The Case for Space

Today was a disappointing day when a SpaceX Falcon 9 rocket exploded a little over two minutes after liftoff.  It was a lot of work, a lot of money, and a lot of supplies for the space station that were lost.  But what else was lost?  Of course, spectacular failures like that bring out the enemies of space exploration. Like vultures waiting on something to die, they swoop in with their simple-minded ideas of why we shouldn't explore space.  Typically, as was the case with the one I saw today, they say the money should be used to "cure cancer" or "feed hungry people" or otherwise save human lives.

That is an ignorant and simple-minded point of view.  The space program has brought countless benefits that have improved and saved lives, and continue to do so every day.  Weather satellites have dramatically increased the accuracy of weather forecasting and can give early warning of large storms so that people can be evacuated.  GPS and communication satellites have improved individual safety and made it possible to locate someone who is lost or injured, or allow someone immediate communication that may save their or someone else's life.  Air, sea, and land navigation have become much safer thanks to communication and weather satellites.  Experiments that could only be conducted in space have led to research that continues to help medical science.  And all this with extremely expensive and limited availability to space.  Currently, SpaceX and other private companies are trying to commercialize space and make it much cheaper and easily available.  It isn't easy.  Or cheap.

But I'm not here to talk about the benefits we have already received from space exploration.  I want to talk about the one big benefit we will all gain.  Survival of the human race.  And we better get on it.

Currently, the Earth is holding about 7.2 Billion people.  That number is growing exponentially.  How many can it support?  We are already feeling the strain.  The UN is recommending we start eating insects because we need the land used to raise animals to eat to grow crops and build housing.  Technology can only go so far.  How many people can we feed and house?  What will life be like when the planet gets so crowded that everyone is crammed together?

On the Wikipedia page on world population there is a nice graph of UN projections for population growth.



There are three possible projections: low, medium, and high.  With the low projection the population is expected to actually decrease beginning around 2050.  The medium projection shows it starting to flatten out around the same time. The high projection shows around ten billion people on the Earth by 2050.  Most other estimates I have seen tend toward the higher number. Unless the numbers do actually start to decline, we will at some point reach the level that the Earth can't sustain the population.  That would mean hard times for everyone.  Just like a growing family in a small "starter" house, we are going to need more room. And if we were to somehow cure cancer, and aids, and end murder and war, what would that do the population?

What about natural disasters?  In recent years large meteor impacts and close encounters have been in the news.  There have been large impacts in the past.  It is believed a large impact caused the extinction of the dinosaurs millions of years ago.  Other large rocks from space have had devastating effects on the Earth.  It is just a matter of time before it happens again.  Will our society survive?  Would the human race survive?  I say the answer is a definite no on the first, and a likely no on the second.  We are keeping our eggs all in one basket.  We need to spread out.

Some might say we should shield ourselves.  Again, there is only so much we can do.  There is no way to completely protect ourselves and our planet from a large body crashing into it.  And, whatever we can do would require a good space program!  The only reason we know about a lot of the possibly dangerous rocks out there is because our small space exploration do date has made it possible.

So, it comes down to this.  Even if you ignore all the proven benefits space exploration has already given us.  Even if you deny that it will likely provide us many more as it gets more common and cheaper.  There is still one great reason to invest more in space exploration.  Our survival as a race depends on it.  Overcrowding and a near certain major impact some time in the future will not allow us humans to continue living here as we do now.  We need to find more places to go. Kids grow up and move out of their parents' homes.  It's time for us to find a place of our own.

Trailers

In a previous post I mentioned that I was going to try my hand at writing some books.  I've been working at that lately and I have a couple of early sneak previews.  There isn't a lot there yet, but you can consider them something like a trailer for a movie.

There are two books: one on electronics and one on embedded systems.  The one on electronics is better thought out and more coherent.  Here are the reasons for posting them as they stand.

1.  You get a sneak preview of what is coming and you may even find something useful.
2.  It gives me a way to track my progress.
3.  You can provide feedback and help guide the development.
4.  Helps keep people interested while they wait for the complete books.

