sensor

254 Articles

Three-Conductor Pivot For E-Textiles Is Better Than Wires

February 13, 2019 by 1 Comment

Pivots for e-textiles can seem like a trivial problem. After all, wires and fabrics bend and flex just fine. However, things that are worn on a body can have trickier needs. Snap connectors are the usual way to get both an electrical connection and a pivot point, but they provide only a single conductor. When [KOBAKANT] had a need for a pivoting connection with three electrical conductors, they came up with a design that did exactly that by using a flexible circuit board integrated to a single button snap.

This interesting design is part of a solution to a specific requirement, which is to accurately measure hand movements. The photo shows two strips connected together, which pivot as one. The metal disk near the center is a magnet, and underneath it is a Hall effect sensor. When the wrist bends, the magnet is moved nearer or further from the sensor and the unit flexes and pivots smoothly in response. The brief videos embedded below make it clear how the whole thing works.

Continue reading “Three-Conductor Pivot For E-Textiles Is Better Than Wires” →

Piezoelectric Gyro Shows How They Rolled Back In The Day

February 7, 2019 by 4 Comments

There’s no doubting the wonders that micro-electromechanical systems (MEMS) technology have brought to the world. With MEMS chips, your phone can detect the slightest movement, turning it into a sensitive sensor platform that can almost anticipate what you’re going to do next. Actually, it’s kind of creepy when you think about it.

But before nano-scale MEMS inertial sensing came along, lots of products needed to know their ups from their downs, and many turned to products such as this vibrating piezoelectric gyroscope that [Kerry Wong] found in an old camcorder. The video below shows a teardown of the sensor, huge by MEMS standards but still a marvel of micro-engineering. The device is classified as a Coriolis vibratory gyroscope (CVG) which, as the name implies, uses the Coriolis effect to sense rotation. In this device, [Kerry] found that a long, narrow piezoelectric element spans the long axis of the sensor, suspended from what appears to be four flexible arms. [Kerry] probed the innards of the sensor while powered up and discovered a 22 kHz signal on the piezo element; this vibrates the bar in one plane so that when it rotates, it exerts a force on the support arms that can be detected. Indeed, [Kerry] hooked the output of the sensor to a wonderfully old-school VOM whose needle wiggled with the slightest movement of the sensor.

Sadly, MEMS made this kind of sensor obsolete, but we appreciate the look under the hood. And really, MEMS chips are using the same principle to detect motion, just on a much smaller scale. Want the MEMS basics? [Al] has you covered.

Continue reading “Piezoelectric Gyro Shows How They Rolled Back In The Day” →

Color Sensor Demystified

January 23, 2019 by 13 Comments

When [millerman4487] bought a TCS230-based color sensor, he was expecting a bit more documentation. Since he didn’t get it, he did a little research and some experimentation and wrote it up to help the rest of us.

The TCS3200 uses an 8×8 array of photodiodes. The 64 diodes come in four groups of 16. One group has a blue filter, one has green and the other has a red filter. The final set of diodes has no filter at all. You can select which group of diodes is active at any given time.

Continue reading “Color Sensor Demystified” →

Howto: Docker, Databases, And Dashboards To Deal With Your Data

January 23, 2019 by 36 Comments

So you just got something like an Arduino or Raspberry Pi kit with a few sensors. Setting up temperature or motion sensors is easy enough. But what are you going to do with all that data? It’s going to need storage, analysis, and summarization before it’s actually useful to anyone. You need a dashboard!

But even before displaying the data, you’re going to need to store it somewhere, and that means a database. You could just send all of your data off into the cloud and hope that the company that provides you the service has a good business model behind it, but frankly the track records of even the companies with the deepest pockets and best intentions don’t look so good. And you won’t learn anything useful by taking the easiest way out anyway.

Instead, let’s take the second-easiest way out. Here’s a short tutorial to get you up and running with a database backend on a Raspberry Pi and a slick dashboard on your laptop or cellphone. We’ll be using scripts and Docker to automate as many things as possible. Even so, along the way you’ll learn a little bit about Python and Docker, but more importantly you’ll have a system of your own for expansion, customization, or simply experimenting with at home. After all, if the “cloud” won’t let you play around with their database, how much fun can it be, really?

Continue reading “Howto: Docker, Databases, And Dashboards To Deal With Your Data” →

Smartphone App Uses AR To Visualize The RF Spectrum

January 9, 2019 by 21 Comments

Have you ever wished you could see in the RF part of the radio spectrum? While such a skill would probably make it hard to get a good night’s rest, it would at least allow you to instantly see dead spots in your WiFi coverage. Not a bad tradeoff.

