For some of us trying to sharpen our PCB layout skills, the right way to handle digital/analog ground planes can be a bit of a confusing topic. Eric Archer points out this straightforward article on the subject from Mr. Henry Ott -

Some people suggest splitting the ground plane in order to isolate the digital ground currents from the analog ground currents.  Although the split plane approach can be made to work, it has many potential problems especially in large complicated systems.  Can you list some of these problems?  One of the major ones is that you can not route a trace over the split in the plane […]  It is always better to have only a single reference plane for a system.

That is an officer of the law holding up a device that was found within a 'PIN pad' in Waterloo, Ontario, Canada. I didn't know what a PIN pad is, so here's a wikipedia article and google images. From the article (November 5th, 2009), it looks like someone has found a couple serial pins on the hand-held credit card reader commonly used within Canadian retail stores. They've wired those pins to a BlueSMiRF. This allows a person sitting ~100 feet away to see all the serial traffic including all the credit card information and pin #s. Not hard - all it takes is a bit of time, and malicious intent... All things can be used for good or evil, including our products. You can build amazing things that encourage children to learn (checkout Gever Tulley's amazing presentation at TED), or you can build things that steal. We believe that sharing knowledge and selling products that encourage innovation outweigh the inherent dangers. We believe that stifling innovation or suppressing knowledge lead to much more dangerous outcomes.

Once you've caught the 'electronics bug', spending time away from the workbench/lab can seem an unpleasant prospect. Luckily, one can carry on learning and experimenting with a minimal amount of hardware. Nick shares his own recipe for ultra-compact electronics prototyping - the Altoids Tin Electronics Lab

This is a small electronics lab in an altoids tin. It contains nearly everything to work on small projects, such as a breadboard, components (including several ICs), and a adjustable power supply. The power supply is a simple LM317 circuit, with the 317's metal tab cut off to make it fit.

As a member of Hack Pittsburgh, our local hackerspace, one thing I've wanted to know if anyone else is there before I make the trek over. Well, so did Andy Leer and Marty McGuire, so they decided to build a shop presence notification system. They reasoned that they could measure the ambient light level to determine if someone was around, because people tend to turn on the lights when they show up. With this in mind, they hooked up a photocell to a donated iobridge module, and had a notification widget up on the website in record time. Excellent work!

By way of Andrew Q Righter of HacDC comes word of this free PDF from Texas Instruments, a 41-page "cookbook" of circuit designs and application notes for TI's LED-related components. [Thanks, Andrew!]

LED Reference Design Cookbook [PDF]

Bruce Heran made this prototyping board for his tube projects. He writes:

This is a project that I made to take care of an ever increasing need to prototype vacuum tube (valve) circuits. As you can see from the photos, it really is a test "board." I do a lot of work with tubes and love to design and improve circuits. In the process I often use various CAD type programs to rough out the designs. I have frequently found that the models do not agree with the final build. Some are right on, but most are off enough to turn a good idea into a waste of time. Thus the need to quickly prototype designs. Now I could have created this board with many additional features - speakers, output transformers, LEDs... But what I needed was a simple way to test single stage tube circuits. So for simplicity I wired the tube pins together (pin 1 to pin 1 and so on). The leads from the pins are brought out to terminals on a "Euro" style terminal strip. I included several other "Euro" strips, a pair of RCA jacks, a 100 k-ohm variable resistor and solderless prototype breadboard. This solderless breadboard is available in various sizes from several sources. If you build one of these boards, feel free to use the idea to adapt it to your needs and use whatever parts you so desire.

[Thanks, Gio!]

DIY Vacuum Tube Prototyping Board

Instructables user peterdr has put together a really excellent tutorial on how to build his CT-1 open-source hardware intervalometer for Canon and Nikon digital cameras. There's more info about the project at his personal website, and a parts kit is for sale on Amazon.com.

There's a funny thing about dads' toys. Very often, kids borrow dad's supposedly grown-up toys and dad plays with toys designed for a much younger demographic. With that in mind, we present the Gifts for Dads list, filled with stuff that may appeal to more than one generation in your household. And you may also want to check out the holiday gift guides over on the GeekDad blog.

One hour of PCB routing with EAGLE, compressed to seven minutes, over at adafruit.

