Dr Richard Stallman to present at Kent State Saturday Oct. 17th

Kent, Ohio – Northeast ACM and the ACM Distinguished Speaker Program in partnership with the Kent State ComputerScience Department will present Richard Stallman Talks, taking place at Kent State University's Kiva Auditorium on Saturday October 17th 2015 featuring Dr. Richard Stallman.

NEOACM and Kent State Computer Science Department are proud to bring Dr. Richard Stallman to Kent State University for the first time. Dr. Stallman's will present his non- technical speech, A Free Digital Society, that addresses the many threats to freedom in our digital society, focusing on issues of proprietary software that controls users, digital handcuffs, massive surveillance, and censorship that undermine the foundations of democracy. Dr. Stallman is a software freedom activist and the main author of the GNU General Public License, the most widely used free software license.

Stallman developed the GNU operating system along with a number of widely used software components including the GNU compiler collection, symbolic debugger, and Emacs installed on millions of computers today. He is also the founder and president of the Free Software Foundation. Following the speech, there will be a Q & A session with Dr. Stallman and attendees will be able to purchase his books and essays.

This event is free and open to the public. Seating is limited. This event will be held in the Kiva Auditorium on Kent State Campus 800 E Summit St, Kent, Ohio.

"If in my lifetime the problem of non-free software is solved, I could perhaps relax and write software again. But I might instead try to help deal with the world's larger problems. Standing up to an evil system is exhilarating, and now I have a taste for it." - RMS

For more information, please visit http://www.neoacmchapter.org/stallman_at_kent or http://www.meetup.com/Northeast-Ohio-ACM-Chapter-Meetup
 
Copyright © 2015 Northeast Ohio ACM (A non-profit organization)

Analog Circuit Design Three Volume Collection. 40% off until May 17th less after.

If you do Analog Circuit Design then the three volume set Analog Circuit Design from Linear Technology must be on your bookshelf.

This week Linear Tech released Volume-III of the series Analog Circuit Design, Volume 3 - Design Note Collection. Edited by Bob Dobkin and John Hamburger.

Analog Circuit Design, Volume 3, Design Note Collection is the first effort to bring Linear Technology's Design Notes into one volume. Design Notes were first published over 25 years ago, and after producing more than 500 notes, the genre is still going strong. The teaching designs in this Design Note Collection help bring new designers up to speed and give experienced designers a starting point for even more sophisticated designs. This book has two purposes: to speed designs by presenting finished examples, as well as providing a teaching resource for designers.

The Design Note Collection is a comprehensive volume of applied circuit design solutions, providing refined and practical design techniques. The book includes an extensive power management section, covering switching regulator design, linear regulator design, microprocessor power design, battery management, powering LED lighting, automotive and industrial power design. Other sections span a range of analog design topics, including data conversion, data acquisition, communications interface design, operational amplifier design techniques, filter design, wireless/RF communications and network design.

If purchased from Elsevier, enter discount code ANACIR at checkout for 30% off each of the three volumes and save 40% when you buy the three volumes together. Promotion applies to print and electronic.

Unitl May 17th 2015, Elsevier, has an other discount to save up to 40% when you buy Science and Technology eBooks.

Richard Stallman Coming to Northeast Ohio Oct 17th

Richard Stallman of the Free Software Foundation (FSF) will be speaking Saturday October 17th 2015 at the Kiva Auditorium of Kent State University, in Northeast Ohio.

The Free Software Foundation (FSF) is a nonprofit with a worldwide mission to promote computer user freedom and to defend the rights of all free software users.

Stallman is frequently mistaken as a supporter of Open Source software, which he is not: Why Open Source misses the point of Free Software.

Stallman has been involved with the computer industry since the last 60's. A must read book for all involved in computers and embedded systems is Hackers - Heroes of the Computer Revolution by Steve Levy.

• Richard Stallman Talk
• Saturday, October 17, 2015
• 1:00 PM to 3:30 PM
• Kiva Auditorium
• 800 E Summit Street
• Kent, OH

Sponsored by the Northeast Ohio Chapter of the Association for Computing Machinery (ACM).

Solving pressure and condensation build up in your Embedded System.

Have you ever had a problem with pressure build up or condensation in one of your embedded devices? Gore-Tex Vents are a good solution today, but I thought you might find The Rest Of The Story interesting. What follows is slightly edited version of a message exchange of mine from the gEDA-User mailing list.

> Dave McGuire wrote:
> > Bob Paddock wrote:
> > I'd put them in a sealed box, with a Gore-Tex Vent so that the
> > enclosure can 'breath' but not pass water.
>
> This is an interesting idea. Can Gore-Tex be found in small
> squares for this type of application, or would one be stuck
> destroying an expensive jacket to get some?

