Maker Faire 2014!

I'm just home from Maker Faire 2014, and it was spectacular.  This is the first year that I've exhibited there, and I am exhausted, sore, sweaty, smelly, and immensely happy.  My exhibit was an LED Shutter Timer which allowed people to see the exposure time, shutter travel speed and shutter direction of their camera, whether it was the electronic rolling shutter on a camera phone, or the travelling-slit curtains of a DSLR.  I talked with people almost non-stop both yesterday and today, and I met an amazing collection of creative, friendly, engaging and engaged people.  If you're reading this because you saw the URL for this blog on my table, feel free to look around, and soon I'll have all the technical information about my project posted.  In the next 24 hours though I need to shower, sleep, and try to recover my voice!

If you went to Maker Faire this year, please leave me a comment and tell me the coolest thing you saw there!

"Fine, continue paying your debts!"

I got a robo-call this morning from someone telemarketing their debt consolidation and reduction services. These places usually provide some combination of loan aggregation and paid negotiation with your current creditors to reduce your balance owed, at the cost of trashing your credit rating for a while.  When I have time I will sometimes play games with telemarketers, because I abhor their business model.  Sometimes I'll even try to convince the person with whom I'm speaking that they should quit and follow their higher aspirations in life, which I'm sure never included sitting in a boiler room call center selling random people things that they don't need.  Today, however, I was in a hurry, so I skipped straight to, "Do you check your calling list against the federal Do Not Call list, of which you are now in violation?"  The woman paused for a moment and said, in a snotty tone, "Fine, continue paying your debts!" And then hung up.

I was amused and somewhat disgusted that of all the things she could have said, she chose to insult me for being someone who continues to pay his debts.  I wonder if she's ever considered that the logical extension of her work and apparent world view is the fundamental breakdown of credit systems everywhere.  After all, there is an enormous amount of unsecured credit extended every day, to individuals and business, in order to keep the economy buzzing along.  Could we live without it?  Sure, but everyone would have to maintain a larger cash reserve, and all large purchases would have to wait until after the funds for the purchase were acquired. You'd also have to send payment for all purchases in advance, or at least through some sort of escrow transaction. Imagine if every time you ordered something online, you had to send payment before the seller shipped.  And it would have to be a check, or money order, or bank transfer, because in a world with no unsecured debt, there can be no credit cards or even charge cards.  But these excellent tools do exist to allow us to smooth money over time, because people, for the most part, continue paying their debts.

I understand that there are times when circumstances make paying debts impossible.  Risky investments, such as venture capital poured into start-ups, are made with the full understanding that the money very likely will never be paid back.  In that case, the investor is taking on substantial risk in exchange for substantial potential upside.  Sure, you're 90% likely to lose your investment, but it only takes one early investment in Google to pay for all your investments in pets.com.  But here I'm talking primarily about unsecured personal debt, such as credit cards.  And yes, if you owe more in interest each month than you're able to pay, the financial hole will just get deeper without bound. In that case, a negotiated reduction in interest rate is preferable to a settlement, which is preferable to bankruptcy.  And bankruptcy is far preferable to protracted destitution.  But writing down debts should be a last resort.  When possible, we should aspire to avoid unnecessary debt, and when it is a necessary and useful evil, we should then continue paying our debts.

A Bad Good Idea...

I am a fan of old 8-bit computers, so when I found an original TRS-80 in the surplus electronics store where I buy things like stepper motors, I had to take it over to the test bench and see if it actually worked.  It did power up, but while I was connecting it up, I discovered this:

There are three connectors on the back of the keyboard unit which are labelled, in raised black-on-black letters, TAPE, VIDEO, and POWER.  All three are identical 5-pin DIN connectors.  This means that any of the cables will fit into any of the connectors.  And they are on the back of the keyboard, so you're very likely to be plugging them in blind, by feel.  This means the chance of plugging the wrong cable into the wrong hole is pretty high.

As with all consumer products, the engineer that designed this computer was desperately trying to keep the cost as low as possible.  By using the same connector, there was only one unique external connector part number on the bill of materials, so their purchasing volumes for that connector were three times as high, meaning they get better volume pricing. They also needed to create only one connector footprint symbol for the printed circuit board.  But from a human factors point of view, this is a terrible decision.  It is absolutely certain that people are going to plug the wrong cable into the wrong connector sometimes, and their computer would be mysteriously not working.  Indeed, depending upon the pinout of the connectors, the computer might even be damaged.  If it is still under warranty, they'll be angry and demanding of a repair, replacement, or refund.  And if it is out of warranty, they'll be angry and they'll tell all their friends about your terrible quality.

