This is totally cool! Mikey writes:

Using electrolysis on this leatherman skeletool brought it back from the dead. The tool was lost two years ago while wendy was planting trees. It slipped out of her overalls and we were unable to locate it. While planting trees this week the tool was found in unusable condition. I put it into a bath with a chunk of metal and connected it to a irobot roomba 22V battery charger. Within two days the tool was working again.

These are great for doing a little heavy lifting with a microcontroller. Most micros can only source or sink about 20mA of current with each pin. If you’re trying to do something like drive a high-power multi-segment LED display, the current from a microcontroller pin just won’t cut it. You could run the micro outputs in parallel for more current, but then you lose pins for other purposes. Using an external array for the switching lets each pin drive a unique load at higher current, with the added benefit of offloading some of the heat from the microcontroller.

The ULN2003/4 and ULN2803/4 are 7- and 8-element Darlington arrays which can switch up to 500mA (MAX!) per channel at up to 50 volts. Channels can be combined to switch higher current loads (still 50V though). Take note of that “500mA MAX”: while the 2×03′s can switch that much current, they can’t do it forever, because they can’t dissipate the heat. The total amount of switchable current will depend on the number of channels you’re driving at the same time, and the duty cycle of the input signal. See the datasheet (PDF) for more information.

The 2xx3 chips have 2.7k input resistors, so they can be driven from a 5V TTL/CMOS line – if you’re using an Arduino, you should get the ULN2003/2803. The 2xx4 chips have 10.5k resistors for inputs of 6-15 volts.

These are great for driving multiple RGB lines with lots of LEDs, or a bank of relays or motors (they have clamp diodes built in!). The following illustrates how to properly connect the ULN for driving an inductive load like a DC motor.

Purchasing note: these chips were originally (and still are) made by TI. The TI chips are great, but recently I noticed Mouser has begun carrying the Toshiba versions for about 30% less cost. I’ve used both, and they perform equally well.

CHECK ‘EM OUT IN THE PARTFINDER!

Happy Friday!

Polo Puzzle: What Goes Into a $155 Price Tag? @ WSJ.com.

Every piece of clothing has a story: There’s far more to a $155 polo shirt than a yard of fabric, four buttons and a length of thread.

The tale of a KP MacLane polo shirt offers a rare look inside the planning and global transactions behind the clothes people wear. To begin, though, there is an actual KP MacLane—Katherine, who founded the brand with her husband, Jared MacLane.

Manufacturing clothing, surprisingly similar to electronics – finding the right suppliers, fab house, making hundreds of decisions.

Dangerous Prototypes CadSoft Eagle style guide and best practices.

If you do all these things, you should award yourself an eagle badge!

Five minute project: Heart-Shaped Hack Box – Evil Mad Scientist Laboratories.

A hack-box to go, filled with interconnects, LEDs, and love. Because, what better way to say I love you, than with the gift of electronics?

The recent discussion about the “new” 6502 from WDC got me thinking about other old and/or unavailable chips that could use a re-introduction, or perhaps just a process facelift. This post is mainly to solicit reactions and suggestions from viewers like you, but I’ll provide my own example too.

Having recently gotten back in to analog synth design after a long hiatus, I was rather shocked to discover that OTAs (operational transconductance amplifiers) suited to such work are few and far between. With the exception of the NE5517 and the LM13600/13700, there are no other audio OTAs currently in production. TI (via BurrBrown) manufactures other OTA devices, such as the OPA860/861, but these are optimized for high-speed analog (RF and transmission line) and they are rather expensive. For many synthesizers, the OTA forms the heart of nearly every voltage-controlled module and using them greatly simplifies the process vs. building with discrete components (such as a Moog ladder). The best OTA for audio was probably the CA3280, which is sadly no longer in production, due to the process becoming obsolete, among other factors. This 2005 blog post by Don Tillman, which explains the whole problem perfectly, was part of the inspiration for this blog post, and I’m going to throw in with Don and humbly request that someone please update the CA3280 to the latest fab, give it 21st-century specs, and bring it back into production.

If the 3280 is a no-go, for whatever reason, then my second choice would be an update of the LM13700 (originally from National). The LM13700, which was designed by Don Blake, is currently available from both National and NJR, but it’s got its problems. It’s somewhat noisy, for one. It also has an output offset current which scales with the transconductance (a problem when building integrators), and the buffer is just a simple darlington pair. It would be great (read: totally awesome!) if someone were to update the chip to a BiCMOS process, while changing the design to drop the noise floor and increase the dynamic range, reduce the output offset current and replace the darlingtons with FET-input opamps. This might sound like a very involved request, but the expertise is already there to do it — analog devices have come a long way in 30+ years, and the basic design of the 13700 is not very complex, compared to modern opamps.

In case you’re wondering what incentive there is for somebody to do this, I submit that, compared to when I was doing it 10+ years ago, there’s A LOT more information out there now about DIY synths, and the increase in homebuilt synth projects has paralleled the increase in DIY ‘tronix in general. There’s definitely a willing (and growing) market for these things, and with a chip redesign they could certainly charge more per chip. There’s also a resurgence in analog electronic music in general right now, which means these new chips may find their way into commercial products as well.

So anyway, that’s my request. I suspect there are lots of different opinions on the subject, however. If you have a chip you’d like to see resurrected and brought back into production, or just updated to modern spec, post it in the comments! Try to include some info with your suggestion, and reasons why you think such an update would be successful.

Fundamentals of Laying Out PC boards. Free “webinar” – Thanks Willard!

Overview:
Laying out the circuit board is one of the last steps in the design process and quite often doesn’t get the attention it deserves, and high speed applications can significantly affect circuit performance if not done correctly. This webcast will cover the ins and outs of PCB design and layout, in a practical and straight forward approach. The presentation is packed with useful information accumulated with tips, tricks and techniques that can easily be implemented into your next design to help improve overall circuit and system performance.

Who should attend?
This webcast is a “must see” for students and those new to PCB design, especially for those concerned with high-speed circuitry.  It will also be a good refresher to those experienced in layout.

Read more…

Turing Fellowship works to fill New York’s engineering pipeline @ Tech News and Analysis.

New York’s got an abundance of almost everything, but engineers are increasingly a precious commodity. But the NYC Turing Fellows Program is revving up in its second year to really take on the problem and start feeding more tech talent to the exploding startup scene.

