This Vibrating Continuity Tester Is Quietly Useful

Continuity testing is one of the most valuable functions on the modern multimeter. It will help you investigate wiring problems in your car, tell you if you’re holding a nullmodem serial cable or the regular kind, and even reveal when you’ve accidentally shorted the data lines right to the power supply. However, all that beeping can get annoying, so [bitelxux] built a vibrating version instead.

The build was borne out of necessity; [bitelxux]’s meter lacked a buzzer, and it grew frustrating to always look at the display. In order to allow late night hacking sessions to go on undisturbed, an unobtrusive vibrating tester was desired, as opposed to the usual audible type. Two whiteboard markers donated their shells to the hack, fitted with small nails to act as probes. Inside, a pager vibration motor is connected, vibrating when continuity is found. The circuit runs from a 1.5V AA battery which neatly fits inside the marker shell.

It’s a basic build, but gets the job done with a minimum of fuss using parts that most makers probably have lying around. Of course, you can always go a slightly more complicated route and throw an Attiny at the problem.

Many Ways to Drive a Small Motor

Tiny motors used for haptic feedback and vibration come in a variety of shapes and sizes. The most familiar is the “eccentric rotating mass” (ERM) variety which just spins an imbalanced weight on a small motor and comes packaged in two form factors. The classic is the pager “pager motor” which just looks like a tiny, adorable motor and the squat cylindrical “pancake style”. ERMs are simple to use but provide imprecise response when compared to their new-age cousin the “linear resonant actuator”. Unlike the motor in an ERM, LRAs are typically an enclosed mass on a spring placed near a coil which pushes the mass back and forth. The name LRA might not be familiar but Apple’s branded implementation, the Taptic Engine, might be a little more recognisable.

[Precision Microdrives] is a vendor of these sorts of devices who happens to have a pleasantly approachable set of application notes covering any conceivable related topic. A great place to start is this primer on ways to drive motors with constant voltage in a battery powered environment. It starts with the most simple option (a voltage divider, duh) and works through a few other options through using an LDO or controller.

If you’re thinking about adding haptics to a project and are wondering what kind of actuator to use (see: the top of this post) AB-028 is a great resource. It has a thorough discussion on the different options available and considerations for mounting location, PCB attachment, drive modes, and more. Digging around their site yields some other interesting documents too like this one on mounting to fabric and other flexible surfaces. Or this one on choosing PWM frequencies.

A Haptic Bracelet for Physical Computing

[Tinkermax] has been reading about the Internet of Things and wearable computing and decided it was time for him to have a go at building a device that turned computing physical. The result is a vibrating wristband that connects his sense of touch to the Internet.

The electronics for this haptic wristband are a mix of old and new technology. The radio and microcontroller come from an ESP-8266 module that was programmed with [Mikhail Grigorev]’s unofficial SDK. The mechanics for the wrist-mounted computer consist of six pager motors mounted around the wrist. These are driven somewhat ingeniously by a TLC5917 LED driver chip. This meant the ESP would only need to use two of its GPIOs to control six motors.

Right now the software is simple enough; just a web page, a few buttons, and the ability to buzz any of the pager motors on the wrist band over the Internet. Now it’s just a question of making this wearable useful, but connecting each pager motor to different notifications – a new email, a new SMS, or some emergency on the Internet – should be pretty easy.

Video below.

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A Tiny Robot Family

Back in the late 80s and early 90s, a lot of young electronics hobbyists cut their teeth with BEAM robots – small robots made with logic chips and recycled walkmans that tore a page from papers on neural nets and the AI renaissance of the 80s. Twenty years later, a second AI renaissance never happened because a generation of genius programmers decided the best use of their mental faculties was to sell ads on the Internet. We got the Arduino, though, and the tiny robot family is a more than sufficient spiritual successor to the digital life of the old BEAM bots.

The tiny robot family is [shlonkin]’s growing collection of small autonomous vehicles that perceive the world with sensors and act with different behaviors. They all contain an ATtiny85, a small battery, two motors, and at least one phototransistor and a LED. One robot has left and right eyes pointing down, and can act as a line follower. Another has a group of LEDs around its body, allowing it to signal other bots in all directions. The goal of the project is to create a whole series of these tiny robots capable of interacting with the environment and each other. Video of the line follower below.

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Steerable bristlebot via IR control

Looking at the size of this bristlebot the first thing we wondered is where’s the battery? All we know is that it’s a rechargeable NiMH and it must be hiding under that tiny circuit board. But [Naghi Sotoudeh] didn’t just build a mindless device that jiggles its way across a table. This vibrating robot is controllable with an infrared remote control. It uses an ATtiny45 microcontroller to monitor an IR receiver for user input. An RC5 compatible television remote control lets you send commands, driving the tiny form factor in more ways than we thought possible. Check out the video after the break to see how well the two vibrating motors work at propelling the device. They’re driven using a PWM signal with makes for better control, but it doesn’t look like there’s any protection circuitry which raises concern for the longevity of the uC.

This build was featured in a larger post over at Hizook which details the history of vibrating robots. It’s not technically a bristlebot since it doesn’t ride on top of a brush, but the concept is the same. You could give your miniature fabrication skills a try in order to replicate this, or you can build a much larger version that is also steerable.

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