Jammin’

IMG_20171014_115733453Well, last Saturday Angus and I went off to Manchester Raspberry Jam with some plans to work on sensors. (Other team members were abseiling at a birthday party!) This pic doesn’t really have anything to do with Pi Wars prep though – it’s the cipher workshop that was running at the Jam, in the side room. Back in the main room, I was happy to find that @the_rasp_blonde has also been successful in her application this year, and one of the other regulars at the Jam (a teacher) will be leading a school team.  Another regular who did enter last year won’t be this time, but he’s thinking about a show-and-tell. Sorry, I’m *terrible* with names!

So anyway, I had a few new sensors to try out, not with any firm plans of using them, just to see what readings I could pull off them. Unfortunately, I didn’t get very far with this. I spent waaaaaaay too much time talking to others about all sorts of fun pi projects, and then discovered that I’d failed to bring sufficient male-female jumper leads with me 🙄 and of course the Maplin just round the corner didn’t have any in stock 🙄  🙄  🙄 But the good news is that I then got to spend waaaaay more time talking others about their fun pi projects, so the day was far from a total loss.

Meanwhile, during the week this week a pile of components – including more sensors – have turned up.  I just need to find some time to do something with them! Meanwhile, we’ve been having significant debate about

  1. Power supplies
  2. Wheels versus tracks
  3. Comms between components
  4. Programming interfaces

Yes, if you’ve been reading my blog you’ll probably realise that at least some of these are things I thought we’d reached agreement on, but it seems not… So it seems that in the time that I don’t have I need to work out the best way of our pis communicating (we’ll have at least two), still figure out what sensors we want to use, and decide how my son should be programming the bot.  I’m not even sure what to do about that last point, because as far as I knew, he was happy using IDLE. Wheels versus tracks is a problem for Peter and Angus to resolve. And power supplies is another group discussion.

Anyway, I guess this post is really a case of “We’re still thinking about it, but no concrete progress made this week.”  Hopefully next week I’ll have some more serious points to discuss!

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We’re in! 😅

We were very excited to receive our acceptance email this morning, as we’d already planned a team meeting (at 10yo’s insistence) for that time. So we had our discussion.

Discussion point 1: Chassis design

Glitterator mark 1 was LEGO-based, and when we put in the application for this year’s entry, we weren’t sure if we would continue this theme. The biggest problem with a LEGO-based robot is that LEGO is designed to be disassembled and reassembled over and over again, which is great for model builders, but has the unfortunately side issue that sometimes it becomes disassembled when you least want it to be… like right in the middle of Pi Noon!

On the other hand, a LEGO-based design is easily adaptable, and our experience with LEGO-based pi-controlled robots didn’t end with Pi Wars 2017: Peter and Angus have spent the summer building a series of pi zero controlled LEGO robots. Some with tracks, some with wheels, and even some with legs. The legged ones were fun, but not really practical (slow and difficult to manoeuvre), but the tracked and wheeled ones have been very effective. (Although the two-wheeled version was given up as too difficult.)

So in the end, we have decided to go with our experience, and use a LEGO-based design again. The big difference is that we will use Technics LEGO, which is considerably more difficult to disassemble, and so hopefully will be more robust. Related question was tracks or wheels? I was quite keen to try wheels, with servo-based steering, but in the end was overruled, so we’ll have tracks again. Different type of LEGO tracks last year – rubber ones last year – and I’m concerned that what we have now are not quite grippy enough, but the plan is to add some rubberised tread to the links, so I think it will be OK.

There are some other particular aspects of chassis design that we went on to discuss too… but we have to keep some secrets 😜

Discussion point 2: Control

Last year, we used a genuine PS3 controller. It’s a bit fiddly to get paired, but once we’d figured that out, it was working pretty well, right up until the day of the competition, when it kept conking out! Turns out it wasn’t just us, but lots of people had similar problems, and not just with PS3 controllers either. In any case, with the explosion of robots in the house over summer, we’ve needed more controllers, and the PS3 ones are just too expensive. Instead we’ve been using Rock Candy controllers, which again, have been working fine. But some people reported similar issues to ours with Rock Candy controllers at the venue.

