Blog - Screaming Circuits

Electronic Business Card Holder, Part III

If you haven't yet read part one or two of this series, find them here:

With all of the key design decisions under my belt, it was time to build. I ordered the boards and parts myself, then hopped onto our website quote engine and placed a kitted order. At the time, I hadn't had anything built for a while, so it kind of freaked people out to get an order from within the company. When I do this, I like to go through our web system, just like any other customer, which sometimes causes a bit of a "we traced the call, and it's coming from inside your house..." moment.

20160324_103054Anyway, we didn't have any problems with the build. Fortunately, I took my own advice and carefully labeled the LED polarity. LED polarity marking "standards" are so unstandard, that extra caution is always a good thing. Anything to reduce ambiguity is welcome.

My calculations suggested that I should get six to nine months of battery life with a few cards being pulled per day. After running the blue LED version for about three months, I was satisfied that battery life would be sufficient. That was good timing, because at about the same time, I was down to about two weeks before the show that I was planning for (one of the Embedded Systems Conferences).

Again, I sent an order through our website. This time a full turn-key, using PC boards from Sunstone. And, this time, no one was 20160324_101515surprised by seeing an in house order. I ended up with plenty of time to program the boards before the show, and was ready to give them away for our in-booth contest.

Since that time, I've left a blue/red card holder and a green/red card holder on my desk with the original batteries. After about a year and a half, the battery voltage dropped enough that the blue LEDs no longer show. The red and green, with a lower forward voltage, are still going strong.

Here are the final specs:

  • 1.5" x 3.5"
  • Two CR2032 coin cell batteries
  • Has a Microchip in circuit (ICSP) programming port
  • Has an I2C/SPI port
  • Microchip PIC18F46k22 microcontroller
  • Freescale MMA8452 3 axis accelerometer
  • Recommended capacity, 10 cards

Next time, I tell you what you need to do to get one of these limited edition Screaming Circuits electronic business card holders.

Duane Benson
A farmer is someone out standing in his field

Happy St Patrick's Day!

In honor of St Patrick's day and all things green, I give you the PCB...


And some trivia. You may have noticed that the soldermask used on most PC boards is green, as is the paint used on most steel truss bridges. Why is that? And what do the two things have in common? Why green PCBs and why green bridges?

To answer, I brought in color expert expert Patty O'Patrick O'Dell, who stated: "Many bridges and PCBs are green because they absorb red and blue light, only reflecting the green."

That wasn't quite what I was getting at, but close enough. The important thing, is that, generally, in commercial products, the PC boards are hidden, so the color doesn't matter that much. With prototypes and a lot of the hobby or development boards, that is not the case, so many companies have chosen to use a different color as a part of their identity.

Arduino products are blue, as are most boards from Adafruit. SparkFun makes theirs red. Ti Launchpads are red as well. The Beaglebone uses color, essentially, as a model number; Beaglebone black, Beaglebone green. This is possible because major PC board fab houses have made different colors more economical than they used to be.

I've been asked if the color makes any difference electrically. In general, no. If you're dealing with super high speeds, RF, or other exotic conditions, it's always best to ask your board house. In those fringe areas, a lot of things have the potential to make a difference. Other than that, if you can afford it, and want to make a statement, go for it. You can often get different color silk screen legend too. Just make sure there's contrast between the two. White silkscreen on white soldermask would not be the best choice.

Duane Benson
Beware the monsters from Id

Electronic Business Card Holder, Part II

If you haven't yet read it, rush on back and read part one of this series... Done yet? Okay, good.

When I left off, I had promised some design decisions, of which, the power source would be the first. I wanted a long battery life. If the batteries need to be changed every other month, it would just get too expensive, and annoying, so I wanted at least six months. A year would be even better.

20160308_090949I did some estimations and determined that a CR2032 coin cell would give me about that longevity. I decided to use two, for good measure, and to make a stable base, but mostly for stability. The two batteries go on the bottom of the card holder, as shown in the photo on the right, and have enough weight to give decent stability. For testing purposes, I also put in connections to use a two-AAA battery holder.

For my first build, I decided to used red and blue LEDs. The blue have a higher forward voltage, so I could get a sense of battery life faster than with the eventual red and green.

