Precision CNC Drawing with EtchABot

Turning the classic toy Etch-A-Sketch into a CNC drawing tablet intrigues a large number of hackers. This version by [GeekMom] certainly takes the award for precision and utility. Once you build something like this, you can hardly stop writing firmware for it; [GeekMom] produced an entire Arduino library of code to allow joystick doodling, drawing web images, and a self-erasing spirograph mode. The topper is the version that runs as a clock!


The major hassle with making a CNC version of this toy is the slop in the drawing mechanism. There is a large amount of backlash when you reverse the drawing direction. If that isn’t bad enough, the backlash is different in the vertical or horizontal directions. Part of [GeekMom’s] presentation is on how to measure and correct for this backlash.

The EtchABot uses three small stepper motors. Two drive the drawing controls and the third flips the device forward to erase the previous drawing. The motors are each controlled by a ULN2003 stepper motor drivers. An Arduino Uno provides the intelligence. Optional components are a DS3231 Real Time Clock and a dual axis X-Y joystick for the clock and doodling capability. Laser cut wood creates a base for holding the Etch-A-Sketch and the electronics.

The write up and details for this project are impressive. Be sure to check out the other entries in [GeekMom’s] blog. Watch the complete spirograph video after the break.

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Mostly Wood Motorized Camera Slider

Camera slides can make for interesting dolly shots in your videos, or can spice up an otherwise drab time-lapse sequence. When it came time for one of his own, [Bob] did what any hacker would do and rolled his own motorized camera slide in the wood shop.

We always like to see work based on a hacker’s own prior art, and [Bob] managed to leverage parts and techniques from his impromptu claw machine build for this slider. The rollers in this project use the same 3/4″ angle aluminum and skateboard bearings as the previous build. The bearings roll on a plywood strip capped with the same angle stock for durability and low friction. The stepper motor bracket and pillow blocks are 3D printed, as are the timing pulleys. [Bob] admits that the whole rig is a little noisy and blames it on the rough quality of the pulley prints. He has plans to replace them with commercially available pulleys, which should help; one further suggestion we have is to code a soft-start algorithm into the ATtiny85 to eliminate that jerkiness you see when he demos the slider in the video below.

There are plenty of ways to move a camera along a single axis, and a surprising number of them use parts from the roller sports. We’ve covered quite a few of them before, like this slide that uses skateboard trucks, or this non-motorized rig built from fence posts and inline skate wheels.

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A Pragmatic Guide To Motors With Jonathan Beri

[Jonathan Beri] is a Maker of all sorts, with an affinity for robots, APIs, and Open Source. By day he works on making Android & iOS SDKs easier to use and by night he can found begging a PID controller to “just work already.” Recently he contributed to, “Make: JavaScript Robotics,” printed by Maker Media (2015).

[Jonathan] covers a lot of ground during his motors talk at the 2015 Hackaday SuperConference. He discusses brushed DC, stepper, servo, and brushless motors. Although just scraping the surface of each type of motor [Jonathan] touches the important details you can use to determine which type of motor is best for your project. The slide show he has put together has quite a bit of information and tips for beginners that might go overlooked when choosing a motor. For instance a list of 30 attributes that should be considered when selecting a motor. Included in that list are the 7 attributes [Jonathan] places priority on when he chooses a motor for one of his projects. We’ll delve deeper into that after the break.

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Giant Stepper Motor Gets You Up to Speed on Theory

Few hackers have trouble understanding basic electric motors. We’ve all taken apart something that has a permanent magnet DC motor in it and hooked up its two leads to a battery to make it spin. Reverse the polarity, reverse the spin; remove the power, stop the spin. Stepper motors (and their close cousins, brushless DC motors) are a little tougher to grok, though, especially for the beginner. But with a giant 3D printed stepper motor, [Proto G] has made getting your head around electronically commutated motors a little easier.

