Much Ado About Nothing

It's shocking how times files when nothing is happening. I completed all the technical requirements for the College of San Mateo Certificate of Achievement. HOWEVER there have been multiple snags. Most of the problems focus on my favorite professor, who will remain nameless because he's a great guy, except when it comes to handling administrative matters.

I have a minimum of four separate grades that need to be corrected, some going back almost five years. These four are not critical, but they do drop my GPA. However somehow an entire class was "lost" from my final semester. I'd taken the class before but needed to to withdraw due to illness. I took it again but I had simply take too heavy a class load and I made the choice to neglect this class. I failed it. I signed up for the class again and completed it without problem. Yet it doesn't exist as far as the records are concerned...

The professor of all these classes could correct this, and I've provided him with the information on several occasions. Yet nothing has happened. I spoke to some people in the administrative offices. He is infamous for not updating class records, class descriptions, etc. He is adored by his students and is a phenomenal instructor. So understandably this weakness is ignored. This is good until you become stuck in the problem... I then discovered the profession suffered a serious illness. He's back teaching but it was both painful and life threatening. It's is somewhat hard to complain about a "B" grade that should be an "A" from four years ago when you know he's been going through such a serious event.

Yet the "missing" class will prevent me from obtaining the Certificate. My hope is that in two days I will be meeting with the professor and correcting this problem.

Now I have to ask myself why am I bothering to do this? All my applications have been ignored. I've yet to receive even the slightest interest, even from companies that come to the school looking for workers. Since I have NO information on what is happening. I only know that I apply and I heard nothing. Not even an acknowledgment of receipt. I guess I'm old school, but I remember when companies treated application like they were at least sub-human. Now they don't really exist.

I can only speculate wildingly. I have to guess age discrimination might play a role. Why hire a 40yo when you can get a 20yo for less money and they are still willing to drink the company koolaid! :)

Still Plodding Along

It's been far too long since I've said anything here, so a brief update is in order.

I'm still taking classes at the College of San Mateo. I changed my original plan of pressing hard to complete my A.S. in Electronic Technology so I could apply for an internship at the FAA. My only comment is my experiences with Corporate bureaucracy hadn't prepared me for what apparently exists at the level of the Federal Government bureaucracy.

So my new plan is to complete all technical courses by the end of this semester and begin looking for work. This will let me leave with a significant Certificate and with luck I can continue to take evening classes to complete the General Education courses required for the A.S.

This semester is- a breath of fresh air compared to the previous semester. I took 17 units (full-time is considered 12) and that was a mistake. From then and previous semesters I have a few Incompletes that need to be finished. I decided to delay looking for work, take a lighter load, and finish all my technical requirements, plus take a couple of G.E. courses. However I won't be able to complete my A.S. immediately.

I'm retaking a Robotics course I had to withdraw from a year ago. For G.E. I'm enrolled in an Astronomy class and an Astronomy lab. I'm very lucky be taking the Astronomy classes now. The school just opened a new Planetarium and much better observing area in the new Science building. If you're in the San Mateo area there are a number of interesting Astronomy related events. See CSM Astronomy.

I have taken the time to read a few books and far too many articles to help me better understand electronics. In a future post I'll list some of my favorites.

A Tech Goddess

I think I've found my hero.. ah, a heroine actually. She lives in New York City and her online handle is ladyada.

I came across her work first on the site Instructables. She has developed a small battery-powered USB charger for an iPod she calls a MintyBoost Kit.

One submitted comment summed up my feelings well; "Every engineer should be required to include a start-to-finish writeup like this with every product. The thing is, I doubt they could."

Her design, writing, planning and general execution skills are top-notch. She's even gone as far as making the parts, with PC board, available as a kit you can purchase online at her site AdaFruit!

I'm gushing because she has done everything I've dreamt of someday doing on this site. Take a look at her work, the attention to detail, the carefully preplanned photographs, the great answer to submitted questions.

I'm fighting to feel inspired and not discouraged. She has set a rather high bar of quality. It will take a long time, but I'll see what I can do.

Under the Weather

I wanted to make a quick entry and apologize for having added nothing in nearly a month . I believe I did fairly well in my mad dash to complete all the labs and homework in my electronics classes. However I ended up not getting much sleep and putting in a lot of hours. This may help explain why I may have picked up this very nasty cold that I've yet to shake completely.

Being under the weather for this long will probably require me to drop the class I was planning to take over the summer. So there might be a delay in my certificate and/or degree completion date. Early in the fall I'll work out the details with a counselor.

This will give me a little more time. While reading and browsing I have come across some interesting people and new products. I promise to bring them up soon.

