Sensors are now mounted to the frame. The holes LASERed (that’s actually a word… if you’re me) into the ABS panels fit perfectly.

Next up is the remote. I built this thing out of some parts from Sparkfun last time around. This time, I actually hooked up the XBee module inside with the proper configuration.

The remote runs on 2 AA batteries and has only the XBee module and the joystick part from Sparkfun. The XBee module is setup to send out messages to a specified destination XBee module (that will be on the robot) when any of the 4 pins coming from the joystick switches changes from 3V -> 0V – which they will, if the joystick is moved in any of the 4 directions. Internally, the joystick just actuates 4 different micro-switches depending on which direction you are pushing it. On the receiving end, you see something like:

This works quite well. But as usual, there is a problem. There is a fairly noticeable lag between pushing the joystick around and seeing the output show up. Also, if the joystick isn’t being held in position long enough, there is no output at all. I think the polling on the XBee module might be a little slow. There is also a lot of random shit being sent along with the pin states.

Long story short, I think this will be replaced with a simpler RF transmitter attached to a PIC that’s programmed to do two things – poll 8 pins and send out their status as a byte over the RF transmitter. The extra 4 pins will me do some things like put in a kill switch signal for the motors in case the robot decides to go sentient.

Aside from the hardware, the project now has a real name and a project page – Stasis. I’ve also started a repository with code for the netduino and other controllers involved at Bitbucket: https://bitbucket.org/lostinspacebar/stasis

Along with the source code, there are other resources such as documentation. The first of these is a Fritzing ”schematic”. This is my first time using this program and it’s actually quite useful. I now have a nice schematic of what’s going on, on the robot. At some point I’ll make one for the remote, and whatever else I decide to include in this madness.

Morning after Gorilla Glue application and things look good. The glue has had time to set and the frame is solid. Even using pliers, the nuts  aren’t budging. I just hope I don’t have to change anything in the frame…

Next up is the motors. These are the same motors and motor mounts from the original MkI Balbot. In fact, most of the electronics are going to be the same with some improvements (more on that later on).

The zip-ties surrounding the motors are there to hold the ends of the motors from pivoting away from the ABS plate they are mounted to. The motor mount in use sadly has no way of tethering down the back of the motor, so when weight is applied from the top, the ABS plate flexes and the motors slowly arch outwards. But after a little zip-tie action, things are good.

Motors done, time for wheels. This time I wanted to use some off-road-y wheels from Pololu, but the shaft adapters they sent with the wheels don’t work with these motors, so for now, the old plastic wheels will have to do. They aren’t anywhere near as badass looking, but they will do for now, while the correct shaft adapters get here.

IR proximity sensors are next on the list. These will be mounted facing both sides of the balbot to measure tilt. This seems to work better when the sensors are mounted at an angle, so I’m using some position hinges to mount the sensors. These position hinges are special types of hinges that have two preset positions – 150 degrees and 180 degrees. And moving between these two settings takes… a lot of force. So basically, they snap into these positions and won’t budge unless you forcibly snap them into their other position.

The ABS frame plates were cut with these in mind -so there are mounting holes for the hinges. The only thing I wasn’t sure of was the alignment of the flanges on the sensor and the flanges on the hinges. But as luck has it, they align enough for #4 screws to work!

Still need to figure out how to mount the brains of the operation + the battery.

Oh noes! So hot glue looked promising but after about a day of abuse, I saw some of the nuts come loose.

So plan B – super glue, or in this case – Gorilla Glue.

This stuff is… awesome.

So there is some white residue after the glue sets. I am hoping it’s not going to affect strength of the plastic. * crosses fingers *

You might be wondering why there were no more updates on the Balbot. Well. It didn’t work as well.

The acrylic was pretty when put together but was very brittle. I never managed to get the software working by Maryland Day, so it was mostly abandoned.

Well Maryland Day is coming up again. Time for Mark II.

This time, I’ve used my experience from last time as a lesson. For MkII, I have forgone the fancy acrylic panels and gone for ABS. And instead of making the panels be the frame, I’ve made them support structures for a main frame made of threaded rods.

Once the nuts were threaded onto the rod frame (very very slowly… and somewhat painfully), it was clear that the nylon nuts don’t hold as well onto the rods when under vibration or shock. Locktite is not a great option as that stuff apparently eats through plastic.

Instead I chose hot glue – mostly because it was most accessible. And…

SUCCESS.

As planned, today was going to be test day (along with haircut day, but that’s a different story).

I mostly continued yesterday’s work of crimping cables. The hammer crimper still makes me happy. In fact, here it is in action (along with some questionable dubstep):

When I am actually using this stuff on a moving kart, I will probably want to maybe add some heatshrink and whack the thing a little harder (maybe from both sides). But so far, the crimps looks solid. Even after wiggling the cable around and pulling in jerks, the lug doesn’t budge. Good deal.

As far the actual setup:

This is the reversing contactor (SW-202). In the current test setup. It’s being used as a non-reversing contactor, i.e., it just turns power on or off.

The controller gets the throttle pot-box input and switched power input along with the main 24V power from the batteries.

Push when you’d rather not shit your pants. Or are already in the process of doing so.

The current setup looks fairly messy, but when it’s on a frame, I’ll have a better chance of organizing things better. Once the final leads were connected to the motor, I was ready to give it a whirl. So I turned on the kill switch, heard the contactor come on and pushed the throttle up. Nothing.

After a little debugging,  I found that the controller was setup (understandably) for 72V. Therefore, the undervoltage setting was at 60V. My batteries were at 24V. I changed the undervoltage to 20V. I also bumped down the max current to 30%. I am not sure how much I can thrash these SLA batteries yet, so I figured it’s better to be safe for now. Time for Run #2:

* maniacal laughter * That is all.

Next step is to test this on the frame. Hopefully not break any fences with my head.