Author: Keegan

A quick demo of the new wrist mechanism for my #piwars robot #MacFeeglePrime!

https://ift.tt/37HvAve

PiWars 2021 has just been announced for the end of March next year with a conference in January, both taking place online!  For the competition in March we’ll be given a course to build using household bits and bobs and will need to send in a video showing our best time a few weeks before hand.

This isn’t just limited to people who have already entered for 2020 either, the competition is open to new entrants!  If you’re interested in having a go, head over to for more information and I’ll hopefully see you (virtually) on the day. 🙂
https://piwars.org/pi-wars-2021-press-release/ 

The plan for the NE-1 is to build a robot that is very versatile that anyone can build for cheap. In theory a clapped out Roomba makes sense but realistically they’ve probably had a hard life already and are broken in a number of incredibly subtle ways…

For a beginner this will lead to frustration and has an increased chance of giving up, as I have done on many occasions with this blasted (or sucky?) vacuum!

To that end I’m switching to the Pololu Rover 5 Chassis, this has either two- or four-wheel drive depending on the version you get and each motor has an encoder too.

I got mine from Cool Components, not sponsored but they’re just solid as a supplier, and for £45 it’s a bargain. The benefit of the door wheel drive model is extra power and the versatility of being able to switch to omniwheels. These allow the robot to move in any direction and I’ve wanted to play with them for a while.
https://coolcomponents.co.uk/products/rover-5-robot-platform?_pos=1&_sid=c080a4b19&_ss=r 

After learning about the issues with interrupts I’ll be switching to a Teensy too, they are a lot more powerful and every digital pin is interrupt capable.  As I’ll have a lot more encoders to deal with this will be ideal:
https://coolcomponents.co.uk/products/teensy-4-1-development-board?_pos=1&_sid=403d66ded&_ss=r 

The plan is otherwise the same, use off the shelf parts to make a simple but versatile robot.  The parts should be delivered this week and I’ll get a video sorted as an intro.

One thing to mention, my plan for phase two includes building an open-source robot hoover so we’ll get back around to that next year. 🙂

I’ve been planning on building an electric skateboard for a while, that’s where most of the scavenged cells will be going, and while I’m waiting on parts for NE-1 I thought I’d get started.

It’s not robot related so it’ll be mostly covered on my Facebook page, link for those interested.
https://m.facebook.com/story.php?story_fbid=3185305014921504&id=288180951300606

The first job for a few of the scavenged batteries is the Roomba, the existing battery finally gave up the ghost and rather than replacing it again and having to use the slow charger it came with I thought I’d upgrade.

The original battery pack has a 2Ah (amp-hour) capacity, the three scavenged batteries in the caddy have 3.1Ah.  Battery tech has come a long way since the Roomba was first released!

The upshot of this is I can reuse the existing battery pack at some point to hold more of these batteries, I should have room for six in total, which would give a lot more running time for sure. I’ll also be able to add in a BMS (battery management system) circuit which will keep the cells balanced and keep them in a healthier state.  I have a bunch of these circuits from MacFeegle Prime and they’re easy to hook up and make a big difference. 

I’ll admit I’ve not made as much progress here as I’d like, part time wasn’t working out as well as I’d hoped.

So, I’ve taken the very scary step and I’m going full time! Notice handed in today, let’s see how far down this rabbit hole goes! 😀

47 out of 56 turned out to be great! One pack had suffered water damage and had to be disposed of.  I’ll be using these across various projects, shortly on the Roomba, and they’ll be incredibly useful.   I’ll definitely be keeping an eye out for more, the packs the grey cells came from especially.  A good few hundred quids worth easy as they’re almost all over 2.5Ah and essentially cost what you all pledged last month so thanks for giving me the power to continue!  

Yeah, the puns aren’t going to get any better and I apologise for nothing! 🤣

Continuing work on the controller, I’m tidying up the rats nest that is the wiring.  The majority of this controller, and MacFeegle Prime for that matter, was designed or put together while massively sleep deprived or in a rush.  

Now I’ve a bit more time, because with PiWars 2020 postponed a few months I *clearly* didn’t have any back then, I’ve decided to use some PermaProto board and actual plugs to make it considerably tidier.

I started off by taking stock of what’s there, other than the mess.  I have a bus bar along the bottom that gives power and ground to the various switches and potentiometers, other than that everything just uses jumper wires to the various headers.

One thing I wanted to do was swap out the potentiometer that was on there for a snazzy rotary encoder that has an RGB LED and a push button too!  This does mean more pins but I’ve just enough so all good there.

Next up I mocked up all the parts in excel alongside the pins, it’s a nice way to keep track of things like this.  I then put all the sockets and whatnot on to some breadboard to make sure it all fit.

Yeah, so I keep forgetting that some of my breadboards are wider than permaproto by one row so when I tried to move over the buggers didn’t fit!

Thankfully I have some right angle sockets so I was able to move things around a bit, everything just fits but fit it does!

Having taken way longer than expected I’ve run out of spoons a little so rather than trying to push through and mess it up I’ll pick this up tomorrow.  Next post I’ll have everything wired in and the Teensy updated with code to use it all!