When you design something, it's important to think carefully about all the ways it could be used incorrectly.  You can't always outwit someone who is determined to do something wrong, but you want to try to make the correct way of doing things the path of least resistance.

PCB Copper Thickness

When specifying the thickness of copper on printed circuit boards (PCBs) the usual metric is "ounces."  One ounce copper means the thickness you get if you flatten one ounce of copper out to one square foot.  The chart below shows the thicknesses of various ounce weights of copper in both mils (thousandths of an inch) and microns (millionths of a meter).

Copper Thickness (in Ounces)	Copper Thickness (in Mils)	Copper Thickness (in Microns)	Resistance per Square (in mOhms)
1/4 Ounce	0.34 mils	8.5 microns	2.0 mOhms
1/3 Ounce	0.44 mils	12 microns	1.5 mOhms
1/2 Ounce	0.67 mils	17 microns	1.0 mOhms
1 Ounce	1.34 mils	34 microns	0.5 mOhms
2 Ounces	2.68 mils	68 microns	0.25 mOhms
3 Ounces	4.02 mils	102 microns	0.167 mOhms
4 Ounces	5.36 mils	136 microns	0.125 mOhms

The table also shows the approximate "resistance per square," which is the edge to edge sheet resistance of any size square area of that weight of copper.  This is very useful for quickly calculating the DC resistance of a PCB trace by decomposing it into a series of squares.  For example, a trace 10,000 mils (10 inches) long and 10 mils wide is made up of 1000 squares, each 10mils x 10mils, in series.  If that trace is 1/2 ounce copper, the DC resistance would be 1000 squares x 1.0 mOhms / square = 1000 mOhms, or 1 Ohm.  If you are running high current through that trace, 1 Ohm can cause a substantial voltage drop.

Super Easy Giant Chocolate Fondue

This is a bit out of the normal realm of my engineering projects.  Last week at work we had a Halloween Party at lunch, with each department kicking in some activity or fun thing for everyone to enjoy.  I volunteered to do a chocolate fondue.  My goal was to make enough for everyone there (about 100 people) to try some if they wanted, and to make it relatively quick and easy to prepare.  I found a recipe here and decided to scale it up.  The original recipe calls for four cups of chocolate chips, which is 24 ounces.  Since Costco sells a 72 ounce bag of chips, I decided to do a triple batch.  This worked out great, because the recipe also calls for 1 and 1/3 cup of half and half.  Triple that and you get 4 cups, or 1 quart!  So it really did come down to:

1 giant (72 Ounce) bag of Nestle semi-sweet chocolate chips from Costco
1 Quart of Half-and-Half

Melt together in a crock pot.  That's it.

I used a 6-quart crock pot, and I might have gotten away with a smaller one, but I was glad I had some room to stir.  I also did use the Reynold's liner bag, which made clean-up very easy, but was probably otherwise not necessary.

To get it ready quickly, I deviated from the source recipe's instructions:  I poured both ingredients into the crock pot and put the stoneware pot (but not the heater base) into a microwave on high for 5 minutes to get it started melting.  Then I put it in the stoneware back into the crock pot heater and set it on high.  I stirred it almost continuously to prevent burning, and in about 15 minutes it went from the consistency of chocolate milk with large melty lumps to a smooth, very nice dipping chocolate fondue.  At that point, I set it back to "warm," which kept is just right throughout the party.  I also stirred it occasionally to make sure it stayed smooth.

This produced about 100 ounces, which is enough for 100 people to have a reasonable taste, or 20 people to go quite nuts.

For dippers, I put out mini snickers, marshmallows, Oreos, pretzels, and strawberries.  Far and away the most popular item was the strawberries, and I ended up wishing that I had bought much more than the two quarts I did.  Lots of other things also work well with chocolate fondue, such as pineapple, apple, and poundcake.  Really, what ISN'T better dipped in chocolate?  One of my clever co-workers took one of the apples from the bobbing-for-apples area and cut it up for dipping.

It's fun, it's quick, and it's an impressive amount of molten chocolate!

I crashed my flashlight...

My dad recently bought some Techlite 200 high-intensity LED flashlights at Costco, and gave me two of them.  They are amazingly bright and well constructed, so they quickly became my favorite hand-held flashlights.  I was reading this extremely detailed review of them on Amazon, and learned that I could skip the somewhat jarring strobe mode when turning them off by just holding down the power button for a couple of seconds.  I tried it, and it works, but after doing it several times, my light would no longer turn on.  I had to remove the cap to disconnect the battery, causing a hard reset of whatever control circuitry they have in there.  I don't know exactly how they implemented the electronics, and I'm not willing to sacrifice this neat flashlight to find out, but I crashed my flashlight...