Speaking of battery life, the accelerometer was the bigger challenge of the two ICs. The MCU (microcontroller) and accelerometer need to sleep when not being used. The PIC18F46k22 MCU will be easy. I don't need any peripherals on while sleeping. It just needs to wake on interrupt. Given that, it'll range in the area of a few tens of nano Amps during sleep. The MMA8452 accelerometer, on the other hand, is up in the micro Amps.

At the slowest sample rate, 1.56Hz, it draws 6 micro Amps. At a sample rate of 800 Hz, it draws a whopping 165 micro Amps. The sampling rate is critical - it's the number of times per second the accelerometer check for movement. Too slow, and it will miss a fast hand picking up a card. Too fast, and the battery life will suffer. After some experimentation, I settled on 50 Hz, drawing 14 micro Amps. 50Hz was the slowest sample rate that gave reliable detection.

Stay tuned for my next installment, where I'll cover the first build, programming, and the test period.

Duane Benson
I'm happy I live in a split level head

Behind the Scenes of Screaming Circuits

We love what we do here at Screaming Circuits. As the first dedicated online quick-turn manufacturer, we've worked hard at delivering on our mission to reinvent electronics manufacturing in North America. It's very important to us to make the design engineer's job (your job) easier, and we take that quite seriously.

We couldn't do it without our parent company, Milwaukee Electronics. In fact, Screaming Circuits started out, back in 2002, as an experiment to help a Milwaukee Electronics customer out of a bind. It worked well, and in 2003, was brought online.

Why do I bring that up now? Well, Milwaukee Electronics hasn't stayed in the old-world of manufacturing. It's improved, expanded, and grown, despite the difficulties the US  manufacturing industry has faced.

And, as testament to that, Venture Outsource just named Milwaukee Electronics as one of the Top-10 EMS Providers in USA-West.

Congratulations to Milwaukee Electronics!

ME Logo sm With Tagline 2014

Electronics Swarms - Overhangs

20160229_144328As I've stated many times before, we see many, many different jobs go through our shop. In those jobs, we see some of the absolute newest components and packages; some not yet available to the public; some are so R&D that they never will be available outside of a lab. We see the best of the best in terms of design practices and complexity, and we see many that aren't so much in that arena.

Given that, it would seem logical that the design problems we see would be pretty much scattered all over the map. By some measures they are, but on a day to day basis, they tend to cluster. For a few months we'll see a lot of QFN footprint issues. In a different few months, we'll see a lot of via in pad issues, etc. I don't know why. It just works that way - problems come in swarms, or storms.

The latest swarm relates to panelized boards and components that stick over the edge of the board. We build things like that all the time. The problem comes in when the panel tabs come out right where the component overhangs. If the component overhangs in the cut out area, it's usually not a problem. However, if the component is on the connection tabs, we can't place that part without first depaneling. 20160229_144238

Probably the most common example is the surface mount USB Micro-B receptacle. It over hangs the board by a small amount, and that overhanging part is actually bent down. If it's at the tab, it won't even mount flush. Take a close look at the images along the right. That connector won't mount as it's sitting on a tab.

So, what do you do about it?

You can have your boards made as individuals. Although if you want short-run production, or if the boards are really small, that might not 20160229_150126be possible or practical. You can also talk to your fab house about it. They may be able to place the tabs in a spot that won't get in the way of the overhanging part, of they might be able to tell you where the tabs will be, allowing you to keep clear in your layout.

Duane Benson
Anyone ever drink Tab Clear?

An Electronic Business Card Holder

I design and build electronics at home, late at night when the spiders are out, and by day, I put my hours into Screaming Circuits. My job here doesn't involve building things. I'm the marketing department, but I like to keep as much manufacturing smeared all over me as is possible. Here's one way I do that.


Business cards are a bit of an anachronism today. I don't give out many, this being the 21st century and all, but I still need some on my desk - I guess to look businessy or something. No one's ever given me a cheap card holder with their logo on it, and I don't want to just scatter cards around. So, why not combine my need to display business cards on my desk with my compulsion to create electronic things? With that thought in mind, I decided to build an electronic business card holder. Of course, I first had to decide just what an electronic business card holder would be.

