ooops!

I should have checked before I ordered them, the WiFi cards are not compatible with the new shields. Only me to blame, I just didn't bother to check. Now I have checked a pair of Bluetooth boards and they are compatible so I have ordered them. The other advantage with Bluetooth is that I will be able to use my phone to control the 'bot and won't need to build a special controller. If you want to know how, check out BTInterface. It's currently a free beta app but it seems to work very well and I suspect it may become a paid for app quite soon. In addition, I have also learned how to interface the cards with a Raspberry Pi and that opens up more opportunities as well. I am now looking forward to TagBot 5 which if all goes to plan will incorporate an Arduino acting as a slave to a Pi which is connecting with a controller and sending back real time video from a pan and tilt unit as well. Well, I can dream............ 

Constructive criticism

is alive and well and working hard at the moment.

Build 1 is up and running. However, it falls over a lot due to the wheels being set too high on the chassis. The wheels also have a slight tendency to fall off if treated roughly because of the mistake I made with the cutting of the base panel. Whatever, the remote control is fitted and, although a bit rough and ready, is also working well enough to be a proof of viability. I am using a very simple 315Mhtz transmitter/receiver set up because of the ease of interfacing to the Arduino and also that the size just fits the shield. A closer look at the front view will explain how the two boards are fitted together. The new shield from Creative Robotics is, as is usual, plugged into the Arduino. In this instance, a Duemilanove is used due to cost and size considerations. The receiver board is stuck to the central prototyping area of the shield with hot glue and hard wired into the power and ports used. (Please note, not the ports you can see in the photo as I have changed two of them for a simpler software option whilst testing.) The wiring for the wheels has been carefully twisted to avoid the wheels themselves due to the small gap between the wheel and board on this build. For anyone contemplating a robot of this type, I would offer some advice based on what this first build has taught me, leave more space between the wheels than this - at least an extra 10mm on each side - extend the base board to at least the height of the vertical panel - in this instance 90mm - and make sure the wheels and the ball at the rear are at the same height as, though amusing to watch the first couple of times, the sight of your little robot falling over can get annoying after a short while. 

Advice for the longer term would be to use one of the new Arduino Due boards for all sorts of reasons and, for the greatest stability, a four wheeler with servo steering. My next build will still be a two wheeler, although with most of the improvements mentioned and a wifi card instead of the 315Mhtz system. I will talk about my software in a later post as the current version is very crude and simply makes the robot work for test purposes.

Let's go!

Well,nearly.

Thanks to another Bob, I was able to build a Tagbot chassis this weekend after all. I am calling it build 1 as several minor mistakes have already surfaced. Firstly, it's just a bit smaller than it needs to be and, secondly, I made one critical part just 3mm too short. It doesn't stop it from working but doesn't look as good as it should. Nonetheless, I have put the first model together and it works. The balance is correct and the remote control module fits where I hoped it would. The battery pack doesn't go where it was intended to but that can be fixed in build 2 so, all in all, a successful first effort. Now I will begin working on the first sketch.
Wish me luck.

Tony Blair, eat your heart out!

Things have only got better.

I managed, thanks Bill, to get hold of a couple of those new boards from Creative Robotics. As I suspected, they do exactly the job I need them to do for the new Tagbots. I built one this evening, plugged it into a Duemilanove set to the Uno version of the test sketch and off she ran. Not literally yet, sadly, as the plastic sheet has yet to arrive and I still have to get it cut on the laser cutter. I had originally hoped to have at least one Tagbot mobile by the end of the weekend but I don't see that happening now.

This is the final design for two chassis to be cut from 3mm thick acrylic sheet. When the first pair have been built to my satisfaction, I will make the actual SolidWorks files available on the code site so that anyone who feels rash enough will be able to cut them. 

Building on my plans

comes this shield from Creative Robotics. Full details are at this URL but this is what it looks like. It allows you to connect two Hub-ee wheels to an Aduino and even access the feedback from the readers. In addition, it also has servo connections so that a pan and tilt camera or maybe an ultrasonic scanner could be run from the same board. As far as I can tell, this board isn't yet available from the distributors.

On a completely separate thought, we have finally discovered what is causing my problems with the laser cutter software. The original files are being produced at the correct size but by the time they get to the cutter software, they are so heavily reduced in size that the software can't see some of the lines and holes. We are still working on a fix. 

Old apps for new!

We may have now cracked the problems with the DXF files for the laser cutter. It seems that by making sure that the files were set to the latest version, I may have caused the problem myself. Our laser cutter has a very old application and my colleague Lee sends the oldest version of the files he is able to in order for them to work. The moral is, I suppose, that new isn't necessarily the best - sometimes old is.

Wha?......................

I am still having problems with my DXF files. They open fine in SolidWorks and DraughtSite but not in the special software used for the laser cutter. All the circles and vertical cuts are missing still. I have no idea what's going on.

Always check the date!

Over the weekend, in the free version of SketchUp, I re-drew the TagBot and Micro Pan and Tilt cutting plans. The results when I opened it in the Pro version looked great and I then exported a DXF file from it. Next, down to the laser cutter to check the export quality. Oh dear, not good at all. Over half the lines missing and all the circles. Went away with head bowed and tried to fathom exactly what I had done wrong. Eventually, I discovered that my copy of Pro had somehow defaulted to version 14. The current version is 2013 which is about six iterations later. I only had version 2010 available to me but I tried it and it's close enough for jazz so the files and some card have been left for a test cut. Once I have measured the test cuts against the actual hardware, I will order the acrylic sheets and get them cut ready for assembly.

Gotcha!

I have played with so many 2D CAD applications over the past couple of weeks that my eyes and brain stopped coordinating for a while. However, I have finally found nirvana. The pro version of SketchUp 8 is magic to learn and use and also exports the .DXF files needed for the laser cutter. I had used the free version of SketchUp before so maybe it wasn't such a big learning curve as it might have been but within about twenty minutes I had created a fully scaled cutting plan with all dimensions scaled. This is still not the definitive plan as I have not got the measurements of the wheels with me to copy across to the plans as yet. Once again, I am very lucky in working for a university as we have a site licence on SketchUp Pro. The cost of the personal licence, unfortunately,  is quite high at £322.00. There are many cheaper options for educational use however.

Forget you? Me? Never!

Or something like that anyway.

I have been exceptionally busy over the last few weeks and I'm afraid this blog has suffered a bit. The Hub-ee wheels arrived and they are terrific. I have worked my way through various pieces of software to design for the laser cutter and I am now checking out SolidWorks. This is fine for me as I work in a university that uses the program and I was able to get a legal copy with licence. Sadly, this will only work until I retire next year so I am still investigating other methods of producing cutting plans for laser cutting. In the meantime, I have taken, and passed, an important exam and been to a wedding reception in the National Marine Aquarium. My life is busy and I will have to find more time for robotics.