Beginner project: Color Sensing with RGB LEDs and a photocell

I’ve seen the concept art for “real world eyedroppers” several times. I haven’t noticed any of the products come to market though. It isn’t the technology stoping them, color sampling can be done a million ways. I picked one of the easiest ways and tossed something together pretty quickly.

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70 watt amp uses an ATtiny

If you’re looking for a DIY amplifier project made with a minimum of parts, this is the build for you. [Rouslan] created a 70 watt class D amplifier using an ATtiny45 and just a few dollars worth of additional components.

A class D amplifier simply switches transistors of MOSFETs on and off very rapidly. By passing the signal produced by these MOSFETs through a low pass filter and connecting a speaker, a class D amp is able to amplify a signal very efficiently. Usually, these sort of amp builds use somewhat esoteric components, but [Rouslan] figured out how to use a simple ATtiny microcontroller to drive a set of MOSFETs.

In [Rouslan]‘s circuit, the audio signal is passed into the analog input of an ATtiny45. Inside this microcontroller, these analog values are sent to the MOSFETs through a PWM output. [Rouslan] threw in a few software tricks (explained in revision 2 of his build) to improve the sound quality, but the circuit remains incredibly simple.

[Rouslan] posted a video going over the function of his ATtiny amp, and from the audio demo (available after the break), we’re thinking it sounds pretty good. Amazingly good, even, if you consider how minimalistic this 70 watt amp actually is.

Thanks [Alec] for sending this one in.

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Hackaday Links: June 3, 2012

When pigs fly…. close enough.

There are too many jokes to be made about this one. It’s a quadcopter made out of a dead cat. [Bert Jansen], the artist behind this, calls him Orville. He died from natural causes, and what better way to remember a feline friend that liked chasing birds?

Refurbishing an Apple ][

That thirty year old computer in your parent’s attic isn’t going to clean itself, is it? [Todd] put up a series of videos tearing down a 1982 Apple ][ plus, cleaning everything along the way, and doing a very nice demo of AppleSoft BASIC. This is where the revolution started, people.

Ohm sweet Ωhm

Cross stitch isn’t for grandmothers anymore. Adafruit put up a cross stitch tutorial to go along with their resistor color code cross stitch kit. Now down to Hobby Lobby to find black cross stitch cloth and make the ‘ol skull ‘n wrenches.

Welcome! To the world of yesterday!

Boing Boing found an amazing cyberpunk photo spread that appeared in the Mondo 2000 ‘zine back around 1992 or 1993. Even when keeping in mind that this is a self-parody, it’s still incredible. Hackers have laser pointers? And pagers?

Making Arduino projects smaller

[Scott] caught wind of a way to shrinkify Arduino projects, so he turned an Arduino protoboard into an ATtiny85 programmer. As a neat bonus, [Scott] can use the attached breadboard to build circuits around the ’85.

 

Do anything with the help of lucid dreaming goggles

In the world of your dreams, you can build an entire world, an entire universe, an entire society governed by your every whim. While lucid dreaming you are a god in your own mind, free to create or destroy at will. You can train yourself to recognize when you are dreaming, but sometimes a little technological help can speed you towards the path of becoming an old testament god. [Will] over at revolt lab built a set of lucid dreaming goggles so he could take control of his own dreams.

To induce a lucid dream, [Will] took a pair of safety goggles and attached red LEDs to shine into his closed eyes. A simple circuit was constructed out of an ATtiny85 that blinks the LEDs two hours after being turned on. The idea is these LEDs will be noticed by the user during REM sleep and they will realize they’re still sleeping. After that, it’s basically Inception.

It is possible to induce lucid dreaming through psychological and not technological hacks; just asking yourself, ‘am I dreaming’ throughout the day may be enough to make a holodeck in your mind while you’re sleeping. You can check out a video of [Will] wearing his goggles after the break.

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Emulating ARM on an 8-pin AVR

Falling on the heels of some fabulous ‘lets see what we can emulate on an AVR’ builds we’ve seen, [Dimitri] emulated an ARM Cortex-M0 on an 8-pin ATtiny85.

The emulator is written entirely in AVR assembly. Unfortunately, the instruction set of ATtinys don’t have a multiply instruction, so that had to emulated in a separate piece of code. Even with this addition, the emulator is very small; the core is just over 1300 instructions and small enough to fit on the Flash of the very small ‘tiny85.

Unlike the ATMega running Linux we saw last month, [Dimitri] won’t be doing anything crazy like making the tiniest and worst Linux computer ever. The Cortex-M0 doesn’t have a MMU, so Linux is out of the question. [Dimitri] could go with μCLinux, with the addition of a I2C EEPROM and RAM, but don’t expect a speed demon for an emulated ARM running at 200kHz.

[Dimitri] put all the code up on his webpage, and the installation is just running ‘make.’  It looks easy enough to get up and running very quickly, so we’re sure some bored hardware guru will come up with something interesting to do with this code.

Poking machine

We may be showing our age here, but we have no idea what a ‘poke’ on Facebook actually means. Whether it’s the passive-aggressive manifestations of online stalkers or an extension of  the ‘like’ button, all we know is [Jasper] and [Bartholomäus] built a machine that translates virtual pokes into our analog world.

The “Poking Machine” as [Jasper] and [Bart] call it, syncs to your phone over a Bluetooth connection. The build is incredibly simple: just an ATtiny running Arduino for ATtiny, a Bluetooth controller (possibly this one from Sparkfun), and a servo. When the Facebook app on [Jasper] and [Bart]‘s phone receives notification of a ‘poke’, the servo is powered and gently taps the wearer on the arm.

One thing we really like about this project is the case made of several layers of laser-cut acrylic bolted together. This case offers a very clean look even if it is a bit ungainly. We suppose the guys could have used a simple vibration/pager motor for this build, but it wouldn’t exactly be a poking machine at that point. Check out the build video after the break.

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Monitoring home electricity usage via a tidy wall display

power-meter-display

[Janne Mäntyharju] wanted to get an idea as to how much electricity he consumed in his new home, mainly to see if using his fireplace for additional heat had any effect on his bill. Luckily his power meter was mounted in the utility room of his house, making it easy to keep tabs on his usage.

His meter features a small LED that blinks a fixed number of times per consumed Kilowatt hour, so he mounted a photoresistor and ATtiny2313 above it to detect the light pulses. [Janne’s] server polls the microcontroller every 5 minutes over an XBee connection, recording the power usage in an SQL database for further analysis. From this database, he generates graphs showing both the temperature in his home as well as the average electricity usage for the specified time period.

[Janne] also wanted to make the data easily accessible, so he constructed a wall-mounted display using a Beagleboard and digital picture frame. The display not only shows his electricity usage, but it toggles between the weather, calendar events, IRC logs, and pictures from his security camera.

We’ve certainly seen this sort of electric meter monitoring before, but it serves as a quick reminder that given the right tools, watching your power usage (among other things) can be as easy as taking a quick glance over at the wall.

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