The Turing Fellows Program last summer placed 19 college interns out of 750 applicants at New York startups including Tumblr, Foursquare and others. Now, the paid internship program is expanding, and will place around 25 to 30 engineering, mathematics or computer science students at startups this summer. The application process, which quietly began earlier this month closes on Feb. 6.

The program is co-organized by Canaan Partners, FirstMark Capital, Tribeca Venture Partners and First Round Capital. This year’s crop of startups include Etsy, Second Market, BuzzFeed, Blip and many others. Other supporting partners include Amazon, SV Angel, David Tisch of New York TechStars, Silicon Valley Bank, and Esther Dyson, along with the New York City Economic Development Corp. and the New York City Investment Fund.

…He said the program tried to pick a diverse group of startups that spanned advertising, mobile, e-commerce and financial technology to give students different opportunities.

Great idea, and a great start. Looks like there are not any hardware companies, maybe next year

8-voices mixed in the micro, with nothing on the output but an RC integrator.

What the heck is a “Fraunchpad”? Well, it’s similar to the Launchpad, but with FRAM (Ferroelectric RAM, not an oil filter). Specifically, it’s the MSP-EXP430FR5739. The song data is stored in the FRAM.

The source code and more info is available here.

Nice hack, oPossum!

A big part my New Year’s Resolution to improve my overall design process was better testing. Better testing is an important part of better and more intentional design, but it means having tools that you can trust and that can consistently give you the results you need.

While I’ve built up a decent little collection of toys over the years, I spent quite a bit of time late 2011 figuring out what I wanted to add or replace on my workbench in 2012 to be able to improve projects I’m working on. At the top of the list was a faster mixed-signal oscilloscope, followed by a more reliable bench-top multi-meter, and a decent function generator rounding the big ticket items out.

After spending quite a bit of time selecting a scope that matched my budget and requirements, and looking (importantly!) at the ecosystem around that scope, I settled on Agilent’s new MSOX2000/3000 series — specifically, the Adafruit Christmas Elves picked out an MSOX2024a (the screenshot above was taken on this scope).  These scopes (in my opinion) are an excellent value for a mid-range scope, and really raise the bar for the competition in the $2-5K range.  I’d like to write a few blog posts on the reason behind that choice and the thinking behind the whole list of items above, but as a first foray into that I thought I’d try to explain some of the details you should keep in mind if you’re thinking about a scope yourself (probably the most useful tool on any EEs workbench after a multimeter).

The most obvious factor when choosing an oscilliscope is bandwidth. 50MHz is better than 20MHz, and 100MHz is definitely better than 50MHz, etc., but what does that number really mean, and how fast is fast enough for your needs? There are already some good resources out there that go into exhaustive details on this … but for the executive summary read on.

The biggest influence on the price of a scope is it’s bandwidth (50MHz, 100MHz, 200MHz, 350MHz, … 2GHz, etc.) and the number of analog samples per second that it can read (1Gs/s, etc.). These two numbers are related, and most people know that the samples per second needs to be at least 3-5 higher than the bandwidth for accurate results (meaning a 100MHz scope should have ~500Ms/s, or even better 1GS/s for reliable results).

But what does the 50MHz or 100MHz really mean? If I purchase a 50MHz scope can I accurately capture and measure 50MHz worth of data? The answer (like everything else in engineering) is: it depends. You should be able to measure frequency up to and even beyond the maximum rated value, so if determining frequency is all that matters (checking how accurate the output of an oscillator is, the pixel clock on an LCD controller, etc.) you can safely go up to the maximum. Where things become more fuzzy is amplitude (the upper and lower voltage values measured by the scope).

The bandwidth of an oscilloscope actually indicates the point at which the measured amplitude on an amplitude/frequency chart has decreased by -3dB (or 70.7%) of the original value! Your frequency will be good up to and perhaps even slightly beyond the maximum rating of the scope, but at the maximum rated frequency, the amplitude will be ~70% the actual value so you’re 5V signal will actually show up as ~3.5V, and 3.3V will show up as ~2.3V! This can cause you to panic and think you have a bad oscilloscope, or that your PCB or circuit is rubbish, simply because you might not have been aware of this principle.

As an example, have at look at the screenshots below. They’re both capturing the 3.3V 40MHz pixel clock of a large (800×480) TFT LCD, and the frequency is the same, but the peak to peak voltage on them is very different. The Tektronix image is from a 350MHz oscilloscope (using a 500MHz probe since this is also important!), and the other is from a 50MHz Rigol scope (sw ‘upgraded’ to 100MHz) using the probes in 1x mode (which is limited to 7MHz bandwidth).  The peak to peak voltage (VPP) on the Tektronix scope is accurate (it says 3.4V since there is a slight peak on the rising edge), but the Rigol only shows 1.4V, though both capture the 40MHz frequency correctly!

Why is that, you ask?  The 1.4V is so low because you also need to pay attention to the maximum bandwidth of the probes you’re using with the scope, since the same effect applies to them as well as the bandwidth on the scope itself!  Use a slow probe on even the most expensive scope and you’ll be throwing all of that resolution (and money) out the window.  In the case of the Rigol scope I was using the probes in 1x mode (you can select between 1x and 10x directly on the probes), which is limited to 7MHz (at 10x they are much more useful with 150MHz bandwidth).  Make sure you know the bandwidth of not only your oscilloscope, but of the probes you have attached to them as well.  Unless you are measuring fairly slow signals with the Rigol scopes, you should always use the 10x mode since the probes will perform much better than in 1x mode, though you need to remember to multiply all the displayed values by ten after the fact (so 300mV is actually 3V, etc.).

The following chart (from Tektronix “ABCs of Probes Primer”, p.35) illustrates the relationship between bandwidth and amplitude:

What does this have to do with selecting an oscilloscope? The biggest take away is that if you need to accurately measure not just frequency on your oscilloscope, but amplitude as well, you need to make sure that the rated bandwidth of both the scope and the probe attached to it are well above the signal you need to accurately capture. If you need the amplitude to be accurate to ~1%, you need to derate your scope by a factor of 0.1x, meaning that on your 100MHz scope you can only capture 10MHz with a 1% error in amplitude. If you require 3% accuracy, you need to derate it by a factor of ~0.3x, so a 100MHz scope can accurately measure 30MHz to 3%.

