Drawing Robot Creates Portraits Using Pen, Paper And Algorithms

October 25, 2021 by Robin Kearey 6 Comments

Although the market for hand-drawn portraits largely collapsed following the invention of photography, there’s something magical about watching an artist create a lifelike image using nothing but a pencil, some paper, and their fine motor skills. Watching a machine do the same is a similarly captivating experience, though often the end result is not so great. Trying to fix this deficiency, [Joris Wegner] and [Felix Fisgus] created the Pankraz Piktograph which seems to do a pretty good job at capturing faces. They were inspired by classic picture-drawing automatons, and made a 21st-century version to be used in museums or at events like trade shows.

The operation of the Piktograph is very simple: you stand in front of the machine, look into the camera and take a selfie. If you like what you see, the robot will then begin to draw your portrait on a piece of paper. It does this using two human-like arms which are made from aluminium and driven by two stepper motors. An ordinary ballpoint pen is held in a spring-loaded carrier, which provides just enough pen-to-paper pressure to reliably draw lines without lifting off or scratching the paper. We can’t help but be impressed with the overall look of the machine: with a sleek, powder-coated aluminium case and a stainless steel stand it’s a work of art by itself.

Inside, the Piktograph is powered by a Raspberry Pi 3, which runs a rather sophisticated algorithm to generate a vector image which doesn’t take too long to draw, but still results in a recognizable image of the subject. The makers’ thesis goes into quite some detail to explain the process, which uses Canny edge detection to create an outline drawing, then fills in the empty bits to create bright and dark areas. A certain amount of noise and wigglyness is added to the lines to give it a more “handmade” feel, and the resulting drawing is divided into continuous lines for efficient drawing by the plotter.

We’ve seen several types of specialized art robots before, capable of drawing portraits with a pen, painting them, or even using an Etch-a-Sketch, but [Joris] and [Felix]’s creation seems to win on speed, workmanship, and the quality of the end result. Video embedded after the break.
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Open Source Autopilot For Cheap Trolling Motors

September 24, 2021 by Danie Conradie 14 Comments

Quiet electric trolling motors are great for gliding into your favorite fishing spot but require constant correction if wind and water currents are at play. As an alternative to expensive commercial GPS-guided trolling motors, [AlexAsplund] created Vanchor, an open source system for adding autopilot to a cheap trolling motor.

To autonomously control an off-the-shelf trolling motor, [Alex] designed a 3D printed steering unit powered by a stepper motor to attach to the original transom mount over the motor’s vertical shaft. A collar screwed to the shaft locks the motor into the steering unit when the motor is lowered. The main controller is a Raspberry Pi, which hosts a WiFi hotspot and web server for control and configuration using a smartphone. Using navigation data from an e-compass sensor and a marine GPS chart plotter, it can hold position, travel in a specified direction, or follow a defined route. [Alex] is also planning to add the option of using a GPS module instead of a commercial plotter.

For an estimated total of $300, including the motor, this seems like a viable alternative to commercial systems. Of course, it might be possible to add even more features by integrating the open source ArduRover autopilot, as we’ve seen [rctestflight] do on multiple autonomous vessels. You can also build your own open source chart plotter using OpenCPN, which rivals commercial offerings.

Light Painting With An 19th Century Inspired Plotter

August 15, 2021 by Lewin Day 9 Comments

The geometric chuck was a device that stacked up multiple rotating wheels that could vary their speed and their offset to a central shaft, in order to machine ornate designs using a lathe. It’s this piece of machining obscura from the 19th century that inspired this light painting build from [Ted Kinsman].

Rather than the complicated gears and wheels used in the distant past, [Ted] instead elected to use stepper motors. Three stepper motors are stacked on top of each other, each one able to rotate at an independent rate. The design only implements three steppers as the slip rings needed to send power and control signals to each stepper are prohibitively expensive.

An Arduino is programmed to run the show, changing the speed of each motor and thus the patterns the system generates. Put LEDs on the spinning plates, or install a pen to mark a piece of paper, and it’s possible to generate all manner of beautiful spirograph-like patterns. Vary the motor speeds or the positioning of the lights, and the patterns vary in turn.

It’s a fun build for light painting, with some great visuals produced. We also appreciate the use of the Arduino which makes varying the parameters far easier than having to change out gearsets in classical designs.

If you miss the old school spirograph, you can always build one out of Lego. Else, consider experimenting with other light painting techniques. If you’ve built a fancy rig of your own, be sure to let us know!

[Thanks to zit for the tip!]