Sooooo… there’s been quite a bit of discussion in the community about what causes the problem. The most plausible explanation that I’ve come across, that I haven’t put to the test, is that our power supplies are not perfect, and that sometimes the voltage drops a bit below 5V – not enough to stop the pi itself running, but enough to cause glitches in the peripherals. So this is something we will take into account.  We’ll also be looking at alternative controllers, but I’m not so sure this will solve the problem, especially if the power glitch hypothesis proves to be the cause.

Discussion point 3: Raspberry piS

So last year we had a pi 3 doing most of the work (motor control, sensing, etc), communicating (via USB) with a separate pi zero that controlled our light show. This year, one thing that I did put in our application was that we wanted to explore this theme further. Now, over summer we’ve developed a very nice base for pi zeroes with remote control for LEGO robots, and I think this will work very well as the base of Glitterator mark 2. But I’d like a separate pi – probably a pi 3 – to do the autonomous control, sending low level movement instructions to the underlying pi zero. And again we plan to glitter, so another pi zero for light control. And then the duck shoot – separate pi zero as well? Well, this discussion didn’t reach firm conclusions about the number of pis, but a separate one for autonomous control seems a fairly firm plan right now.

Action Plan

So, this has been a rather brief summary of what was a rather long (and sometimes heated) discussion. But the result of it is an action plan.

  1. I will be experimenting with various sensors – some we used last year, some new – to decide which we will be using for various challenges.
  2. Angus will be assembling a Technics-based chassis, with ground clearance, and some secret features that we want to test.
  3. Peter will be looking at what we can do with the camera. He’d like to use it for more than just the rainbow challenge; I think other sensors will be more effective. But we’ll experiment and see.
  4. And Erin, who is just 7, has declared that she wants to help with the coding this year. So she’s starting to learn Python! (Angus did it at age 9.) So there’s a challenge that she and I will work together on (with the help of the brilliant Kano tutorials). (She did actually get a taste of Python at a Pi Jam workshop run by Ben Nuttall last year.)

Hmm.

Well, this week has mostly been about thinking, and waiting for parts ordered from afar. Last year, our main aim was to build a robot that could complete the challenges; we weren’t really thinking too much about optimising performance. But this year, having gone through the trial and error of different sensors, voltage regulators, and so on, we’re feeling a lot more comfortable about what we can do. There are two new challenges, of course, but we’ve already done some vision stuff with the pi camera, so sort of know where we’re going with that one, and my kids are great NERF gun fighters, so guess what we’ll be using for the shooting range? A was most interested when we pulled apart a battery-operated one to see how it was controlled.

Last year, we didn’t really look at the scoring schemes for the different challenges – as I said, we were just focusing on getting them done!  This year though, we’re thinking a bit more strategically, and it’s clear from the scoring system that reliability is important, because every go on a challenge counts, and so doing it once perfectly is no good if the other two are flops. (Unless of course everyone flops on all three goes!)

And speaking of reliability, there’s been a bit of discussion about the problems that many of us had with controllers dropping out.  One theory is that it’s down to the unreliability of power supplies – that they sometimes dropped to 4.8V from 5V, and this meant USBs & bluetooth failed. I can sort of see this, but wonder why, if this was the case, for many of us it was only a problem at the venue, not something we encountered at home. Anyway, we’re not sure at this stage what sort of controller we will use. We were thinking of switching from the genuine PS3 controller (bluetooth) to a RockCandy or similar (wireless), but if it’s power that is the problem, this will not fix it!  (Since Pi Wars 2017, we have been playing with other raspberry pi robots that are controlled with RockCandy controllers, and they’ve been working very well.  But as I said, the PS3 controller was working fine for us at home too…)

So at the moment, we’ll keep planning, and waiting for our sensors. And maybe putting the chassis together… although at the moment, parts have been appropriated for the other “battle bots” that the boys have been playing with. (LEGO-based robots, controlled by pi zeroes, with hammers to bash at each other.)

Ooh! The challenges have been set!

Yay! The challenges for 2018 Pi Wars have been set, and we’re excited.  We’ve no idea yet what Glitterator mark 2 will look like – except that it will glitter! – but we’re super excited about the new challenges.  I’m loving the “Somewhere over the rainbow” idea, while my son has big plans for nerf gun attacks on ducks.  Let’s just hope we are selected to compete 🙂

(Feature pic above is of the original Glitterator. You can read all about it at glitterator.wordpress.com)