Screaming Circuits: Engineer stories


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

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

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.

20160226_100559

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

How to Make Your Child Interested in STEM

STEM (Science, Technology, Engineering, and Math) careers are getting a lot of press these days. They are important for global competitiveness and the general advancement of human-kind. STEM is also one of the few job markets (especially the “engineering” component) with good salaries and a lot of opportunity. It’s natural to want your kids to head in this direction; so how do you go about doing that?

First, and most important, if your child has no interest in STEM - maybe wants to be an artist or a welder -  shut up, be a parent, and support them. We need artists and welders too. Those aren’t second rate choices. They’re just choices, like an engineering career is a choice. We need kids that will grow up to be happy adults, not puppets. You can introduce STEM, but don’t push it and don’t make them feel bad if they’re not interested. Someone who has passion and support for what they do is more likely to be happy and productive than someone pushed into something they don’t want.

Beyond that, you again need to be a parent. Listen to them carefully and look around to see what they are up against. My daughter started in the FIRST Lego robotics program in the 4th grade. Her teams were about equal proportions of boys and girls. But, by the time she left middle school for high school, she was one of two girls left in the program. Through high school, she was always a tiny minority in her science and technology classes. It’s not just girls that drop out, but it seems to be most noticeable with girls due to the numbers.

The peer and societal pressures have been described many times in many places before. It’s sufficient to say that, in many circles, being a geek is not seen as being socially acceptable; except in the context of a TV sit-com. It’s funny when the “geeks” can throw out one-liners that have been crafted by a team of Badge 700professional writers. Not so much when it’s the kid in the next seat over that struggles to respond to conversations about football or beer brands. Help your child to understand that technology and knowledge are not qualifiers for the “weird club.” Make sure they also understand that labor and grease also are not qualifiers for a different kind of “weird club.”

The recent case (late September, 2015) of the 14 year old boy arrested for bringing his “homebuilt” clock to school is a good case in point. Many people fear wires. In the movies, blue, green and red wires are what you have to choose wisely between to successfully defuse a bomb. In the real life world of a 14 year old kid, with a mind thirsting for knowledge, blue, green, and red wires are signal, ground, and power.

There is quite possibly a lot more to this story than has been published, but maybe not. Later articles talked about the fact that his clock was simply a purchased clock, taken out of it’s plastic case and hacked into a mini-suit case. Deriding him for that is a sure fire way to stifle curiosity. When I was 14, most of my “electronics projects” were of a very similar nature. Many were even less complex.

The first time you open up an electronic gadget is like opening up a grab bag. You don’t know what it is, nor what you can do with it. You see shiny metal, wires, chips, and display. You know that whatever makes it all work is truly amazing, but you have yet to grasp the significance of any of the parts. Over time, you will. Or, you will if you manage to keep the interest up and avoid being branded a delinquent over your quest for knowledge.

If your child takes apart a clock, your obligation, as a parent, is to make sure they don’t electrocute themselves or burn the house down. After that, it’s your mission to encourage. Explain, if you can. If you can’t explain, teach them about research and self-learning. Don’t treat their interest like a disease. Treat it like what it is: the quest of an explorer for knowledge.

Duane Benson
Sit tight, energetic martians

Disruption and The Internet of Things

Every few years something new rears its head and changes everything. The old rules break, convention gets unconventional, storied institutions get shaken to the core. We call this, "Disruption."

Automobiles disrupted the horse and buggy industry. Airplanes disrupted the passenger ship industry. Computers disrupted the typewriter industry. In 2003, Screaming Circuits brought disruption to the electronics manufacturing industry by bringing it online, with performance and flexibility previously unheard of.

The latest disruptive current is the Internet of Things (IOT). It means everything will be connected. Everything will be intelligent, and everything will be complex inside.

I recently spoke on "The Peggy Smedely Show", a part of the Connected World Network, about disruption, the IOT, and how Screaming Circuits is, again, driving disruption, this time by helping enable the IOT. 

Give yourself a little over twelve minutes and hear what I had to say.

Duane Benson
A QFN says "What?"

 

Running Out of Time - You'd Rather be up on the Mountain

How many times can the project manager come in and ask how the PC board design is doing? Why can’t management understand that it’s difficult to say how long it will take to do something that’s never been done before? This is totally new ground. It’s innovation in its purest form. And you, the designer are driving it home.

If only you could squeeze a few more days into the week. If only you could have the confidence that the boards will be built right – this is complex stuff, with wafer scale 0.4mm pitch micro BGAs, QFNs all over the place, and 0201 resistors and capacitors sprinkled around like salt and pepper.

 - You can squeeze more time in. You can be assured that the complex parts will go on right. You can keep the boss happy. Screaming Circuits quick-turn assembly service can build your job remarkably fast. Mount_Hood_reflected_in_Mirror_Lake,_OregonShort deadlines and difficult boards are our bread and butter.

It’s 6:00 pm on Friday. Hit “save” on your CAD file for the last time, and hop on over to ScreamingCircuits.com. A quick quote, order, and files upload, and you’re off to join your college buddy on the climb up My Hood you’ve been talking about for a month.

Don't delay, the mountain awaits your boot prints.

Duane Benson
Because it's there...

What's In Your Way?

If you're attempting to cross the median of a busy four-lane highway, it's entirely possible that there's a Jersey Barrier in your way. In that particular setting, having something sturdy blocking your way is probably a good thing. On the other hand, I would bet that, for the majority of you reading this, there are some barriers around you that you'd much prefer not to run into.

Jersey barrier dimensionsBarriers can bring on stress, uncertainty, risk, and a general sense of despair. Despair can lead to hopelessness. Hopelessness can lead to you being rolled up in a fetal position under your desk, tangled up in the nest of cables that every good engineer has under their desk. As everyone knows, if you're under your desk tangled in cords and whimpering when your boss walks in the room, you're probably not going to get a Christmas bonus.

