Category: Robotics Construction

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A New Tool Part 11

Good Morning from my Robotics Lab! This is Shadow_8472, and today, I’m reporting the trickle of progress on the Pac Man Ghost Pi case. Let’s get started!

When last I left off, the paint needed a little sanding to get rid of brush strokes. I used 1000 grit sandpaper on it, but I ended up smearing the blue touch up paint onto the white iris. Additional sanding to get the smudges and strokes off the white rubbed straight down to the red plastic.

I ended up having to repaint the whole thing. Dealing with paint on this project has been a two-person affair, and my father has been quite busy any time I’ve been thinking on the project, and time to dry just compounds the problem.

The first layer to be redone was the biggest, red body of the ghost. As a pro-tip, my father showed me how he peeled back the masking on the eyes a little to get that bit more of coverage. From a diagram I saw some months ago, I believe that will help avoid a hard line in the final product after all the tape comes up and everything.

The second layer was the whites of the eyes. Nothing much special happened here, except the eye holes were covered with tape this time. To my dismay, my father explained the correct tool for the job if I wanted to spray the eyes on. It turns out an Air Brush is a lot more handy than a full spray can, but he did figure out why it didn’t work so well the first round of touch ups.

The solvents in spray paint evaporate quickly, so he maximized the amount of solvent by spraying upside down to get some extra propellant, as well as use some mineral spirits to help combat premature paint clumping.

As it stands now, there was a little bit of an accident with the blue spilling into white territory. Without an Air Brush, it looks like I will just have to endure a few brush strokes on an imperfect surface. At least the clear coat will still protect the looks it does get in the end. The whole thing is already looking awesome, but my dream of it looking absolutely perfect is something that will need to wait for a bit more experience.

Final Question: Have you ever wondered why you couldn’t do something, only to realize you don’t have the best tool for the task?

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A New Tool Part 10

Good Morning from my Robotics Lab! This is Shadow_8472, and today, I am covering the finishing touches of the physical side of my new prototyping assistant. Let’s get Started!

I left off with the glue mask drying on the ghost’s foot area. When I peeled off the tape from around the stuff I actually wanted to paint, I ended up pulling bits of the glue mask off along with it. I ended up spending the week touching up the glue and waiting to paint the foot.

The lower half of the Pi case finally did get painted, but at present, I am waiting to put a clear coat on the whole thing. Order of operation keeps getting in my way, though, as the upper half of the case needs some touch up paint from where I goofed on the original masking.

In other news, I went to that workshop again. I hooked up the camera to the Pi and had it look through the pinhole. I was expecting a blue haze around the picture’s outer rim, but somewhere in the process of painting, likely when I was first painting the blue pupil and I stuck a pin in it, I must have expanded the hole just enough so it doesn’t show.

To finish this week’s project (late) I just need the touchup finished with a paint brush, a light sanding to remove the strokes, and a clear coat to protect the paint. After that, the foot’s masking can come off and I can mount the Pi board and tape the camera in place. As the file I printed up is meant for a slightly different board, I will only be able to use two of the four screw holes that align at once. I’m slightly worried about too much torque on the Pi’s circuit board, but if I’m always careful, it shouldn’t be a problem.

Final Question: I’m slightly worried I won’t have enough to write about when I get around to programming the thing. Will you be up to more technobabble style posts when they come?

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A New Tool Part 9

Good Morning from my Robotics Lab! This is Shadow_8472, and today, I am bringing another slow progress report. Let’s get started!

In retrospect, I spent a little more time on my project than I would likely have given myself credit for. Nevertheless, I didn’t make my goal of fully painting the case. I had to plan every step before hand, and carry them through.

Early on in the week, I once again sacrificed the texture of my fingertips as I sanded the Pi case. When I sanded the pyramid, aside from only doing half of it, I had the sandpaper flat. Flat sandpaper doesn’t work so well with curved surfaces unless you have some sort of machine to sand evenly. I’m working by hand, without any power equipment. I used different grits, mainly skipping some of the lower ones and working with something a little more appropriate to the quality it’s already on.