Does this mean you need a $15K 500MHz scope to accurately measure anything, and the entry-level 50MHz scopes out there are useless? Absolute not! I’m still convinced the entry level digital scopes out there (Rigol, etc.) are an absolutely amazing deal and an exceptionally smart investment for any budding young engineer … but you do need to understand the table above to get the most from them. This table allows you to measure signals at the maximum bandwidth of your scope … you might just need to do a bit of math to scale them up after the fact.

Oscilloscopes are incredibly useful tools and one of the best investments you can make, but it does take time to understand the limitations of this type of test equipment. As with anything else in electronics, you really need to understand where the weakest links in your system are, and if you can’t replace those weak links, you at least need to fully understand them and compensate for that in the best way possible. I wouldn’t hesitate to recommend any serious newcomer to electronics picks up an entry-level Rigol oscilloscope. It’s a far better investment than any of the toys on eBay, and an exceptional value for the money … but it is important to learn your tools, and to know where their limits are.

The moral of the story: for the least amount of work on your part, always buy the best tools you can afford. If your means are limited, still buy the best tools you can afford, but make sure you understand what you are measuring and the limitations of your tools, and find creative ways to work around them.

Further Reading

If you’re new to oscilloscopes or just looking for a bit more information on this or other subjects, the following links might be useful to you:

• Evaluating Oscilloscope Bandwidth for your Application (Agilent)
• ABCs of Probes Primer (Tektronix … registration required)
• Evaluating Oscilloscope Fundamentals (Agilent)
• XYZs of Oscilloscopes (Tektronix … registration required)

Basics: Power dissipation and electronic components @ Evil Mad Scientist Laboratories.

An ever-present challenge in electronic circuit design is selecting suitable components that not only perform their intended task but also will survive under foreseeable operating conditions. A big part of that process is making sure that your components will stay within their safe operating limits in terms of current, voltage, and power. Of those three, the “power” portion is often the most difficult (for both newcomers and experts) because the safe operating area can depend so strongly on the particulars of the situation.

In what follows, we’ll introduce some of the basic concepts of power dissipation in electronic components, with an eye towards understanding how to select components for simple circuits with power limitations in mind.

Read more!

Interesting news for chiptune and 8-bit folks — the 6502 is back! From h-online:

The 6502 processor from the 1970s is alive once again – and as a proper 40-pin chip in a dual in-line package (DIP) housing, not just as an embedded core. Mouser Electronics has added the 8-bit classic, since modernised by WDC(Western Design Center), to its product range, making it available in the UK for £4.90.

Apparently, the W65C02S6TPG-14 – its current name – is pin and software compatible with its grandfather, a 1975 drawing board design by Bill Mensch and Chuck Peddle that was later used in the early Apple and Commodore computers as well as the UK’s own BBC Micro. Like other members of the 6502 family, the W65C02S6TPG-14 offers an extended set of instructions and a clock speed of up to 14 MHz (instead of the original 1 MHz). Incidentally, WDC also offers a “virtual” version of the 65C02: an IP core designed for field-programmable gate arrays (FPGAs).

It’s currently selling at Mouser US for $7, which sounds a bit steep for a 30+ year old 8-bit micro design, but I have no idea what the production volume is.

[via Dave Jones]

Veronica – ROM Board @ Blondihacks.

It seemed so simple. The best ideas always do. However, sometimes the smallest problems end up taking the most time to solve. There was some swearing, I won’t lie.

You see, I had a really swell circuit that could take a ROM image and dump it into an SRAM. Since parallel EEPROMs exist that are accessed just like SRAMs, I figured I could just buy one, drop it in, and presto- ROM for Veronica. Flawless plan, right?

Well, a hundred hours or so later, it turns out the plan was in fact pretty darn solid, but the parts were against me. To recap,  I designed a board for Veronica that would hold an EEPROM chip, and had a built-in ATTiny that acted as an interface between the EEPROM and my USBTinyISP programmer. Since EEPROM programmers are very expensive, this was a way to leverage the tools I had to program the ROM that Veronica needs to boot up.

Read more, Veronica continues…

David Clift-Reaves has created MezzoMill, a PCB router which can provide custom single-sided PCBs in short order. He’s currently running a kickstarter to get the project into production. He writes:

The conversation that I had hoped that MezzoMill would help to shine a light on is the need for individuals, hackerspaces, and schools to have small-scale electronics manufacturing facilities. I believe that there are 3 key technologies that are necessary to a modern electronics fab. First is the ability to print circuits. Second is the ability to place modern components on the circuit. Finally, the third is the ability to do reflowing.

Like the iBooks Author program, I feel that these disruptive technologies have the ability to empower people and transform an industry. Clearly all of the technologies already exist for creating these machines. People hack together various versions of them all the time. There needs to be work done towards mass producing them and a guiding vision for making all of them work together seamlessly.

I designed the MezzoMill to simplify the problem of printing circuits. It turns the experience of printing circuits from EAGLE to one like from your word processor to your inkjet. It makes the process safe and repeatable while reducing the user interaction with the process as much as possible. It is the only solution in its price range that provides this user experience to individuals.

Very cool! I see hacks all the time where people have put together PCB routers using gantry dremels and the like, but the focus here is on self-contained, user-friendly repeatability and flexibility. That’s something which a lot of home builds lack — not intentionally, mind you, but they are built by users for themselves and require less generalization. I think a general machine designed for a wider user base is the next logical step.

Check out the MezzoMill page or the Kickstarter page to learn more.

My first recommendation is to not blindly trust library parts created by others.  The problem is that I have found way too many errors in libraries created by others.  You might think that since someone else has a working design using a part from the library, that the part must be right. While it is a good sign, the reality is they may have corrected an issue in their copy of the library, or worked around it somehow.

So I check any part I use for the first time from another source very carefully.  It takes some time to do a thorough check, but it is far less time than you will loose if you have PCB’s built with errors.

…

I start a design by downloading the datasheets for parts I am going to use in my project. Usually near the top of the datasheet you will find pinout information, and near the bottom you will find the package dimensions and sometimes a recommended footprint.

The manufacturer’s recommended footprint is meant for volume production on automated machinery.  I will take it as a starting point, but I usually increase the pad sizes for hand assembly, to give me more pad to touch with the soldering iron.  This is especially true for SMT parts.

