July Robotics Class Week 1

Photo essay for week 1 of the July robotics class I'm teaching.

A simple H-bridge with switches and LEDs.

Omni-wheel proof of concept; 3d printed plate that fits on a motor shaft.

Printrbot has been printing lots of stuff.

Stickers, buttons, and temporary tattoos for prizes.

Robots under construction.

Another partially finished robot.

Robotics Course Picture Essay

I'm too exhausted to do a write up about my Robotics course. I'm also about to move to another location and teach it again to new students. So for now, here's a bunch of photos, a few videos, and a quick description.

We ended up using Vex kit parts, hot glue, foam board, assorted motors, and other stuff for building materials. The brains were Arduino Leonardos, and the wireless connection was accomplished with a Wixels. We used April Tags with an overhead camera to track the robots and send them position data wirelessly.

A note about H-bridges

If you are a n00b like I was back in freshman year, or just forgetful (like I am now) you might want to take note before you burn out a bunch of transistors.

At some point you may realize you only need 2 inputs to control your h-bridge. You will tie the left hand inputs (base of Q1,Q3) together, and the right hand inputs (base of Q2, Q4) together.

Likely, burning transistors will at some point result, because the inputs will be left floating. For me, I accidentally pulled out the input wires.

"The important thing is you cannot leave any of the terminals AC and BD float. Let’s look at the AC terminal in more detail. Since A and C are tied together, and if it is left float then there will be a path for current through the collector of Q1, through its base, through the base of Q3, through its emitter to the ground. So, Q1 and Q3 are on resulting a short circuit. So, you must be careful if you are thinking about reducing the control pins by tying A with C and B with D. You just can’t leave the tied terminals open or float. They should be either grounded or pulled high."

Read more here: DC Motor Interfacing to PIC Micro. Scroll down to the "Important Note."