Crunch Week

Spent this Saturday from 9am-4:30pm in the school lab working on various assignments. I could easily think of a dozen places I'd rather have been. However Professor Brixen takes an extra Saturday every semister to help us procrastinators get our work done. The very least I can do is make good use of the time.

Professor B. gives his time; provides us with donuts and coffee for breakfast and pizza for lunch. I suspect he gets a bit of grief on the home front, yet he always manages to get us a good portion of a day.

I've never met a more generous, helpful and supportive slave-driver in my life. He's works us all pretty hard, but it's for a good cause. Compared to so many classes you actually learn stuff! Not just gain a temporary ability to recite a few memorized facts and answer multiple-choice tests.

Next week will be spent frantically finishing more lab assignments. Then the following week is finals. After that I hope to move forward on a couple of projects.

Y.A.E.T. - Yet Another Electronics Tutorial

Through my classes I've been introduced to a very good electronics education site: Work Ready Electronics.

Under Modules it offers instruction on a wide range of topics such as Electronic Careers, Switching Power Supplies, Fourier Theory, Data Conversion, MOSFETs, Digital Signal Processing (DSP), etc., etc.

After you've reviewed a module you can take an optional test to see how much you've retained. You're prompted for an email address, but you can skip this. Only three very basic questions regarding personal information are required before you can review a module. No required email address, date of birth, income level or other prying questions you find on many sites.

So whether you're just brushing up, or learning the subject for the first time, you might find this site useful. Please let me know what you think.

The Shipping News - The End

The wait is finally over. The EasyPIC 3 from MikroElektronika finally arrived! The board has no apparent damage, despite a slightly dented box. There was the expected PIC16F877A-I/P MPU, the Real-Time Clock board and Compact Flash expansions. There was also a surprise PIC18F4550-I/P MPU. I'll have to look it up.

Sadly I don't know when I'm going to have the time to power it up and run it through it's paces. There are many DIP switches so this is a case where reading the manual is mandatory...

The Shipping News II

The EasyPIC 3 from MikroElektronika still hasn't arrived. Not that big a deal except tomorrow is the last day of my Spring Break. So any free time I might have had will be over... Still about 11 more days before I can start really whining.

Geek Notes: Electronic Water

For most people, me included, find it difficult to intuit electrical behavior. I spent time trying to find analogies to the real world. I'd considered a "water-based" system to emulate electron flow. Voltage, Current, Power, Resistors and simple Diodes seemed simple. Capacitors and Transformers left me stumped. My understanding of Transistors was rather weak at the time, yet I still saw the analogy to a "water-based" system would be strained at best. I evenually come to the conclusion that the only real analogy to electron flow was electron flow.

While researching an earlier Geek Notes entry I came across a term that was new to me; The "Hydraulic Analogy" of Electricity in the Wikipedia. After a review I see I simply wasn't creative enough to come up with appropriate analogies. I'm not going to try and describe the system in detail here (see the Wikipedia link). It's far from perfect, but I find it helpful.

Geek Notes: It's the Law!

---

From time to time I will be writing entries that begin with the words Geek Notes. These are intended to let be write about some technical aspect of electronics, or pretty much any other geeky topic, to let me explain what I think I know, thus helping me grok the subject matter.

---

After spending many hours in class studying analog and digital electronics I've found a small handful of mathematical relations that popup again and again. I wish that early on I'd known how absolutely critical these would be in circuit analysis. So for your edification (I love that word) and my personal review let's discuss these relationships.

Before continuing there are a few prerequisites:

• Knowledge of basic algebra.
• Understanding of Scientific Notation (ie. 6.241×10¹⁸) and the related Engineering Notation.
• The use of symbols such as: pico(p), nano(n), micro(µ), milli(m), kilo(k), mega(M), and giga(G).
• Access to a scientific calculator (or equivalent utility).
• At least a vague concept of Voltage, Current and Resistance.

If you have these this will be easy. I can promise whatever math involved will be simple, with me it has to be simple.

The most important formula in electronics is Ohm's Law: V = I * R Voltage(V measured in Volts) is equal to Current(I measured in Amps) multiplied by Resistance(R measured in Ohms).

Using simple algebra you can derive the other two equations: I = V / R and R = V / I. These are rather simple, but with my poor memory I can't always remember. So I've found the following image to be helpful. It's easy to remember and let's you "see" all three equations.

What's great is if you know any two of the variables you can determine the third using one of the three equations.


An example is shown above. If you have a 6V battery connected to a 120K Ohm resistor you can calculate the current being drawn. In this case 50µA or 0.00005A. If you increase the Voltage of the battery, and keep the Resistance the same, the amount of Current will increase. Assuming 12V then it would be 12V / 120K Ohm = 100µA.


