Raspberry Pi Trackpad From Salvaged Trackpad Plus Arduino

Old laptops are easy to find and many have a trackpad with a PS/2 interface hardwired into the guts of the laptop. [Build It] wanted one of those trackpads for use in the DIY Raspberry Pi laptop he’s working on. But the Raspberry Pi has no PS/2 input, and he read that a PS/2 to USB adapter wouldn’t be reliable enough. His solution? Wire the trackpad to an Arduino and have the Arduino convert the trackpad’s PS/2 to USB.

After removing a few screws, he had the trackpad free of the laptop. Looking up the trackpad’s part number online he found the solder pads for data, clock and five volts. He soldered his own wires to them, as well as to the trackpad’s ground plane, and from there to his Arduino Pro Micro. After installing the Arduino PS/2 mouse and the Mouse and Keyboard libraries he wrote some code (see his Instructables page). The finishing touch was to use generous helpings of hot glue to secure all the wires, as well as the Arduino, to the back to the trackpad. By plugging a USB cable into the Arduino, he now had a trackpad that could plug in anywhere as a USB trackpad. Watch [Build It] put it all together step-by-step in the video below.

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Bootstrapping Motion Input with Cheap Components

Motion control is a Holy Grail of input technology. Who doesn’t want an interface that they can control with simple and natural movements? But making this feel intuitive to the user, and making it work robustly are huge hills to climb. Leap Motion has done an excellent job creating just such a sensor, but what about bootstrapping your own? It’s a fun hack, and it will give you much greater appreciation for the currently available hardware.

Let’s get one thing straight: This device isn’t going to perform like a Leap controller. Sure the idea is the same. Wave your hands and control your PC. However, the Leap is a pretty sophisticated device and we are going to use a SONAR (or is it really SODAR?) device that costs a couple of bucks. On the plus side, it is very customizable, requires absolutely no software on the computer side, and is a good example of using SONAR and sending keyboard commands from an Arduino Leonardo to a PC. Along the way, I had to deal with the low quality of the sensor data and figure out how to extend the Arduino to send keys it doesn’t know about by default.

The Plan

The plan is to take an inexpensive SONAR module (the HC-SR04) and an Arduino Leonardo and use it to perform some simple tasks by mimicking keyboard input from the user. The Leonardo is a key element because it is one of the Arduinos that can impersonate a USB keyboard (or mouse) easily. The Due, Zero, and Micro can also do the trick using the Arduino library.

I wanted to determine how many gestures I could really determine from the HC-SR04 and then do different things depending on the gesture. My first attempt was just to have the Arduino detect a few fingers or a hand over the sensor and adjust the volume based on moving your hand up or down. What I didn’t know is that the default Arduino library doesn’t send multimedia keys! More on that later.

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What is the Matrix…Clock?

We’re surprised we haven’t seen this kind of clock before, or maybe we have, but forgot about it in the dark filing cabinets of our minds. The above picture of [danjhamer’s] Matrix Clock doesn’t quite do it justice, because this is a clock that doesn’t just tick away and idly update the minutes/hours.

matrix clock

Instead, a familiar Matrix-esque rain animation swoops in from above, exchanging old numbers for new. For the most part, the build is what you would expect: a 16×8 LED Matrix display driven by a TLC5920 LED driver, with an Arduino that uses a DS1307 RTC (real-time clock) with a coin cell battery to keep track of time when not powered through USB. [danjhamer] has also created a 3D-printed enclosure as well as added a piezo speaker to allow the clock to chime off customizable musical alarms.

You can find schematics and other details on his Hackaday.io project page, but first, swing down below the jump to see more of the clock’s simple but awesome animations.

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Physical Keys Not Just For Doors Anymore, Now Available For Windows

Physical Key Locks and Unlocks Windows Computer

If you have ever forgotten your computer password after a long weekend or maybe you can remember it but just can’t seem to type it correctly, [Thomas] has a project for you. It’s a physical key that locks and unlocks your PC.

So how does it work? The heart of the project is an Arduino Leonardo. You may recall that this board is a bit different from the preceding Arduinos as it can enumerate on a host computer as a Human Interface Device (HID), such as a keyboard or mouse. The Arduino sketch continually reads an input pin using an internal pull-up resistor to make it logic high with the key switch connecting the signal to ground. When the Arduino sees the pin change from high to low, it sends out a keyboard command consisting of the Windows Key and “L”, which is the keyboard shortcut for locking the computer.

When the physical key is turned again, the Arduino sees the pin change back to a high state and it again emulates a keyboard but this time enters your password. You do have to include your password in the Arduino sketch for this to work. In addition, there are two LED’s wired up to show if the computer is locked or not, but you’ll be able to tell pretty quick when trying to get back to work.

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Unlocking your Computer with a Leonardo and an NFC Shield

Manually typing your login password every time you need to login on your computer can get annoying, especially if it is long and complex. To tackle this problem [Lewis] assembled an NFC computer unlocker by using an Arduino Leonardo together with an NFC shield. As the latter doesn’t come with its headers soldered, a little bit of handy work was required.

A custom enclosure was printed in order to house the two boards together and discretely mount them under a desk for easy use. Luckily enough very few code was needed as [Lewis] used the Adafruit NFC library. The main program basically scans for nearby NFC cards, compares their (big-endianned) UIDs against a memory stored-one and enters a stored password upon match. We think it is a nice first project for the new generation of hobbyists out there. This is along the same lines as the project we saw in September.

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