Use A Brushless Motor As A Rotary Encoder

The electric motor is the fundamental building block of almost all robotic projects but, without some form of feedback, it lacks the precise positional control required for the task. Small servos from the modelling world will often use a potentiometer to sense where they are on their travel, while more accomplished motors will employ some form of shaft encoder.

Commercial shaft encoders use magnets and Hall-effect sensors, or optical sensors and encoder discs. But these can be quite expensive, so [Hello1024] hacked together an alternative in an afternoon. It uses another motor as the encoder, taking advantage of the minute changes in inductance as the magnet passes each of its coils. It’s a technique that works better with cheaper motors, as their magnets are more imperfect than those on their expensive cousins.

The sensing is rather clever in its economy, sending a pulse to the motor through an off the shelf motor controller and measuring the time it takes to decay through the body diode of the driving MOSFET. It requires a calibration procedure before first use, and it is stressed that the whole thing is very much still in beta, but it’s a very impressive hack nevertheless. He’s posted a video demonstration which you can see below the break.

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Innocent TV Imprisoned Behind Mirror

After following along with all the Magic Mirror builds, [Troy Denton] finally caved in and started building one for his girlfriend for Christmas. These popular builds are all pretty much bespoke, and this one is no different.

mirror2His victim TV didn’t have the ability to be switched on and off by the Raspberry Pi using HDMI/CEC, so he came up with an alternative. He got a couple of opto-isolators and soldered one to the on/off button on the TV’s control board. The Pi didn’t know whether it was switching the TV on or off, it just knew it was switching it. To solve this, [Troy Denton] connected another opto-isolator to the TV’s LED, this one the other way around. When the TV is turned on, the Pi now detects it.

The enclosure is fabbed from 2×4 lumber, the mirror is one-way acrylic which runs somewhere in the $75-100 range for this 27-9/16″x15-1/2″ application. The top and bottom rails include lines of holes to encourage airflow to keep things cool. the face plate is picture framing which makes it easy to mount the mirror. An ultrasonic range finder finishes off the build and when someone stands in front of this magic mirror, the Pi senses it and turns the monitor on.

Included in [Troy]’s post are the Python code and shell scripts he wrote as well as a bunch of pictures of the build process. We’ve seen Magic Mirrors builds before, including some small ones. They’re a cool addition to the house and a fairly simple build.

Open Sound Control of Kitchen Lights

Controlling the Internet of Things is all about passing information around. Realistically, it doesn’t matter what is used, be it MQTT, HTTP, serial data, whatever, and it doesn’t really matter what data is sent as long as the sender and receiver agree on what the data means. MIDI could be used to pass information back and forth, for example and while MIDI is good for some things, Open Sound Control is a more modern alternative and one area where OSC excels over MIDI is Internet connectivity. [Matt] used OSC to control the lighting he installed in his kitchen.

ESP8622-1 and Buck Converter

[Matt] had moved in to a new house and wanted some under-cupboard lighting for his kitchen. He got a few cheap warm white LED lights from the Internet and went about wiring them together. For the controller, an ESP8266-1 was used as well as a 12 volt constant-current buck converter. The software runs on the Sming framework, rather than the Arduino framework, and listens for incoming OSC messages. When it receives a command on a specific channel, a callback function turns the lights on and off.  [Matt] also added a switch on the outside of the control box to manually turn the lights on and off.

OSC might not be the right choice for this project, and even [Matt] doesn’t know why he used it, but [Matt] got it working and uses an app on his phone to control it. If he wanted to, he could have used Ableton or another controller to control the lights. (He hasn’t wanted to yet.) OSC is an interesting alternative to MIDI and can also be used with an Arduino without an ethernet shield, or with RFID tags.

What Makes the Perfect Hardware Badge

There are only a handful of people who can say they’ve built several successful electronic badges for conferences. Voja Antonic is not just on that list, he’s among the leaders in the field. There are a lot of pressures in this type of design challenge: aesthetics, functionality, and of course manufacturability. If you want to know how to make an exposed-PCB product that will be loved by the user, you need to study Voja’s work on the 2016 Hackaday SuperConference Badge. The badge is completely open, with all the design files, firmware, and a manual on the badge project page.

Between travelling from Belgrade to Pasadena and guiding production of 300 badges across the finish line before the conference deadline Voja took ill. He made it to the conference but without a voice he asked me to give his badge design talk for him. You can check that talk out below but let’s touch briefly on why Voja’s design is so spectacular.

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CES2017: Astrophotography In The Eyepiece

If you’ve never set up a telescope in your back yard, you’ve never been truly disappointed. The Hubble can take some great shots of Saturn, nebulae, and other astronomical phenomena, but even an expensive backyard scope produces only smudges. To do astronomy properly, you’ll spend your time huddled over a camera and a computer, stacking images to produce something that almost lives up to your expectations.

At CES, Unistellar introduced a device designed to fit over the eyepiece of a telescope to do all of this for you.

According to the guys at Unistellar, this box contains a small Linux computer, camera, GPS, and an LCD. Once the telescope is set up, the module takes a few pictures of the telescope’s field of view, stacks the images, and overlays the result in the eyepiece. Think of this as ‘live’ astrophotography.

In addition to making Jupiter look less like a Great Red Smudge, the Unistellar module adds augmented reality; it knows where the telescope is pointing and will add a label if you’re looking at any astronomical objects of note.

While I wasn’t able to take a look inside this extremely cool device, the Unistellar guys said they’ll be launching a crowdfunding campaign in the near future.

Visualization of a Phased Array Antenna System

Phased array antenna systems are at the cusp of ubiquity. We now see Multiple-Input Multiple-Output (MIMO) antenna systems on WiFi routers. Soon phased array weather radar systems will help to predict the weather and keep air travel safe, and phased array base stations will be the backbone of 5G which is the next generation of wireless data communication.  But what is a phased array antenna system?  How do they work?  With the help of 1024 LEDs we’ll show you.

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Hacked Television Uses No Power In Standby Mode

How much effort do you put into conserving energy throughout your daily routine? Diligence in keeping lights and appliances turned off are great steps, but those selfsame appliances likely still draw power when not in use. Seeing the potential to reduce energy wasted by TVs in standby mode, the [Electrical Energy Management Lab] team out of the University of Bristol have designed a television that uses no power in standby mode.

The feat is accomplished through the use of a chip designed to activate at currents as low as 20 picoamps.  It, and a series of five photodiodes, is mounted in a receiver which attaches to the TV. The receiver picks up the slight infrared pulse from the remote, inducing a slight current in the receiving photodiodes, providing enough power to the chip which in turn flips the switch to turn on the TV. A filter prevents ambient light from activating the receiver, and while the display appears to take a few seconds longer to turn on than an unmodified TV, that seems a fair trade off if you aren’t turning it on and off every few minutes.

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