Micro Sawppy Rover Cardboard Box Testbed

Proving that I could control DRV8833 DC motor driver IC using an ESP32 was the final piece of the foundation I knew I needed before I seriously start building a micro Sawppy rover brain on an ESP32. During my development of this software, I will need a physical chassis to test code on. While I could go straight to my Micro Sawppy Beta 3 (MSB3) chassis, doing so has the risk of breaking physical robot hardware. Anything from a servo moving beyond intended limits, to embarrassing mistakes like driving the rover off the table.

A safer option is to have a representative testbed with fewer risks than a physical robot. For my original Sawppy rover, I removed all ten LX-16A serial bus servos and laid them out on a table. I found that a line of servos wasn’t very good at conveying system behavior, since I had to do some mental spatial transforms in my head to interpret those servo movements. Some bugs slipped through this process because I made mistakes in my mental visualization. From that experience I thought it would be better to have a testbed that better represented the physical layout of the rover chassis, and this is an opportunity to put that idea to the test.

In line with my recent discovery of cardboard for mockup purposes, I pulled a cardboard box from my paper recycle bin. I turned the box inside-out to give me some clean note-scribbling surfaces, plus I’m not advertising that product on this site anyway. Holes were cut in the cardboard so I could use twist ties to fasten six TT gearmotors in the same relative location as they would be on a rover. I also cut four rectangular holes for the steering micro servos. Since I cut those holes by hand, the imperfections of the manual cut gave the servos enough friction to sit in place without any fasteners.

Wires for all of these components went into the box, and small holes were cut so they could poke through to this top surface. This routing keeps all excess lengths of wire out of my way making for a neater work area. The ESP32-based control board, whatever it ends up being, should fit in the center area I kept clear for it. Excess wire isn’t the only thing I kept in the box, it was also a convenient place to store all the related auxiliary pieces related to the project. Each micro servo has a plastic bag with spare control horns as well as their mounting screws not needed for the testbed. And each gearmotor came with a wheel that’s not strictly necessary for the testbed. There’s a chance I’ll want these wheels later, to better visualize relative rotation velocity of the wheels. If that should occur I know where to find the wheels: they’re in the box!

But first I need to get started with Sawppy ESP32 software.

Jumper Wire Headaches? Try Cardboard!

My quick ESP32 motor control project was primarily to practice software development for FreeRTOS basics, but to make it actually do something interesting I had to assemble associated hardware components. The ESP32 development kit was mounted on a breadboard, to which I’ve connected a lot of jumper wires. Several went to a Segger J-Link so I had the option of JTAG debugging. A few other pins went to potentiometers of a joystick so I could read its position, and finally a set of jumper wires to connect ESP32 output signals to a L298N motor control module. The L298N itself was connected to DC motors of a pair of TT gearboxes and a battery connector for direct power.

This arrangement resulted in an annoying number of jumper wires connecting these six separate physical components. I started doing this work on my workbench and the first two or three components were fine. But once I got up to six, things to start going wrong. While working on one part, I would inadvertently bump another part which tugs on their jumper wires, occasionally pulling them out of the breadboard. At least those pulled completely free were clearly visible, the annoying cases are wires only pulled partially free causing intermittent connections. Those were a huge pain to debug and of course I would waste time thinking it was a bug in my code when it wasn’t.

I briefly entertained the idea of designing something in CAD and 3D-print it to keep all of these components together as one assembly, but I rejected that as sheer overkill. Far too complex for what’s merely a practice project. All I needed was a physical substrate to temporarily mount these things, there must be something faster and easier than 3D printing. The answer: cardboard!

I pulled a box out of my cardboard recycle bin and cut out a sufficiently large flat panel using my Canary cutter. The joystick, L298N, and TT gearboxes had mounting holes so a few quick stabs to the cardboard gave me holes to fasten them with twist ties. (I had originally thought to use zip ties, but twist ties are more easily reused.) The J-Link and breadboard did not have convenient mounting holes, but the breadboard came backed with double-sided adhesive so I exposed a portion for sticking to the cardboard. And finally, the J-Link was held down with painter’s masking tape.

All this took less than ten minutes, far faster than designing and 3D printing something. After securing all components of this project into a single cardboard-backed physical unit, I no longer had intermittent connection problems with jumper wires accidentally pulled loose. Mounting them on a sheet of cardboard was time well spent, and its easily modified nature makes it easy for me to replace the L298 motor driver IC used in this prototype.

Cardboard Absurdity: Sexy Minion

I abandoned the first draft of my cardboard Mike Wazowski for another attempt later, but I did not abandon my other Hallowing. An idea to put it to use came courtesy of Emily’s reply to my cardboard minion tweet.