That's where smart outsourcing can help. We talk about PCB Assembly as being our thing, but conceptually, it's more of a case of us trying to remove some of your barriers. We'd prefer that you get your Christmas bonus rather than getting carted off on a gurney, too afraid to open your eyes for fear of the glare of your abandoned co-workers.

Here's what we suggest:

  • Spend a little extra time on design review to increase your confidence (ever find an overlapping trace the day after sending the design out?) 
  • Double check that your BOM and or parts kit is current (If you chose the parts a few weeks ago, some may have gone out of stock)
  • Drink some water (dehydration can interfere with a clear, logical thought process)

If the extra day or two doing so causes a problem, just order a faster turn-time.

Duane Benson
129 °F in June of 2013?!
Well, what did you expect from a place called "Furnace Creek"?

Using the Newest gen ARM, Part III

The continuing saga of the 0.4 mm pitch KL03 ARM microcontroller. If you haven't yet done so, read part I, and part II.

Today, I have a look at the good, the bad, and the ugly - or more accurately, the good, and the bad and ugly. As I expected, I was quite pleased with the job done here in house. The board is nice and clean, the parts are well centered, and the solder joints are solid. No surprise here.

Here's a top-view of one we did here in Screaming Circuits:

4mil top view 800

Next, I've got one that I did at home. It actually surprised me and came out better than I had expected. Here's a top-down view of the one I did at home with home-grade tools (No, I didn't intentionally make it look bad. The board surface is just a bit shinier than the one above.):

Home top view 800

Of course, "better" is a relative term. I didn't say good. I could call this both bad and ugly. I did manage to center the parts quite well - that took a lot of careful nudging with sharp tweezers and and an X-Acto knife blade.

All of those little round shiny spots are solder balls. That's what happens when you get too much solder on the board, get solder off the pads, or have the wrong reflow profile. They might look harmless, but if there are too many under the chip, the connections could be shorted.

The fillets on the 0201 capacitor are a little lean on solder in the one I did, and there's a solder ball on the right side, but, again, it looks better than I expected.

Next time, I'll post the X-rays and show what's under the hood.

Duane Benson
Carburetors, man.
That's what life is all about

USING THE NEWEST GEN ARM, Part II

I'm a bit behind in my blog work - well, way behind, actually. I started this series back in January with the intro post.

Here's where I am right now:

  1. I have three different sets of PC boards.
  2. One set, I took home to see if it's possible to solder a micro BGA at home. (As someone working at a car manufacturer might want to see if they could balance a crankshaft at home, for fun)
  3. Two sets, from our partner, Sunstone Circuits, are here in my desk with parts, ready to go through our machines.

After I've got all three sets built, I'll have them X-rayed to see how they look under the hood. Finally, I'll solder thru-hole headers on and fire up the chips to see if the shared escape system works.

Here's one of the boards without access to the inner pads:

KL03 SunstoneFF 4mil (2)-001

And, here's the shared escape:

KL03 SunstoneFF 4mil (3)-001

The main concern I have is that Reset is on one of the inside pins (B4). I'm not sure if I can get the chip to a state where it will operate properly without unobstructed access to reset.

The routing I've chosen is probably the only possible option for reset. Pin A4, right above, is used for the single-wire debug (SWD) clock. I'm assuming that can't be shared. B5 is Vdd, so that's out. It might be possible to go down. C4 defaults to one of the crystal pins, and D4 defaults to a disabled state.

In the route I've chosen, B3 is an ADC input, so it should start out high-impedance, and therefore not interfere. A3 defaults disabled, so it won't get in the way.

Next step: solder time!

One other thing - The images above show non-solder mask defined (NSMD) pads. Those are standard for BGAs 0.5mm pitch and higher. This part is 0.4mm pitch. Some manufacturers recommend solder mask defined pads (SMD) for 0.4mm and smaller. I'm actually testing several pad styles: SMD, NSMD and solder mask opening = copper.

KL03 footprint contenders

Duane Benson
Run it up the flag pole and see who solders

Using the Newest gen ARM Microcontrollers

KL03 on stampI've written a few times about the new Freescale KL03 ARM Cortex M0+ microcontroller. This particular part comes only in very small packages, with the smallest being a 1.6mm x 2mm WLCSP (wafer level, chip scale package) 0.4mm pitch, 20 bump, BGA. That's a mouthful - albeit a very tiny mouthful. Maybe just a toothful.

On the left, here, I've got a pair of them on a US postage stamp.

For us, it's not a particularly difficult part to assembly; just a garden variety 0.4 mm pitch BGA, as far as we're concerned. We place loads of them. But, it can be a very different story for a designer. Conventional wisdom says that a PCB designer has two choices with a part like this: a very expensive PC board, or don't use the part.

Escape routing becomes very difficult (read: expensive) at 0.4 mm pitch. This part only has six connections that need to be escaped, but that can still be a problem. You can't fit vias between the pads KL03 SunstoneFF 4mil 800to escape out the back side. You can't put vias IN the pads, unless you have them filled and plated over at the board house. That's expensive in small quantities.

This blog post series is going to examine some possible ways to use these parts with more of a standard fab, such as Sunstone quickturn. I've got three different process blank PC boards, each with four different land patterns.

I've been asked about home reflow too, so as a bonus, I've done my best to duplicate hobbyist conditions for one of the board sets.

Check back next week for the first set of results, and be sure to quote your assembly job at Screaming Circuits or your PC boards at Sunstone.com.

Duane Benson
"Screaming Reflowster" not sold here