Instructables user jvalal didn't like the look of his Powermat inductive device charging station, so he stripped out the guts and "re-skinned" it with a handmade wooden case.

Instructables user garagemonkeysan made this guitar amp from the popular Little Gem circuit, and put it in this useful little case with a cord reel on the back. Nice work!

More:

Flashback: The $5 Cracker Box Amplifier

Synth DIY's amphibious mascot, better known as "Mr. Braska", has been visiting a series of home labs via postal transport. The photo galleries of his modeling efforts serve as a nice way to bring together otherwise unconnected, private workspaces - plus he's getting pretty good with an iron -

See a whole lot more from Mr. Braska's travels over at SynthFrog.

Among the hairier of my hare-brained schemes involves formulating a safe-to-drink chemiluminescent cocktail. I think the first person to do it will become a very wealthy laughingstock, which, as I understand it, is the very definition of The American Dream.

So I got really excited when I first saw this post over on TheDieline.com, because I thought somebody had pulled it off. Unfortunately, it's just the labels that are glowing, not the booze itself, but still it's pretty cool. If you ignore the crass commercialism, the shameless marketing, the horrors of alcoholism, drunk driving, etc., etc. [via Geekologie]

Got a pedal-powered TV, but still have to keep replacing the batteries in that remote? Then you might want to keep an eye on this piezoelectricity batteryless remote (machine translation), being developed by NEC and Soundpower. Energy harvesting devices are nothing new, but this one seems interesting because it is apparently efficient enough to work off of the vibrations caused by pressing the buttons on it. They claim that it uses piezoelectric elements, which can generate electric current when bent or deformed, to capture the kinetic energy of your button press.

Of course, if you don't have access to fancy piezoelectric development tools or want to wait for their device to come out, you could probably whip up something similar by combining one of those shake flashlights and a regular remote. [via technabob]

By Steven Lemos, engineering intern

Making the Hydrogen-Oxygen Bottle Rocket (that Adam Savage is posing with on the cover of the new MAKE, Volume 20) was a pretty basic endeavor, with the exception of the circuit. The original schematic diagram had a flaw in it, but only after we breadboarded the circuit -- twice -- did we catch it.

I guess that's the reason we MAKE interns build the projects that run in the magazine, so it's us who bang our heads against the table and not you. I will kindly take that cookie now.

The experience showed me that, sure, when working with electronics it's easy to misplace a component or wire, or completely miss something, which I already knew, but it's just as easy to have a diagram be the culprit. So a word to the wise (a word I'm sure all the experienced hobbyists have already discovered for themselves): if you take care when putting together these tedious circuits it will pay off, for if you can trust in your work, then you'll know the culprit lies in the plans, and you won't spend hours chasing that metaphorical wild goose.

Twice we breadboarded this bad boy before discovering an error in the schematic -- so you won''t have to.

But on to the actual launch. :) We had talked to the local electronics store owner, who at the time was making his own hydrogen using a more sophisticated apparatus, and who was interested in what we were doing with ours. So he came to watch, and brought along his professional pyrotechnician friend, who showed us how to make fuses with 12V and tiny resistors (basically the resistors pass so much current that the wire heats up and can act as a fuse to light stuff -- voilà, cheap fuses).

Our beautiful 2-stage HHO rocket ready for test launching -- before being crippled by a crash.

The first launch was a success, with the two stages going off rather quickly in succession, so we dialed in a little more delay time in the circuit before the stage 2 ignition. This was good and bad. We got more height out of the rocket on our second launch, but on its return it landed electronics side down. This resulted in our circuit behaving oddly.

So, not ready yet to call it a day, we began firing off only one stage at a time, adjusting the proportions of HHO (hydrogen and oxygen gases), water, and air, and testing the makeshift fuses, which worked fine for a single stage, but due to the time they take to ignite (3sec@12V) might not work for 2 stages.

We probably launched 12 times that day, attracting passersby. Good weather, new friends (who like blowing stuff up), and multiple launches. All in all, a good day. Houston, we have liftoff.

• Related: MAKE, Volume 20: "For Kids of All Ages"

As the holidays approach this year, money is tighter than ever for everyone. When thinking about gifts to give, consider the gift of DIY electronics and kits, not only could a loved one learn a new skill, but it could start them on a journey to a wonderful lifetime hobby, possibly a career! Helping someone learn electronics is more than just giving a circuit board and a bunch of parts, you're giving the gift of time, hours of new experiences exploring the wonders of engineering and science. In the end, they'll also have something to show and share!