Here is what I ask of you.  If you are interested, take a look at what is there.  Provide feedback to me on what you like or don't like.  If you think it is crap, tell me that.  If you see things that could be improved, let me know that.  Keep in mind I'm not asking for proofreading -- there is a lot of editing yet to be done.  What I am really interested in is how you like the overall feel of the books.  Do they seem like they will be helpful?  Do they explain things well?  Too much hot air?

The books are located in the "projects" section of my web site, here:
projects
The files are in PDF format.  I look forward to hearing what you have to say.

Travel to the Beat of a Different Drum

Lately, I have run into some professional programmers that didn't even know what a kilobyte was.  They are so used to dealing in megabytes and gigabytes that the idea of measuring memory in the thousands of bytes was foreign.  With modern computer main memories measured in gigabytes and storage measured in terabytes we are spoiled.  In the 1950s kilobytes were precious. And expensive.  The first ten or fifteen years of computing was filled with new technologies to use as memory.  In the past I have written about the vacuum tube registers in ENIAC and the mercury delay lines and CRT memories of later computers.

Another technology that found fairly widespread use in those days was the magnetic drum.  Compared to delay lines and CRTs the magnetic drum memory was large.  Typical sizes were 8 to 64 kilobytes early on and expanded later.  Drums were used as main memory (RAM) and as storage, like a modern hard disk drive.  They were manufactured into the 1970s and used until the early 1980s.  They fell out of favor in the late 1950s and early 1960s as RAM when magnetic core memory became available.  They were eventually replaced for storage by the hard disk drive.

A magnetic drum is similar in concept and operation to a modern hard disk drive (HDD.)  But the HDD consists of flat disks that spin like an old vinyl record and store data on the flat surface.  It normally has a single read/write head for each storage surface and the head has to move back and forth across the surface to read different tracks of data.  In contrast, the magnetic drum was a single cylinder that stored data on the outside surface.  It spun around the central axis and typically had a read/write head for each data track.  That did away with the time needed to position the head over the needed track, but it still required time waiting on the proper data to spin around to the head.  To help overcome the rotational latency waiting on the proper data to spin around, it was common to place the next instruction of a program at the data location on the drum that would be just coming available as the previous instruction completed.  Some drum machines had the same number of read/write heads as the computer had bits in its instructions.  With that arrangement, an entire word of memory could be read or written at once.

As an example, the drum used in the IBM 650 was 16 inches long and had 40 tracks.  It could store 10 kilobytes. It spun at 12,500 RPM meaning that if you just missed the data you wanted you would have to wait 80 microseconds for that data to come back around.  In these days of multi-gigahertz computers one microsecond delay is an eternity.  But such were the rules of the game in those days.


Magnetic drums from (left) UNIVAC computer and (right) IBM 650.
Photo from royal.pingdom.com

Magnetic core memory became available in the 1950s and gave the drum a short life as main memory.  The cheaper, faster, smaller, and larger capacity of core quickly replaced the drum in most computers.  As storage memory the drum lived a while longer.  But the invention of the hard disk drive with similar improvements eventually killed the drum in that role as well. Core memory would rule for about 20 years and soon we will take a look at it.

Riding the Rough C

C is probably the closest thing there is to a "standard" programming language.  You would be hard pressed to find any modern computing system that doesn't have C available.  Although it has somewhat fallen out of favor for large computing systems, like PCs (don't tell the Linux kernel developers that!) it is almost universally used for embedded systems.  In the embedded world it is the runaway winner, although C++ is gaining ground.

But C (and C++) has a downside.  I will write about C here, but keep in mind that pretty much everything I say applies to C++ as well.  One of the characteristics of C that made it so popular is flexibility: one is allowed to do just about anything in any way they please.  But that flexibility is the achilles heel.  I am going to show a few examples to make the point.  If you haven't been bitten hard by at least one of these, you can't call yourself a C programmer.