Attempts to reproduce the failure on the other Techlight 200 I have were unsuccessful, so it is apparently not an inherent design flaw, just an edge marginality.  Still, I crashed my flashlight!  There is some sort of cautionary story in here somewhere...

"Revolution" TV Show.

This entry is some thoughts about the new television series "Revolution."  This latest invention from the imagination of "Lost" creator J.J. Abrams premiered Monday, September 17th, on NBC.  The pilot episode was released early on Hulu, so I took a look at it.  I'll try to write this entry without spoilers, or at least without any more spoilers than the ads and website for the show provide.  Still, if you prefer to avoid even a hint of fore-knowledge, you may want to read this after you watch the pilot episode.

"Revolution" is set "fifteen years after the blackout."  In a video on the show's website, Abrams says, “The question the show asks is, 'What would happen if everything powered by electricity suddenly turned off?'” Because I'm interested in worst-case scenarios, disaster preparedness, and knowing what to do when the zombies come, I'm intrigued by ideas like this.  But this a problematic scenario...  People are really ingenious and given the proper motivation (say, the loss of civilization as we know it), they would come up with some pretty clever stuff.  Let's consider how...

While it's true that we use electricity for an enormous number of things, we can still do a lot without it, as we did in the past.  Energy can be harvested mechanically in the form of movement, with windmills and water wheels or water turbines. In 1890, George Westinghouse suggested that the energy of Niagara Falls would best be transmitted to Buffalo not as electricity generated on site, but as compressed air. Compressed air can also be used to store mechanical energy in high-pressure gas cylinders.

Furthermore, a lot of technologies that we think of as “electrical” don't have to be. In many cases, we use electricity to provide mechanical energy that could be provided by other sources. Refrigeration, for example, uses electricity to turn a motor to run a compressor. But there's no reason the compressor can't be turned by a water wheel or a windmill. Or a steam engine...

In the event of a “Revolution” scale blackout, the world would quickly see the return of the steam era. Boiler technology and steam engines would be the next big growth industry. Coal and wood fired steam railroads would quickly provide critical transportation links, first on a small scale as museum exhibits were pressed back into service, but then growing as fast as more equipment could be built. Central steam engines in factories could provide mechanical energy for all sorts of tasks, such as machining, cooling, cutting, building, and so on.

And if the “Revolution” world really just precludes electronics, it wouldn't be limited to steam engines. Diesel engines use the compression of the piston to ignite the fuel-air mixture, without any electrical spark plug. And they can be built to be started using only compressed air. It may take a lot of tedious pumping, but you could prime a compressed air system with a hand or foot pump. Then, once you've got the engine running, you could use it to drive a compressor to charge up the compressed air cylinder for the next time you need to start.  All without electricity. Virtually all large scale modern engines are highly dependent upon electronic engine control modules  (ECMs) to manage every aspect of their operation. But that's in order to make them as efficient as possible. You can trade away some of that efficiency for a much simpler, all mechanical control system. That's how they all used to be. And there would be enormous motivation for people to return to and advance these sorts of technologies.

Refrigeration also illustrates the case where the current state of the art is only one of many ways to achieve the desired goal, in this case of making things cold. Anyone with a propane fueled refrigerator in their camper knows that you can keep a fridge full of food or drinks cold just fine using a small flame to drive an absorption refrigeration cycle.

A permanent loss of electricity would limit the production of some materials. Aluminum, for example, is refined using an electrolytic process, without which, it is becomes a very precious metal. Fortunately, there is already a significant stock of metallic aluminum in the world that could be recycled almost endlessly. But anything that depends on an electrolytic manufacturing process could no longer be made.

Otherwise, I can think of only a few key technologies that would be impossible to at least approximate in a “Revolution” world: high-speed computing and high-speed, long-distance, and wireless communication. And even some level of both computation and communication can be done mechanically. Mechanical calculators existed for years before modern electronic logic circuits, and I'm sure the world would see new heights of sophisticated mechanical computers being built. It would be a steam-punk enthusiast's dream come true. I can also imagine a telegraph system based on mechanical modulation of something like a metal bar, in order to send messages significant distances at the speed of sound in metal, or around 13,000 miles per hour. Or perhaps we'd just see the return of other pre-electronic communication technologies.  Sure, neither of these are as good as what we have now, but they are still a major step above the pre-industrial, agrarian civilization portrayed in the show...