New Year Blues
02 Jan 2017Long time no see! Happy New Year to all readers. As of today, it’s exactly three months to go until PiWars 2017!
KEITH 3 has been sat in his box for some time now waiting for some action. Harry has been concentrating on his A Levels and university applications, so KEITH has taken a bit of a back seat. I’ve spent some time on AutoCad tweaking dimensions here and there to improve track fit and add a few holes here and there, but nothing really significant.
So, the Christmas holidays arrived and for the first time ever we were spending it at home - just the four of us - giving an ideal opportunity to set a few things up and do a bit of testing. Harry put together a motor controller board using a breadboard and a couple of H-bridges (big enough to cope with stall current on the motors this year!) together with a UBEC to provide a stable 5v supply for the Pi.
Harry had obtained a cheap Chinese arduino-like board to use to translate the radio receiver signal to something the Pi could use. Initial tests of that were not good, until he discovered that the processor was running at 1/8 full speed because of a default setting. The addition of a little code reset that to allow it to run at full speed and the problems were solved. Oh I wish I knew what he was talking about, sometimes…!
We plugged everything together and clipped on the battery pack. With KEITH sat on a tin of bamboo shoots we pushed the joystick forward. Harry made a few code adjustments to get things running in the right directions and off we went. The first problem was radio reception. This had been anticipated… our new kittens had found the orange aerial wire hanging out of the box and had promptly shortened it by about two thirds! That will be sorted in due course, but for the purpose of the testing we just made sure the transmitter was kept close.
We have used motors that are similar to those we used in KEITH Evo, except that they are geared to run faster. This does reduce torque, but we wanted to make sure that KEITH 3 was quicker than Evo and we had had no problems at all last year. In a straight line KEITH 3 was great. Much faster than Evo, so the first box was ticked. However (actually it was HOWEVER), he could not turn! Our fab new grippy wide tracks, intended to avoid the loom-band issue we had with KEITH Evo, were simply too grippy. He was better on carpet, but still not good - and the events are on a smooth surface anyway.
What to do? Bigger motors, we reasoned, would need more current and batteries would become an issue. We also thought they would add significantly to the cost. Swap the tracks for wheels? This was considered only long enough to remember that KEITH 3 is an iteration of KEITH and KEITH Evo, both of whom are tracked robots. Different tracks? Having spent hours finding the tracks were already have we were a little reluctant to do this. We were not keen on using the Vex tracks we used last year and the little Tamiya stretchy tracks used on KEITH would not be any good on a larger robot. However, a little searching on Ali Express identified some potential options and new tracks, cogs and idler wheels have now been purchased and are winging their way from China as I write. They will necessitate a complete redesign of the chassis but they should allow more space.
On a more positive note, I have acquired a couple of solenoids and successfully tested a flipper system for the skittles challenge :-)
Harry is still collecting ‘things’ and won’t tell me what the bottle of glycerol is for. He assures me that it is safe and has something to do with a little pump and some silicon tubing…
More soon!
Andy
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