The Value of Open Source

There were a number of interesting sessions and debates last week at the DesignWest show. One of the more passion filled, was on the value of Open Source hardware. Some people think it will save the world,if only everyone will do everything open source. Some people think it's a stupid waste of time without a real business model.

Personally, I see more value in it than either of those extremes. What I see is that open source hardware (and software) has lowered the barriers to entry for people who want to create, design, build and sell. Yes, big companies innovate, but a vast amount of innovation and employment comes from small companies that start out without anything more than ideas.

A decade ago, before open source hardware became well know, it was pretty difficult and expensive to start a hardware company. In fact, I recall quite a few predictions and discussions about the death of hardware as an industry in the country. Open source hardware has lowered the barriers to entry and raised the level of awareness of hardware to the point that now, in my opinion, the environment is as ripe for start-up companies and innovation as was the late 1970's and 1980's.

Open source hardware has given us that, and that will be far more positively economically impactfull than whether or not an specific business can find a way to make money with open source hardware. These new businesses may or may not sell open source hardware. Again, that's far less important than the fact that open source hardware has really enabled so many more people to create.

Fun With QR Codes

Does anyone remember the CueCat? I think it came out in 1999 or something like that. It was a system that involved putting bar codes in print articles, advertisements and such. Users would buy a CueCat scanner and could then scan the bard codes which would send their web browser to a specified URL .

Chart2011-10-25 Chart2011-11-28Kind of cool and a bit ahead of it's time, but really? Who's going to spend a hundred dollars to buy something that makes it easier to look up advertisements? That reminds me of a job interview I had around that same time. The gentleman interviewing me had invented a system that would push advertisements to cell phones via text message for businesses close by. The idea was that phone owners would sign up for the service by giving their number to the company. Other companies like grocery stores, coffee shops or insurance agents would also sign up for the service and would send ads or coupons to people close by. Again. Really? Someone's going to sign up to get ads on their phone? And that was back when most phone plans still charged per text message.

Chart2011-12-21Well, today, we have QR codes to more or less do the same thing. They're square bar codes that can contain information such as an electronic business card or a URL. The big difference now is that you don't have to sign up for anything or buy anything. Most smart phones can read them with a free app.

That was a long, round-about way of saying that I'm trying the system out. All of the QR codes here link to a blog posts of mine. There are no advertisements in these and none of them will sign you up to visit a timeshare sale pitch. I just like these particular posts. Get out your phone and try it out.

Duane Benson
Fight Uni!

Chart2012-04-24 Chart2012-06-13

 

 

 

 

Chart2012-06-27 Chart2012-07-05

LEDs - Seeing Double

Dual LEDLike I do so often, I'm being a bit redundant. While I'm all for stamping out and eliminating redundancy, this is redundancy with a purpose (not a porpoise). Not long ago, in a galaxy not far away, I blogged about annoyances in surface mount diode polarity markings. You can read that here.

I'll wait.

Messy isn't it? Well, after reading that blog, someone asked me about dual diodes. For some reason, I can't seem to find the page covering dual diodes in my IPC book, but that's not the important part. What is important is the way the diodes are marked on the PC board.

We do ask for centroid data which, in theory, contains the component rotation. That would be cool except that we find that far too often, the zero degree orientation (and the rotation from that) differs from the standard. That, and there are seemingly half a dozen or so standards.

Since LEDs don't work too well backwards, we really would like to see everything marked in a non-ambiguous way in silk screen (or in an assembly drawing if you don't have silk screen). A "cathode bar" won't work because it could be a bar indicating the cathode or negative. The cathode isn't always negative, especially when looking at TVS or Zener diodes.

Mimicking the diode markation pattern printed on the part may not be secure either. Read that article I linked to right at the start of this blog. What if you put silkscreen down to match one of those LEDs but ended up buying the other one? That's exactly what I did myself. Trust me. It just leads to disappointment and possible soldering iron induced finger burns.

So what is the answer, and why am I talking about single LEDs and TVS diodes when the blog is about dual LEDs? Well, the answer is the same. The best way to communicate the desired polarity of an LED or any kind of diode is with a mini version of the schematic symbol. It doesn't matter if it's a single LED, dual LED, Schottky, Zener or what ever kind of diode. The schematic symbol is the clearest way to go.

