Classy Chassis 2.0

At last!  A hellish semester is now over and I have some time to update this blog with all the things I've accomplished in the past few months.  I'll start off by describing how I've upgraded the chassis for differential steering and end with the power wiring I've done.  Plus I'll try and add a video of it actually working!

So when I last left off I had decided to go with differential steering and buy an extra set of Power Wheels motors to give it four wheel drive.

Motor Pictures with shoddy wiring

The new motors I bought are slightly different from the original ones I bought and set me back roughly $70.  However from the tests I've done so far the two sets of motors are compatible enough.  It's also hard to see in this picture, but this motor came without the stock leads so I had to make some pretty poor quality ones by attempting to solder wires inside of the motor casing.

Here's a better picture of the bad motor leads.  The other ones are also a bit fragile so I'll have to be careful they don't get jerked around too much.

These are the wheels I got along with the new motors.  Pretty and purple!

The existing support for the original wheels didn't work for the new ones so I had to build an all new support system out of angle aluminum from Home Depot and Lowes.  It's essentially an aluminum H, closes at the bottom with the wheel axle and closed at the top with a flat piece of aluminum.  Some more pictures are below.

Here's on of the axle caps to keep the wheels attached.

The mounting panel all taped and glued together.

Here's an overview of the total chassis.  I decided to put the new wheels in the back since they're larger,  but it looks a little weird since the front wheels are wider.

The axle width also makes it difficult to fit through doors, which is a little disappointing since I was hoping the robot could be used indoors and outdoors.  But it looks like it's going to turn out being just an outdoors robot which will still be pretty cool.

I also got around to upgrading the electronics system a bit to make it a little less of a rats nest, though I'm not really sure it works.

I finally got the chance to take the breadboarded motor controller and solder it onto a PCB.  The wires are a little fragile and occasionally need resoldering but overall it works well.  For my next iteration of motor controller I'm hoping to upgrade to a custom PCB with MOSFETs, speed control, and temperature detection.

I also bought some power distribution blocks from Radioshack to help regulate the power better.  The white block on the bottom is for the 12V from the batteries and the motor outputs and the black block on the top is for the logic from the Arduino below.

I'm still trying to figure out the logic and control for the robot, but I do know that the first revision will have an Arduino in control of the sensors and movement.  For those of you who don't know anything about the Arduino or microcontrollers I'll try and put up a write up about them soon.

Here's a servo that will eventually be used to sweep the distance sensors back and forth.  This sort of radar/sonar system will use distance sensors to map out any obstacles in the path of the robot.

And lastly for the electronics, I got a fancy new charger for the batteries!  The crappy charger that comes with the power wheels provides a steady current the batteries and doesn't protect against overcharging the batteries if you leave them plugged in too long.  Leaving the battery in the charger for too long could result in hydrogen building up inside the battery and eventually an explosion.  This charger, however, optimizes the charging of the battery and turns it off when the battery is full.  Considering the fact that the batteries were really expensive, it was well worth the $30 for the charger to help elongate the life of the batteries.

And I got a fancy new laptop!  The Lenovo X220 is supposed to be a highly mobile laptop that you can squeeze 10 hours of battery out of!  If I manage to get the system advanced enough to warrant it, I hope to at some point use this laptop as the main brain of the robot and have it do a bunch of cool image processing stuff.

I've also heard that Lenovo laptops are built like tanks so it should be plenty capable to survive the rough ride the robot will give, though to be safe I'll try and add some shock absorption.

So that's what I've accomplished in the past six months or so with the robot.  In the two weeks before school starts again I'll try and get it up and running and put a video up on here.  This semester will probably be far less stressful and busy than the last one so hopefully I'll have more time to work on this!