2016
06/26

Category:
Computing

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The first cut is the… scariest

A status update on my little yellow robot is long overdue, sorry for the huge delay (yeah, like anyone cares, Ian…)

I am now delighted to be at the point where I can almost put it all together. I have working code (which should be in my GitHub repository, if anybody wants to take a look). This has been a big step for me as I ended up not only experimenting with GPIO Zero, but actually submitting a pull request, as the motor board I picked up (the Pololu one) had a different motor control approach than the usual, default ones supported in the current library.

The final hurdle for me, then, was the actual “maker” side things. The part where I actually have to start cutting the robot to make the new innards fit. It was scary. I dithered, procrastinated and generally put this part off… until something else came up that I needed to escape from.

So now, after diligent use of a Dremel I am all-but ready for the final assembly.

There were a few decisions to make on how, why and where to cut. First, can the new motor block be squeezed into place? Answer, just… if I first:

  • trim off the screw pillar that holds the original motor block in place
  • shave off the interior buttressing on the two corner screw pillars
  • whittle away a few unnecessary bumps from the outer faces of the motor block, and
  • cut a small chunk out of the new motor mounting brackets so the entire assembly slots neatly into place:

The last little quandary was how I going to fasten the tracks back on, now that the motor block takes up so much space? Obviously I needed to trim just enough off the mounting points that they can still clip into place and be screwed down, but so that they don’t foul on the new motor block. Yup, we’re getting there.

What about the IR sensor? A quick Google tells me that I shouldn’t expect any success if I mount it inside the device, so where to put the sensor? My initial gut reaction was to put it at the back, so it was facing you when you drive it… but then I realised that at some point you could pretty much bank on turning the robot around, so the sensor wouldn’t be facing you any more! Thus it came down to maintaining that all-important balance between how it looks, and what’s easiest.

There were two possible mounting sites, one at the rear, in a fin, the other at the front in a cluster of fake headlights. In the end, I decided that the front was the best choice for both practical and aesthetic reasons, so another hole was duly cut to allow the sensor to poke out above the light cluster with the wires available to feed down into the chassis.

The final result in this regard work out very well indeed – I’m very happy with where the sensor will sit and don’t think it will look too out of place.

The last little part of the challenge, at this stage, was to fix the little roller back in place – this sits on the underside of the chassis and ensure a smooth roll for the robot as the tractor treads don’t hold the whole thing off the floor. For this, I had to carve up the original motor housing as it served to not only encase the motor, but also pin the roller in place.

Now all that remains is to try and fit/solder the various parts together and… well… test it! I can’t wait.

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