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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Electronic Ruler Works Out Logic Truth Tables

Like [Brad], we’ve seen a number of PCB rulers out there. [Brad] was looking to take the idea and run with it. His DigiRule is a ruler with a logic gate simulator. What he built is a mash-up between PCB rulers, and the concept of electronic business cards.

All told it simulates seven logic gates, four flip-flops, and includes a four-bit counter. On one end of the ruler a CR1220 battery feeds the 18F43K20 which is performing the logic operations using buttons and LEDs. Of course the truth tables are printed on the back silk-screen, but playing with the lights is a lot more fun. We do find it fairly amusing that the centimeters on the bottom of the ruler are notated in binary.

It makes a lot more sense to hand out rulers than business cards; people might actually use them after you leave and you can still include contact info. This form-factor also breaks the mold. You can have a lot more space on a ruler and you’re not constrained by thickness (although [Limpkin] solved that problem). While we’re on the topic of business cards [ch00f’s] USB etch-a-sketch style card and this logic-based information delivery device top our favorites list.

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What do you get if you cross a software defined radio (SDR) and an iconic children’s drawing toy that we are sure is a trademarked name? If you are [devnulling], you wind up with the Etch-A-SDR. The box uses an Odroid C1, a Teensy, and the ubiquitous RTL-SDR.

The knobs work well as control knobs (as you can see in the video below). When you are bored listening to the radio, you can reset the box and go into Etch-a… um, drawing mode. The knobs work like you’d expect and you can even erase the screen with a vigorous shake.

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Peculiar Radial Mill from Car Parts

Whether 3D printer, lasercutter, or mill, most CNC machines use human-friendly, square-angle Cartesian geometry. This intriguing concept mill instead uses radial axes where motion is derived from scrap Chevy flywheels. It may look and feel weird at first, but it works – sort of.

Cartesian axes are intuitive. If you want to go to the right, increase X. If you want to go to away from you, increase Y. If you want to lift, increase Z. On a manual mill this is easy for making rectangles and blocks, or, with creative clamping, straight lines of any sort. But if you want to carve a circle? As we all learned on an Etch-A-Sketch, you increase your swearing and then throw it in the corner.

HAD - Radial Mill2[Jason] knew that with a CNC machine all geometry problems are reduced to math done by software. With two offset discs, any position is possible by rotating both the correct way. It may look odd that both plates drunkenly meander about just to draw a straight line but the computer is ambivalent. Software can be complicated without penalty and is free once written – more on that later. If a machine is physically simple then it can be built and repaired easily and cheaply. This design does away with almost all the familiar – and [Jason] argues complicated – components of normal hobby CNC machines. No slides, rails, carriages or belts here. His design uses only about a dozen parts.

Because automotive flywheels are made from cast iron the machine is rigid and naturally dampening. Sticking with the junkyard theme he pulled bearings from an F-450 truck, good for a few thousand pounds. Some steppers and a Raspberry Pi and he was done – well, sort of.

[Jason] let us know that his project has sat for long enough that he has become passionate about other things and decided to move on. He documented his progress and submitted the tip in hope to inspire someone else to continue the design further. Any type of CNC is possible, not just a mill. 3D printer perhaps?

Two big caveats: it needs a Z-axis (linear, probably standard) and there appears to be deeper-seated-than-expected G-code demands to chit-chat about rectangles and only rectangles. Nothing insurmountable, just nothing he has solved yet himself.

[Jason] said not to expect any further updates from him but he would love to see what the next person could do with it.

See the video after the break of the mill drawing our skull and wrenches logo, (soft of, without a Z-axis to lift).

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The Thurber Feeder 5000 Helps to Slow Fido Down

Does your dog eat too fast? [Thurber] does, and he even chokes occasionally while snarfing down the kibble — naturally this worried his owners, so [Jason] stepped up to the challenge to slow him down. Introducing the Thurber Feeder 5000.

[Jason] is a seasoned maker, and has built a few CNC machines in his day — he’s even automated an Etch a Sketch with stepper motors. Making the Thurber Feeder 5000 was a piece of cake. He designed the entire thing in 3D CAD and then used his home-made CNC machine to cut out all the parts, 3D printing a few of the more complex mounting brackets.

It’s a fairly simple device consisting of a food hopper (seal-able to keep Thurber away), a stepper motor and an auger bit borrowed from a chocolate fondue fountain. The stepper goes through a 6:1 belt pulley ratio which gives it a whopping 200 oz-in of torque to push those kibbles and bits through the feeding pipe. The speed is adjustable by programming the Parallax Propeller, so once they found an acceptable eating speed [Jason] set it as default. A single button turns it on, and while the machine is running it lights up — turning off when little [Thurber] is done.

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Hackaday Links: July 20, 2014


Etch-a-Sketch spray-painted silver with electronics bolted onto the side? Sign us up! This art installation adds one thing that we don’t often see in these types of hacks, eerie audio.

If you’re still mining bitcoin you need to do it faster than anyone else… that’s pretty much how the whole thing works. [Lewin] has been using the Antminer USB ASIC and toyed around with overclocking to 2.2 GH/s (gighashes per second) but to make sure his hardware holds up to the overwork he hacked his own water cooling system for the dongle.

Smart phones are the best bang for your buck on portability and power. Better yet you can get slightly broken ones for a song. If you manage to find an Android device with a broken touch screen but functioning LCD try this trick to add a mouse to it. There must be another life for this in a future hack!

We have a love-hate relationship with this particular crowd-funding campaign. First this hate: It’s basically a 100% clip-art video presentation with an $800,000 ask. Yeah… good luck buddy. On the other hand, this is the type of stuff we actually want to see as crowd funding. The idea is to use modern materials and techniques to build [Nikola Tesla’s] Wardenclyffe Tower, which was designed and built to research wireless energy (both as a means of communication and actual energy transfer). It was never fully functional and ended up being demolished. Wouldn’t it be great if teams of highly skilled and motivated people took grand ideas like this, crossing every theoretical “t” and dotting every theoretical “i”, and then proposed a crowd funding campaign to build a test platform? Oh wait, that sounds very much like a government research grant. Anywhoo… check out the Global Energy Transmission’s campaign.

Isoscel-Ease Drawing Robot is Mesmerizing

Isoscel Ease Drawing Robot

Drawing is difficult for a lot of people… So, why not build a robot to do it for you? [Darcy] had an idea for a rather unique drawing robot — he calls it the Isoscel-Ease.

Instead of using a boring XY gantry, a deltabot, or using a scissor linkage (actually that one is pretty cool!), [Darcy] decided to try harnessing of the power of triangle geometry! As you can probably guess, the linkage forms an isosceles triangle, hence the name. A pair of stepper motors increases and decreases the odd side of the triangle, allowing for a full range of continuous inky movement (there’s no pen actuator) over the page.

It’s a very cool little drawing robot, and it was completely designed in SketchUp — He has lots of photos of the build process and example drawings on his site — But don’t forget to stick around after the break to see a video of it in action!

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