Your caps lock key is, of course, there for a reason, and there are many legitimate situations when you need to type out long strings of capital letters. But we all know that it’s also quite the nuisance. If it’s not causing you to pull your hair out while trying to enter a password, then it’s being used by some irate stranger on the internet to yell obscenities at you. Your keyboard almost certainly has a light to let you know when caps lock is on, but that can be easy to miss. The solution is to make it impossible to ignore, which is what Glen Atkins’ Annoying CAPS LOCK Warning Buzzer does.
This device serves only one purpose: to sound an irritating buzzer whenever your caps lock is turned on. It plugs into your computer via standard USB cable, and it should work on any modern computer without the need for additional drivers or software. That’s because it relies on the fact that it’s your computer that stores the state of the caps lock function—not the keyboard itself. Whenever caps lock is activated, the computer sends out a periodic update to any attached keyboards telling them so and giving them the opportunity to turn on the caps lock status LED.
In this case, the Annoying CAPS LOCK Warning Buzzer looks like a keyboard to the computer. But instead of an LED, it turns on the buzzer when it receives the “caps lock on” message. This unit is nearly identical to Atkins’ previous One Key USB Keyboard project. It utilizes a Microchip PIC16F1459 microcontroller, which was chosen because it has a built-in USB 2.0 implementation that eliminates the needs for additional components. That keeps the parts count and size of the custom PCB down, while also making it easy to configure as a USB HID device.
The buzzer is sounded through a simple transistor, which is triggered by the output that would normally be used for the caps lock status LED. The entire thing is housed within a tiny and unobtrusive 3D-printed enclosure. Atkins also recently revised the device to improve the ground plane and ESD protection, and to add a button and status LED for switching the USB bootloader for firmware updates. If you often find yourself accidentally leaving caps lock on, this device would make for a great weekend project.