# Exploring Woodworking Mysteries With Strain Gauges And Raspberry Pi

If you’re not a woodworker, you might not have heard of the “45-degree rule.” It goes like this: a clamp exerts a force that radiates out across a triangular region of the wood that forms a right angle — 45 degrees on each side of the clamp’s point of contact. So, to ensure that force is applied as evenly as possible across the entire glue joint, clamps should be spaced so that these force triangles overlap. It’s a handy rule, especially for the woodworker looking to justify the purchase of more clamps; you can never have too many clamps. But is it valid?

The short answer that [ari kardasis] comes up with in the video below is… sort of. With the help of a wonderfully complex array of strain gauges and a Raspberry Pi, he found that the story isn’t so simple. Each strain gauge lives in a 3D printed bracket that spaces the sensors evenly along the wood under test, with a lot of work going into making the test setup as stiff as possible with steel reinforcement. There were some problems with a few strain gauges, but once he sorted that out, the test setup went into action.

[ari] tested clamping force transmission through pieces of wood of various widths, using both hardwoods and softwoods. In general, he found that the force pattern is much broader than the 45-degree rule suggests — he got over 60 degrees in some cases. Softwoods seemed to have a somewhat more acute pattern than hardwoods, but still greater than the rulebook says. At the end of the day, it seems like clamp spacing of two board widths will suffice for hardwoods, while 1.5 or so will do for softwoods. Either way, that means fewer clamps are needed.

A lot of woodworking is seat-of-the-pants stuff, so it’s nice to see a more rigorous analysis like this. It reminds us a lot of some of the experiments [Matthia Wandel] has done, like load testing various types of woods and glues.

# Binary Calculator For All 0b10 Types

You know the old joke: There are 10 types of people in the world — those who understand binary, and those who don’t. Most of us on Hackaday are firmly in the former camp, which is why projects like this circuit sculpture binary calculator really tickle our fancies.

Inspired by the brass framework and floating component builds of [Mohit Bhoite], [dennis1a4] decided to take the plunge into circuit sculpture in an appropriately nerdy way. He wisely decided on a starter build, which was a simple 555 timer circuit, before diving into the calculator. Based on an ATMega328P in a 28-pin DIP, the calculator is built on an interesting hybrid platform of brass wire and CNC-routed wood. The combination of materials looks great, and we especially love the wooden keycaps on the six switches that make up the keyboard. There’s also some nice work involved in adapting the TLC5928 driver to the display of 16 discrete LEDs; suspended as it is by fine magnet wires, the SSOP chip looks a bit like a bug trapped in a spider web.

Hats off to [dennis1a4] for a great entry into our soon-to-conclude Circuit Sculpture Contest. The entry deadline is (today!) November 10, so it might be a bit too late for this year. But rest assured we’ll be doing this again, so take a look at all this year’s entries and start thinking about your next circuit sculpture build.

# Hacklet 17 – Keyboards

This week on The Hacklet we’re featuring some of the best keyboard hacks from Hackaday.io!

Hackers are really into their keyboards. Everyone has a favorite, and those favorites vary wildly. Mechanical, soft touch, ergonomic, QWERTY, DVORAK, chorded, you name it, there is a hacker, maker, or engineer who loves it, or absolutely hates it. For some, no commercial product is perfect. All is not lost though, as a custom keyboard is just a hack away!

[Warren Janssens] gets things rolling with Ergo60, his 60 key ergonomic keyboard. [Warren’s] layout is a pair of 25 key hand clusters, each with a matching 5 key thumb cluster. This layout minimizes lateral wrist movement. With the reduced key count and stacked keys, the user’s hands never move from the home row. [Warren] rolled his own PCBs for Ergo60. A Teensy 2.0 running a fork of TMK serves as Ergo60’s controller. [Warren’s] is running Cherry Black switches and his keycaps are from Signature Plastics. [Warren] is using Ergo60 as his daily driver these days, so it’s no surprise that he’s set the “Completed Project” tag.