You can read his whole post here — lots of good advice in there!

Have you ever had a pin on a 0.1″ header that you just couldn’t get to reflow properly, especially with lead free solder (which requires a higher temperature to work with)?  If so, it was almost certainly a GND pin connected to a large GND plane.  The problem is that the GND plane dissipates a lot of the heat from the soldering iron.  You can try using a much larger tip (larger tips do a better job of conducting heat that small ones), and/or you may need to jack the heat up quite a bit, but sometimes it just won’t reflow well to form a solid joint.  The solution is easy, but you need to keep the problem in mind when designing the PCB.

What you need to add on any GND pin connected to a GND plane (a large area of copper connected to GND) is to restrict the connection to GND to a single bridge, limiting the other areas with layers 41 (tRestrict) or 42 (bRestrict).  Just select the rectangle tool and draw a small rectangle beside the pad over 3 of the four bridges, and you should have a MUCH easier time soldering those pins on after the fact.  This can also be a good idea with certain large surface-mount parts.

Learning to design your own PCBs and being able to put together a schematic to solve a specific problem is both a valuable and rewarding skill.  There are a number of resources out there to help you avoid common mistakes, but it isn’t always obvious to know where the values of certain common components come from, particularly common parts like resistors and capacitors.  Figuring this out is part of the learning process, but it isn’t always easy to know where to look since you first need to know exactly the right terms to search for.

One good example that I haven’t seen a lot of attention paid to is deciding which crystal to use for your board and which caps go with it. Most people just copy and paste what they found on some other schematic (“12MHz + 22pF? … sounds good!”).   Unfortunately, if you want to get accurate and stable results out of the crystal, you need to match the capacitors to the specific crystal you chose, and it varies from model to model even with the same manufacturer.   Fortunately, it’s trivial to calculate the right capacitors for your crystal.

A 12MHz crystal that I use quite a bit is the NX3225SA-12.000000MHZ from NDK.  It’s a good size, stable (+/-15 ppm), and easy to find.  I use the more expensive +/-15 ppm model for better input to the PLL, but if you don’t use the right capacitors along with the crystal your signal will never be anything remotely close to +/-15ppm and you may as well buy a much cheaper crystal.

So how do you know which capacitors to use?  Easy.  Every crystal datasheet lists something called the Load Capacitance (CL).  In the case of the crystal above, it’s 8 pF.  C1 and C2 need to match this Load Capacitance, with the following formula being the key:

CL = (C1 * C2) / (C1 + C2) + Cstray

C1 and C2 are the two capacitors that you see attached to the crystal, but you might be wondering what Cstray is.  Unfortunately, every trace, every lead on your component, just about everything on your PCB has some stray capacitance.  The total of these values is represented by Cstray.  You can usually guestimate this in the neighbourhood of 2-5pF as long as you follow good layout practice and keep the trace from the crystal to the pins on the MCU as short as possible with no vias, etc.

We know CL since it’s stated in the crystal datasheet (8 pF), and we know Cstray (say ~5 pF), so all we need to do is test our value for C1 and C2 to make sure that it will match CL taking into account Cstray.  A commonly tossed around rule of thumb is to start with a pair of capacitors two times the CL of the crystal, which will get you to CL.  In this case, that would be 2*8 pF = 16pF for the capacitors.  Unfortunately, this ignores the stray capacitance (Cstray), and won’t give you the best results.  Even if you are guestimating Cstray you will get better results taking it into account, but it means just using a capacitor 2* CL won’t work:

CL = 8 pF
C1, C2 = 16 pF
Cstray = 5pF

(16 pF * 16 pF)/(16 pF + 16 pF) + 5 pF= 13 pF

13pF is much too high to get the best results from your crystal.  If instead of 16pF, we take a lower 6 pF value this will give much better results:

(6pF * 6pF)/(6 pF + 6 pF) + 5 pF =8 pF

If you think the stray capacitance is a bit lower, say 3pF, you might try a 10pF capacitor:

(10 pF * 10 pF)/(10 pF + 10 pF) + 3 pF = 8pF

There’s an obvious tradeoff between choosing a standard capacitor value, and having a good idea of what your Cstray is, but the above formula should at least explain HOW to determine what value those capacitors should be relative to your crystal.  Even using a ballpark Cstray plud good layout should give you far more accurate results than just copying and pasting a value you saw on another schematic unless you’re using the exact same crystal model (which is unlikely since they are rarely even listed in the schematic).

A better rule of thumb is: C1, C2 = 2*CL – 2*Cstray

Further Reading

AN2867 – Oscillator design guide (ST Microcontrollers)

Why College Students Leave the Engineering Track @ NYTimes.com.

mid broader discussions about the future of the American work force, the National Science Foundation has just released a comprehensive report on the state of engineering and science in America. There’s a lot of meat in the report, but I found this chart to be particularly striking…

Interview with Mikey Sklar @ EEWeb. One of our favorite people gets some nice digital ink…

How did you get into electronics / engineering and when did you start?
When I was a kid my school sent me to a NeuralLinguistic Programming center. They said I had some sort of learning disability. The NLP folks suggested to my mom that I get a computer and play games with it. Mom bought me an Apple II clone and we both tried to figure out how to use it. At 16 years old I decided to finish High School at a community college which freed up many hours that I used to get to know the computer. By the time I was twenty I worked for three fortune 100 companies (AT&T, Morgan Stanley and Hughes Aerospace) as a UNIX admin managing 3 of the top 100 supercomputers in the world. Mom became a computer teacher.

Years of debugging hardware issues on the big iron helped me to realize that my interest was in the small parts that made up these systems. Without an EE background I started out by reading the usual EE literature, Forest M. Mims III and Horowitz and Hill. At 25 I began programming microcontrollers.

Around the same time a friend suggested that I make illuminated clothing to prepare for my first year attending the desert art festival called Burning Man. In the festivals temporary city called Black Rock it is customary to wear illumination, many wear glow sticks or self made electronics, in order to avoid being run over by a rogue bicycle rider or art car. I took his advice and started connecting up LEDs and EL-Wire and adhering them to my clothing. The same friend scoffed at what I made and suggested that I sequence the lights with a microcontroller. Thinking that this was a fine idea I I took his suggestion and found myself in a 10 year long infatuation with hardware development and the proud owner of a closet full of illuminated garments.

