they are linked with small metal rods, not just a giant rubber band like some of the toy tanks. There are replacement metal tracks you can buy for this tank, But I hope I won’t be needing those. FYI, these tanks are very fast on full power, if your program had a bug, and the tank went nuts, you’d never catch it !!!

The base is about 18inches long, and I will put a gripper on the front, or maybe a 5 DOF arm on top later on.

For now, just tweaking my program to work with the DC motors instead of the the servos on my old platform (boe-bot).

4

Wow ! Sounds like a very

Wow ! Sounds like a very good quality one perfect to build and expand on!

Would be perfect for an all terrain bot! But batteries must not last all that long with its size and weight.

Might want to test it off the ground first because that thing on the run would be devastating !! :wink:

Hope you have fun building your bot and good luck :slight_smile:

5

I’m also building a robot

I’m also building a robot with a R/C tank as base.
But mine is just a toy tank with a long rubber bang as threads.
Yours looks really solid.

Can’t wait to see the result :slight_smile:

6

Lots of wheels

I also started with the boe bot, but it grew using erector set parts and mattrax treads from an old r/c car. Have a prop development board but think it is a bit overkill for robots and may go with the prop proto board and just build accessories on. Is the prop SPIN easier then PBASIC? I have seen in the Parallax forum they have a program that changes the prop to PBASIC. You don’t see many parallax users here and it is refreashing to see a couple now and then. Waiting for the video.

 

7

I think spin just feels like

I think spin just feels like an advanced version of Pbasic, it’s definately more challenging, but when you read into it, it’s so much more powerfull. And with eight COGS (processors) all working at once, you can be a sloppy programmer (I am), and everything still functions at lightning speed.

The best place to start for the Propeller (SPIN) is the PE LAbs, can be found and downloaded on the Parallax website under resources, very good documant for newcomers to SPIN.

There is now a program for translating Pbasic comands into assembly for the prop, I have not used this, since I was already learning spin, and my brain could not handle any more strain !!! Best just to learn SPIN if you ask me. Just start with the basics.

If your considering the propeller for your robot, using the MSR1 board will save a lot of headaches, since the prop is 3.3v, it has 5v translators on board for driving servos directly.

 

Sorry about the dark photos, my camera doesn’t do well indoors, I’ll try to get some better ones this weekend, and maybe some video too.

 

8

Thanks
I just purchased a prop protoboard with all the necessary interface and 2 power supplys 3.3V and 5V. It has places for optional I?O stuff but willprobally go with some sort of H bridge setup built onboard. Been experimenting with a H bridge similar to a L298 as far as I/O but eats up I/O. Electronics was my major but programming is a whole new ball game. I already frequent the Parallax forum under the same name. I respect parallax for all their support. Good luck and thanks again. I may be able to get something to hack off you someday. lol

9

Encoders

What encoders did you end up using to fit in the HL tank?  (I built a robot on an HL tank as well, now looking to add encoders)

10

I built my own encoders

I built my own encoders using the QRD1114 IR emmiter / senser pair. Mounted inside the gearbox the work very well.