Some say he needs no keyboard at all, and that his heartbeat sounds just like an IBM Model M. All we know is he’s called [Brian Benchoff]. [Brian’s] created a pair of minimalist keyboard projects. The Unhappy Hacking Keyboard takes us back to basics. After all, computers run on 1’s and 0’s, right? What more could a person need? Apparently just a space and return. Unhappy Hacking Keyboard uses an ATtiny85 with V-USB as the controller and the interface. Keys are cherry MX blues. The keycaps are [Brian’s] own Hackaday Cherry MX Keycaps printed by Shapeways.

An entire generation of hackers don’t know the joy of typing on a tiny rubber keyboard. [Alistair MacDonald] aimed to fix that, so he turned an old computer into a keyboard with his ZX Keyboard. [Alistair] started with a broken ZX Spectrum. He gutted the original electronics and added an Ardunio Pro Mini running the V-USB library. [Alistair] directly wired the row and column I/O lines from the keyboard to his Arduino. The result is a keyboard which is the perfect size for cell phones, Raspberry Pi’s and the like.

[Servo] teaches us new ways to type with Chordy KEY, his chording keyboard project. Chordy Key is meant to be used in the left hand. Five finger buttons and three thumb buttons are all that is needed to chord out 64 different letters and symbols. [Servo] utilized an ATmega32U4 powered Sparkfun pro micro to control his keyboard. Chordy Key is a proof of concept, but with [Servos’s] use of 3D printed parts, Chordy Key looks like it’s ready for your next wearable computing project!

[jmptable] is also working on a chorded keyboard design. Chord Keyboard uses only 7 keys to send the entire ASCII character set and a few control combinations. [jmptable] used an ATmega328P as his processor. Chord keyboard isn’t wired though. An RN-42-HID module provides bluetooth connectivity to the world.

[jmptable] has provided an amazing amount of detail on his research, including one of his goals of adding a chorded keyboard to the Gameboy Advance. They keyboard itself would be mounted on the spine of a game cartridge. We would love to see that idea come to fruition, [Servo]!

Finally we have [Gertlex], who just wanted a scroll wheel embedded in his keyboard. He got there with the help of an Apple Mighty Mouse. Keyboard with Apple Mouse Scroll Ball is one of those hacks that looks like it original equipment. [Gertlex] took a drill to a Targus slim USB keyboard, putting a small hole right between the ESC and F1 keys. He fit the scroll ball from his Apple Mighty Mouse in the hole. Electronics are as simple as plugging the mouse and keyboard into the same USB hub. The only downside to the design is that [Gertlex’s] keyboard doesn’t recognize fast enough to send key presses during the boot process.

That’s just about enough keystrokes for this episode of The Hacklet. As always, see you next week. Same hack time, same hack channel, bringing you the best of Hackaday.io!

Update – check our our keyboard list right here!

# Hacking The Right Side Of A Keyboard Completely Off

The form factor of this keyboard just doesn’t look right. What’s missing? Oh, the numpad has been completely removed! We use our numpad almost exclusively (especially when coding) so it’s a little hard to figure out why [Ludw] did this. His only mention of motive is that he wanted the mouse closer to the main part of the keyboard and that he didn’t use the numpad. No matter what the reason, we still think he did an amazing job of giving new life to the older keyboard.

It started out as a plain old beige Cherry G80-3000 keyboard. After cracking open the case [Ludw] carefully traced out the connections between the key matrix and the PCB which provides the USB connection. This is because the controller is mounted over on the part of the PCB he his about to remove. Before making the cuts he desoldered all seventeen switches (these can be reused to fabricate a new keyboard, or add switches to various projects). He then lopped off the depopulated substrate and used point-to-point soldering to reconnect the controller. A bit of case alteration removed the extra space while also reusing the nicely molded edges. A clean and tidy paint job finishes the hack.

[via Reddit]