So let's get started. I've put together my 20 favorite (mostly) under $20 electronic kits and resources, some are from the Maker Shed, some are from other places (SparkFun, Adafruit, Instructables, TechShop, Solarbotics, Evil Mad Scientist Laboratories, Parallax). Many of them are open source hardware projects, so if $20 is still too much, you might be able to put these together on your own and print out the instructions for free too! Our gift guides are meant to inspire your suggestions, so if you know of a great $20 or under electronics kit, post it in the comments!

Fresh out of 8-pin DIP sockets, I broke off a couple rows of female machine pin headers as a substitute - using the chip itself to align the pins for soldering. That was about a month ago, and I've continued using them ever since. Though it seemed a bit 'kludgey' at first, this process has proven a lot easier than trying to keep a variety of socket sizes at the ready. As always, your mileage may vary.

Jim did some experimenting with homemade thin-film zinc oxide and zinc-tin oxide, developing his own homemade transistors devices -

I did manage to achieve (with a liquid dielectric) voltage and current gain, as well as construct a functional astable oscillator using two of the devices constructed on a single substrate. While the speed of the devices (due to the liquid dielectric) is such that they are only interesting as a technology experiment, they've been a lot of fun to experiment with.

Spotted in the MAKE Flickr pool:

ITP students Hana, Ania, and Greg built this augmented xylophone, the multixylophoniomnibus. Despite having a basically unpronounceable name, the project looks nice and they have a very in-depth review of the process that they went through in order to produce a working product. Nice job!

They also have a large number of photos available in their Flickr photo set.

It's the McLVDT, a linear variable differential transfomer, made from McDonald's straws. The creator writes:

I made a primary coil on a normal sized straw, and made two secondary coils on the outside of the larger McDonald's straw. Since the McStraw is large-bore (perfect for those thick high calorie shakes), the smaller straw with the primary winding fits nicely inside. The position of the inner straw can be determined by examining the amplitude and phase of the combined signals of the secondary coils, which is shown in raw form on the oscilloscope.

"Mc"LVDT

Like many of us, Nyle Steiner has long aspired to building a homemade transistor. While considering possible way to achieve this, he stumbled upon the interesting idea of building a FET transistor from a cadmium sulfide photocell.

Normally used to detect light, the photocell is pretty close to what one would need to make a transistor. The device consists of two pieces of metal that are separated by a very thin layer of a cadmium sulfide semiconductor. The semiconductor is normally an insulator, which means that no electricity can flow from one of the metal legs to the other. However, when light (photons) hit the surface of the semiconductor, they knock electrons free, and allow some current to flow across the semiconductor. To make a transistor, though, the device needs to react to electricity, not light. Nyle realized that the photocell could be used as a transistor if an insulated gate was added to the top of it. A bit of scotch tape and water later, and he claims to have a working transistor.

Of course, this isn't a truly homemade transistor, it's more of a DIY transistor conversion. The device appears to be functional, however it requires fairly high voltages to work, and only acts as a power amplifier instead of a voltage amplifier. Even so, it looks like an interesting way to experiment with transistors at home. I'd like to build one, and vary thickness of the insulator (scotch tape) to see what the results are. Anyone else have experience with this?

Related:

• Adafruit's CdS tutorial
• MAKE presents: The Transistor
• The lost transistor

Yusynth has a nice PCB layout for building a classic voltage-controlled Moog filter. This particular iteration appeared in MiniMoog synths, utilizing Robert Moog's signature transistor ladder design for sweet, sweet analog sounds.

Miketron converted his random MIDI note generation software(MAC/PC) into hardware form via an ATMega168 chip -

A couple of months I took my MAX/MSP code for Random7 and rewrote so I could embed it into a hardware version.  Random7 Hardware Version 1 (R7H) is a very basic version of the Random7 software.  The core element of R7H is still the same,  the program pick from 7 different midi notes randomly.  As of now the key R7H is preset to the key of A Major, and the only control is a potentiometer that controls the speed of R7H.  Output for R7H is a midi port, an on/off switch, and there is also a red led the flashes everytime a note is sent.