So, you know I'm going to show some examples of things that can gotcha in C.  These will be isolated code fragments that you know have a problem.  Even considering that, notice how difficult it is to find them all.  Then consider you have one of these bugs somewhere in your thousand or so lines of code, but you don't know what or where.  Consider how hard that will be to find.  C gives you enough rope to shoot yourself in the foot.

Let's start simple:

if( my_array[n]=1)
   printf("true\n");
else
   printf("false\n");

What does that do?  Hint: there is only one answer, with two parts, and it probably isn't what you think.  First, it will set the array element "my_array[n]" to 1, even if that element doesn't exist,  and then it will print "true."

It's likely you would have said something about "it depends on what is in my_array[n]."  But it doesn't.  The programmer probably meant to write "if( my_array[n] == 1)."  The operator "==" is the equality comparison operator, and the operator "=" is the assignment operator.  The "if" statement looks at the value of the expression within the parentheses to decide which branch to take.  By writing "my_array[n] == 1" it would compare the value stored in my_array[n] to 1 and if they are equal execute the "true" part otherwise execute the "false" part.  But writing "my_array[n] = 1" assigns the value 1 to the array element and an assignment returns the value assigned as the value of the expression. So, since 1 is always assigned, 1 will always be the value inside the parentheses, which is considered true, and the "true" branch will always run.  Plus, you just put a 1 into your array.  This is perfectly legal C and you might sometime want to do an assignment that way, but not likely in an "if" statement like that.  But a standard C compiler must compile it as is, and most won't even give a warning.  This one gets even experienced, professional programmers all the time.

Remember the other part of the answer?  "Even if it doesn't exist?"  What if you declare the array like this:
int my_array[20];
and when the "if" statement above runs n is equal to 20?  The declaration "my_array[20]" means to allocate an array of 20 elements numbered 0 to 19.  There is no my_array[20].  It doesn't exist.  But the C compiler will happily produce code that writes the 1 to element 20.  Since there is not an element 20, it will write over whatever is stored there!  Chances are that some other variable is allocated that chunk of memory and it will get changed without you knowing it.  That is a really nasty bug to find.

Here is another that is quite common and hard to find.  It shows up in a lot of different forms and not always easy to even notice there is a problem.

int x = 10;
while( x>0);
{
   printf(" x = %d, x^2 = %d\n", x, x*x);
   --x;
}

What will it print? Nothing.  The program will stop when it gets to the "while" statement.  It goes into an endless loop, never getting to the next statement.  In C, the while statement is defined to be like this:
 "while  expression statement"
A statement is terminated with a semicolon.  Usually a statement does something, and a statement can be a compound statement, which is a series of statements inside curly braces ( "{  }" .)  C also allows the "null statement" which is nothing terminated with a semicolon.  Look at the while statement in the example above.  The condition is "x>0" and the statement is the null statement ";".  After that is a compound statement ( " { printf ....} ").  That means the "null statement" (";") finishes off the while statement so no code gets executed as part of the "while" loop.  The variable x never changes.  It just keeps looping.  Since the code below it (" { printf....} ") is a perfectly legal compound statement, the compiler will merrily compile it without any warnings.  But the program will effectively halt at the "while" statement.

Here is another variation of that one:

int x = 10;
while( x> 0)
   printf( "x = %d\n", x);
  --x;

What does this print?  An infinite series of "x=10" lines.  Look again at the definition of the "while" statement.  The "while expression" is followed by a single statement.  Often, that will be a compound statement, but it can be a "normal" statement.  In this example, the "printf" statement gets executed as the loop body.  But since it is not a compound statement enclosed in curly braces, the next line ("--x") is not part of the loop body.  It's all perfectly legal C and the compiler won't even warn you.

