It’s amazing what a little disk can do … when it’s layered with piezoelectric crystals. Piezo disks are impressively sensitive to vibration and can easily be adapted to work as a contact microphones. The trick is the preamp – a basic circuit used to match the piezo’s signal to levels compatible with modern audio gear inputs. The resulting piezo/preamp combo can be used for electrifying an acoustic guitar or simply exploring the lesser-heard world of small sound around us.

Schematic for piezo preamp

The preamp I built is a variation of James T. Hawes’ design. In order to simplify construction, I reversed the MPF102′s source & drain connections from their usual orientation – which works fine in this case.

This thing really is an awful lot of fun to play with – you’ll likely here it used in some of my upcoming video soundtracks!

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Check out more episodes of Collin’s Lab.

Schematics are the functional diagram of electronic circuits. With so many designs available on the web, understanding how to read schematics can unlock a world of possibilities for the electronics maker. In fact, if you can read a schematic, you can build a circuit before even understanding how it works!

The above video covers some vital basics. For more great info on the subject, be sure to check out Paul Spinrad’s Skill Set: Reading circuit diagrams.

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Infrared light may be invisible to the human eye, but its usefulness in the world of electronics is easy to see. From simple object sensors to wireless data transmission, IR emitters and detectors can be used in a variety of different ways. And their low cost and wide availability makes them a great choice for enhancing an electronics project.

Those interested in building their own IR Light Barrier (as demonstrated in the above video) can pick up the relevant PCB/parts kit here.

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I’ve amassed a decent collection of tools since I started working in electronics – some useful & some that seemed useful at the time of acquisition. Not surprisingly, it’s the basics that prove indispensable – and the above video gives you my take on what those are exactly. Here’s hoping it helps get a few newcomers properly geared up – and maybe put a smile on the face of a few seasoned solderers.

Oh and do drop a line in the comments listing any vital items / glaring omissions (note: I classify multimeters as “test instruments”, just so yaknow)

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A true classic for DIY synth makers and circuit benders, the Atari Punk Console can kick out some ear-catching square waves. It’s easy to build and a lot of fun to play around with. It may be challenging to make traditional music with an APC, but hey, there’s enough of that around already, right?

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Oh, and here’s a schematic for the APC I built in this video:
(The 556 timer chip is shown in two parts in order to emphasize the two separate timers included in the IC.)

The requisite starting point for anything electronic – you won’t get much blinking, buzzing, or processing done without a power supply. Get familiarized with some important power supply basics and join me while I assemble an adjustable dual linear regulated supply kit.

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Not all electronic signals are communicated via electricity. By transmitting information in the form of light, we can avoid many limitations inherent to traditional wiring. And on top of all those benefits – fiber optics are just straight-up cool!

Curious minds interested in experimenting with the transmission of sound as light should check out the Fiber Optics kit I use in this video – could also be interesting to exploit the kit’s ability to send a signal much further …

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Easily overlooked, but elemental to electronics hardware, the manually operated switch is the simplest of electromechanical devices — and likely the most familiar. While the most basic switch is… well, quite basic, there’s a crazy-huge variety of switch types and sizes available to the electronics maker nowadays. Those new to the soldering and schematics scene will surely benefit from an introduction to some of the terms and formats relevant to various switch species.

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Another clever trick from the world of electronics – Pulse Width Modulation is a simple method for controlling analog devices via a digital signal. It’s also a very efficient way to drive motors, lamps, LEDs, & more.

If you’ve ever faded an LED with an Arduino – you’ve used PWM. But you don’t need a microcontroller to generate a PWM signal. The ever-versatile 555 timer chip can be configured to modulate its output duty cycle in response to a potentiometer – with the help of some relatively simple circuitry. Or for a more robust solution, consider the DC to Pulse Width Modulator kit suitable for sending up to 6.5A of current and built around the Motorola SG3525 – a chip dedicated to the art of PWM.

Oh and – I’d be denying my own nature if I didn’t mention at least one audio-related application. Indeed, PWM comes in very handy for generating simple sound from a microcontroller – melodies too!

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Measuring brainwaves is not just for neuroscientists anymore – new affordable consumer level EEG devices ( & even some toys) do a respectable job at measuring tiny voltage pulses given off by neurons firing in the brain. Cool – but how shall we use these new found sensory powers? To automatically compose electronic music, of course!