…

What direction do you see your business heading in the next few years?
I’m following the Adafruit model. I setup a Zen Cart based an on-line store. I sell my projects in two forms, as kits and pre assembled. I plan to produce 2 to 4 new electronics kits each year and I hope to limit the amount of consulting that I need to do as a result.

Read more!

Basics: Introduction to Zener Diodes @ Evil Mad Scientist Laboratories.

Zener diodes are a special type of semiconductor diode– devices that allow current to flow in one direction only –that also allow current to flow in the opposite direction, but only when exposed to enough voltage. And while that sounds a bit esoteric, they’re actually among the handiest components ever to cross an engineer’s bench, providing great solutions to a number of common needs in circuit design.

In what follows, we’ll show you how (and when) to use a Zener, for applications including simple reference voltages, clamping signals to specific voltage ranges, and easing the load on a voltage regulator.

Temperature sensor – A trip to Steinhart-Hart, Gaussian elimination and thermistors @ skytee.

I made a thermistor-based, water-resistant temperature sensor to be used with a micro controller. Here I document the process on how to get the thermistor calibration data.

Recently, my friend w0z visited after 28c3 and we ended up checking out Segor, a brick-and-mortar electronics shop in Berlin. It’s to me like a candy shop is to kids. Among other things, athermistor module picked my interest, mostly because I had never used one before.

The thermistor module I got came as a thermistor and an op-amp on a PCB. I hooked it up to an Arduino’s analog input pin and sure enough I could see the input data change when I exposed the sensor to warm air.

A really good summary of how to use thermistors and solve the Steinhart-Hart equation.

Veronica – EEPROM Programmer @ Blondihacks.

Well, now that Veronica is up and running in real hardware form, she needs some real ROM to play with. That means I need a way to burn an EPROM (UV-erasable) or flash an EEPROM (electrically-erasable). The latter seems easier to use, but the programmers for them are very expensive. So what’s a girl to do? Well, I may not have an EEPROM programmer, but I do have the excellent (and cheap!) USBTinyISP in-circuit programmer for AVR microcontrollers. Can I leverage its abilities to program an EEPROM? I bet I can…

Digi-Key Continuing Education Center

As part of the new the Digi-Key Continuing Education Center, Design News has engineered 180 days of free interactive courses. These courses will cover microcontrollers, sensors, lighting, embedded Internet and cloud, wireless, power, and much more. Take one or all. 

Looks pretty good!

My friend Alan (w2aew) has done a great little video about bandwidth factors in scopes. He writes:

I’m often asked by hams and hobbiests – I want to buy an oscilloscope, what bandwidth scope do I need? I usually answer – buy as much as you can afford, even if you are working on low frequency circuits. This video shows an example of why. Even simple audio circuits might have some hidden evils!

Such is the treachery of oscilloscopes — ceci n’est pas un signal!

(Also, that trace at the 3-minute mark looks like the Bat Signal — na na na na na na na na band-wiiiiidth…)

UPDATE: Alan has made a follow up video covering digital scopes as well — check it out:

Nanoscale wires defy quantum predictions @ Nature News & Comment.

Microchips could keep on getting smaller and more powerful for years to come. Research shows that wires just a few nanometres wide conduct electricity in the same way as the much larger components of existing devices, rather than being adversely affected by quantum mechanics.

As manufacturing technology improves and costs fall, the number of transistors that can be squeezed onto an integrated circuit roughly doubles every two years. This trend, known as Moore’s law, was first observed in the 1960s by Gordon Moore, the co-founder of chip manufacturer Intel, based in Santa Clara, California. But transistors have now become so small that scientists have predicted that it may not be long before their performance is compromised by unpredictable quantum effects.

It’s true that I posted the video of the Open Hardware Summit version of this talk back in September, but that was shot with my Flip video and as a result you couldn’t always read the beautiful slides. The video production here is a lot better — meanwhile, the talk is still awesome!

Yay, w0z!

Check out this video by Giorgos Lazaridis, in which he dissects a cheap digicam power supply from eBay and finds some surprising things inside, including some very questionable inductors.

[via HaD]

Veronica – CPU Board @ Blondihacks.

Now that we have Veronica’s backplane mostly sorted, we have everything we need to move the 6502 itself off the breadboard and into “the real world”. No more training wheels! *sniff* I just hope she holds her balance when I let go of the seat…

Happy Birthday C64! Introduced 30 years ago this month at the 1982 Consumer Electronics Show! From HLNTV:

Would you pay $1,400 for a computer with less than one megabyte of memory?

Oh yes, you would.

In fact, in 1982 more than 300,000 people did just that, dropping $595 (or, $1,400 in 2012 dollars) to snap up the awesome, brand new, super-powerful Commdore 64 – and all of its 36 useable kilobytes of memory.

The classic machine is celebrating its 30th birthday this week. It was first introduced at the 1982 Consumer Electronics Show in Las Vegas.

And while those quaint specs seem flimsy now — those 36 kb are the equivalent of 1/10th of a typical MP3, so basically the whole machine could store the first 40 seconds of the 1982 Survivor smash hit “Eye of the Tiger” – they were revolutionary and a relative bargain back in ’82. And the Commodore 64 even displayed color graphics!

During its mid-1980s peak, the PC sold 2.5 million units a year and generated a lifetime of passion and loyalty from many of its users, many of whom are now dropping nostalgic tweets.

Awesome on-board hardware like the VIC-II graphics chip and the SID audio synthesis chip ensured that the C64 would remain a popular platform in the demoscene. The list of C64 demos is enormous, and it grows regularly.

If you ever meet somebody who worked at Commodore (or MOS Technology) in the 1970′s-80′s, give them a hug or a high-five!

Driving 595 Shift Registers. Mike writes in -

Thanks for the ATmega32U4 Breakout Board and TPIC6B595 chip. They are super! I am using them to learn basics.  I always write a blog entry about what I learn. This way I am forced to learn the details and remember things better. Currently learning about shift registers and SPI.

This is so cool, and it has enormous potential — think nanotransponders for the Internet of Things (or sub-dermal radios). From nanotechweb:

The first graphene device capable of significant voltage amplification (more than 10 dB) has been fabricated by researchers in Italy. The result confirms that the “wonder material” could compete head-on with silicon as the material of choice in electronics and is not simply limited to niche, low-voltage gain, high-frequency applications as currently thought.