As I mentioned at the start, C is available everywhere.  It is standardized.  You would think this means it works the same everywhere, but that isn't true.  A common development method, and one I recommend, is to develop code on a PC with C that will eventually run on a microcontroller.  The PC has much greater resources for development and debugging and makes it much easier to write much of the code.  But you have to watch out for differing behaviors.  Take a look:

int x = 0;
while ( x < 40000)
{
   // do something useful here
   ++x;
}

If you run that on a PC, say with Visual Studio or gcc, it will work just fine and "do something" 40000 times.  But when you transfer that code to a small microcontroller, say an Arduino, it will hang at the "while" statement in an endless loop.

The C standard defines an "int" to be the "natural" size of integers for a given machine.  On a PC, which is a 32 or 64 bit machine, an "int" will be either 32 or 64 bits and have a range of more than plus or minus 2 billion.  But on an 8 or 16 bit microcontroller an "int" will be 16 bits.  A 16 bit integer has a range of -32768 to +32767.  Because of the way computer hardware works, as the variable "x" is counting up when it reaches 32767 and adds one, it "rolls over" from binary 0111111111111111 (32767) to binary 1000000000000000 (-32768),  and start counting up again.  But it can never reach 40,000.  Your compiler may or may not give an error or a warning with this one, but there are plenty of variations that certainly will not.

C is a great language.  It's very versatile and very popular.  You can run it on just about anything and write any kind of code you want.  But it is full of traps.  I have only scratched the surface.  It would be easy to fill a large book with examples.  If you plan to use C (or C++), put in the effort to learn enough of the language to at least be able to recognize these pitfalls when you encounter them.  There are plenty, and no list of examples could ever be complete.  It will be up to you to watch for them and find them when, not if, they happen to you.

Hitting the High Notes

In college, I was constantly told by my professors how important it was to keep a lab notebook.  They were right.  Anyone who does technical things, either professionally or as a hobby, needs to keep a good notebook.  As you progress through your hobby or career, the value of your notebooks increases.  The little nuggets of hard-won knowledge are priceless.  You can refer back to old notes and find solutions to current problems.  You can look back at what you tried before and find out if it did or didn't work.  You can track your progression over time.  There are lots of other benefits, too.

Now imagine you suddenly got access to the notebooks of some very experienced engineers.  You can imagine they would be full of useful information.  Those notebooks certainly wouldn't  relieve you of the obligation of taking your own notes, but they would be very valuable.  Well, now you can.

Today, while visiting one of my favorite websites, embedded.com, I came across this article which is more or less a review of a new, free, e-book from Texas Instruments.  I want to thank David Ashton for writing that review and I highly recommend you read it. I won't repeat his work: he's done a much better job of reviewing it than I could.

Embedded.com is geared primarily toward working engineers (although hobbyists should still read it!)  Since a lot of what I write is aimed at hobbyists, I want to take a little different path.  I want to tell you why should read the book and how you should use it.

Since this book is essentially a collection of notes from working engineers, it assumes you know what all the terms mean.  For example, there is a section on modeling capacitors.  It briefly mentions equivalent series resistance (ESR) and equivalent series inductance (ESL), but doesn't really explain what they are.  A typical hobbyist probably won't really know what those terms mean.  But that stuff is very important when it comes to how to actually use capacitors in a circuit and why.  So here is what I recommend. Find a section of the book that is either relevant to what you are doing or that seems interesting.  Read briefly through it and Google the terms you don't understand.  Use the full names when possible (equivalent series resistance instead of esr) since you will get better results.  Read through the explanation: Wikipedia often has good explanations.  Then come back and read that section of the book again with your new knowledge.  You will likely find a lot of mysterious things, like why certain types of capacitors are needed for different uses, will suddenly be much clearer.

As I mentioned above, don't just look up things as needed.  Skim through the book looking for things that seem interesting or useful.  Read those and Google what you don't know.  Taking in the new knowledge in the context of how and why it is used will help to make the concepts much clearer than if you were just reading a textbook that explains them out of context.

I think this ebook is a great resource for hobbyists (and engineers!)  Texas Instruments is huge and they produce a LOT of good documents.  Not to mention useful parts.  So download the book now.  You will have to register with TI, but that isn't a bad thing.  They might notify you of new, interesting parts and documents.  Keep the book easily available on your computer and check it out often.  Treat it as a virtual mentor, always available to ask questions.

