OddBot's blog

21-5-2010

A few things have happened this last month. I meet Xiao Yue (Little Moon) about a month before I went to Australia. She can't speak much English and my Chinese is still very bad but she seems to like me anyway.

This was taken on her birthday. There was a bit of a food fight with the cake so we ended up with cream on our faces.

31-5-2009

The last 6 months of my life have been full of ups and downs. I have been on workcover for the last 6 months for an injury I sustained at work. This gave me the time to discover LMR and make new friends (and robots). Thanks to LMR, Jack from DAGU discovered me and is now producing not only my robots but will soon produce other robots from other builders at LMR.

One of the most important parts of a robot is it's sensors. If it cannot sense it's surroundings then it cannot respond. Unfortunately good sensors are usually expensive. For this reason I am always experimenting with cheaper home made alternatives such as my light up antenna, conductive foam touch sensor, IR obstacle detector and my not so successful laser range finder.

I have seen a few people asking questions about controlling Mr. basics motors. One problem is that they draw more current than an L293D can handle. A L298N will do the job but you will want at leat 6V. Below is a schematic of the simplest way I know of to control your motors. Using a 5V relay you can run from 3.6V to 6V. I suggest a 9V relay if you want to use 7.2V.

Building an arm for your robot can be the hardest part of robot design. There can be many different designs besides a humanoid design. For example you might have a CNC style XYZ axis or even a tentacle design where multiple joints are surrounded by cables. For BoozeBot I've decided to go for a humanoid design because I would like him to be able to pick things up like a person would. Reguardless of your design the first problem you are likely to face is strength vs weight.

** Update **

I delivered the gun to KJ precision engineering for testing. It has been named "Soldestroyer" by my former boss.

This was my camera tripod used for videoing my robots at ground level.

After videoing Turbo Trike I left it in the car by mistake. I forgot all about it. After the car being in the hot sun for nearly a week, I found my tripod like this............

One thing most robots need is a power supply that can put out a reasonable amount of current for servos and other small motors as well as run a processor and sensors. Probably the best setup is 5x 1.2V NiMh cells to provide 6V for motors and servos with a low dropout regulator providing 5V for the processor and sensors. Unfortunately this isn't always practical. Sometimes you have motors that need higher voltages or maybe the only battery you have lying around is a 7.2V battery from a RC model.

There have been a lot of questions lately about transistors, NPN vs PNP, Bipolar or BJT vs FET and their use in "H" bridges. I had considered doing a tip/walkthrough on the subject but typing "transistor" into google gave lots of great results. Same happened when I typed in "H bridge design". I realised I would be wasting my time writing a tip/walkthrough on either subject as there is better more detailed explainations already available. So for those who are afraid to google I present these links.

Every now and then I want to test a circuit or a new sensor or even some new idea for code but I don't have a starter kit or anything. While shopping for some robot parts I had an idea for a simple base that could be my equivalent of a starter kit, a power supply and a small robotic platform. This is what I came up with in 5 easy steps.

This is my second attempt at a homemade laser range finder now with video. I nearly gave up after hearing about the Sharp IR sensors but I think this has potential as it focuses on an area the size of a laser pointer spot. The other sensors work on a much larger area. After a lot of frustration I've finally got all the circuitry working properly and hope to have a video posted as soon as I work out one last difficulty. Click on the photo for a full sized image. This is a work in progress, not a finished product.

My laser range finder got a lot of interest so I thought I'd try to explain it in more detail.

It's not finished yet as it still needs to be mounted on it's stepper motor with a home position switch.

The sensor side has been tested on an oscilliscope. When I moved my hand in front of it, the pulse width varied to match.  Below is a diagram showing how the sensor works.