Interfacing An Old Engine Cowl Flaps Indicator To USB

November 29, 2022 by Dave Rowntree 9 Comments

[Glen Akins] had a WW2-era aircraft engine cowl flap indicator lying around (as you do) and thought it would make a jolly fine USB-attached indicator. The model in question is a General Electric model 8DJ4PBV DC Selsyn, which was intended for four-engined aircraft. For those not familiar with the purpose [Glen] explains in his detailed writeup, that piston-engine aircraft of that era were air-cooled, and during conditions of maximum engine power — such as during take-off — flaps on the side of the engine cowling could be opened to admit additional cooling airflow. These indicator dials were connected to a sender unit on each of the flap actuators, providing the pilots an indication of the flaps’ positions. Continue reading “Interfacing An Old Engine Cowl Flaps Indicator To USB” →

Break The Caps Lock Habit With This Annoying Buzzer

November 13, 2019 by Tom Nardi 57 Comments

The much-maligned Caps Lock key has been causing problems for decades, and its continued existence is controversial enough that Google decided to drop it all together in their Chromebooks. Until the rest of the industry decides to follow their lead, they’ll likely be no shortage of awkward emails or overly aggressive comments that are the direct result of this treacherous key.

But [Glen Akins] thinks he has the solution. His creation is a tiny little USB notification device that has only one purpose: to make a terrible noise as long as the Caps Lock key is engaged. Think of it like the little indicator LED on your keyboard, but one that makes a terrible screeching noise that you simply can’t ignore. This is made possible by the fact that the Caps Lock status is handled at the OS level rather than the local input device.

The notifier is built around the PIC16F1459, as it allowed him to implement USB 2.0 while keeping the part count low. Beyond the PIC, the board uses a handful of passives and a transistor to drive the buzzer from a PWM signal. To avoid duplicated effort, everything was designed to fit inside the enclosure he already developed for his single-key keyboard that we covered last year. [Glen] and a fellow coworker from Keysight put together an excellent video on the creation and use of the buzzer that you can see after the break.

On the other end of the spectrum, and even smaller, is the “USB Capslocker” which is designed to weaponize this already troublesome feature of your keyboard.

Continue reading “Break The Caps Lock Habit With This Annoying Buzzer” →

One-key Keyboard Is Exercise In Sub-millimeter Design

May 19, 2018 by Donald Papp 15 Comments

As [Glen] describes it, the only real goal in his decision to design his single-key USB keyboard was to see how small he could build a functional keyboard using a Cherry MX key switch, and every fraction of a millimeter counted. Making a one-key USB keyboard is one thing, but making it from scratch complete with form-fitting enclosure that’s easy to assemble required careful design, and luckily for all of us, [Glen] has documented it wonderfully. (Incidentally, Cherry MX switches come in a variety of qualities and features, the different models being identified by their color. [Glen] is using a Cherry MX Blue, common in keyboards due to its tactile bump and audible click.)

[Glen] steps though the design challenges of making a device where seemingly every detail counts, and explains problems and solutions from beginning to end. A PIC16F1459, a USB micro-B connector, and three capacitors are all that’s needed to implement USB 2.0, but a few other components including LED were added to help things along. The enclosure took some extra care, because not only is it necessary to fit the board and the mounted components, but other design considerations needed to be addressed such as the depth and angle of the countersink for the screws, seating depth and clearance around the USB connector, and taking into account the height of the overmold on the USB cable itself so that the small device actually rests on the enclosure, and not on any part of the cable’s molding. To top it off, it was also necessary to adhere to the some design rules for minimum feature size and wall thicknesses for the enclosure itself, which was SLS 3D printed in nylon.

PCB, enclosure, software, and bill of materials (for single and triple-key versions of the keyboard) are all documented and available in the project’s GitHub repository. [Glen] also highlights the possibility of using a light pipe to redirect the embedded LED to somewhere else on the enclosure; which recalls his earlier work in using 3D printing to make custom LED bar graphs.