You may ask how is this useful? A simple case, show above, assumes you're going to use a 5V power supply, a commonly used voltage, to power an LED (Light Emitting Diode). If you don't include a Resistor the Current flowing through the LED will be as great as the power supply can provide. It will be a race between which will fry first; the power supply fuse or the LED. Of course it will be the LED, a power supply that cannot burn out an LED is rather pathetic. [This is not a problem in a standard handheld flashlight because the small incandecent bulb behaves as a resistor and glows as a result of current flow. But if you increase the Voltage enough the Current will increase and you will eventually burn out the bulb.]

A typical LED can handle a maximum about ~30mA, or 0.03A, before it will either be destroyed or the overheating will limit it's operating life. If you want to keep it safe you need to calculate what size Resistor you need to limit the Current to no more than ~30mA. Using R = V / I you have 5V / 30mA = 167 Ohms. The nearest commonly available resistor value is 180 Ohms.

If you change the Voltage, the Current will also change. So to protect the LED you need to recalculate the Resistance required to keep the Current under 30mA. If you drop the Voltage to 3V, from two AA batteries for example, you now need 3V / 30mA = 100 Ohms at a minimum to keep the current at 30mA or less. In this case it would be safe to leave the 180 Ohm Resistor in place, the LED will be fine, yet it will be slightly dimmer.

It was pointed out to me that because the LED is a diode it is a semiconductor device and has certain properties that are beyond the scope of this entry. However the use of a Resistor to protect components from excessive Current is all but universal. A Resistor that prevents too high a current flow is referred to as a Current Limiting Resistor.

That's all for now. Next time: Part II - Power Mad!

(I'd like to give special thanks to William E. Den Beste of Bill's Electronics Reference Library for his assistance in creating the schematic illustrations above and helping me better understand what I'm talking about. All errors are mine and mine alone.)

The Shipping News

I received this email today from MikroElektronika regarding my order.

...
Your order has been assembled and delivered to
customs yesterday.I am so sorry because delivery
delay, we have many orders and our delivery was
not fast as it was several months ago.

It can take 1 - 3 days to get though customs
and 3 - 9 days for airmail delivery Europe or
7-18 days to all parts of the world.

Please let me know as soon as you get your
items.

Thank you for your order,  
...

Best case that means only an 11 day wait, worst case it's 30 days! So it's feeling more like a month before Christmas.

If It's Thursday, This Must Be Belgrade

Well this is a first. I placed a direct order to MikroElektronika in Belgrade. I ordered one of the products I wrote about a week ago. The EasyPic 3, a PIC USB programmer with lots of bells and whistles. I was swayed a bit by the many resonably priced options and 30% discount on their compilers. I haven't bought a compiler yet, but I suspect they will extend the discount for awhile.

Normally when I order direct from a manufacture it's a US company. Not because I think they are better, but it's just more convenient. I often see the high shipping fees that overseas customers have to pay. Now I'm the overseas customer and while the shipping was reasonable, I wonder how long I'm gonna have to wait? (Sorta feels like the week before Xmas)

A Day Late and a Volt Short

I'm not happy with myself. I overlooked something fundamental regarding the temperature sensor project. It was to work in the Fahrenheit scale and in accordance with the demands of small size and low power everything was to work off of one 3V type CR2032 lithium battery.

I've worked with the LM35 Precision Centigrade Temperature Sensor before. It's a good sensor but won't work in this project because it's approximate 1^oC accuracy is too course. Also without a negative power supply it bottoms out at 2^oC. That is low enough for here in Northern California, where it rarely freezes. Elsewhere lower temperature are far more common and the point of the sensor is to detect and record highs and lows.

I've ordered a couple of LM34s, these are Fahrenheit sensors, so I get the resolution I want. Without a negative power supply these bottom out at 4^oF, that's much better. This is plenty cold to be useful everywhere but the coldest laboratory freezers, polar weather stations or Minnesota.

Just one small, 2 volt problem. The LM34 and LM35 both require a 5V power supply, not 3V. I guess I get to start again...

I've begun a search for a precision temperature sensor that works at 3V. So far they have all been Centigrade only. Often with a ±3^oC accuracy. I don't see how these can be labeled "Precision". I can work with a Centigrade sensor if it has a ±¹/₂^oC accuracy.

So far the other sensors that work at 3V have been more complex affairs with built in ADC and I²C interfaces, etc. These might work. If so then I could drop the requirement that the PIC have a built in ADC.

I'm still searching...

PIC's Everywhere!

I'm at the stage of deciding exactly which PIC MPU I should use for the temperature sensor project. There are a few absolute considerations; at least one 8-bit ADC, enough I/O ports to comunicate with the I²C EEPROM and analog switch (to power down components) and of course enough RAM and EEPROM memory to hold the software to measure, record and format the temperature data.

