Advent Calendar Of Circuits

December 16, 2011 by Mike Szczys 2 Comments

We missed 60% of it already, but luckily you can easily watch the back catalog of [Alan Yates’] 2011 Advent Calendar of Circuits. As with traditional Advent Calendars he’s got a treat for every day in December leading up to Christmas. Instead of chocolate, the treat is a video about a different electronic circuit.

We didn’t find a playlist link, but you can just head over to his YouTube channel as each day is clearly labelled in the video titles. He starts off with a current limiting voltage regulator. A couple of days later he busts out a metal detector that will be fun to play with. Day 7 brings an AM transmitter/receiver pair, and Day 12 illustrates a burnt-out Christmas light detecting tool which we’ve embedded after the break.

The sheer volume of projects he’s putting out every day is remarkable and delightful. He doesn’t even limit himself to one video a day, but has posted several ‘extra’ editions with quick, circuit demos. Continue reading “Advent Calendar Of Circuits” →

This Toy Intercom System Is Way Better Than A Pair Of Tin Cans And Some String

December 6, 2011 by Mike Nathan 36 Comments

toy-intercom-system

On his blog, [Kenneth Finnegan] recently showed off a replica of a fun toy he used to play with as a kid, a telephone intercom system. The setup is pretty simple, requiring little more than a pair of analog phones, a battery, and a resistor.

The phones are connected to one another using a standard telephone cable, but [Kenneth] uses a 9v battery to introduce a small bias current into the loop, allowing the speakers at either end to hear one another. He also added a small LED into the circuit so that there is a visual indication as to when both handsets are off hook.

The setup is very simple at the moment, though [Kenneth] does have some ideas in mind to enhance his intercom system. He hopes to tweak the remote phone to ring when the local phone is picked up, among other things.

Telephone technology is nothing new, but for just a few dollars (or less) your kids can be entertained for hours as [Kenneth] was way back when.

Continue reading to see a short video overview of the phone system, and be sure to share your ideas for enhancing it in the comments section.

Continue reading “This Toy Intercom System Is Way Better Than A Pair Of Tin Cans And Some String” →

Multivibrator In Theory And Practice

December 1, 2011 by Mike Szczys 60 Comments

We must admit that we’ve been guilty of using a microcontroller to make two LEDs blink alternately in the past. It’s not the worst transgression, but it stems from our discomfort with analog circuits. Luckily, [Ray] published an illustrated guide on building multivibrator circuits. This is a simple method of assembling a two-output oscillator. All it takes is a pair of NPN transistors, which are then switched by on and off based on a resistor-capacitor (RC) timer.

[Ray] does a good job of walking us through how the circuit works at each stage of one complete cycle. You’ll need to read carefully, but the supplementary schematics he uses to water down snap shots of the various electrical states really helped us understand.

Of course, blinking LEDs isn’t the sole purpose of a multivibrator. It is a method of producing a clean square wave which can be used as a clock signal for TTL logic chips. Oh, who are we kidding, see the blinky goodness for yourself in the video after the break.

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Analog Test Interface For Your Computer

October 20, 2011 by Mike Szczys 6 Comments

Wanting to test the response curves on some analog parts, [Don Sauer] devised a way of using simple tools to graph analog tests on a computer. Here you can see the results of testing NPN, PNP, NMOS and PMOS transistors, but modifying the input circuitry would let you test just about anything you want.

[Don] is using an Arduino as the hardware interface. He needed some additional parts, like an op-amp and some passives. Instead of building this on a breadboard, he printed the circuit out on a piece of cardboard, hot glued the components in place, then wired them up. This will let him reuse the interface in the future, but is quicker than designing and etching a PCB.

He uses a Processing sketch to capture the test data streaming in from the Arduino. Once recorded, he uses SciLab to create the graphs. He also covers a method of sifting through the data using Octave, another open source program that feels somewhat like MATLAB.

Slick Music Synchronized Light Show Uses UV LEDs And Water

October 12, 2011 by Mike Nathan 20 Comments

music_synchronized_light_show

[mike6789k] wanted to spice up his dorm room, so he built a cool music synchronized light show that struck us as being very well thought out. We have seen similar music-based visualizations before, but they tend to be pretty basic, relying on volume more than actual audio frequencies to trigger the lighting.

[mike6789k] didn’t want to build “just another” synchronized light show, and his all-analog approach gives a true representation of the music being played instead of just flashing lights along with the beat. Using a trio of simple filters, he broke the audio signals down into three distinct frequency bands before being driven through a high gain transistor to power a set of LEDs.

We were pretty impressed at how bright the display was given that he is using UV LEDs, but the 1W diodes seem to have no problem lighting up the place when aimed through the UV-reactive water, as you can see in the video below.

If you’re looking to make something similar for your next party, the folks over at Buildlounge were able to wrangle a schematic out of [mike6789k], which you can find here.

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Why Wasn’t This Magnetic Cello Made In The 70’s?

September 22, 2011 by Brian Benchoff 34 Comments

[magnetovore] made himself an electronic cello. Instead of pulling a few cello samples off of an SD card, he did it the old school analog way. The finished build is really impressive and leaves us wondering why we haven’t seen anything like this before.

[magnetovore] uses a permanent magnet to play each ‘string’. A lot of details are in this post and [magnetovore]’s provisional patent (PDF warning). From what we can gather, each string is a resistive ribbon sensor connected to a voltage controlled oscillator. The output of the VCO is sent to a variable gain amplifier that is controlled by a coil of wire and the magnetic ‘bow’.

From the video (after the break), [magnetovore] already has an amazing reproduction of the cello sound. It’s a bit electronic on the lowest parts of the C string, but with a little bit of processing it could definitely pass for an acoustic instrument. We’re left wondering why we haven’t seen anything like this cello before. VCOs and VGAs were the bread and butter of the old Moogs and even the ancient ondes martenot. Ribbon controllers were being attached to electronic instruments back in the 50’s, so we’re really at a loss on why a magnetic cello is new to us. If any Hack A Day readers have seen anything like this before, leave a message in the comments.

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Record Sound Without A Microcontroller

September 15, 2011 by Brian Benchoff 14 Comments

For his A-level electronic course work, [Andrew] decided to build a digital sound recorder that doesn’t use a microcontroller.

[Andrew]’s build captures audio from an on board microphone at 8000 samples/second. The audio is digitized into 8-bit sound data and sent to an SRAM. The recording and playback functions are controlled entirely by 4000-series logic chips. He admits the sound quality is pretty poor; this is mostly due to the 8kHz sample rate. In some circles, though, a terrible sample rate is seen as being pretty cool so we’re not going to say [Andrew]’s build is useless.

There’s some pretty smart design choices in [Andrew]’s build, like a cut off filter on the microphone set at 4000 Hz (the Nyquist frequency of his system). For the recording medium, he used an SRAM that can hold about half a megabyte of data. At 8000 samples/second, [Andrew]’s build can store a little more than 60 seconds of audio. The build may not be a logic chip computer, but there’s not any question in our mind that [Andrew] learned something. Check out [Andrew]’s 66-page coursework report here (PDF warning).