Here's what I came up with:

  • It should be small, about the size of a business card
  • It should have a lot of blinky lights
  • It should do something when a card is removed
  • It should have a long battery life
  • It should use tiny parts to show off our manufacturing capability a bit
  • It should be 100% buildable within our electronics manufacturing process (meaning it should be just electronics; no bolts or case)

That's not a long list, but does involve a few decisions. I'm pretty familiar with Microchip PIC processors, so that would be a logical choice to drive the thing. Arduino compatibility would be cool, but I'd have more trouble with battery life, and 20160226_095148the PIC microcontrollers come in some pretty inexpensive forms.

I'd recently been using a variant of the PIC18F46k22 on another project. I comes in a 5mm x 5mm QFN package and can be purchased for less than $3.00 in small quantities. it has plenty of I/O and can be set to a very low power sleep mode. I settled on that MCU and a CR2032 coin cell battery for power.

20160226_094829Rather than add any extra hardware to hold the cards, I came up with an arrangement of pin headers and small push-button switches. (as in the photo on the right) One header is the six pin Microchip in circuit programming (ICSP) header, and the other is a six pin I2C/SPI header. Not that I need I2C or SPI, but with that, you could turn this into a robot business card holder or something.

I considered a light sensor to detect when a card is being picked up, but that would require leaving the A to D powered up, and it would be less reliable due to changes in lighting. I looked around my junk box at home, and found a Freescale MMA8452 3 axis accelerometer in a 3mm x 3mm QFN package. It also has a decent low power mode, and can be talked to over I2C.

19 GPIO pins remained open, so naturally, I had to put in 19 LEDs. Stay tuned for my next installment, where I'll go through some of the design decisions. At the end of this series, I'll be giving out ten of these, so stay tuned to see how you might be able to get one.

Duane Benson
If you dreamed you saw the silver spaceships flying
That's a okay. They're RoHS compliant

Raspberry 6.283185307 Zero

AKA, A second post on the Raspberry Pi Zero.

It's been two months since the release of the $5.00 Raspberry Pi Zero, and I still haven't been able to buy any. As I discussed in my prior blog about it, there is plenty of discussion around the fact that, out of the box, it's not real useful without adding enough accessories to make it as expensive as any other Pi model. I certainly understand that point, but here's another way of looking at it.

If you want to learn software, buy one of the other Pi models. If you want to learn about hardware design, buy the Pi Zero and download some CAD software. Then go online and get the Pi Zero dimensions and start designing accessories for it. You can start with one of the many open source Pi Zero accessory designs, or come up with your own. Don't look at it as a system that's missing too many parts. Look at it as a base for a different type of learning.

One of the scariest things about designing a plug-in/on board for a bigger computer is the possibility of a mistake that will fry the expensive board. With the Pi Zero, you're risking $5.00.

Like I said, I still don't have one, but I've drawn up my for Pi Zero accessory:

PiZero LiPoly

It will plug right on to a Zero as a rechargeable Li-Poly power supply. Not at all a complex circuit, but it's only the first in a series. As a small board, it doesn't cost much to get fabbed, so for about the price of one PCB sized to fit the bigger Pi boards, I can get two of these.

Next, I'll design a motor driver, and then possibly an IMU, or sensor board.

Duane Benson
If you have your Pi calculate Pi, would that Pi be Pi enough for Pi?

UPS and the Weather

The weather's just fine out here in Oregon. Well, that depends on your exact definition of "fine." It's raining out here and I'm not sure it will ever stop.

But that's not the point. Parts of the East Coast are bracing for a big winter storm. In fact, UPS has sent out a warning of possible shipping delays (read it here). Given that we ship primarily with UPS (and I'm sure other carriers will be just as impacted), there may be some weather-caused delays in getting your board to your doorstep.

UPS will do their best, and hopefully you'll get everything when you need it.


Language dialects for the engineer entrepreneur

Much of marketing can be summed up with the word “communication.” It's communicating about a product or service, about wants and needs, or the past and the future. Good marketeers take this to heart and work hard to understand their market. But, it's more than just understanding the market; it's understanding all aspects of their language.

Wrong footprintI often talk about the language, or dialect, that people use. When I do, I'm not talking about English English vs. USA English. I'm talking about the difference between hearing and speaking; or between reading and writing. And I'm talking about that within the same person. Knowing the difference is often the deciding factor between winning or losing this game.