Analog Engineer's Pocket Reference

Living Trees and Dead Dinosaurs

I enjoy writing sometimes, when I think I have something useful or interesting to say.  Perhaps that's obvious by the existence of this blog.  I will leave it to your judgement whether anything I write is useful or interesting.  I also enjoy teaching others the little bit that I know.  I think that learning is a wonderful and pleasureful thing and I like helping others experience that.  I also like to tell myself that I know a little bit about electronics and building and programming embedded systems.  

Since the "maker movement" has caused a resurgence of interest in electronics and with it a new interest in embedded systems (e.g. Arduino, Raspberry Pi, Beaglebones in assorted colors, etc.) I think I may be able to add something.  I've decided to write some books.  

If you know me, you know that very often I start on a project and it never gets finished.  There are a lot of reasons for that, but essentially it comes down to limited time.  As a project goes on, I find new things that get my attention.  So how am I going to keep interested long enough to finish?  That's where you come in.  If people find it useful and encourage me to continue, that will keep me interested.  To make that happen, they will need to see the work in progress.

So, here is the plan.  I have two books planned: one on electronics, and one on embedded systems.  I have actually already written a good amount of the embedded systems book.  The electronics book is just in outline form.  As I complete a chapter I will post about it here, with perhaps a highlight or two.  The actual book, as it develops, will be available as a download on my website.  I hope to get feedback so people can tell me what they like or don't like about the book(s) as they are written.  I can make changes I see fit and get encouraged to continue from that feedback.  That's the plan.  As I said, the results will depend on you and anyone else you find that may be interested.  Feedback from readers will be essential.

Are you or someone you know interested in such a thing?  Would you be interested in reading what I have to say about these subjects?  If so, please leave a comment so I can gauge the interest up front.  And point others that you think may be interested to this post.

Maybe you are wondering about the title of this post.  I don't intend to publish these books in the traditional paper format.  For now the intent is only to have them in pdf form online.  So, no dead trees will be involved: they can continue to live.  But some dead dinosaurs will have to give up their hydrocarbons to power your computer while you read.  Sorry, but that's how my twisted mind works.

Remember to leave your feedback comments!  Thanks.

Wherever I End Up

The automobile.  How has it affected your life?  Can you imagine what our lives would be like without it?  The subject of books and movies and songs.  The sketches and dreams of teenage boys.  Do you remember getting behind the wheel the first time?  Remember what it felt like the first time you drove alone?  The freedom and excitement of finally having your driver's license?  For roughly about a hundred years the automobile has been a fixture of daily life in most of the world.  But the times they are a changin'.


"1919 Ford Model T Highboy Coupe". Licensed under CC BY-SA 3.0 via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:1919_Ford_Model_T_Highboy_Coupe.jpg#/media/File:1919_Ford_Model_T_Highboy_Coupe.jpg

If you compare the 1919 model T in the picture above to most any common car of the late 1970s, there aren't many major differences.  Both would most likely have an internal combustion engine burning gasoline, connected  to the wheels through a gearbox and mechanical linkage.  Of course the newer model would have more refined technology and some creature comforts like air conditioning and power steering and brakes, but the technology is nearly identical. When you push the accelerator pedal on either one a mechanical linkage would open a valve to allow more air and fuel into the engine. The brake pedal would similarly have a mechanical or hydraulic linkage to the brakes on the wheels.  Pretty simple and straightforward. For about sixty years the automobile didn't change much from a technological standpoint.

Much more refined, but technologically nearly the same.

"74 Corvette Stingray-red" by Barnstarbob at English Wikipedia. Licensed under CC BY-SA 3.0 via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:74_Corvette_Stingray-red.jpg#/media/File:74_Corvette_Stingray-red.jpg


But what is in your garage now?  Much of the technology is probably the same.  It probably still has an internal combustion engine.  But a lot is new and the new is taking over quickly. If you are still making payments on your car, it probably has more computers in it than existed in the world in 1953 when the Corvette was introduced. Those computers are leading a revolution in automobile engineering, as we shall see.


