Watt Meter build walks you through Power Measurement basics

You almost never hear of a DC Watt Meter – one just does some mental math with Volts and Amps at the back of one’s head. An AC Watt Meter, on the other hand, can by pretty useful on any workbench. This handy DIY Digital AC Watt Meter not only has an impressive 30A current range, but is designed in a hand-held form factor, making it easy to carry around.

The design from Electro-Labs provides build instructions for the hardware, as well as the software for the PIC micro-controller at its heart. A detailed description walks you through the schematic’s various blocks, and there’s also some basics of AC power measurement thrown in for good measure. The schematic and board layout are done using SolaPCB – a Windows only free EDA tool which we haven’t heard about until now. A full BoM and the PIC code round off the build. On the hardware side, the unit uses MCP3202 12 bit ADC converters with SPI interface, making it easy to hook them up to the micro-controller. A simple resistive divider for voltage and an ACS-712  Hall Effect-Based Linear Current Sensor IC are the main sense elements. Phase calculations are done by the micro-controller. The importance of isolation is not overlooked, using opto-isolators to keep the digital section away from the analog. The board outline looks like it has been designed to fit some off-the-shelf hand-held plastic enclosure (if you can’t find one, whip one up from a 3D printer).

Although the design is for 230V~250V range, it can easily be modified for 110V use by changing a few parts. Swap the transformer, change the Resistive voltage divider values, maybe some DC level shifting, and you’re good to go. The one feature that would be a nice upgrade to this meter would be Energy measurements, besides just Power. For an inside look at how traditional energy meters work, head over to this video where [Ben Krasnow] explains KiloWatt Hour Meters

 

Video Voice Visualization

For their ECE 4760 final project at Cornell, [Varun, Hyun, and Madhuri] created a real-time sound spectrogram that visually outputs audio frequencies such as voice patterns and bird songs in gray-scale video to any NTSC television with no noticeable delay.

The system can take input from either the on-board microphone element or the 3.5mm audio jack. One ATMega1284 microcontroller is used for the audio processing and FFT stage, while a second ‘1284 converts the signal to video for NTSC output. The mic and line audio inputs are amplified individually with LM358 op-amps. Since the audio is sampled at 8KHz, a low-pass filter gets rid of frequencies above 4KHz.

After the break, you can see the team demonstrate their project by speaking and whistling bird calls into the microphone as well as feeding recorded bird calls through the line input. They built three controls into the project to freeze the video, slow it down by a factor of two, and convert between linear and logarithmic scales. There are also short clips of the recorded bird call visualization and an old-timey dial-up modem.

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CAMdrive is an Open Source Time-lapse Photography Controller

[Nightflyer] has been working on an open source project he calls CAMdrive. CAMdrive is designed to be a multi-axis controller for time-lapse photography. It currently only supports a single axis, but he’s looking for help in order to expand the functionality.

You may already be familiar with the idea of time-lapse photography. The principal is that your camera takes a photo automatically at a set interval. An example may be once per minute. This can be a good way to get see gradual changes over a long period of time. While this is interesting in itself, time-lapse videos can often be made more interesting by having the camera move slightly each time a photo is taken. CAMdrive aims to aid in this process by providing a framework for building systems that can pan, tilt, and slide all automatically.

The system is broken out into separate nodes. All nodes can communicate with each other via a communication bus. Power is also distributed to each node along the bus, making wiring easier. The entire network can be controlled via Bluetooth as long as any one of the nodes on the bus include a Bluetooth module. Each node also includes a motor controller and corresponding motor. This can either be a stepper motor or DC motor.

The system can be controlled using an Android app. [Nightflyer’s] main limitation at the moment is with the app. He doesn’t have much experience programming apps for Android and he’s looking for help to push the project forward. It seems like a promising project for those photography geeks out there. Continue reading “CAMdrive is an Open Source Time-lapse Photography Controller”

A Camera With Computer Vision

Computer vision is a tricky thing to stuff into a small package, but last year’s Hackaday Prize had an especially interesting project make it into the 50 top finalists. The OpenMV is a tiny camera module with a powerful microcontroller that will detect faces, take a time-lapse, record movies, and detect specific markers or colors. Like a lot of the great projects featured in last year’s Hackaday Prize, this one made it to Kickstarter and is, by far, the least expensive computer vision module available today.

[Ibrahim] began this project more than a year ago when he realized simple serial JPEG cameras were ludicrously expensive, and adding even simple machine vision tasks made the price climb even higher. Camera modules that go in low-end cell phones don’t cost that much, and high-power ARM microcontrollers are pretty cheap as well. The OpenMV project started, and now [Ibrahim] has a small board with a camera that runs Python and can be a master or slave to Arduinos or any other microcontroller board.

The design of the OpenMV is extraordinarily clever, able to serve as a simple camera module for a microcontroller project, or something that can do image processing and toggle a few pins according to logic at the same time. If you’ve ever wanted a camera that can track an object and control a pan/tilt servo setup by itself, here you go. It’s a very interesting accessory for robotics platforms, and surely something that could be used in a wide variety of projects.

Ask Hackaday: Your Very First Microcontroller

Necessity is the mother of invention. It is also true that invention necessitates learning new things. And such was the case on the stormy Tuesday morning our story begins.  Distant echos of thunder reverberated in the small 8 x 16 workshop, drawing my attention to the surge suppressor powering my bench.  With only a few vacation days left, my goal of finishing the hacked dancing Santa Claus toy was far from complete. It was for a Secret Santa gift, and I wanted to impress. The Santa moved from side to side as it sang a song. I wanted to replace the song with a custom MP3 track. In 2008, MP3 players were cheap and ripe for hacking. They could readily be picked up at local thrift shops, and I had picked up a few. It soon became clear, however, that I would need a microcontroller to make it do what I wanted it to do.

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Electricity Usage Monitor is Linked to Google Spreadsheets

If you want to make your home more energy-efficient, chances are you will need a way to monitor your electricity usage over time. There are off-the-shelf solutions for this of course, but hackers like us tend to do things our own way. Take [Karl] for example. He recently built himself a solution with only a few smart components. We’ve seen similar projects in the past, but none quite like this.

[Karl’s] home has a power meter that blinks an LED to indicate the current amount of used electricity in Watt-hours. He knew all he needed was a way to electronically detect the blinking LED and he’d be able to accurately track his usage without modifying the meter.

The primary components used in this project were a CC3200 development kit and a photoresistor module. The dev kit contained a WiFi module built-in, which allows the system to upload data to Google spreadsheets as well as sync the built-in clock with an accurate time source. The photoresistor module is used to actually detect the blinking LED on the power meter. Everything else is done easily with code on the dev kit.

Never Forget Your USB Stick Again

USB sticks are very handy. They are a very portable and relatively inexpensive means of storing data. Possibly the most annoying part about using one of these devices is when you inevitable leave it behind somewhere by accident. This is especially true if it contains sensitive information. [Eurekaguy] feels your pain, and he’s developed a solution to the problem.

[Eurekaguy] designed a custom cap for USB sticks that beeps approximately every minute after the USB stick has been plugged in for five minutes. The cap is 3D printed and then slightly modified with four 1mm holes. Two wires are routed between these holes to make contact points for the VCC and GND pins of the USB stick.

The beep circuit is comprised of a tiny PIC12F629 microcontroller along with a couple of other supporting components. The circuit is wired together dead bug style to conserve space. Three AG5 batteries power the circuit. A small piezo speaker provides the repeating beep to remind you to grab your USB stick before you walk away from the computer.

[Thanks Irish]