The 3pi robotics bundle includes:

• (1) Pololu 3pi Robot $99.95 value
  
• (1) Orangutan USB Programmer $27.99 value
  
• (1) 3pi Expansion Kit without Cutout $19.99 value
  
• (1) Maker's Notebook $19.99 value
  

Learn how to program the 3pi:

Don't forget to read our How-to Tuesday: Getting started with the 3pi for a lot more information about this little bot.

I love etching my own PCBs. It's a great way to incorporate some of art-school skills with my love for DIY electronics. Up until now, I'd always used traditional ferric chloride to etch my boards, though I'd heard many sing the praises of an alternative etchant easily made from common ingredients. Tired of mail-ordering ferric and dealing with proper disposal, I decided to give cupric chloride a try.

Following Open Circuits' recipe, I picked up some muriatic acid from the local hardware store and a bottle of hydrogen peroxide 3% from the pharmacy. After setting up next to my big window fan, I slowly added 16oz of the muriatic to an equal amount hydrogen peroxide, resulting in a clear solution. Shortly after immersing my masked PCB and agitating a bit, the etchant turned a brilliant green hue as it began work on the exposed copper. Several minutes of gentle sloshing left me with a perfectly etched board - plus a etchant that can will last me a very long time. For me, that's the real 'selling point' of cupric chloride - by oxygenating (air-bubbling) or adding some more H2O2 to the solution, I'll be able to refresh this batch once it's spent - awesome. I'm left wondering why I hadn't tried this sooner!

Here's a Design News Gadget Freak column on using an ARM-powered processor (the MBED ARM Cortex-M3 MCU Dev Board) to make a Billy Bass animatronic fish speak and move as you wish. [Caution: mild cursing in the video.]

Gadget Freak Case #150: Hotrod Your Billy Bass

Want to fly your plane or drive your car using GPS signals, but finding that your receiver just isn't accurate enough to make things work? Well, MAKE subscriber Bruce Mueller writes in to point us at an impressive solution: an open-source real time kinematic GPS receiver. Researchers Tomoji Takasu and Akio Yasuda of Tokyo University developed the RTKLIB library to perform the RTK-GPS calculations, and then ported the whole thing to run on a low-cost beagle board and commodity GPS receiver. Want to try it out? Full source code, circuit layouts and instructions are provided on their site.

So, how does it work? A GPS receiver normally works by measuring the delay between an internally generated signal and one received by a satellite. This specially crafted signal makes it possible for the GPS receiver to find and latch onto the satellites signal, however it's wavelength limits the accuracy of the receiver. The real time kinematic system gets around this limitation by measuring the phase delay in the carrier signal. Because this signal has a much sorter wavelength, it is possible to make a system that is accurate to the centimeter.

Recently I've been helping a friend's 11-year-old daughter get started in electronics. The use of a solderless breadboard was counterintuitive to her until I gave her one of these clear-cased versions, available through Solarbotics. As she puts it, "you can see where the metal is."

Let's get started with the CupCake electronics assembly. I ordered the deluxe kit from batch #8, so most of the electronics were already assembled. Yay! Not that soldering isn't fun, but I'm happy to skip the soldering for this build and get to printing faster!

The stepper boards:

Not much to do here since the board is already soldered together. However, you do have to add the insulation-displacement connector (IDC) to the ribbon cables, and perform a simple test.

All you have to do is insert the ribbon cable into the plastic IDC connector and squeeze it closed. You might want to use some pliers to help snap the top down.

Take notice of the arrow on the connector. The brown wire is the index wire, and it should be directly above that arrow on both ends of the cable.

Rinse and repeat. You need to make three cables, each with an IDC connector on the end.

If you don't have any bomb-sniffing bees around to look for trance quantities of explosive gas, why not use your iPhone instead? That's exactly what Jing Li and a team of researchers from NASA have done with their cell phone chemical sensor. By interfacing a postage stamp-sized sensor to a popular smart phone, they were able to create a device that can sense airborne ammonia, chlorine gas and methane, and report its findings over the cellular network or WiFi. Admittedly, it took a bit more than just a bit of software to add an electronic nose to the iPhone, but it's still pretty neat use of a consumer device. [via inhabitat]