The 660 piece I used up was the only one in stock, so I ended up getting and using 1000 grit for polishing it. I will say, though, it wasn’t the surface without blemish I was expecting. I kept getting these rings as if the vertical layers were slightly scaled wrong.

My technique while sanding evolved as I worked. At first, I was just trying to conform the paper to the surface to sand. After a while of mildly frustratingly flimsy sandpaper slowing me down, I folded it over and focused on smaller spots at a time. Later still, my father got in there and gave me a wash cloth to use as a flexible sander block.

After sanding came masking. Now, I have two pieces. The head, and the body. The head is basically a dome with eyes, one of which I hollowed out for the camera. The body houses the Pi and has screw holes on mini shelves and ventilation holes stuffed into a waffle cone “foot” section. After an overnight test on the test pyramid, I painted the eyes first. I got out the blue painters’ tape and covered the whole outside of the head. Then I took a razor blade and cut out the pupils, scratching the lens pupil in the process. Oh well. After spraying that blue, I found a tip online to use some Elmer’s school glue as a mask. I covered the pupils in glue and uncovered the rest of the eyes before the glue finished drying. When I peeled back the glue, I realized this project might not look absolutely perfect, but it’s going to be far from ugly. I missed a few tiny spots with the glue, and still have to do a little cleanup. As it stands now, I have two coats of red paint on the main dome.

The foot is another interesting story. I decided early on I wanted to leave the inside of the case alone. I also added the uneven underside to the immunity. Since glue gets into annoying, little places, I went with that to mask off the inside of the case and the bottom of the foot. However, the inside of the case has some spots I doubt I will ever be able to clean, such as screw holes. So I covered the little holes on the inside, masked off the parts I wanted covered, and applied glue as the positive mask; this is where it stands now, waiting for the globs of glue I used to finish drying. Once that’s done, I will remove the negative mask and paint the lower half. With any luck, I will just have to get the glue out and install the hardware and I will have a tiny prototyping assistant for many projects to come.

Final Question: With any luck, I will be working on the software side by the end of next week, but I still don’t have a way to physically make the high frequency to repulse naughty cats. What would be a good place to look?

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A New Tool Part 2

Good Morning from my Robotics Lab! This is Shadow_8472, and today, I am continuing coverage of my new prototyping tool. Let’s get started.

I didn’t get as far as I thought I would this week. The mission this week was to get the top all printed, but that didn’t happen. The problem was that I didn’t already have all the skills to accomplish the task already, mainly proficiency in Blender. That’s my goal for next week, learn Blender well enough to finish modifying the upper half of the case.

As for what did get done, I managed to start developing the camera mount. The case I’m printing for my Raspberry Pi is based off a PacMan Ghost, printed in red. The first print, I used Blender to isolate the target eye from the rest of the 3D model, and printed it on fast. It took about 20 minutes, as opposed to a full day plus if I were doing the regular top on a respectable quality level. I drilled a hole in the printed piece and held it over the camera, using larger and larger drill bits until I didn’t see a red plastic border anymore.

For my second draft, I added a cylinder mesh in Blender and scaled one end down, forming a truncated cone. I used a Boolean filter on difference mode to cut out a hole for the lens. It didn’t fit well enough, so I printed another one with a more embellished cone.

My father taught me how to properly use a Vernier caliper. I already knew about the outside and inside edge measurement spots, but the the depth on the end of the ruler was new to me. Also new to me was the use of the Vernier scale; I never before got the idea that the extra marks on the slider were offset just a little bit. I think I had heard about the extra digit of precision, but only now did I get that only one was supposed to line up at once.

I used the caliper to measure up the camera. The plan from there is to model up a crude representation of it in Blender and use that to design the hole before I try printing up another pass. Giving some new thought to it, I want to angle the camera such that the ghost is looking at you, instead of “using peripheral vision.”

