Bluetooth Security and Capacitive Sensing Tool Cabinet Handles

Locking tool cabinet

[Andy] needed a new set of locks for his tool cabinets at work, but not wanting to carry around another key (or to remember a combination!) he decided to throw this little hack together — solenoid locking, capacitive sensing, tool cabinet door handles.

To do this he’s using a Bluetooth low energy breakout board coupled with an Arduino, two solenoid locks, and two capacitive sensors. He’s modified a pre-existing iPhone app to control the system, dubbed: The BlueLock Control.

When [Andy] is present with his phone, the system can be activated, allowing for automatic unlocking the moment you touch the metal handle. Usually he leaves it unlocked for the majority of the work day, but as soon as the day is done it’s just a simple swipe on his phone to engage lock mode for the night. And just in case he’s also added manual push-buttons for both solenoids in case anything goes wrong with the capacitive sensors. Cool hack [Andy!]

While you’re at it, why not make a keyless entry system for your car using Bluetooth too?

 

The State-Based Nixie Multimeter

state

Instead of numbers the IN-15A Nixie tube has symbols, specifically n, μ, P, -, +, m, M, k, Π, and %. The related IN-15B Nixie has letters: A, F, H, Hz, Ω, S, V, and W. These should look familiar to you. [kittan] decided it would be really cool to have a Nixie-equipped multimeter, and since he’s going retro fabulous anyway, he might as well make his multimeter controllerless, with discrete logic and comparator ICs. It’s a state-based Nixie multimeter, and it’s going to be freakin’ awesome.

The basic plan of the multimeter is a precision 1V voltage reference, a bunch of opamps, and a ton of resistors to form a ladder All the opamps in each decade are XOR’d together, so when one of the ten comparators for each decade stage is tripped, only one number will display on the (numeric) Nixie tube.

With a reasonable plan for measuring a voltage, it’s not too hard to expand the design for other measurements. V=IR, so with a constant current, V=R. The same equation can be used with a fixed resistance to determine current. Capacitance can be measured by comparing the change in charge of a known capacitor. Inductance, conductance, power, and frequency are all planned for this monster of a multimeter.

The initial PCB design is completed (and shown above) and it’s theoretically possible to do on a single-sided board with a minimum of jumpers. An amazing project, and even though you could probably find a similar, ancient meter in a trash heap or on a collector’s shelf, this is by far one of the best Nixie projects we’ve ever seen.

 

Wooden Band Saw Fears Its Wood-Cutting Brethren

DIY Wooden Bandsaw

What is cooler than building a band saw out of wood? Building two, of course! And that is exactly what [Pekka] did. The first was a small bench top model while the second was a much larger version with the saw blade strung between big 13-3/4 inch wheels. For those who are unfamiliar with band saws, they are tools that have a long thin blade that is routed around rotating wheels. The wheels are spread apart to make the blade taut. Unlike the reciprocating action of a jigsaw, saws-all or scroll saw, the band saw blade continually rotates in one direction. These blades are typically thin making it easy to cut irregular and curved shapes.

The frame of [Pekka's] larger machine is made from 35mm (~1-3/8″) plywood. This proved to be a sturdy frame material. The previously mentioned wheels were made by gluing pieces of oak together, mounting the assembly on a wood lathe and turning the outer diameter down to size. By using multiple piece of wood to construct the wheels allows the grain direction of each portion to be parallel with the blade. This method of construction ensures any expansion/contraction of the wood is uniform around the wheel. A strip of rubber around the blade’s outer diameter provides the friction required to prevent the blade from slipping.

[Pekka's] friend was nice enough to turn the flanged axle shafts on his metal lathe. These shafts support the wooded wheels and are mounted in pillow block bearings. The upper pillow blocks are mounted to a sliding support that allows adjusting the tension of the saw blade. [Pekka] was not going to be satisfied with a one-speed band saw so he grabbed a motor he had kicking around that originally came from a wood lathe and already had 4 different sized pulleys mounted on the shaft.

This is a great project that shows what can be done with a little desire and ingenuity.