Salvation Army or Good Will would be a good place to look if you want to go the clothing route, but there is more to the story.

The whole story goes like this: Gore-Tex was invented ~1978, used in clothing as everyone knows, and didn't really find many other uses then. Jump forward to 1982. I was designing a hand held control to run some 50 Ton Coal Mining Equipment. The control was a sealed box with a membrane switch on the front. We very shortly ran into problems. Taking it down into the Mine would cause a pressure reduction that would suck the switches in, activating the switches. Having a stuck switch on a 50 Ton machine with sharp cutting bits is *bad*. Very **bad**. Also found that taking it up in a plane, as non-pressurized luggage, would deform the switch by causing it to balloon out to about four times what it should be. From flat to nice dome. You then had worthless junk, it did not recover.

I had recently read about the properties of Gore-Tex, tracked down one of the engineers in the factory and asked him if he thought it would make a good vent for such an application. He said he had no idea, but he would send me several different types of the stuff to try out. Which he did.

Putting cloth over a whole in mining equipment would last a few minutes, on on optimistic day. So a colleague of mine, Don F., came up with this labyrinth sandwich to put the Gore-Tex between.

Take two flat disks, we used thick fiberglass, each about 1/4" thick. Mill out a pocket in both disks, place them face to face, then drill a hole through both disks at one of the ends of the milled circle. Now rotate a single disk 180 degrees. Put the Gore-Tex between the disks and epoxy. If you try to stick your Sharp Pointy Coal Mining Implement into the hole you hit the fiberglass and not the Gore-Tex. The assembly was then held in the box by a screw in the four corners. Pressure problem was solved.

Went back to the fellow at Gore-Tex to get more material, which he supplied. Thought our idea was a good one and filed for the patent. So he got it and Don and I did not.

Today you can buy Gore-Tex pressure relief vent off-the-shelf. Most a screw in type plug, but they come in all kinds of sizes.

Q: Why does my FET, IGBT, SCR keep going up in smoke? A: Spot Heating

A common problem I see in message boards is that someone's circuit failed, and went up in smoke. People in the more esoteric realm's blame this on things like "Subtle Energy" overload and other such minutia. Here is the far more realistic explanation:

The very old "GE SCR Manual" goes into all of the Gorey details of what is happening inside the part, when the "Magick smoke comes out", as it is unlikely you have the Manual at hand, in a nut shell:

What lets the Magick Smoke out of IGBTS, FETS and SCRs in most cases is turn them on to slowly, causing 'Spot Heating' of the die.

Think of a FET as hundreds of thousands, possibly millions, of very small resistors all in parallel, where each one can be turned on and off individually. The 'resistors' closest to the gate turn on first, and as the gate potential spreads across the die the rest turn on. The ones farthest from the gate turn on last.

With a slow gate turn on, a few of the small resistors nearest the gate are trying to carry all of the load, which they can't do, so they burn up, but the device does not fail quite yet. The next time the device is turned on, which may be only milliseconds away depending on your switching frequency, or days away depending on the application, some more of the resistors further in burn up. When the point is reached that there is simply not enough of the 'resistors' left to carry the load is when the Magick Smoke escapes, and the part dies a catastrophic death.

This is why the parts generally run "for a while" before failing. If it fails as soon as you fire it up the first time, you either had a catastrophic short in the load, possibly shorted caps that take a bit of time to 'wake up' before they hold a charge, generally fixed with 'Soft Start', or the gate drive really sucked big time.

There needs to a be a few *amps* of current pumped in the gate of the larger parts, for short periods of time, to get the gate potential to spread across the entire die as fast as possible.

You also want to get the thing turned off as fast as possible.

If you are not familiar with the concept of Magick Smoke, this is where all electronic parts run on Magick Smoke, because once the smoke comes out of the part, it no longer runs...

Is there a rule of thumb for estimating the cost of getting circuit boards assembled?

A reoccurring theme I see on message boards is why does it cost so much to have some electronic widgets manufactured. Here is some background for you that might help explain that.

Is there a rule of thumb for estimating the cost of getting circuit boards assembled?

In a past life I worked for a large Contract Manufacturer, Matric Limited . I don't mean this to a plug for them, but the view of the place is helpful for the discussion.

To a CM it is all about *Time*. When it comes to parts, the actually part cost is really insignificant as far as cost contribution to assembly cost goes. Most of the cost goes to the time it takes to setup and tear down.

