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.

MIDI Keyboard with Frickin’ Laser Keys

MIDI instruments are cool, but they’re not laser cool. That is, unless you’ve added lasers to your MIDI instrument like [Lasse].

[Lasse] started out with an old MIDI keyboard. The plan was to recycle an older keyboard rather than have to purchase something new. In this case, the team used an ESi Keycontrol 49. They keyboard was torn apart to get to the creamy center circuit boards. [Lasse] says that most MIDI keyboards come withe a MIDI controller board and the actual key control board.

Once the key controller board was identified, [Lasse] needed to figure out how to actually trigger the keys without the physical keyboard in place. He did this by shorting out different pads while the keyboard was hooked up to the computer. If he hit the correct pads, a note would play. Simple, but effective.

The housing for the project is made out of wood. Holes were drilled in one piece to mount 12 laser diodes. That number is not arbitrary. Those familiar with music theory will know that there are 12 notes in an octave. The lasers were powered via the 5V source from USB. The lasers were then aimed at another piece of wood.

Holes were drilled in this second piece wherever the lasers hit. Simple photo resistors were mounted here. The only other components needed for each laser sensor were a resistor and a transistor. This simple discreet circuit is enough to simulate a key press when the laser beam is broken. No programming or microcontrollers required. Check out the demonstration video below to see how it works. Continue reading “MIDI Keyboard with Frickin’ Laser Keys”

TightLight: A 3D projection mapping assistant


Anyone can grab a projector, plug it in, and fire a movie at the wall. If, however, you want to add some depth to your work–both metaphorical and physical–you’d better start projection mapping. Intricate surfaces like these slabs of styrofoam are excellent candidates for a stunning display, but not without introducing additional complexity to your setup. [Grady] hopes to alleviate some tedium with the TightLight (Warning: “music”).

The video shows the entire mapping process of which the Arduino plays a specific role toward the end. Before tackling any projector calibration, [Grady] needs an accurate 3D model of the projection surface, and boy does it look complicated. Good thing he has a NextEngine 3D laser scanner, which you’ll see lighting the surface red as it cruises along.

Enter the TightLight: essentially 20 CdS photocells hooked up to a Duemilanove, each of which is placed at a previously-marked point on the 3D surface. A quick calibration scan scrolls light from the projector across the X then Y axis, hitting each sensor to determine its exact position. [Grady] then merges the photocell location data with the earlier 3D model using the TouchDesigner platform, and bam: everything lines up and plays nice.

Building a color sensor using luminosity

[Richard Osgood] is back again with an interesting project. This time he has constructed a color sensor. His initial design was to use three LEDs and a photoresistor. He would shine a red, then green, then blue LED on a surface and record the reflected light with the photoresistor allowing him to determine how much reflected light there was of each color. Unfortunately, he found it to be completely unreliable. An attempt at using a light frequency sensor didn’t work either. What did finally work, was a luminosity sensor shown above.

Finally, his prototype worked. Unfortunately only the red LED gives readings that he considers to be adequate with the blue and green being “not all quite right”.  With this type of circuit, he could build a clone of the magic chameleon lamp.