This “sexy minion” is certainly not something I would have found on my own, and my initial reaction was probably what Emily intended: vaguely disturbed and resignation to the fact I can’t un-see that image.

But it’s on Twitter now, and it’s also in my brain now, and I do have an extra Hallowing on hand, so I decided to play along with the joke with a minimum-effort project. I imported the image into a photo editor and scaled it so the eye is the right size to use with a Hallowing. Fortunately it fit on a sheet of standard letter-sized paper so I didn’t have to crop any part of it off.

I tried to print it on my color inkjet printer, but that thing hasn’t printed anything in months (possibly years) so naturally its print nozzles were clogged. A standard unclog routine did not fix it and I didn’t want to spend time troubleshooting. (Remember: minimal effort.) So I printed on my monochrome laser printer and colored it in manually afterwards using markers.

Given the minimal effort I didn’t try to trace the outline curves with my new favorite cardboard tool the Canary knife, just a rectangular piece of cardboard and the marker-colorized paper taped on top. My X-Acto blade made quick work of the eyehole, and the second Hallowing was taped in place. I set it up my convertible photo studio for a quick video and threw it up on Twitter.

This silly little project couldn’t have taken more than half an hour (even less if I subtract fussing with the clogged inkjet) and it turned out to be unexpectedly (or is that disturbingly?) popular. As a result I have the sinking feeling this is not the last I’ve seen of “sexy minion”.

I also felt a bit bad that I didn’t put in the time to research where that drawing came from. It wasn’t a big deal when I thought it’d just be a throwaway joke between friends, but with thousands of views the artist’s name should have been attached. I can’t edit my original tweet, but I could at least credit the artist @nicoisesalade here:

Cardboard Companion: Mike Wazowski

My trial run using a Canary cardboard cutter was far more successful than I had expected, resulting in a little cardboard companion minion perched on my shoulder. I was extremely happy and joined this month’s (Virtual) Wearables Wednesdays event at CRASHSpace to show off my minion as a wearable electronic project. And also to thank Barb (who usually attends the event) for telling me about the Canary cutter.

Barb immediately (and correctly) recognized the minion’s eye as the Adafruit HalloWing default program. She had several sets of similar eyes on hand, some incorporated into projects, but all the units within reach came as pairs so there were no immediate advice on how to get my two units to synchronize. But by now I didn’t really want to synchronize them anyway, because that would mean taking apart my minion which I’m not ready to do just yet.

So I asked the attendees what I should do with the other eye. People started brainstorming and tossing out ideas. They were fine ideas but they didn’t capture me as much as when Liz said “Mike Wazowski”. I said “Yes!” and got started immediately while the meeting was still underway. This is falling back on old patterns, as it is pretty typical for work to happen during non-virtual Wearables Wednesdays meet.

I found a picture of Mike Wazowski on the internet and traced out a rough outline on cardboard. For the minion I wanted to keep the eyehole small so none of the electronics are visible. For Mike I thought I’d explore how things looked if the eye hole was larger.

Once I had Mike cut out and popped my second HalloWing into the eyehole, I decided I did not like how it looked. I much preferred the minion approach where the circuit board was hidden. If I wanted to build a Mike Wazowski with a properly obscured HalloWing eye hole while still maintaining proportions, I will need to cut a smaller Mike. There’s also a second reason to want a smaller Mike: this one is too wide to sit properly on my shoulder. Maybe someone with much broader shoulders can pull it off, but this Mike’s butt is too wide for me to carry around.

I will abandon this cardboard cutout and stick “try again with smaller Mike” on the to-do list. This is the beauty of experimenting with cardboard: cost of failure is low, and speed of iteration is fast. I could very quickly follow up this abandoned project with an absurd project.

A Canary Corrugated Cardboard Cutter Convert

One of the bonus motivations for building my cardboard companion minion was a test run of the Canary Corrugated Cardboard Cutter (*). After my experience in that project, I am now a big fan of this tool.

I learned of the Canary cutter via CRASHSpace, a longstanding maker community in the greater LA area. As they are on the opposing side of downtown LA it is not trivial for me to visit. But now that everything is virtual, I actually have more interaction with members of that community than I would have otherwise.

One of the recent discoveries started by watching Barb Noren‘s session “Tinkering @ Home” for Virtually Maker Faire 2020. One of the topics was their Tinkering Toolkit and the Canary cutter in that kit caught my eye. Given the popularity of home delivery in these times, many of us are going through a large number of corrugated cardboard boxes. We could throw them in the recycle bin, but Barb Noren asserts that is a waste: they are useful raw material for projects! And the Canary cutter is how reDiscover Center can set children loose on cardboard, as young as seven years old, under adult supervision.