The voltage amplifier (a device capable of amplifying small alternating voltage signals) is the main building block in analogue electronics. Thanks to its unique electrical and mechanical properties, graphene (a sheet of carbon atoms arranged in a honeycomb-like lattice just one atom thick) should be ideal for use in a host of technological devices – such as high-speed transistors – and in photonics. However, many scientists believe that it cannot compete with silicon in applications requiring voltage amplification, like analogue amplifiers and digital logic gates.

…

Even though it is their first graphene amplifier, it already shows “remarkable performance”, according to Sordan and colleagues – with a flat frequency response well exceeding the audio range (>20 kHz) and a very low total harmonic distortion (<1%).

Read more…

(above: Paul Dirac, who was totally rad and probably could’ve answered this question)

My friend Bill pointed out a terrific question recently asked on Quora: “what is it like to have an understanding of very advanced mathematics?” — something I’ve definitely wondered myself. I have a pretty solid understanding of calculus and linear algebra, but the really advanced stuff just seems kind of like magic to me, and the people who understand it are sort of like superheroes.

There are about a dozen answers given to the Quora post, but the first one — an anonymous response — is just superb:

• You can answer many seemingly difficult questions quickly. But you are not very impressed by what can look like magic, because you know the trick. The trick is that your brain can quickly decide if question is answerable by one of a few powerful general purpose “machines” (e.g., continuity arguments, the correspondences between geometric and algebraic objects, linear algebra, ways to reduce the infinite to the finite through various forms of”compactness) combined with specific facts you have learned about your area. The number of fundamental ideas and techniques that people use to solve problems is, perhaps surprisingly, pretty small — see http://www.tricki.org/tricki/map for a partial list, maintained by Tim Gowers.
• You are often confident that something is true long before you have an airtight proof for it (this happens especially often in geometry). The main reason is that you have a large catalogue of connections between concepts, and you can quickly intuit that if X were to be false, that would create tensions with other things you know to be true, so you are inclined to believe X is probably true to maintain the harmony of the conceptual space. It’s not so much that you can “imagine” the situation perfectly, but you can quickly imagine many other things that are logically connected to it.
• You are comfortable with feeling like you have no deep understanding of the problem you are studying. Indeed, when you do have a deep understanding, you have solved the problem and it is time to do something else. This makes the total time you spend in life reveling in your mastery of something quite brief. One of the main skills of research scientists of any type is knowing how to work comfortably and productively in a state of confusion. More on this in the next few bullets.

You can read the whole thing here. It’s quite thorough and informative.

Thank you, anonymous mathematician(s), whoever you are!

[h/t Daniel Lemire via Bill Ward]

An extremely entertaining article from New Scientist:

LATE one June afternoon in 1903 a hush fell across an expectant audience in the Royal Institution’s celebrated lecture theatre in London. Before the crowd, the physicist John Ambrose Fleming was adjusting arcane apparatus as he prepared to demonstrate an emerging technological wonder: a long-range wireless communication system developed by his boss, the Italian radio pioneer Guglielmo Marconi. The aim was to showcase publicly for the first time that Morse code messages could be sent wirelessly over long distances. Around 300 miles away, Marconi was preparing to send a signal to London from a clifftop station in Poldhu, Cornwall, UK.

Yet before the demonstration could begin, the apparatus in the lecture theatre began to tap out a message. At first, it spelled out just one word repeated over and over. Then it changed into a facetious poem accusing Marconi of “diddling the public”. Their demonstration had been hacked – and this was more than 100 years before the mischief playing out on the internet today. Who was the Royal Institution hacker? How did the cheeky messages get there? And why?

…

That things would not go smoothly for Marconi and Fleming at the Royal Institution that day in June was soon apparent. Minutes before Fleming was due to receive Marconi’s Morse messages from Cornwall, the hush was broken by a rhythmic ticking noise sputtering from the theatre’s brass projection lantern, used to display the lecturer’s slides. To the untrained ear, it sounded like a projector on the blink. But Arthur Blok, Fleming’s assistant, quickly recognised the tippity-tap of a human hand keying a message in Morse. Someone, Blok reasoned, was beaming powerful wireless pulses into the theatre and they were strong enough to interfere with the projector’s electric arc discharge lamp.

Read more…

Decades later, a Cold War secret is revealed.

It was dubbed “Big Bird” and it was considered the most successful space spy satellite program of the Cold War era. From 1971 to 1986 a total of 20 satellites were launched, each containing 60 miles of film and sophisticated cameras that orbited the earth snapping vast, panoramic photographs of the Soviet Union, China and other potential foes. The film was shot back through the earth’s atmosphere in buckets that parachuted over the Pacific Ocean, where C-130 Air Force planes snagged them with grappling hooks.

He describes the white-hot excitement as teams pored over hand-drawings and worked on endless technical problems, using “slide-rules and advanced degrees” (there were no computers), knowing they were part of such a complicated space project.

Thank an Engineer @ TI E2E Community.

What would happen if we finally invented personal teleportation? Who are the engineers responsible for creating the artificial heart and Moog synthesizer?

What happens when you take four engineers, film them walking in slow motion, and put a sweet guitar riff in the background?

Thank an Engineer is here to answer those hard hitting questions. From funny videos to blogs to forums, thx is where engineers go to interact with their peers outside of the lab and get the recognition and admiration they deserve.

You should know that resistance to the program’s hold is futile…if less than 1 Ω.

Read more…

mate cosies: warm hands, cold mate. fabienne writes -

I’m offering a small run of mate cosies: “warm hands, cold mate” for this winter season. Each mate cosy is produced on my hacked kh930 knitting machine, by hand by me (the machine isn’t motorized yet) and then finished by hand by me. They are available in this limited run (probably around 40 pieces total) for a price of 60 euros for either black/white or black/red. If you would like a special order QR code on the front of your black/white cosy, that will cost 80 euros. The QR codes don’t really work very consistently since little knit v’s are not easily recognized as square pixels. They sort of work in the dark. You could improve this by writing a QR code reader filter that “sees” v’s as pixels. If you are the first to code such a filter, or if you are the first to code up any other means for creating readable QR codes for knitting, and you open source the code, I will give a cosy to you for free.