Led marking

The diode footprint has the manufacturer's polarity marking, but I don't care. I still put the diode schematic symbol next to it. If you don't have room for silk screen, put it in an assembly drawing. You won't regret it.

Duane Benson
And they called him Flipper...

DesignWest; San Jose April 23 - 25

DesignWest map 2013Will you be there? We will.

If you're in San Jose April 23, 24 or 25, stop by the McEnery Convention center, in San Jose, California. We're in booth 838 and would love to see you and say hi.

We'll be demoing our on line, real-time turn-key prototype quote and order system.

The show is open:

Tuesday 11:00am to 7:00pm
Wednesday 11:30am to 5:30pm
Thursday 11:30 to 4:00.

If you'd like, you can also look up the sessions I'll be speaking at:

Designing a Tele-Presence Robot - What Was I Thinking?
Processors and Programmable Devices
Session Code:   ESC-212
Location:   Salon 4
Date:   Tuesday, April 23, 2013
Time:   9:15 AM - 10:15 AM

FPGAs: I know nothing ... yet.
Lessons and Lessons Learned
Session Code:   STS-304
Location:  210 GH
Date:   Wednesday, April 24, 2013
Time:   2:00 PM - 2:45 PM

I also play a very small part in:

Gadget Freaks
Session Code: ET-06
Location: Expo Theater
Date: Tuesday, April 23, 2013
Time: 5:00 PM – 5:45 PM

and

10 Computer Languages in 45 Minutes
Tech Fundamentals
Session Code:   FUN-300
Location:  210 EF
Date:   Wednesday, April 24, 2013
Time:   8:30 AM - 9:15 AM

It will be a busy show and with all of the class sessions and exhibitor booths, there will be plenty to do. I think it's hot in San Jose now, so I'm going to leave my coat at home.

Duane Benson
Someone told me it's a long, long way, but I'm not walking so I don't care.

 

 

 

Creating a QFN Footprint - the center pad

I've written bits and pieces about creating footprints in Eagle and a lot about what the QFN solder paste layer should look like, so maybe it's time to connect the two dots. I'm using Eagle CAD here, so your process will likely be different unless you're using Eagle, but the concept should be the same. This process takes place in the package section of the Library editor. I'm assuming that you're already part way through and just need to put in the center pad.

Center pad Center pad position and sizeFirst, add the center pad to your QFN using the "Smd" tool and set the size based on the recommended pad size specified in your part datasheet.

The center of the pad should be located at 0,0 unless you have a QFN with odd shaped or multiple pads.

Make sure you un check the "Cream" box in the lower left corner as we'll be doing that manually.

After the pad is there and sized right, you need to add in the cream (solder paste) layer. You'll be drawing the cut-outs in the stencil with the rectangle tool. Use the rectangle tool to draw the stencil cut-outs. Set the rectangle to the "Cream" layer. In my installation of Eagle, the Cream layer defaults to layer 31.

Most parts should get 50 - 75% paste coverage to prevent floating (read this for more details). If your Stencil rectangle Stencil rectangle position and sizepart datasheet gives a specific number, use that. However, in my experience, most part datasheets just show a wide open stencil with 100% paste coverage. Unless you have good reason, don't do that.

Without any specific guidance, I usually aim for about 70%. In high volume manufacturing situations, the manufacturing engineers will likely spend time tweaking the coverage, but it'll be close and for a prototype, 70% is a good number.

Duane Benson

Screaming Circuits introduces new Cordwood assembly service!

Tired of all those small parts? Can't figure out how to route traces to all 1,900 balls on that hot new FPGA? If 0201 passives have you running scared and the thought of 0.3mm pitch parts has you on the floor, Screaming Circuits has the answer.

Take a few steps back and use our new Screaming CordwoodTM assembly process. It'll feel good to put your hands on a honk'n 2-Watt, through-hole resistor again. No need for fancy, multi-headed SMT assembly robots with Screaming Cordwood. No need for precision anymore. Just put those parts a quarter inch apart and you'll be suckin amps just like the good old days. And if you don't think it's high-tech enough; consider that Cordwood construction has taken man to the moon and back. You can't say that about surface mount!

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Duane Benson
He likes both of me and I like both of him 'cause I live in a split-level head

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