Clever Re-purposing of a Power Drill Results in a Mini Wood Lathe

Power Drill Wood Lathe

Ever use a lathe? No? Neither had [Jack Hauweling], but that didn’t stop him from building his own and learning how!

Lathes are a lot of fun, especially for small wood working projects. Using mostly wood and a few small pieces of hardware, [Jack] was able to build one in an afternoon that works quite well!

He’s using a cheap corded power drill to drive the work piece, but what we really like is how he made the spur center and spur live center out of a few pieces of threaded rod and a standoff. It’s a simple system that lets him secure the work piece fairly easily simply by tightening the threaded shaft of the live center.

In the video after the break he goes through the entire build process and even shows off his first attempts at using the lathe — he actually was able to make a very nice tool grip on his third try!

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The Analog Swiss Army Knife

11300

While FPGAs get all the credit for being the hip new thing, they are inherently digital devices. Without a proper ADC and DAC, you won’t be delving into the analog domain with your programmable logic. Maxim has just put out a chip that does just that: an analog swiss army knife with 20 pins that are configurable as analog to digital converter, digital to analog converters, GPIO, or any mix of the above.

The MAX11300 includes twenty IO ports, each capable of becoming an ADC, DAC, or GPIO, with pairs of ports capable of being configured as a logic level translator or an analog switch. The ADCs and DACs are 12-bit, with input and output ranges from -10V to +10V.

As a nice little bonus, the chip is controlled over SPI, making this an interesting device for a small “do anything analog” tool we’re sure will hit Tindie or Seeed Studio before the year is out. Luckily for whoever would create such a device, Maxim has a nice GUI for configuring each of the 20 pins on their chip, Of course Maxim already offers an evaluation kit for the MAX11300. It’s $100 USD and is Windows only.

The MAX11300 is available in either 40-pin TQFN or 48-pin TQFP packages (with the larger, easier to solder TQFP shipping later) for about $5.80 USD in quantity 1000, or $11.37 in quantity one.Video below showing off the MAX11300 reading and writing analog values to a few pins, and a good look at the configuration software.

[Read more...]

Miter Saw Stop Saves Time and Aggravation

V Wheel Adjustable Miter Saw Stop

Miter saws are great tools for cutting pieces of wood at a variety of angles. If you have ever cut a really long piece on a miter saw there is no doubt you’ve either propped up the extended end on a pile of scrap wood or asked someone to hold the dangling piece so you could get an accurate cut. Doing either is a little hokey and is a general pain in the butt.

[Kram242] started a project that could eliminate these problems and also provides a solution to consistent length cuts of multiple pieces. It’s an adjustable stop that is sure to make miter saw cuts much less annoying.

The rig is extremely simple and consists of a piece of aluminum extrusion, v-wheel carriage and lever-actuated clamp. The movable carriage lets the operator quickly position the stop to ensure the wood is cut at the appropriate location. This stop also makes it easy to cut several pieces of wood to the exact same length.

If we had to make any suggestions for improvements it would be to add supports to the carriage that emulate the saw bed and backstop as well as an adhesive measuring tape guide.

V Wheel Adjustable Miter Saw Stop

I2C From Your VGA Port

Breakout board for VGA to I2C

VGA, DVI, and HDMI ports use Display Data Channel (DDC) to communicate with connected displays. This allows displays to be plug and play. However, DDC is based on I2C, which is used in all kinds of electronics. To take advantage of this I2C port on nearly every computer, [Josef] built a VGA to I2C breakout.

This breakout is based on an older article about building a $0.25 I2C adapter. This adapter hijacks specific lines from the video port, and convinces the kernel it’s a standard I2C device. Once this is done, applications such as i2c-tools can be used to interact with the port.

[Josef] decided to go for overkill with this project. By putting an ATmega328 on the board, control for GPIOs and LEDs could be added. Level shifters for I2C were added so it can be used with lower voltage devices. The end product is an I2C adapter, GPIOs, and LEDs that can be controlled directly from the Linux kernel through an unused video port.