Those interested in listening to beats made by their own brains (with help from a MindSet device) can download and run the MindSet Beat Sequencer code for Processing. The software has not been optimized/streamlined as of yet, but if you familiarize yourself with the required proMIDI & MindSetProcessing libraries, it will likely make sense. Those without a MindSet might consider modifying the Beat Sequencer code to automatically generate MIDI loops by choosing random patterns every second or so (fun!).

As I mentioned in the video, I struggled with recurring connectivity issues between the MindSet and Processing within Mac OS 10.6.7. (still unsure as to a cause, though a snafu in the serial RXTX library seems possible) Removing the device from Bluetooth preferences, shutting down, rebooting, and re-pairing the device was my only therapy. Sean Montgomery (author of the Biosensing Primer in MAKE Volume 26) assures me he had no such issues using WIndows.

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I just used a hammer & nails to build a circuit – and I liked it!

Yes, I could rattle off a list of reasons to use more popular prototyping solutions, but none of them are as satisfyingly straightforward as nailing components to a piece of wood. Unfortunately, incorporating ICs into the build would likely be … well, tedious. Using the so-called “dead bug” approach would require soldering an individual breakout lead to each pin – do-able, but less than desirable.

In any case, this highly visible ‘classic breadboarding’ technique seems a great way to introduce newcomers to schematics and circuit construction – just be sure to keep any mechanical components free of crumbs.

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Piezoelectric materials are about as close to magic as you can get. They turn physical pressure into electricity and can even turn electricity into physical pressure – an amazing sort of bidirectional converter for mechanical and electrical energies. Perhaps even more amazing is the fact that you can easily ‘grow’ your own piezoelectric crystals overnight using just a couple of common ingredients – awesome.

Ever since I made my first contact microphone, I’ve been amazed by piezos and their unique abilities. I was more than psyched to learn I could make my own piezoelectric crystals after finding recipes online. Now I just need to figure out how I’ll put these little guys to good use … feel free to leave any ideas/suggestions in the comments below!

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The Monotron mini analog synthesizer is a simple but sweet-sounding little synth that sports a few basic features that give a nod to us hardware hacker-folk. In the above vid, I merely scratch the surface of how this little guy could be put to creative use – even still, I had a lot of fun.

It’s great to see how a schematic and a few clearly marked solder pads can get people making & modding with hardware. Check out beatnic, 2CV, and Fengland‘s work for more examples – and of course the many SX-150 hacks & mods, if you haven’t already.

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It’s true – I love DACs. There’s something awesome about the role they play, translating information from one paradigm over to another form. Sure, you can pick up a precision DAC chip with serial interface for a little over a buck, but building a barebones version from a handful of resistors is a pretty dang sweet trick. If you’ve never built one, I do recommend it. Doing so has a way of demystifying all sorts of related circuits and processes.

Worth noting: If you’re looking for precision, you’re best off sticking with premade DAC ICs. Resistor tolerance alone can have a massive influence on an R-2R DACs output. Adding an op amp configured as a voltage follower will also do wonders for stability.

Update: As promised, here’s the schematic for buffering the R-2R DAC – quite simple, actually:

Why do we need a buffer, you ask? Well without proper protection, any device connected directly to the resistor DAC will effectively act like another resistor and therefore distort our DAC’s output. By using an operational amplifier configured as a voltage follower, we recreate the resistor ladder’s output voltage while keeping it free from outside influence.

Do note that the op amp buffer in the schematic is powered by a voltage level higher than our DAC’s maximum output – this ensures we have enough headroom to accurately recreate voltages approaching and including 5V. For more helpful info on the topic be sure to check out Ikalogic’s page on the subject.

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USB devices are so common nowadays – wouldn’t it be nice to use one with your homebrew electronics projects? I wanted to use my compact USB-MIDI keyboard with my homebrew synth circuits. It seemed a simple enough prospect at first – listen to the data output, press buttons, note the changes, and then program a microcontroller to turn those changes into something I could use (like basic serial MIDI data).

After a little investigating, I learned a bit about how USB works and that I’d need some extra hardware capable of playing the role of “USB Host” (a job normally left to a full computer) in order to properly work with my keyboard. Enter the USB Host Shield from Circuits@Home. This Arduino compatible shield uses a MAX3421E peripheral/host controller + supporting code library chip to quickly solve my ‘USB-without-a-computer’ problem.