"An ECM from a 1996 Chevrolet Beretta- 2013-10-24 23-13" by User:Mgiardina09 - Own work. Licensed under CC BY-SA 3.0 via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:An_ECM_from_a_1996_Chevrolet_Beretta-_2013-10-24_23-13.jpg#/media/File:An_ECM_from_a_1996_Chevrolet_Beretta-_2013-10-24_23-13.jpg


Computers in cars started off in the engine control unit (ECU).  Engine parameters like timing and fuel-air ration need to be changed for best efficiency, performance, and pollution as the operating environment change.  The ECU replaces a lot of complex mechanical contraptions that still were less than optimal.  Now it is quite likely that your accelerator pedal is not connected directly to the fuel supply.  Rather, it is probably an input to the ECU.  The ECU considers your placement of the accelerator, and even the rate of change of placement, as a request.  It considers your request in conjunction with all the other parameters it monitors to determine how much fuel to send to the engine and when.  It probably does a lot more, too.  And as time goes by it takes over more and more of your driving.

What about the brakes?  They probably still have the same hydraulic system they had in 1979.  But it has been augmented with a computer too.  Do you have anti-lock brakes? In an anti-lock brake system a computer monitors the brake pedal and wheel rotation when you are braking.  If it detects that a wheel is stopping before it should, indicating an impending skid, it will release pressure on the brake of that wheel.  To do that requires that the computer have some way of controlling the pressure on the brake for that wheel.  Modern systems have evolved to do more than prevent skids.  They now enhance stability and traction as well.  So again, your pressure on the brake pedal becomes something of a request to the braking system.  The computer now has control of the brake at each wheel and the messy, heavy, and space-consuming hydraulic lines become almost redundant.  In the future we will likely see more electronic brakes, where the wheel cylinder is actuated electrically by the computer, doing away with much or all of the hydraulic system.

What about safety systems?  Many new cars have rear-looking cameras in addition to the standard mirrors so that the driver can see what is behind the car, especially when backing up.  In addition, obstacle sensors are becoming more common to warn of an impending collision with something the driver may not be able to see.  Since all these systems are computerized, and the various computers in the car are linked by a network, it is possible to control the brakes and engine to stop the vehicle without the driver having to take action.  Systems have also been developed to detect when the vehicle is about to leave the lane or road it is traveling in and warn the driver to take action.

And then there are communication and navigation aids.  Many new cars have some sort of cellular or Internet connection.  These are sometimes used to call for help automatically in the event of an accident, or manually request assistance for various troubles.  Navigation aids allow the driver to enter a destination and get turn-by-turn directions to get there, taking current traffic and obstacles into account.  One possible future development that I think has a lot of merit is taken from modern aircraft.  In many modern aircraft, especially military, there is either a Head Up Display (HUD) or Helmet Mounted Display(HMD), or both.  These systems provide a transparent overlay in front of the operator's field of view that provides real-time data overlaid on what the operator actually sees. That data can be the typical data displayed on the dashboard.  My wife's 1995 Pontiac Grand Prix had a simple Head Up Display that projected most of the dash information onto the windshield, allowing the driver to get that information without having to look away from the road.  But how about if instead of your navigation system speaking to you to give directions, it instead overlays a line on the screen showing the exact route you need to take as you drive?  Current military systems are large and expensive, but automotive requirements are more lax and easier to meet at low cost.  No helmet is required: Google Glass or an Oculus Rift would probably provide a working solution combined with a navigation system.  Mass production would bring the cost way down, making it available to almost all car owners.  I hope we don't need weapons integration, which helps keep the cost down as well.