Veronica @ Blondihacks.

It’s time to starting making some of these bits (pardon the pun) solid, both so I can work on new interesting abilities for Veronica, and so I can have some damn breadboards back.

I spent a lot of time thinking about this, and planning out various strategies. I’ve settled on what’s called a Backplane Design. Essentially, every component of the machine is treated as a module that is plugged into a large master bus. Wikipedia has a nice treatment of this topic. Ideally, everything is completely general, so you could have multiple CPUs, multiple memory systems, or any other weird combination of components. In reality, that’s a lofty goal, and mine won’t be so fancy. This is in contrast to a motherboard design, where most major systems are on one large board, and you have a couple of connectors or slots for expansion in specific ways.

So cool! Check out the first post about this project.

The Comeback of Xerox PARC  @ Technology Review.

Last month, a small Norwegian company called Thinfilm Electronics and PARC, the storied Silicon Valley research lab, jointly showed off a technological first—a plastic film that combined both printed transistors and printed digital memory.

Such flexible electronics could be an important component of future products, such as food packaging that senses and record temperatures, shock-sensing helmets, as well as smart toys. But the story of how PARC’s technology—the printed transistors—wound up paired with memory technology from an obscure Norwegian company also provides a window onto a 10-year struggle by Xerox to transform the way it commercializes R&D ideas.

For most of its 40-year history, PARC (for Palo Alto Research Center) was as famous for squandering new technologies as it was for inventing them. The mouse, the graphical user interface, and the drop-down menu were all born at PARC—but it was Apple and Microsoft that commercialized them and made them cornerstone inventions of the PC industry.

STOCKING STUFFERS FOR ENGINEERS – Modular snap-together boxes, these are awesome. We’re going to have a stocking stuffer-per-day post now until the holidays. Here is today’s suggestion!

We sold out fast when we first got these in, but we just received another shipment of these awesome snap-together boxes. Perfect for all your electronic component storage needs!

BACK IN STOCK- Modular snap-together boxes, these are awesome. Got OCD? SMD? You need these boxes! For storing small parts (especially SMT/SMD components), these little modular boxes are ideal. They have individual clear pop-open covers so you can keep only the ones you want open – less risk of mixing up parts or having a spill. The brilliance of these boxes is that they also snap together, in any configuration you want. You can mix all the sizes to make the ideal box for your needs, and add on more containers as necessary. There’s a leaf-spring hinged top that will last much longer than an all-plastic molded top.

Small, medium and large:

Small Modular Snap Boxes – SMD component storage – 3 pack – Green

Medium Modular Snap Boxes – SMD component storage – 2 pack – Pink

Large Modular Snap Box – SMD component storage – Orange

Antistatic!:

Antistatic Modular Snap Boxes – SMD component storage – 5 pack – Antistatic

Tiny boxes for SMD! In every color of the pastel rainbow!

Tiny Modular Snap Boxes – SMD component storage – 10 pack – White

Tiny Modular Snap Boxes – SMD component storage – 10 pack – Orange

Tiny Modular Snap Boxes – SMD component storage – 10 pack – Green

Tiny Modular Snap Boxes – SMD component storage – 10 pack – Blue

Tiny Modular Snap Boxes – SMD component storage – 10 pack – Pink

EmbeddedEric saw last week’s Oscilloscope Christmas Tree post, and decided it would be a fun project to do with his kids. He writes:

I thought this would be a fun project to replicate with my 2 and 4 year old daughters, but I wanted to make a small tweak and display a picture of Frosty the Snowman. My two year old discovered the old Frosty the Snowman cartoons this year and is constantly asking to “watch a frosty”.

I downloaded John’s Arduino sketch and took a look at it to see what I’d have to do to change the picture displayed on the scope. His code is very well laid out and the picture is defined by the number of points and the X Y coordinates stored as two arrays.

Now how do I draw a picture of a snowman and get X Y coordinates out of it? I tried GIMP and Paint, but ended up using Scilab…… yes a fancy math program to draw a snowman! The nice thing about Scilab is you can plot pictures using the same X & Y arrays needed for the Arduino sketch.

I could have gotten all fancy and used sin & cos equations to get a nice smooth circle, but a line segment circle gets the job done too, and is equally impressive to a two year old

…

My daughters had fun making him taller and shorter and skinny and fat all with a few button presses.

Awesome!

Source code and more at his blog. Nice work, Eric!

Editor’s note: Something which I neglected to mention when I originally posted the Christmas Tree was that I used the Eagle PCB editor to generate the drawing points. I enclosed a square 2.56″x2.56″ and then did my drawing in there, with a 0.01″ snap, using the line tool. Then I simply multiplied by 100 to get the points for the matrix. One of the nice things about Eagle is that the window needn’t be active for the coordinates to be “live”, so you can type into the Arduino IDE without having to go back and forth between them — just mouse over the point of interest. Thought I’d share that, since I forgot to mention it before.

Part of our new sewing and textiles section of the partfinder, we’ll be including where to buy sewing and crafting supplies!

First up is the little plastic bobbins we use to spool our conductive thread http://www.adafruit.com/products/603 on, these little guys are basic plastic bobbins. They’ll work in many machines as well, but for spooling small amount of thread these are awfully cute and very low cost – about 15 cents per and with fast shipping from a USA seller.

Exclusive: Made in Texas: Apple’s A5 iPhone chip | Reuters.

Apple Inc is famous for relying on low-cost Asian manufacturers to both source and assemble its popular gadgets, but the consumer device giant recently started receiving a critical component in its iPad and iPhones from closer to home – Texas.

The A5 processor – the brain in the iPhone 4S and iPad 2 – is now made in a sprawling 1.6 million square feet factory in Austin owned by Korean electronics giant Samsung Electronics, according to people familiar with the operation.

One of the few major components to be sourced from within the United States, the A5 processor is built by Samsung in a newly constructed $3.6 billion non-memory chip production line that reached full production in early December.

UPDATE: You could actually get (Chip)MADE IN THE USA engraved on the back on iDevices.

