GRBL compatible Arduino CNC shield


By the time you get to the point in a home CNC build where you’re adding control electronics you may be ready for the simplest means to an end possible. In that case, grab your Arduino and heat up that etching solution to make your own GRBL compatible shield.

This familiar footprint manages to contain everything you need for a three-axis machine. The purple boards slotted into the pairs of SIL headers are Pololu Stepper motor drivers. Going this route makes replacing a burnt out chip as easy as plugging in a new module. The terminal block in the center feeds the higher voltage rail necessary for driving the motors. The DIL header on the right breaks out all of the connections to the limiting switches (two for each axis), spindle and coolant control, as well as three buttons for pause, resume, and abort. There’s even a header for SPI making it easier to add  custom hardware if necessary.

This is a dual-layer board which may not be ideal for your own fabrication process. [Bert Kruger] posted his Gerber files for download if you want to put in a small run with OSH Park or a similar service.


Use your ears as an oscilloscope


When work on an engine control circuit [Scott] found himself in need of a way to compare the performance of two control circuits at once. The hobby quality oscilloscope he owns wasn’t up to the task. After thinking about it for a bit he ended up using his ears as the oscilloscope.

The signals he was measuring are well suited for the challenge as they fell within the human range of hearing. He used some wire wrapped around each of the three conductors on the jack of his headphones in order to connect them to a breadboard. Then he simply connected each channel to one of the motor driver circuits, and connected the common ground. Listening to the intonation of the pitches in each ear he was literally able to tune them up.

If he had been looking for a specific frequency he could have used his sound card to take and analyze a sample. But balance was what he needed here and you must admit that this was an easy and clever way to get it!

Qube robots use well-designed laser-cut acrylic

These robot cubes, called BOXZ, use an interesting interlocking part design to mount and protect the parts within. But to really make them pop you need to color and apply your own papercraft skins.

The actual hardware is quite simple. They’ve used an Arduino, along with motor driver and Bluetooth shields, to control a set of geared DC motors. There’s a battery pack which holds four AA cells and a pair of servo motors which seem to be there to act as arms. This base can then be adorned with sensors to add functionality (line following, wall following, obstacle avoidance, etc.).

Despite the simple appearance of the cube, the chassis is the most complicated part. It uses sixteen pieces of acrylic, but they may also be hand cut from cardboard by printing out templates and gluing them onto the material. The parts are designed with interlocking tabs which we often see used on laser-cut wooden box parts.

We’ve embedded the video presentation of BOXZ after the break.

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Doubling down on motor drivers

Motor driver chip too weak for your needs? Just use two of them. That’s the advice which [Starlino] gives. He stacks motor driver chips to product move powerful controllers.

When stacked as shown, the driver combos should be able to drive at 4A. This is partly because he ganged together the outputs in pairs, and also because of the stacking. That’s a lot of juice, but [Starlino] documented his testing stage which shows that they’re up to it. It’s a bit hard to see from this angle, but he is using a serpentine heat sink. It snakes its way between the stack of chips, then over the top chip before folding back and spreading its wings. The motors he’s using have a stall current of 3.7A, and he included resettable fuses graded at a 2A hold current. He’ll be glad to have that extra protection is something goes wrong with the drivers.

[Thanks Roger]

Building a Variable Frequency Drive for a three-phase motor

Here are the power and driver boards that [Miceuz] designed to control a three-phase induction motor. This is his first time building such a setup and he learned a lot along the way. He admits it’s not an industrial quality driver, but it will work for motors that need 200 watts or less of power.

The motor control board uses an MC3PHAC driver IC and an IRAMS06UP60A handles the power side of things. The majority of the board design came from studying the recommended application schematics for these two parts. But that’s far from all that goes into the setup. Motor drivers always include levels of protection (the whole reason to have a driver in the first place) and that comes in several different forms. [Miceuz] made sure to add EMI, over voltage, and over current protection. He discusses all of these, sharing links that explain the concepts of each.

Fully loaded electronics lab makes your projects a breeze

There’s really nothing special about this hack. [Craig Hollabaugh] needed an Arduino shield for hosting a Pololu motor driver and making connections to external hardware. What really caused us to spend way too much time reviewing his posts is that [Craig's] narrative style of documenting the project is delightful, and we’re envious of his electronics lab. That link points to the first of four project pages. The next page is linked at the bottom of each page, or you can find the collection after the break.

[Craig] starts by designing a single-sided shield in Eagle. It’s been years since he made his own PCB, and it takes him about four tries to get the toner transfer right (we’ve also been victim to the wrong mirroring of the resist!). When it comes time to drill for the pin headers [Craig] uses his 3D printer to make a bracket allowing the Dremel to mount to the drill press. There’s a good tip here about buying carbide bits from Harbor Freight; we thought eBay was the only place to get these. Many of us would need to put in a parts order, but this workshop has a well-organized stock of everything he needs. He also has the solder paste and PID outfitted toaster oven to reflow the board. Oh, and when he forgets to add a resistor it’s off the rework station to add one.

See what we mean… one can never have too many tools.

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