Let's Make Robots!

Where to start...

Alright, I'm kind of stuck in my mind where to begin.  I have my idea together but not sure on what board to get and where to go after that.  I have the following board:

orig_board.jpg

This board is what was in the RC tank.  It was controlled by the remote control.  It moved back and forth and steered left and right.  I'm sure I don't need this board anymore.  The board is 1 5/8" and 1 1/4" in size.  I'm needing a board this same size and able to move around, detect it's surroundings with an IR sensor I'm guessing, and swivel the top gunner 360 degrees.

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I just remembered, I did this before. As I remember, I didn't hack the car, I hacked the remote. I simply found which pads on the PCB were the Fwd, rev and turn buttons and clicked them on and off using some NPN transistors that were run off of my picaxe brain. Here's the post:

http://letsmakerobots.com/node/209

There is an example of using some of the onboard electronics in a robot called Skatebot, pretty fast little robot. Bob traced a couple signal lines from teh reciever chip over to the transistors, to determeine which ones could be driven by a micros' pins, for autonomous control. At the same time, he can drop back to RC control whenever he wants. This saves having to add a seperate h-bridge that may or may not be suitable for the motors being used, and lets youn learn a bit about tracing circuits down, seeing how things work. 

For mechanics, was there a spring that returned the steering to center? So that when the steering motor was not driven one way or another, the wheels were pulled to center? Did not appear in disassembly, but wondered if it had been there.  

 

Yeah there is a spring that does force the steering column to return back to the straight position which it's actually pretty strong too.  So again I think the middle steering really can't be that hard.  I'm familiar with coding cause I'm getting a bachelor's degree in it and I have two senior programmers that write scripts in C, C++, and BASIC so I'm sure they can help out if I run into any snags as well as you guys here on the site.
The steering isn't that bad. True it won't turn on the spot but a 3 point turn isn't that hard, Frits has a walkthrough on that. You might want to add a pot for feed back. See this walkthrough.
It's really not that biga deal, it is just that, when you are stuck in a corner, let's say, it is a lot easier to code a center-turn bot. One motor fwd and one motor rev is super-simple. With your set-up, you will have to figure-out a 3 point turn and sorta sync both your drive motor AND your steering motor -This is a little more complicated and thus, a little harder to code. If you are just learning code (not to mention the wiring aspect) it is just one more thing to figure out. In addition, I think you will probably end up with a "bang-bang" system. Your robot brain will have no way of knowing where you steering is pointing, therefore it will tend to "bang" all the way to one side and the other, this will result is a big issue when you want it to go to the center position. There might be some sorta sensor included with your model that might be able to be incorperated in the final robot, I dunno. At any rate, good-on-you --start with the "start here" bot and you will quickly learn all of the issues you will have to deal with when you get to your tank.

First off, the "resistor" on the motor is a cap and is there to help elimnate electrical noise. Also, the black things are transistors, not diodes. I would suggest modifying the "start here" robot into this chassis. Here are some problems you will have:

-steering in front is much harder to work with than a wheel on each side (center turn)

-I don't think there is any "feed back" from the front steering so your robot brain will have no idea how far to turn it or where it is

-Forget trying to hack into your reciever, I would just wire your 2 motors directly to your motor driver chip and do it that way.

-you can use a servo on the turret, but you will not have 360, rather somewhere between 90 and 180.

-As standard advice, I would start with a picaxe chip and just get an LED blinking. From there you can start adding your motors and sensors. Don't bite off more than you can chew, there is a lot to learn here.

I think I'm going to build the "Start here" bot as it follows and then upgrade the bot to this chassis and make upgrades as we go.  So to keep the topic going and my brain thinking on the project, the first issue you described was the steering in the front... What would be the problem in only having one motor in the center.  I've provided pictures and a video on the steering column for the tank.

 Front of steering