Detecting Ripeness In Fruit And Vegetables Via Neural Networks

July 22, 2021 by Lewin Day 11 Comments

Humans have an innate knack for identifying food that is fit to eat. There’s a reason you instinctively enjoy fresh fruit and vegetables, but find maggot-infested rotting flesh offputting, for example. However, we like to automate as much of the food production process as possible so we can do other things, so it’s necessary to have machines sort the ripe and ready produce from the rest at times. [kutluhan_aktar] has found a way to do just that, using the power of neural networks.

The project’s goal is a straightforward one, aiming to detect ripeness in fruit and vegetables by monitoring pigment changes. Rather than use a camera, the project relies on data from an AS7341 visible light sensor, which is better suited to capturing accurate spectral data. This allows a better read of the actual light reflected by the fruit, as determined by the pigments in the skin which are directly related to ripeness.

Sample readings were taken from a series of fruit and vegetables over a period of several days, which allowed a database to be built up of the produce at various stages of ripeness. This was then used to create a TensorFlow model which can determine the ripeness of fruit held under the sensor with a reasonable degree of certainty.

The build is a great example of the use of advanced sensing in combination with neural networks. We suspect the results are far more accurate than could have reasonably be determined with a cheap webcam, though we’d love to see an in-depth comparison as such.

Believe it or not, it’s not the only fruit spectrometer we’ve featured in these hallowed pages. Video after the break.

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Plotter Uses Dual Disks

February 19, 2021 by Al Williams 19 Comments

If you want to move a pen (or a CNC tool, or a 3D printing hot end) in the X and Y plane, your choices are typically pretty simple. Many machines use a simple cartesian XY motion using two motors and some sort of linear drive. There’s also the core-XY arrangement where two motors move belts that cause the head to travel in two directions. Delta printers use yet another arrangement, but one of the stranger methods we’ve seen is the dual disk polar printer which — as its name implies — uses two rotating disks.

The unique mechanism uses one motor to rotate a disk and another motor to rotate the entire assembly. The print head — in this case a pencil — stays stationary. as you can see in the video below.

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Open Source: It’s The Little Things

February 13, 2021 by Elliot Williams 108 Comments

I use open source software almost exclusively; at least on the desktop — the phone is another matter, sadly. And I do a lot of stuff with and on computers. Folks outside of the free software scene are still a little surprised when small programs are free to use and modify, but they’re downright skeptical when it comes to the big works of professional software. It’s one thing to write xeyes, but how about something to rival Photoshop, or Altium?

Of course, we all know the answer — mostly. None of the “big” software packages work exactly the same as their closed-source counterparts, often missing a few features here and gaining a few there, or following a different workflow. That’s OK, different closed-source programs work differently as well. I’m not here to argue that GIMP is better than Photoshop, but rather to point out what I really love about open software: it caters to the little guys and gals, the niche users, and the specialists. Or rather, it lets them cater to themselves.

I just started learning FreeCAD for a CNC milling project, and it’s awesome. I’ve used Fusion 360, and although FreeCAD isn’t “the same” as Fusion 360, it has most of the features that I need. But it’s the quirky features that set it apart.

The central workflow is to pick a “workbench” where specific tasks are carried out, and then you take your part to each bench, operate on it, and then move to the next one you need. But the critical bit here is that a good number of the workbenches are contributed to the open project by people who have had particular niche needs. For me, for instance, I’ve done most of my 3D modelling for 3D printing using OpenSCAD, which is kinda niche, but also the language that underpins Thingiverse’s customizer functionality. Does Fusion 360 seamlessly import my OpenSCAD work? Nope. Does FreeCAD? Yup, because some other nerd was in my shoes.

And then I started thinking of the other big free projects. Inkscape has plugins that let you create Gcode to drive CNC mills or strange plotters. Why? Because nerds love eggbots. GIMP has plugins for every imaginable image transformation — things that 99% of graphic artists will never use, and so Adobe has no incentive to incorporate.

Open source lets you scratch your own itch, and share your solution with others. The features of for-pay, closed-source software are driven by the masses: “is this a feature that enough of our customers want?” The features of open-source software are driven by the freaky ideas of nerds just like me. Vive la différence!

XChange Promises Inexpensive Tool Changes For 3D Printers

December 24, 2020 by Al Williams 11 Comments

[Teaching Tech] has been interested in adding a tool changer to his 3D printer. E3D offers a system that allows you to switch print heads or even change out a hot end for a laser or a (probably) light-duty CNC head. The price of the entire device, though, is about $2,500, which put him off. But now he’s excited about a product from PrinterMods called XChange. This is a kit that will allow rapid tool changes on many existing printers and costs quite a bit less. Preorder on KickStarter is about $150, but that probably won’t be the final price.

Not all printers are compatible. It appears the unit attaches to printers that have linear rails and there is an adapter for printers that have V rollers in extrusions. Supposedly, there is an adapter in the works for printers that use rods and bearings.

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