A night vision scene through a modern Helmet Mounted Display
http://jhmcsii.com/features-and-benefits/

The common thread through all of this has been that technology is improving safety, performance, and comfort by taking more responsibility away from the driver.  But so far, the system has been limited to assisting a single driver of a single car.  What happens when the cars start communicating between themselves and with the roadways?  We already have the Google self driving car which works mostly alone, driving on the road with human drivers.  According to Wikipedia, cars are the largest cause of injury related deaths in the world.  Most accidents are caused by poor human judgement.  With a computer in charge, the human factor is removed.  If all the cars are networked together and with the roadway and traffic signals there can no longer be poor human judgement involved.  Although it is unlikely that accidents would be completely eliminated, they would become much less common.  The reduction in loss of human life or injury and of property damage would be dramatic.


Driverless Car
"Jurvetson Google driverless car trimmed" by Flckr user jurvetson (Steve Jurvetson). Trimmed and retouched with PS9 by Mariordo - http://commons.wikimedia.org/wiki/File:Jurvetson_Google_driverless_car.jpg. Licensed under CC BY-SA 2.0 via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:Jurvetson_Google_driverless_car_trimmed.jpg#/media/File:Jurvetson_Google_driverless_car_trimmed.jpg


The technology of actually propelling the vehicle is changing as well.  Fully electric cars aren't very common yet, but Tesla Motors has proven their viability.  There are several models available.  Replacing a large, heavy, complex internal combustion engine and drivetrain with two or four simple electric motors on the wheels has great benefits.  It also reduces pollution and dependence on the limited oil supplies.  More common now, though, is the hybrid vehicle.  It combines electric assistance with an internal combustion engine to reduce fuel use.  Look around.  You will probably see several hybrids close by, and maybe even an electric car.  Electric is the wave of the future.

The changes in automotive technology over the last thirty five years have been dramatic and far reaching.  Computer and electronic technology has led that change, as with many other fields.  In the not-distant future, what we know as the automobile will not look much like what we grew up with.  Other than having four wheels, it is likely to be completely different.  What will it look like?  I don't think anyone can definitively answer than, but I have some predictions.

Let's look twenty years into the future. Limited oil supplies and pollution concerns will make the internal combustion engine a small niche market.  It will become nearly impossible to buy a standard passenger car with anything other than electric power.  That car will drive itself, perhaps with some possible input from the "driver."  It won't be driving alone, though.  It will be communicating and negotiating its actions with all the nearby cars and with the roadways themselves.  A car won't proceed through an intersection until the intersection gives it permission.  It will know where all the other cars around it are, and where it is safe to go without hitting one.  Since it will be much safer and much less likely to be involved in an accident, many of the safety features we know now will go away or decline in prominence.  That will allow the car to be lighter and roomier without becoming any larger.  Communication will overtake control of the car as the dominant feature set.  Costs will likely come down since most of the technology will be electronic, which historically as rapidly decreases in cost.  The materials used will be less and of lighter and cheaper construction.  The soccer mom in the mini van will be a lot less common: the kids can get to the game on their own since no driver will be required.

The automobile has changed the face humanity drastically over the last hundred years.  But the changes coming now will be in some ways even more dramatic.  I've made my predictions, but only time will tell how it actually turns out.  I'm interested to hear what you have to say about it all.  Leave a comment below.

Where are we headed?  Wherever we end up.

I See What You Did

Some strange things have been used as computer memory over the years.  Previously I have written about the vacuum tube memory of ENIAC and mercury delay line memory used in some early computers.  Here I want to tell you about a really odd memory technology that was used early on.

For many years, until very recently, the Cathode Ray Tube (CRT) monitor was the standard computer display, as well as television sets.  If you are over 21, you most likely remember these large, heavy  monitors.  You may also remember that if you turned off a CRT monitor or TV in a dark room, the screen would continue to glow for some time.  And you may even remember that the screen usually had a considerable static charge on it after being used.  It turns out that CRTs had some interesting properties.  What is interesting to us is that CRTs were used as early computer memory by taking advantage of one of those strange properties.  As a side note, the name Cathode Ray Tube dates back to the late 1800s when the principals of operation were first discovered.  It is rather incorrect, but has stuck around for over a hundred years despite that.  It is an interesting story how the name came about, but that's another story for another time.  Let's see how CRTs were used as memory.