Speaking of games, in baseball, right handed players catch the ball with their left hand and throw with their right. Lefties do the opposite. Except me. Baseball was always difficult for me because I both catch and throw with my right hand. It slows things down considerably when you catch the ball in your right hand, take it out of your glove with the left, drop your mit, hand the ball back to your right hand, throw it with your right hand, and then pick your mit up off the ground.

In the same vein, a lot of people speak and listen in different dialects. Like the baseball, information comes in one way, and goes out another. If you don't plan your communication with that in mind, your conversation may go over about as well as I would as a shortstop in game seven of the world series. The thing is, most people don't realize that they do this. It's a perfectly normal, but often not recognized aspect of human communication.

Is it “form over function” or “function over form”?

Case in point, electrical engineers. Material written by a typical engineer is detailed, accurate, comprehensive, and often barely readable by anyone but the author. A common phrase heard in the technical world is that the content is what's important, not the spelling or grammar. An interesting contradiction is that engineers are often the quickest, harshest, and most pedantic of the “grammar police” that toss flame around in the social media world when someone chooses the wrong member of the set “there, their, or they’re.”

I maintain that both statements: “it's form over function” and, the counterpoint: “it's function over form” are incorrect. The correct maxim is: “form can’t get in the way of function.”

Form works with engineers. It works with everybody. Good advertising works with engineers. Where marketeers run into trouble is when they consider form to be too important, and they obscure the message. The reverse, putting too much weight on function, and not enough on form will be just as ineffective.

Engineers getting into marketing, either as an entrepreneur, for their own startup, or as one moving from a technical job into one that requires a lot of writing, need to pay special attention to this phenomena. You can’t write for yourself.

Anyone, not just people in the same technical field, should be able to read good writing. They may not understand all of the technical details, but they should be able to comfortably read and feel a sense of organization. Order, structure, and simplicity are important, regardless of the intended audience. My recommendation is that you have someone, with a lot less knowledge of your subject than you have, read your material. If they can get through it, you’re at least on the right track.

Duane Benson
Do you speak MBA?
Do you speak EE?
Are you an interpreter?

Predictions For The End of the Decade

Half a decade ago, back in January 2010, I wrote up a list of predictions for the end of the decade. You can read that list here. It's still 2015, so I can plausibly say that we're half way there, which is a good time for a status update.

0000: In 2010, I said: By the end of the decade, 50% of all passives will be embedded passives and 20% of all PCBs will have 90% or more of their passives embedded.

In 2015, I say: This doesn't look to be coming true, but it still might. As mobile devices and wearables get smaller, or more powerful, more electronics will need to be stuffed in progressively smaller areas. Those passives need to go somewhere. That somewhere could be into the PCB, or into the chips. I think the PCB is more likely.

0001: In 2010, I said:By the end of the decade, Quad stack POP (package on package) will be commonplace.

In 2015, I say: Quite likely. Double layer POP is showing up on low cost devices, like the $5.00 Raspberry Pi Zero. If it can go there, it can go pretty much anywhere. It won't be long before double stacking won't be enough. Although, the layers may end up being inside the chip package, rather than individual chips as layers.

0010: In 2010, I said: By the end of the decade, Each individual human will have their own IP address. Several of us will have more than one. That way, we can jury rig accelerometers into our hands and feet so we can wirelessly know where each of our extremities are at all times. Cats will have them too.

In 2015, I say: Yep, and then some. I already carry one in my pocket. In five years, we'll likely see personally assigned I.P. addresses that won't be device dependent. We'll be able to buy I.P. enabled clothes, like gloves, which will do a lot more than just know where each finger is. The pet ID chips that today, use NFC, will be available in wireless Internet connected versions.

0011: In 2010, I said: By the end of the decade, solder paste will be used less often than not when assembling components on to PCBs.

In 2015, I say: We will be seeing welded copper, additive embedded 3D printing processes, conductive glue, and other non-solder methods of assembly, but nowhere near to the degree I was thinking back in 2010.

0100: In 2010, I said: By the end of the decade, nearly all hydraulics and pneumatics in new motor vehicles will have been replaced by electrics.