For a broad brush overview of cost steps:

One shot fee for getting your project into the system. Someone has to enter your Bill of Materials (BOM), and schedule into the amorphous blob known as "The System". Any change that you do triggers a recalculation, that you either pay for or is amortized across your boards. Every future order you place will have a small "trigger fee" to pay for someone to enter your order.

Included in that is a fee for someone to do a time analysis of the number of operations that your project will require. A unit time value is assigned to each operation, and each operation has a cost, that is, as far as I know, calculated by Magick (All CM's use Magick for this step to my knowledge).

If you supply the parts there will be fees for entering a carrying fee per new part number into The System. They will also charge higher fees if you send them parts that require extra steps to handle such as reels of parts without leaders etc. Some cost analysis guru at GM, long ago, decided to simply have a number in The System carries a charge of $50 or so per year per part number. The accountants just love to beat up the engineering department for "we have to many parts in the warehouse". Company owner wants to keep inventory turnover high. Also cost for physically getting your parts into The System, such has putting them in the warehouse, typing in the data etc.

There will be a scrapping fee to get your stuff out of The System if you take your project someplace else.

Those Non-Recurring Engineering (NRE) fees you either pay up front, or are amortized across the number of boards. This is why the range is highly variable between different CMs. Some hide the fees, some don't.

Also, when you supply the parts the price of each part will be market up by a *minimum* of 33% (More Guru calculations). If you don't mark the price up by this amount, you lose money each time you touch the part. You are charged for the use of the warehouse space, like renting a storage unit.

Now lets say you let the CM supply the parts, in general this will get you a lower per part cost for the commodity parts. As they will be using 100,000 0.1 uF 0603 caps a day, the pick and place machine will have that loaded. So you don't have to pay for loading your reel of much smaller volume part. Also the CM will have negotiated a much better price than you got from DigiKey. The downside here is that you lose some measure of control, which can be a problem if you have to meet UL/MSHA/FDA etc. regulations.

There are extra charges for projects that involve FDA paperwork, such a per lot tracking etc. Other acronyms apply as well, UL, FCC etc.

There is a fee for having the solder paste stencil made.

Now that the NRE's are out of the way, lets build a thousand Widgets.

Someone answers the phone and enters an order into The System to build a thousand Widgets.

The System checks the warehouse to see what parts are in stock. Your order is then routed to Purchasing to get the parts that are out of stock, or routed to planning to get your order into the build Que.

When your build hits the top of the Que:

Someone pulls the parts from the warehouse, at the minimum your PCB; time.

Your bare boards are put in an oven and baked to drive out any moisture, you pay the handling and electricity; time.

Your parts are loaded on the Pick-and-Place Machine; time.

The board go from the oven to SMT Assembly; time.

Someone pulls your stencil out of the rack and puts it in the paste machine; time. Paste is applied to your board; time and paste costs.

Your board is put into the Pick-and-Place and your parts are mounted; paste, electricity and time.

Your board then goes through the IR reflow oven for soldering; electricity and time.

The boards are then cleaned; fluids and time.

Any of your parts left on the P-and-P are removed, and put back in the warehouse, when Widget #1000 comes out the end of the machine; time.

The stencil is cleaned. You pay for whatever the cleaning fluid is and time.

The stencil is put back in the rack; time.

If your boards are in a array, they are then cut apart. It is cheaper to build arrays, but it adds this cutting fee; time.

If there are parts that could not be mounted in the P-and-P Machine they are done by hand, or put through the wave solder machine, then cleaned a second time. There is a big hit in costs for anything done by hand such as connectors, transformers, cable assemblies etc. Time.

The boards then go to Quality Control for the level of inspection that you paid for. Simple visual to full functional test. Time.

Boards leave QC and go to shipping where they are put in Anti-Static bags and cardboard boxes and shipped off to you. Time. You pay the shipping one way or the other.

There could also be Added Value items such as your boards are put in an enclosure. You pay for someone to do it, right down to the number of seconds it takes to tighten down the screws.

By now you probably have gotten the idea that Time is important. When you were looking up stuff in the DigiKey catalog were you billing yourself the time it took to do it? Probably not...

The 500 piece cost for the electronic parts from Digikey is about $4.20

Did you include the Anti-Static Bag, the yellow Anti-Static Sticker that seals the bag, the solder (price of metals is going up every day), and any board cleaning fluid chemicals / deionized-water in that price of $4.20, and the time to do those items? I didn't think so...

A good CM knows the cost of every operation and will be around a long time. A new CM doesn't know his costs. Hence the wide variation in CM quotes.

Matric developed a reputation for being a high price CM, and customers would leave based on cost, rather than value. However many of them would return after a while saying "we got what we paid for", and never left again.

In the end my advice is to analyze the value of the services you are paying for, not the cost of the parts.