Unwilling to go full [Geordi La Forge] to be able to visualize RF, [Ken Kawamoto] built the next best thing – an augmented-reality RF signal strength app for his smartphone. Built to aid in the repositioning of his router in the post-holiday cleanup, the app uses the Android ARCore framework to figure out where in the house the phone is and overlays a color-coded sphere representing sensor data onto the current camera image. The spheres persist in 3D space, leaving a trail of virtual breadcrumbs that map out the sensor data as you warwalk the house. The app also lets you map Bluetooth and LTE coverage, but RF isn’t its only input: if your phone is properly equipped, magnetic fields and barometric pressure can also be AR mapped. We found the Bluetooth demo in the video below particularly interesting; it’s amazing how much the signal is attenuated by a double layer of aluminum foil. [Ken] even came up with an Arduino with a gas sensor that talks to the phone and maps the atmosphere around the kitchen stove.

The app is called AR Sensor and is available on the Play Store, but you’ll need at least Android 8.0 to play. If your phone is behind the times like ours, you might have to settle for mapping your RF world the hard way.

Continue reading “Smartphone App Uses AR To Visualize The RF Spectrum” →

Arduino Heart Rate Monitor Has Star Trek Chic

December 23, 2018 by 10 Comments

Building a real-life version of the Star Trek tricorder has been the goal of engineers and hackers alike since the first time Dr McCoy complained about being asked to work outside of his job description. But while modern technology has delivered gadgets remarkably similar in function, we’ve still got a long way to go before we replicate 24th century Starfleet design aesthetic. Luckily there’s a whole world of dedicated hackers out there who are willing to take on the challenge.

[Taste The Code] is one such hacker. He wanted to build himself a practical gadget that looked like it would be at home on Picard’s Enterprise, so he gathered up the components to build a hand-held heart rate monitor and went in search for a suitable enclosure. The electronics were simple enough to put together thanks to the high availability and modularity we enjoy in a post-Arduino world, but as you might expect it’s somewhat more difficult to put it into a package that looks suitably sci-fi while remaining functional.

Internally his heart rate monitor is using an Arduino Pro Mini, a small OLED screen, and a turn-key pulse sensor which was originally conceived as a Kickstarter in 2011 by “World Famous Electronics”. Wiring is very simple: the display is connected to the Arduino via I2C, and the pulse sensor hooks up to a free analog pin. Everything is powered by 3 AA batteries delivering 4.5 V, so he didn’t even need a voltage regulator or the extra components required for a rechargeable battery pack.

Once everything was confirmed working on a breadboard, [Taste The Code] started the process of converting a handheld gyroscopic toy into the new home of his heart rate monitor. He kept the battery compartment in the bottom, but everything else was stripped out to make room. One hole was made on the pistol grip case so that a finger tip could rest on the pulse sensor, and another made on the side for the OLED screen. This lets the user hold the device in a natural way while getting a reading. He mentions the sensor can be a bid fiddly, but overall it gives accurate enough readings for his purposes.

If you’re more interested in the practical aspects of a real-life Star Trek tricorder we’ve seen several projects along those lines over the years, including a few that were entered into the Hackaday Prize.

Continue reading “Arduino Heart Rate Monitor Has Star Trek Chic” →

Cyborg, Or Leafy Sensor Array?

December 12, 2018 by 17 Comments

Some plants react quickly enough for our senses to notice, such as a Venus flytrap or mimosa pudica. Most of the time, we need time-lapse photography at a minimum to notice while more exotic sensors can measure things like microscopic pores opening and closing. As with any sensor reading, those measurements can be turned into action through a little trick we call automation. [Harpreet Sareen] and [Pattie Maes] at MIT brought these two ideas together in a way which we haven’t seen before where a plant has taken the driver’s seat in a project called Elowan. Details are sparse but the concept is easy enough to grasp.

We are not sure if this qualifies as a full-fledged cyborg or if this is a case of a robot using biological sensors. Maybe it all depends on which angle you present this mixture of plant and machine. Perhaps it is truly is the symbiotic relationship that the project claims it to be. The robot would not receive any instructions without the plant and the plant would receive sub-optimal light without the robot. What other ways could plants be integrated into robotics to make it a bona fide cyborg?

Continue reading “Cyborg, Or Leafy Sensor Array?” →