In 2015, I say: This is already well on the way. With electric and hybrid electric cars growing in numbers, and with weight and fuel mileage being such a concern, this has to happen.

0101: In 2010, I said: By the end of the decade,the first semi-autonomous passenger vehicle will be on display on the auto-show circuit. Hobbyist built semi-autonomous cars will already be on the road.

In 2015, I say: I may have missed the boat on this prediction, in the pessimistic direction. Part of it has already happened. I haven't yet seen hobby kits, but most of the major car manufacturers have shown models. Tesla has a really good driver assist "auto pilot", and is promising fully autonomous vehicles for sale within two years of this writing.

0110: I said: By the end of the decade, "airline pilot" will generally be a really, really, really boring job. That's a bit of a problem.

In 2015, I say: The necessary level of automation required for this prediction to come true is already installed in most airliners. The only real question remaining, is how long before it changes from "Pilot primary, systems secondary" to "Systems primary, pilot secondary."

0111: In 2010, I said: By the end of the decade, most military "foot action" will consist of two soldiers in command of a squad of robots and those two soldiers will as likely be in Fort Lewis, Washington as in the combat zone.

In 2015, I say: Sadly, I still think this will happen. Not sad that fewer humans will be shooting and getting shot, but sad that we as a species will still consider war important enough to be throwing large quantities of money and resources at.

1000: In 2010, I said: By the end of the decade, the president of the US will be promising health care reform as the highest priority.

In 2015, I say: Yep. The president, presidential hopefuls, senators and representatives will still see this as a hot issue. One side will be trying to make quality healthcare more accessible, the other side less. One side, more publicly funded, the other side, less. I'm not really sure which side will be doing which, but I'm certain that each side will say they want to fix it and the other side wants to destroy it. Ugh.

1001: In 2010, I said: By the end of the decade, routine bioengineering will be, well, routine. Very scary.

In 2015, I say: I'm not so sure about this one. When I wrote it, I was thinking that home bioengineering would be happening and a class of bio-hackers would be emerging. That may still happen, but it won't be common. Governments, agriculture, and medicine will be doing a lot more of this, but I'm not sure the term "routine" will be accurate.

1010: In 2010, I said: By the end of the decade, the 2019 recession will be looming large and all of the people that have forgotten about the 2009 recession and the 2001 recession and the 1985 recession and the 1975 recession... will be freaking out again.

In 2015, I say: Is there any doubt? Does this ever not happen?

1011: In 2010, I said: By the end of the decade, lead will be gone from 98% of new electronics. Bummer.

In 2015, I say: Exemptions are going away. This will happen.

1100: In 2010, I said: By the end of the decade, four of the substances that replaced the substances removed from electronics due to ROHS and similar regulations will have been found to be significantly more harmful to the environment and the people recycling the materials than are the substances that they replaced.

In 2015, I say: I was being tongue-in-cheek, but it still might happen. The only caveat is that if it does happen, the data will be so obscured by politics, that it likely won't be possible for anyone to come to an informed opinion.

1101: In 2010, I said: By the end of the decade, the world of intellectual property will be in even more of a mess than it is today. Virtually everything will be accessibly for easy theft and cheap replication. (this is pretty much a big "duh")

In 2015, I say: This is still well on the way. Any industry that designs things will need to adapt to keep competitive. The patent world will still be a mess. Copyrights will be more of a litigation attack weapon than a protection tool. The best defense against pirates will be faster innovation. On the positive side, a lot of I.P. sharing will be intentional (by the inventor) and many businesses will be built based on collaborative innovation.

1110: In 2010, I said: By the end of the decade,building your own mutli-purpose robot will be as easy as building your own PC was in 1988. Hardware components and operating systems will be off the shelf, but standards will be pretty loosely defined, interoperability will be more theory than reality and applications will be sketchy and buggy.

In 2015, I say: This will happen, but it may be a little later than the end of the decade. The technology will very much exist for this to happen, but the capability of the hardware will probably be advancing so fast that even the limited amount of standardization needed for this won't be possible.

1111: In 2010, I said: By the end of the decade, still no flying cars and personal jet packs, dadgummit!

In 2015, I say: And, still no real hover boards.

Duane Benson