I used the examples included with the shield’s Arduino library to gather some info from my USB-MIDI keyboard (an Akai LPK25) and then plugged those values into one of the included demo sketches. After figuring out what messages I was receiving, I redirected those bytes to an outgoing serial connection, and voilà – a USB-MIDI to MIDI converter was born!

I did run into a few hiccups in the process, but once I was able to actually read the output from the keyboard’s USB port, I simply applied the basic hacking technique of pressing buttons and observing results. HexDecBin came in very handy for the many binary to decimal conversions I made along the way.

Update: Almost forgot – the sketch I wrote for use with the LPK25 can be found here

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In the Maker Shed:

MIDIVOX for Arduino

5mm or 10mm LEDs will work just fine for most projects, but if you really want to light up a room, consider using some of the “high-power” variety. With forward currents of up to a full amp, you’ll need a way to dissipate heat – but the results are very much worth the extra effort.

I’ve had color organs on the brain since the last installment of the Circuit Skills series, so I decided try my hand at a new incarnation of the basic 3-channel sound-to-light machine using high-power LEDs. This time, I took advantage of the fact that I play all of my music from a computer, and created a ‘patch’ in MaxMSP to calculate high, mid, & low values of the outgoing audio stream. Max then sends these values out to an Arduino via serial connection over USB. The Arduino uses these values to set the PWM output levels of 6 pins – each of which are wired to a couple of Tri-Driver boards powering my display. Alternatively, a much more affordable low-power display could be created by simply connecting each of those PWM outs to a 5mm LED and resistor wired in series.

Update: Head over to Make: Projects for the Arduino code, Max patch & basic instructions for this one.

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I’ve used quite a variety of sound-isolating personal audio gear; around-ear cans, in-ear buds, as well as active noise-canceling models. All of these posed problems for me in one way or another. Most often, it came down to issues with comfort and how well each design could maintain a good seal on my substantial noggin.

I was excited to find out that there are custom-fit headphone services out there, but my enthusiasm withered upon learning the price for such a thing. Thankfully, I did find a DIY custom-mold earplug kit available for relatively cheap. So, I dug out my old pair of Shure E2C earbuds, ordered myself up a kit, and then put together a very simple but satisfyingly effective project.

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Also – for those who prefer more static imagery in their tutorials, I added this project to the very excellent Make: Projects site. Check the relevant step-by-steps here.

More:
See all of Collin’s Lab videos

Fingertip input is great for most touchscreen usage like typing, web-browsing – all sorts of virtual button-pushing tasks. But for many people, drawing remains an activity best approached with a pen, pencil, brush, etc.

With a bit of conductive foam and wire, it’s surprisingly easy to make your own conductive stylus, suitable for use with iPhone, iPad and similar capacitive touchscreen devices – and you’ll likely find it a lot more precise compared to regular fingertip input.

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This one’s a bit different from the topics I usually cover in video form – it’s quick, super-simple, and requires no soldering, chemicals, or schematics (no worries – more of the good stuff’s a comin’). The results made drawing/digital-painting on the iPad much more enjoyable for me, and I hope it can do the same for others. Of course this basic conductive stylus should work well for most capacitive and resistive touchscreens – and I’m positive it could be made with far greater care for aesthetics

Also worth mentioning: If a metal pen barrel is used instead of plastic, then the wire can be omitted entirely – as long as the foam is connected to a relatively sizable conductive object (i.e. – a human being), it should register as input.

Oh – and if anyone’s looking for a stylized depiction of the Gakken SX-150, I’ve got you covered -

Inspired by last month’s DIY Movie Making theme, I present to you the above-seen piece of homegrown science fiction. While waiting patiently for what is likely the galaxy’s slowest turbolift, spacefaring duo Metalmags(Erica Magrey) & The Alien Ambassador(yours truly) take a casual stroll through the seams of their own chroma-keyed reality, in search of an answer to that age-old question, “Why are we here?”

If the two pressed on in their search, they’d eventually stumble upon the two-dimensional plane of my laptop display running Apple’s Final Cut editing software. Luckily, FC’s chroma keying filter was able to accommodate our somewhat shadowy green-screen with a bit of tweaking. (FC Tip: be sure to try adding a Color Smoothing filter to the top of your stack + a Matte Choker @ the bottom)

The soundtrack for the vid was composed entirely in Ableton Live along with a monome 64 controller. Like most digital audio apps nowadays, Live can handle concurrent video playback – which makes the scoring process more or less a cinch. Also – the dialogue’s campy vibe is a pleasant side-effect of our necessary vocal dubbing (original audio had much unwanted background noise!)