The next step may be boring, but it’s something I need to do. This week, I need to actually watch a few video tutorials on Blender. I already want to go through the videos by Blender Guru, Link to his channel. I’ve already tried going through his videos on the basics of Blender before, but I kept getting distracted. And no wonder! I just added the length of the videos I think I’ll need, the core Blender basics and the modeling basics, and it came out to almost six and a half hours! And most of that is in 45 minute chunks. The basic tutorial includes lighting and rendering tutorials, so in theory I could skip them for now, but I really should know how to use them.

Final Question: I’m at least somewhat likely to get more than one Pi computer in the foreseeable future. What kind of case should I search for to print up for the next one?

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A new tool

Good Morning from my Robotics Lab! This is Shadow_8472, and today, I have shelved the boat race port pending review and started on a new project. Let’s get started.

My next goal is a project to keep the cat off the counter. After some early research, I came across OpenCV, an open source computer vision library. Some people have even already gotten it to identify cat faces. Keeping my long-term goal of a social robot in mind, this sounds like the direction to go, rather than a motion detector attached to a deterrent.

Now, to chose the hardware. I don’t know what the system requirements my program will need, so I decided to overshoot and make a “lab assistant” computer to help me with future small projects. A day or so of research later, taking into account Linux as a platform, system specs, community size, and likeliness of support form said community. Of note, I did try to include Fair Trade or equivalent as a criteria, but with electronics, it’s almost impossible to find a supplier who’s sure their product doesn’t include slave labor in their supply chain. In the end I narrowed it down to the Raspberry Pi 3 model B+. Also of note, the Pi is made in the UK (or China in peak times), so my guess is that at least some of the workers were more likely paid a fair living.

The assortment of starter packages is abundant. You can get the Pi alone for about $35, but starter packages tend to include other necessary things like a power cord and case. This led me to look into them and along the way, I learned that the Pi needs a micro SD card to run.

Before I even picked out the Pi for sure, I found a case to 3D print for it. In this case, it’s a Pac Man Ghost by Darren Furniss on MyMiniFactory.com. I started printing one up, but accidentally interrupted it about 10 out of 28 hours into printing the first part. No more heavy objects in front of a pressure based touch screen for me. While the second attempt was underway, the Pi itself arrived, and I set it up. A camera arrived with it, and I even managed to get a picture, though one test picture crashed the system. I haven’t gone to investigate yet.

The upper part of the case is the ghost’s head. Since I’m mounting a camera as part of the setup, I want to have the Pi look out one of its eyes (I’d need a second board to use a second camera). My first thought was to drill a hole but when I saw the narrow walls in the base with infill, I figured pulling the file into Blender and digitally drilling would be more effective. Before I do that, I need measurements so I drill the right hole and can actually mount the Pi camera correctly.

I started encountering small problems when I realized the Pi was mounted upside down in the ghost’s lower half, extending the distance the already short camera’s ribbon cable has to cover. After sundown Saturday, (I let my family have a day of peace from the printer’s constant whining during Sabbath hours) I started up a fast quality of the top. The file online said both parts were supposed to print without a support structure, but as I suspected, a short, long gap didn’t form correctly. I canceled the print, but learned a lot from the partial print.

Pulling the Pi from it’s kit case and putting it in the printed base, I discovered three things: The screw holes don’t quite line up (The case is meant for a Pi B and I have a Pi B+), and the gap in the top is necessary for port access for the power, if not the HDMI, and finally, by comparing the partial print to the 3d model, I discovered the eye does not line up at all with where the camera cable wraps around.

None of the challenges I’ve encountered so far are insurmountable. My only big concern is that the Pi will melt though the PLA case I have for it. Next week, I’m going to come up with a good 3d model for the ghost’s top where I can mount the camera.

Final Question: There is a real possibility I will need to switch to ABS for computer casings. What colors should I start with?

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