I’ve built many projects with corrugated cardboard, using X-Acto blades for fine detail and large box cutter knives for large cuts. And yes, I’ve had my share of accidental cuts and so I was immediately interested in the idea of a much safer cutting tool. I was willing to trade off some cutting effectiveness if it would gain me more safety. And after asking Barb a few questions about it at a virtual CRASHSpace event, I ordered one of my own to try.

When my Canary cutter arrived, I saw a well built tool with a plastic handle for manipulating the metal cutting blade, which was edged with fine serrations. It looked fine but did not inspire great expectations. That attitude changed as soon as I took a test cut. I had expected the serrated teeth to tear rough edges in the cardboard, and I had expected the less-scary blade to also be less effective than a sharp blade at cutting.

I was wrong on both counts.

The Canary cutter cut through corrugated cardboard amazingly quickly, with less effort than box cutter blades, and left a pretty clean edge. Yes, if I compare it side-by-side with something cut by a sharp knife I can see a difference, but when we’re working with corrugated cardboard we’re not exactly working with precision tolerances anyway. And the serrated edge cuts enough clearance that the blade does not get stuck, which my box cutter knives tend to do. Freeing a stuck sharp knife is the major cause of my crafting injuries, so just by eliminating that scenario, things became a whole lot safer.

However, it is still a cutting knife that demands respect, as I’ve already managed to draw my own blood once. But it is much less dangerous than putting big box cutter knives in the hands of children. Since Barb’s session video, reDiscover Center has posted another video about using the Canary cutter.

I’m pretty amazed at how well the Canary cutter worked. This reduces the barrier of entry for corrugated cardboard projects in the future. As the above video stated, it is not suitable for all cuts. We’d still need to have scissors and our old friend the X-Acto blade for fine detail, but for large cuts the Canary cutter is pretty amazing. Anyone who wants to unleash their creativity on corrugated cardboard should get one. (*)

Naturally, with my hands on such a fun new tool, I didn’t stop at just one project and found another cardboard project to start on.

(*) Disclosure: As an Amazon Associate I earn from qualifying purchases.

Cardboard Companion: Minion

I’ve long admired the robot companions built by Alex Glow and Odd Jayy but never dedicated the time and effort to build a good one of my own. I still haven’t done so… but I’ve spent roughly an hour or two to build a low-effort companion out of cardboard.

This project was kicked off when I was moving a few boxes around and noticed the Hallowing I received at Supercon 2018 almost two full years ago. When I wrote about it earlier I thought it had full of promise and should be a lot of fun to play with. That is still true, it just never came to the top of my priority list. I actually have two of them now, as Emily gave me hers saying she’d never do anything with it. I said I would definitely find something fun to do but nothing had happened since.

So when I saw them again, I had an urge to do something with them right now. Today. The pair of Hallowing deserved to be dusted off, literally and figuratively. If I can’t do something unique and cool, I can at least do something to verify at least they still function.

When I plugged them into a USB power bank, they started right up. A good start!

I thought I’d use them both by following Adafruit’s instructions to synchronize two of them. Unfortunately I made a mistake somewhere and the two eyes remained stubbornly independent. So I switched to a backup plan: what do I know that has a single eye? The first one that came to my mind is a minion from the movie Despicable Me.

I made a rough sketch and cut out the shape of a minion. I wanted the minion to sit on my shoulder, so the outline was placed such that the existing fold for this box lid is roughly at the (not terribly well defined) waist of the minion. The cutting tool visible in this picture is a Canary corrugated cardboard cutter. This was my first time using it and I am now a big fan.

After I cut out the eyehole, a quick size comparison test confirmed it was in the ballpark. I decided to stop cutting at this point. A hole that’s slightly too small like this will obscure a portion of the eye, not a big deal. In contrast a hole that’s slightly too big will show the wires at the edge of this LCD module or the circuit board underneath, either of which would spoil the look and thus something I wanted to avoid.

A black marker helped make the cardboard look more like a minion.

The minion’s work overalls courtesy of blue highlighter marker.

I used cardboard to build a tripod to help the minion sit on my shoulders, but it is top-heavy with the Hallowing and prone to falling over. I decided to tape some magnets to the bottom of the minion.

Once I set the minion on my shoulder, I could install matching magnets inside my shirt. The two magnets pinch fabric of my shirt, holding the minion in place.

Voila! A low effort cardboard companion.

It only scratches the surface of what the Hallowing can do, but far better than just letting it gather dust. Will it find a place in a cooler and more sophisticated project? Check back in two years!