While we’ve seen 3D printed stepper motors before, the size and simple layout of this one really lends to understanding the theory. With a 3D-printed frame, coils wound on nails, and rare-earth magnets glued to a rotor, this is an approachable build that lays the internals of a stepper motor out for all to see and understand. You can easily watch how the rotor lines up as the various coils are energized in a circular pattern, although it might be more revealing to include bi-color LEDs to indicate which coils are energized and what the polarity is. Those would be especially helpful demonstrating the concept of half-stepping. We’d also like to see more detail on the controller electronics, although admittedly all the video-worthy action is in the motor itself.

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Robot on Rails for Time Lapse Photography

What do you get when you cross a photographer with an Arduino hacker? If the cross in question is [nukevoid], you wind up with a clever camera rail that can smoothly move with both shift and rotation capability. The impressive build uses an Arduino Pro Mini board and two stepper motors. One stepper moves the device on rails using some Delrin pulleys as wheels that roll on an extruded aluminum track. The other stepper rotates the camera platform.

The rotating platform is very cool. It’s a plastic disk with a GT2 motion belt affixed to the edge. The stepper motor has a matching pulley and can rotate the platform easily. The GT2 belt only goes around half of the disk, and presumably the software knows when to stop on either edge based on step counts. There’s even a support to steady the camera’s lens when in operation.

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Hackaday Prize Entry: Orchestral Invention Defies Convention

Like many of us, [Laurens] likes video game music and bending hardware to his will. Armed with a Printrbot, a couple of floppy drives, and some old HDDs, he built the Unconventional Instrument Orchestra. This 2015 Hackaday Prize contender takes any MIDI file and plays it on stepper and solenoid-based hardware through a Java program.

A while back, [Laurens] won a Fubarino in our contest by using a MIDI keyboard and an Arduino to control the Minecraft environment with Legend of Zelda: Ocarina of Time songs. The Unconventional Instrument Orchestra uses that Fubarino of victory to control the steppers of two floppy drives. He only needed three pins to control the drives—one to enable, one to set the head’s direction, and one to make it step once per pulse.

If ever you’ve been around a 3D printer, you know they make music as a natural side effect. The problem is getting the printer to obey the rests in a piece of music. In order to do this, [Laurens] used his software to control the printer, essentially withholding the next command until the appropriate time in the song.

The percussive elements of this orchestra are provided by a hard drive beating its head against the wall. Since it’s basically impossible to get an HDD to do this as designed (thankfully), [Laurens] replaced the control board with a single transistor to drive the coil that moves the head.

[Laurens] has made several videos of the orchestra in concert, which are a joy all their own. Most of the visual real estate of each video is taken up with a real-time visualization of the music produced by the software. There’s still plenty of room to show the orchestra itself, song-specific gameplay, and a textual commentary crawl in 16-segment displays. Check out the playlist we’ve embedded after the break.

The 2015 Hackaday Prize is sponsored by:

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Rotary Indexer gives Mill a 4th axis (sort of)

Rotary indexer’s are standard issue in most machine shops. These allow you to hold or chuck a work piece, and then a graduated handle lets you to rotate the workpiece. Useful when you want to drill or tap axial or radial features. A rack and pinion drive ensures that the workpiece does not move under machining load. Quite often, these indexers also have a manual lock to take care of gear backlash and play. Automating them is not too difficult either. You could use just a stepper motor (open loop) or servo+encoder (closed loop) to drive the turntable.

[smashedagainst] needed to drill six radial holes on a part. And he had to do it on 500 pieces for a total of 3000 holes. That was just for the first initial run, with more drilling likely in the future. The part in question was small and light weight. So instead of using a heavy duty, industrial grade unit, he built an all-electric rotary indexing jig using a stepper motor and an Arduino, giving him a sort of rotary 4th axis. His idea was to directly use the stepper motor to rotate the workpiece without any gearing, but he needed to build his own rig to do so.

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