botpics

Lego Robot:

01-Oct-2000

(Photo Gallery Below)

WSU_Bot

Index ...

Legacy_Bot

click image for link
use [BACK] button to return
The images below are presented here to show the lego robot project that Rik and I tried to build from start to finish in just over one week to compete in the fire fighting robot competition back in '98.
In the 1&1/2 week time frame, Rik and I developed schematics, wire wrapped working controler boards, developed low level software drivers for much of the hardware on the board. Then we built multiple sets of sensor PCB's and populated them, developed the motor driver boards and built and populated the PCB's for them, and finally, designed and built switching power supplies including PCB layout and fabrication. All of the PCB fabrication was done out in my shop as we did not have the time or money to have comercially fabricated PCBs built.
At the time unbeknownst to Rik and I we had been sabatoged. It wasn't until over a month later (after the competition) that I discovered an error in the C compiler we'd been using. As it turns out the compiler incorrectly handled the use of the volatile directive when the optimization option was invoked.
The second major failing we experiences was trying to develop the switching supply with such a small amount of lead time. Special thanks goes to Hidy, Rik's wife, who paitently hand wound the special mutually wrapped inductors for us.
Additional thanks goes out to Ralph who during the last three days voulenteered to write some navigation software for us as we were already greatly over stretched on our time budget. Ralph stepped up and developed a way point data structure to guide the fire fighting robot successfully through the contest. Had he not been sabatoged by the C compilers bugs, Ralph's code would have take our robots through a successful completion of the competition.

Click Image For Enlarged View

Robot overview:

The overview photo to the left shows the lego body frame built to support the electronics, sensors, batteries, motor drivers, and LCD screen.

Wheel Mounting:

This close up shows the wheel mounting. If you take a minute to look at the close up, in the lower left you can see one of the swivel mount casters

Motors & Drive Locomotion:

Clearly visible in this view are the two double stacked stepper motors used to provide locomotion. There is a 10:72 gear ratio on the output. This was accomplished by building a special mounting fixture in my milling machine and cutting the 1/4" steel shafts into the "+" shape to fit the existing lego gear. In the picture, the two motors are mounted back to back, and wiring is run up throught the frame for connection to the motor controler. (Below)

Battery Mounting:

In this photo the battery has just been set in place. The idea, since we had only one week to accomplish this task, was to either use large produce rubber bands to hold the pair of batteries in place or to use hot glue. The design of the robot is symentrical, so a pair of 6V gel-cells was used to give the 12VDC required for the robot and to help ballance the weight.

Lego Motor Driver Board Link:

The link to the right will take the reader to the controllers secion of this web page. There you can read about the motor controller built out in my shop for this lego robot control project.
The board was built using artwork printed on an inkjet then photo coppied onto an overhead transperancy. Finally, the transparancy was exposed in a UV exposure frame I built and put through a generic photo etch process.

Lego Sensors Link:

The link (right) will take the reader to the controllers section of the web page. Here you can read further about these sensors that were made "overnight" out in my garrage!

Lego Robot Micro-Controler:

Again, this link (right) will take the reader to the controllers section of the web site where you can read further information on the wire wrapped controler board used for this robot.
At this link schematics, board layout and and additional photo's are presented.

Lego Robot Power Supply:

The link (right) forwards the reader on the the controllers section of the web site for additional reading.
The photo (left) shows the PCB and associated components used to build the switching power supply. We had problems getting the supply to operate, and in hind sight Rik and I would have been better served by using an off the shelf solution, or even a linear regulator, to at least quickly get past the road block and into the competition.
I'll mention it here again, but Hidy, Rik's wife deserves special credit for the work she put in hand wrapping the coils visible in the picutre. These are two seperate sets of wraps with two gagues of wire and a lot of work getting the spacking right. Thanks Hidy!
There are two switching regulators here. The first centers around the L296 by SGS Thompson. The second hardly visible sticking out from behind the inductors (upper left) was to provide regulated negative voltage to the board.

Eventually, I'll get around to finishing up this one just for the sake of it. I've decided not to upgrade the processor, but rather to keep it the way it is as a reminder of the levels of techonology used in times past.

For additional resource information, or help on trying to locate components, electrical or mechanical, refer to the Links section of this page, left.