Alan just tipped me off to this great 2-hour+ presentation all about the history and use of scopes, complete with an online textbook:

The New Jersey Antique Radio Club, continuing a long tradition of technical training for the electronics hobbyist, conducted the club’s first Oscilloscope School in March, 2011. This hands-on “boot camp” introduction to using oscilloscopes was presented at the historic site of Marconi’s 1914 Transatlantic Receiving Station, later home of the U.S.Army’s Signal Corps Laboratories at Camp Evans, and now the home of the InfoAge Science and History Learning Center.

The program is presented in three parts:
Part 1: History of Oscilloscopes, by Al Klase, Technical Coordinator for NJARC
Part 2: Basics of Oscilloscopes, by Alan Wolke, Application Engineer at Tektronix Corporation (begins at 15 min. 42 sec. into the program)
Part 3: A Brief History of Oscilloscope Tubes, by Nevell Greenough (begins at 2 hr. 13 min. 35 sec. into the program.)

I hereby declare today Oscilloscope Friday!

Don’t Know How? Well, Find Someone Who Does @ NYTimes.com.

IS advanced technical knowledge necessary to become an inventor? Look at the story of Katherine Bomkamp, and you will see that it isn’t.

Ms. Bomkamp, 20, came up with the idea behind the Pain Free Socket, a prosthetic device that is intended to ease phantom limb pain in amputees. The device, now awaiting a patent, works by applying heat to the amputee’s joint socket through thermal biofeedback. The theory is that as the nerve endings are warmed, the brain is forced to focus on the heat rather than send signals to the absent limb.

Now a sophomore at West Virginia University, Ms. Bomkamp was in high school when she began working on her invention. At the time, she had zero background in chemical or electrical engineering, which were essential to the creation of the device.

“It was all completely foreign to me. I had no interest in engineering before this,” said Ms. Bomkamp, who was a criminal-justice major at her magnet high school in Maryland. In college, she’s studying political science, with plans to attend law school.

It’s inevitable that as you get more and more into the electronics hobby, you’ll find yourself in need of an oscilloscope. While multimeters are great for DC measurements, most of them are pretty bad at AC measurements, particularly at higher frequencies. For folks who have little experience with them, scopes can be baffling things. There are so many switches and dials and knobs, and they have a lexicon all their own. But all is not lost….

My friend Alan Wolke (w2aew) makes these great analog scope tutorials, covering subjects like probe selection, AC/DC coupling and timebase control which will help get you started understanding how to use these amazing tools. Alan drops a lot of knowledge here — you may have to watch these more than once to pick up all that he puts down — but it’s worth it. Knowing how a scope works will save you a lot of time when you make your measurements. Even if you don’t have you own scope yet, this is a good introduction to the terminology.

Check them out and enjoy!

STOCKING STUFFERS FOR ENGINEERS – Sugru!. We’re going to have a stocking stuffer-per-day post now until the holidays. Here is today’s suggestion!

Sugru – multicolor pack. Soft-touch silicone rubber that molds and sets permanently. Sticks to aluminum, steel, ceramics, glass, wood and some fabrics + plastics! sugru is the incredible new air-curing rubber for hackers, makers, gadget lovers & anyone else who wants to make things or make their stuff work better. Self-adhesive to most other materials, and flexible when cured, sugru is a versatile tool for hackers and makers – Repair and strengthen damaged cables and housing, mount components where you want them, strengthen attachments and protect against vibration, and a hundred other uses we’re sure youʼll find for it. This is great for prototyping. Be sure to read the entire product page including the tabbed sections before purchase.

Multi-colour 12 x 5g minipacks inside a lovely big pouch for $17.95. Sugru does have a ‘use by’ date – this batch is good till May 2012!

Top 10 uses of sugru for hackers and makers:

• Repair and strengthen damaged cables
• Mount components semi-permanently e.g. webcam / microphones / wires / switches
• Replace missing feet on speakers, laptops etc
• Mount components, and add feet to PCBs
• Repair casing / housing on computers and earphones
• Insulate wires
• Strengthen attachments, protect against vibration
• Enclose prototype electronics, make them waterproof
• Add feet under harddrives to allow air to circulate underneath
• Make awesome custom housing on USB flash drives

Properties, self adhesive sugru bonds to:

• Aluminum
• Steel
• Ceramics
• Glass
• Wood
• Some fabrics
• Some plastics

Features:

• Form by hand – no tools needed
• Colors can be mixed
• Cures at room temperature to a tough flexible silicone overnight
• Waterproof and dishwasher proof when cured
• “Loves” a bit of heat or cold, sugru is resistant from -60 degrees C to 180 degrees C
• UV resistant

Includes:

• Two 5 gram mini-packs of Blue Sugru
• Two 5 gram mini-packs of Green Sugru
• Two 5 gram mini-packs of Orange Sugru
• Three 5 gram mini-packs of Black Sugru
• Three 5 gram mini-packs of White Sugru

In stock and shipping now.

Fine tip curved tweezers – ESD safe. When soldering small surface-mount (SMD/SMT) components, one thing you’ll need is a good pair of tweezers. These are a great pair of every-day tweezers. They’re anti-static, anti-magnetic and made of hard stainless steel.

The tips are fine and pointy to pick up any size component. This particular model is 120mm long with a 9mm / 0.35″ gap at the tips while open, this allows it to pick up components with better precision for placement and steadying during soldering.

In stock and shipping now!

Fine tip straight tweezers – ESD safe. When soldering small surface-mount (SMD/SMT) components, one thing you’ll need is a good pair of tweezers. These tweezers are a great pair of every-day tweezers. They’re anti-static, anti-magnetic and made of hard stainless steel.

The tips are fine and pointy to pick up any size component. This particular model is 135mm long with a 12.5mm / 0.5″ gap at the tips while open, this allows it to pick of fairly large TQFP’s and SSOP’s for placement and steadying during soldering.

In stock and shipping now.

STOCKING STUFFERS FOR ENGINEERS – Mitutoyo – Absolute Digimatic Digital Calipers. We’re going to have a stocking stuffer-per-day post now until the holidays. Here is today’s suggestion!

HamRadio2008 writes -

The demonstration is of the Mitutoyo Electronic Caliper measuring SOT-223 component and 1 inch reference. Also a small voltage monitor that I added to a battery I use for microcontroller projects..

This tutorial is for the Mitutoyo digital calipers we carry in the Adafruit shop. They’re the best calipers one can get and we’re pleased to offer them. We’ve put together a basic usage guide here to help people get started…

Read more!