Breaking and Fixing

Posted by Erin, the RobotGrrl on Wednesday, November 10th, 2010

How do you know what is going to break, and at what time? Robotics is full of detailed hardware and software implementations where if one thing breaks, it can cause many other things to not work as well. Being a ninja in preparedness can go a long way, but what can be expected in demo-ing robots?

At the Ottawa Mini Maker Faire, one of the first perf-board circuits that I designed, for MANOI’s hockey stick, got a short circuit and didn’t work. Granted, the circuit wasn’t the best designed, I recall that I went for an “artsy” approach by making it three dimensional. Also, the LEDs were in series, so once one of them burnt up, the other ones didn’t work.

I guess you can expect old things to break eventually. But what about new things?

The force sensitive resistor on MANOI’s wrist snapped and tore the conductive plastic. This was due to the motion that MANOI was undergoing. But why didn’t it break the other times MANOI did the motion? Also, why didn’t it just pop out of its header socket, like it was designed to?

Here is the fixed version of the perf board that I did in many hours. It looks much more neater and “one dimensional”.

As for the force sensitive resistor, I’m probably going to make a capacitive sensor or a sensor using conductive foam and felt. That way everything will be more flexible.

To sum up, I think this is an answer that we’re always chasing in robotics: How do we prepare for the things that can break? One way is with simulation, avoiding the dangerous environments for robots in the real world. Or maybe we could have robots that test robots. That would be pretty cool. Either way, it’s something to think about for the future, especially when we can have serious implications of such events happening, with UAVs and rovers.

Posted in: Other, Projects.

Friday Night Robotics – CMUcam2

Posted by Erin, the RobotGrrl on Friday, February 5th, 2010

The CMUcam2 is a really cool camera for robotics made by CMU. The version that we’re using for this Matlab project (that I mentioned before) was actually used in FIRST competitions a long time ago.

The first problem we faced with this was that it requires 7.2V, in a range of 5.2V – 8.6V. What gives 7.2V?! Crazy! If you take 6 AA rechargeable batteries together, they can add up to be 7.2V exactly. (1.2V * 6 = 7.2V). Battery packs naturally don’t come in sixes, so I ended up making one:

This was actually my first time making a series battery pack. It’s in series because we want to use Ohm’s law, where the voltage is added together. Thanks to the people in the Fat Man and Circuit Girl IRC chat room, they helped me figure it out. Here’s a drawing that I made incase others too need help with this someday. Basically, connect the positive to negative over and over again! ^_^

The next step is to get the camera working. This is by far the hardest part. There’s numerous methods of communicating to the CMUcam2, all of which use RS232. Arduinos also use RS232, so at least we’re in known territory.

The CMUcam2 has a serial port, a TX/RX/Gnd line, and a TTL port. On my Mac, I tried the serial port, it didn’t work. I tried the TX/RX/Gnd line into an Arduino, it also didn’t work. I also tried to use the TTL, but it also didn’t work. I’m not really sure why nothing works on my Mac, especially since the camera works with a PC just fine.

This is where I’m at right now. No idea what to do to make the CMUcam2 work on my Mac. Do any of my blog readers have any ideas?

WOOT~~~ TWIST ENDING!! READ ON!!!

I was thinking that it would be really lame to end the blog post without some sort of screenshot of Matlab or something. So I gave the CMUcam2 another shot… I made it work!!! IT WORKS!!! IT WORKS ON MY MAC!!!!!! =) The code that I was using to test the camera is from Instructables.

So, now that it works we have things to do… like figuring out how we can get the RGB data for each pixel, and then saving that to an image. After its in an image, we can do some form of edge detection. Matlab probably has a toolbox for that. More fun later!

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Posted in: Programming, Projects, School.