How to Actually Take My Course

I was reading through my blog earlier today and to my horror, I realized that there is really no direct link from my blog to my course. Considering the amount of time and effort I poured into “Introductory Electronics,” I think it’s important that there’s some sort of easy-ish way (read: step-by-step directions) to access my course on the blog.

So here they are:

  1. Make an account on Global Classroom’s K12Virtual section.
  2. Go to my course.
  3. Buy a Basic Stamp Activity Kit.
  4. Learn lots and lots of cool things in very little time!

So now I suppose you’re wondering if my course is right for you. The answer is yes. Okay, that seems a little broad. You’ll probably enjoy the course a lot if you:

  • Are interested in how computers and other modern electronic devices work
  • Want to build your own electronic devices
  • Have little previous experience with electronics and circuitry
  • Would rather learn from video than from text
  • Are a savvy computer user

Regardless, there’s no risk in watching a few videos before you buy a BASIC Stamp Kit: the course is absolutely free.

A Fun JavaScript Game I Threw Together

Perhaps you have heard of some keyboarding speed-improving websites such as 10fastfingers.com and TypeRacer, perhaps not. At any rate, my friend David Chen (follow him on Twitter – @Ninchendoz95) has been playing these games a lot, and I was inspired to create something similar. For once, I didn’t go over the top. There’s no glorious database of the most common English language words, no web service that sends the JavaScript behind the game a JSON string full of words to put in, no leaderboard, and minimalist styling on the game web page itself.

You can play my little game here.

I should warn you – there are some issues with TextRacer. It uses the KeyPress event, so words are always somehow one character behind. You can change “keypress” to “keyup” but that introduces another slew of bugs: multiple keys pushed down at once and repeated characters (from holding keys down) registering incorrectly. Luckily, TextRacer more or less works and is amusing to try out a few times.

The code is by no means production-worthy! I was attempting to build something extensible at first but then just started hard-coding the names of divs I was using into the JavaScript.

Here’s TextRacer in action:

TextRacer in action

It almost looks kind of good…

As always, I am amazed by how useful jQuery was in this whole development process. I tested TextRacer in Firefox and Chrome, and the code worked just as well in both.

Have fun tinkering!

Introducing Cannon

Continuing my alliterating-c tradition of robot names is Cannon, an antweight version of Lolcat. On paper (and in CAD), Cannon looks like it’s going to be a lot of fun.

Cannon CAD Drawing

Very rough, yes, but it still lets me visualize everything and make sure the parts fit.

Here are the specs I have planned out:

  • Weapon motor: Turnigy Aerodrive SK3 2826-1240. It is rated at 150W and will provide more than enough weapon power. The old “Beloved Shardy” undercutter I built simply did not have a powerful enough weapon motor, and this one will be sure to suffice!
  • Weapon ESC: Thunderbird-18. It’s tried-and-true, and the weapon motor is rated at 16A continuous so a fire seems unlikely right now. Unlikely.
  • Battery: Turnigy Nano-tech 3S 460mAh LiPoly. I love the idea of three cells, and in theory, a 460mAh can supply about 14 amps for an entire two-minute fight (throwing out any drops/inefficiencies). I think I will have bigger problems than the battery if the robot requires 14A continuous for two minutes!
  • Drive motors: Fingertech Silver Spark 33.3:1 gearmotors.
  • Drive ESCs: Fingertech tinyESC v2.1, the same kind used in Lolcat. I can’t say I’m wild about these controllers; I killed five or six of them before I learned that I’d discovered a hardware issue. They now seem to work okay, and I do have to say that Fingertech customer service is phenomenal!
  • Weapon: 3.0ish ounce 2.5-inch diameter titanium eggbeater spinning at about 9200rpm. It will be supported by ball bearings and connected to the weapon motor by a urethane belt with a gear ratio of 3:2. The weapon shaft will be hardened S7.

I already ordered some of the parts, and I was actually very impressed by how much higher-quality everything appears. Just look at the packaging.

Turnigy Product Packaging

Look at those beautiful graphics. It’s almost worth the huge premium over normal Turnigy products for the SK3…

Actually, just look at the motor and battery!

Aerodrive SK3 Motor

These motors are actually a little bigger than I expected but feel very solidly built.

460mAh Nano-tech Battery

Speaking of big, these batteries are HUGE for their capacity. Maybe I’m just used to dealing with Lolcat parts.

I do have some small quips with these parts.

  • Both the battery and motor are enormous. It’s a good thing I have minuscule drive ESCs because I may have a hard time getting everything to fit, and the body I designed for Cannon is fairly large.
  • The brushless magnets don’t feel very strong, though the motors feel very precise when you turn them. My feeling is that I am mistaken and when I actually wire the motor up, I’ll be in for a pleasant surprise.
  • The motor wires are small and flimsy.
  • The battery came with a JST connector on it. The battery is rated for 25C (11.5A) continuous, 40C (18.4A) burst. JST connectors are rated for 5A. That’s a waste of plastic.

Still, despite my minor complaints, I am happy with my purchase so far. I can’t wait to see that motor spin.

The motor isn’t the only part of Cannon I am excited about. I learned a lot about building eggbeaters well with Lolcat, and I believe most of it will apply in the antweight class as well. For one, protecting your belt is very important. Lolcat’s belt almost got sliced twice at Bot Blast, so I’ll try to get the side rails to cover up the pully. However, the bottom of the side rails is far more important. Tracked Terror kept getting underneath Lolcat and flipping it over. I worry that wedges could do the same with Cannon, but I have devised a fix of sorts.

Cannon Side View

Side view of the above image.

Notice that the sides are swept back. The beater extends way forward of the front of the supports. I am concerned about what effect this will have on stability. Since the beater, likely the heaviest individual part of the robot, will be centered in front of the support, the entire robot will act even more front-heavy. It could lead to some flipping over on hits; only time will tell. I am also concerned by how small the bottoms of the supports are, but they will be 3/8″-thick UHMW so antweight weapons shouldn’t be able to completely wreck them.

The only way we’ll see how this plays out is in the arena. I will continue to post progress updates on this blog as Cannon comes together.