The CRT is an interesting device.  It is a vacuum tube that works on the same principal as any other vacuum tube.  A large glass "tube" that is somewhat bell shaped is evacuated to cause a vacuum.  At the back (narrow) end is placed a cathode, or negative terminal.  The large, somewhat flat display area at the front has another terminal (anode) that is positive.  The cathode is heated to a point that causes the electrons to "fly off" the metal terminal and create a cloud of electrons around it.  Because of the difference in voltage applied to the cathode and anode, the cloud of electrons is attracted to anode and fly toward it in a stream.  They prefer the straightest, easiest path and without any coercing will hit the anode right in the middle.  Perhaps you have seen an older CRT monitor or TV when the power first comes on or goes off with a bright spot right in the middle.  The Cathode is created in a shape that minimizes the size of the electron stream and is therefore called an "electron gun."

We now have a stream of electrons from the cathode to the anode.  But how does it display a picture?  The anode (display) area is also covered with a phosphorescent chemical compound that glows  when struck by the electrons.  The intensity of the electron stream determines how bright it glows: stronger means brighter.  To get more than just a small spot in the center, the electron stream is deflected from side to side and up and down.  In most monitors and TVs the electrons are deflected by a magnetic field.  Around the sides of the tube, near the skinny cathode end, are some large coils of wire.  The coils have current passing through them that creates a magnetic field which attracts and repels the electrons, causing their path to curve.  By changing the strength of the field the beam of electrons can be made to hit any part of the screen.  In some types of CRT, normally used with oscilloscopes and "vector monitors," the coils of wire are replaced with large metal plates.  A voltage on those plates attracts and repels the beam similarly to the magnetic field.  The electrostatic plates are able to deflect the beam faster than changing the magnetic fields, so are used where high speed is needed.  But in either case, the beam is able to reach any point on the screen and create light and dark spots.  With a TV and most monitors, the beam is "scanned" from left to right to create a line, then from top to bottom to create a series of lines, creating an entire image on the phosphor.

That is neat and all, but how is it used as memory?  Before I get to that let me tell you that some of this information was found at radiomuseum.org and you can get more details and some neat pictures there.  Check them out for some really neat information on early radio and electronics technology.  So, to use something as a "memory" it has to be able to store information.  It turns out that when the electron beam strikes the anode, it leaves a small amount of electrostatic charge.  Remember I mentioned the static charge on a CRT?  You may have experienced that before.  The charge is localized to where the beam hits, and will bleed away in a short time.  But it can be detected if the beam hits the same spot again before it bleeds away. The voltage measured at the outside surface of that spot on the screen will be just a bit higher when the beam hits it again because of the added static charges.  A one or a zero can be stored for a short time by either lighting or not lighting a small area (or lighting a smaller or larger area) and then reading the voltage on a second scan.  By dividing the screen up into storage areas and placing a grid of voltage measuring contacts over the display, the screen can store data for a short time.

Most computers today use dynamic RAM (DRAM) that stores charge in a capacitor.  The charge will also bleed away in a short time and must be refreshed periodically by reading the data and rewriting it to keep the information.  Much like modern DRAM,  the CRT had to be refreshed.  The same was true with the mercury delay lines we looked at before.  So the electronics were made to feed back the read out signal back to the input and refresh the display.  An interesting point about CRT memory was that a second CRT could be added without the sensor grid over the face.  That one would have the screen visible and you could see the contents of the memory!  That is a great debugging tool.  A typical CRT could store a thousand or so bits.  A few dozen would be used to store a few kilobytes of data, which was a considerable improvement over the accumulators of ENIAC or the mercury delay lines.

I hope you are enjoying this series of posts.  Please leave some feedback so I know if this is interesting or not.  And if you think others may enjoy what I write, please spread the word.

Thanks.