All of the included sets, artwork, and costumes come courtesy of Erica’s handiwork – except for the Ambassador’s ocular prosthesis which I upcycled from a couple of Poland Spring bottles More Metalmags+Ambassador antics can be found over at Tag Sale Cosmology – and be sure to check out our DIY Movie Making roundup(s) for more homebrew cinema goodness. See you @ the Elsinor launch!

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More:

• Top 10 Make: Online posts from DIY Movie Making Month

• DIY Movie Making article roundup
• Video Making Archive

When recently faced with the dauntingly tedious task of assembling my first-ever batch of electronics kits, I was lucky enough to have the ever-helpful eye of seasoned kit-maker Becky Stern close by. While observing my one-man assembly ‘process’, Becky advised a more efficient, modular assembly line technique using intermediary storage vessels. Streamlining the process left me with plenty of time to cook up some unusually fancy title/motion graphics for the above-seen video.

Of course, there’s a lot more to creating kits than just filling anti-static bags. The prototyping process alone could (should?) have it’s own dedicated print handbook. Which could easily be followed up by “Part Sourcing for Noobs” or similar. Then of course there’s cost/sale price calculation, shipping, packaging, and a myriad of other small-but-important considerations that become clear once you run into them. Though you can safely skip implementing your own online storefront/etc by selling your kitwares through our shiny, new Maker’s Market.

One person who has likely fielded just about every curveball the kit business can throw is Adafruit Industries founder Limor Fried. Thankfully, she’s taken the time to post a variety of helpful kit-biz resources, materials, and suppliers over at LadyAda.net – plus there’s a discussion forum dedicated to the topic on Adafruit’s site.

Do leave a comment if you’ve come across any particular site or related tip(s) you’ve found helpful!

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After checking out a few projects involving IR heart monitors, I decided to have a go at the interface myself. Seen above are the results of my first experimentation with pulse oximetry. Getting the setup up and running satisfactorily required a bit more time and tinkering than I’d expected – especially after reversing a premature mod to my emitter/detector pair. The next version I try will either use a higher output emitter (see Charles Martin’s version) or
some amplification hardware (as used in Meng Li’s sensor).

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Related:

Heartbeat MIDI controller

Instead of chaining multiple guitar effects in search of a new sound, I decided to mod just one. Using an Arduino microcontroller board + digi-pot chip (MCP41100), I was able to add a variable gating effect to a fuzz pedal fairly easily. I definitely dig the resulting sounds and a bit of rewiring should reduce the unwanted noise in the output. Switching to the MCP42100 would allow control over a second pot – perhaps the volume control for a tremolo effect.

You can find the “WavePot” sketch I used (including the necessary wiring list) here.

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Sound can have some amazing effects on liquids – and some downright bizarre effects on non-newtonian fluids such as the conveniently simple mixture of cornstarch & water. I’d experimented a bit with cornstarch cymatics in the past, but never quite matched the writhing results I’d seen from others. Now, after bringing my own small puddle of goop to ‘life’, I feel pretty much satisfied =]

Some additional pics from the session -

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From the pages of MAKE:

Chladni Plate  Volume 16, Page 122

After a recent post on the topic, I decided to experiment with a bit of IC decapping by way of propane torch. My first chip roast went relatively well allowing access to the precious chip within. I imagine a more evenly distributed & thorough torching would have made the hammer unnecessary – but I was happy with it as a first try.

Now I find myself in need of better optics – anyone have any microscope recommendations?

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Update:Already some very helpful tips rolling in! -

Marc writes -

The hottest part of a flame is the tip of the inner cone (blue part). You should never touch the cone to the work-piece. (sorry, I majored in product design – metals)

Duely noted & Thnx!

Keith writes -

Boy Scout tip — be careful heating porous rock and concrete. If it has a high moisture content and the water boils faster than it can be driven out, the rock could potentially explode.

It certainly doesn’t look like that was an issue here, but one might recommend baking the moisture out at < 100°C for a while before torching.

Another reason I should’ve stayed in scouts – good point.