I want to use the least expensive and lowest pin count I can, just to make this a bit more challenging. The more popular (ie. supported) the chip the better. The final circuit is to fit inside a old 35mm film roll case. I'd like to avoid SMT packaging if possible, I don't want soldering to become a major problem. Therefore the 40-pin, and maybe the 28-pin, DIPs are too big.

You'd think this would narrow it down to only one, but it not quite that easy. The Microchip site was too much with too many options. I decided to take a look at the Jameco catalog, assuming they would limit their selection to the more popular MPUs. I was surprised, there were 128 different PIC MPUs available just in the DIP package (ignoring SOIC, SSOP, TSSOP and PLCC packages).

After examining at least eight datasheets so far my eyes feel like they about to bleed... I'll let you know when I'm down to two or three, but this might take awhile...

Another PIC Parameter

I spoke with Prof. Brixen today about the best way to interface the LM34 temperature sensor with a PIC microcontroller. I've wanted to keep the PIC used to be as simple as possible. (I must admit I do wish the smaller 8-pin versions had the I²C hardware interface, but that's asking alot).

I going to need to use a PIC that has at least one 8-bit ADC. I'm trying to avoid using a op-amp to increase the 10mV/^oC to a wider voltage range to use the full 8-bit range. I need to study the PIC families and see if any allow you to change the reference voltage of the ADC. (Update: Several of the PIC MPUs allow you to use either V_DD or another reference voltage for the ADC. This may require an additional chip to provide precision voltage reference.)

Off to look at a lot of datasheets...

Compilers, Assemblers, Debuggers Oh My

I've been spending time reviewing what development tools exist for the PIC microcontroller line. It's overwhelming.

There is the free Microchip PIC Assembler. I want to re-introduce myself to assembly language programming. I know some who believe wanting to program in assembly is masochistic in the extreme. It can be painful, yet you gain a deep understanding of what's exactly going on inside the CPU.

I may sound like a grumpy old man, but the majority of today's programmers have never used an assembler or even reviewed the op-codes for the CPU's they use. Of those I know, most have no interest either. To them the computer is just a "virtual" object that executes their code. This attitude certainly contributes to the abundance of bloatware in the software industry. Why optimize code for size or speed when there are always bigger harddrives, larger RAM chips and faster CPUs? Besides the code as to be out the door yesterday so there's no time...

Sorry, just pining nostalgicially for past jobs as a grunt programmer. :)

Back to tools. There are a number of C compilers, BASIC compilers and even a Pascal compiler. I want to avoid BASIC if possible. I worked for six years using a version of BASIC that was years ahead of it's time back in the mid-1980's. I know when done right BASIC can do good things. Yet it does separate you from the hardware, as would Pascal.

Assembly is intense, and remains an option. The C compilers look the most interesting. I never liked C when I wrote business applications. I can't understand why it was once such a popular tool for high-level applications. I've always seen C as a glorified Assembler with great data structures. Which is great when working in an environment with limited resources or you need to twiddle bits, but lousy for a business app.

There are several C compilers from various vendors. Microchip offers a free version of their C compiler, targeted for the PIC18 series, with the limitation of a 12K code size. I don't know if I'll be using a PIC18, but the compiler availability makes it attractive.

Also I need a development board for the PIC line. Microchip offers a basic development board for around $50US. I've read it's the most popular tool used. However I discovered another development board that supports a very wide range of PIC controllers and had some wonderful bells and whistles. It's offered by MikroElektronika based in Belgrade. Their EasyPIC 3 Development System is a little more than twice the price of the basic Microchip board, with a lot more features.

Before I buy I'll checkout some newsgroups and websites. Unless I hear very bad things about the company I suspect this will be my choice. If you buy the development board from them they offer a discount on any of their related compilers. I'll keep you informed.

Simpson's Did It!

While browsing the Maxim website I came across a surprise. They have a series of single chip (iButton packaging to be exact) that contain a temperature sensor, EEPROM memory, Real-time clock, serial protocol, etc. The DS1922L,DS1922T Temperature Logger iButton with 8kB Datalog Memory. It's everything I've been wanting to create with my Temperature Sensor/Datalogger project, but better, stronger, faster and smaller.

I should not have been surprised by it's existance. Because logging a temperature, over a long period of time, is such an obvious need. Being so obvious was a major reason I considered the project in the first place. But finding the entire circuit done much better in a rugged package depressed me for part of the day. I definately need to develop a thicker skin if I'm going to be working with such circuits for a living.

The DS1922 series is impressive. However I checked all the usual sources; Jameco, Digi-Key and Mouser. None of them carried the chip. Maxim gives the prices as $49US @ 1 unit, or $28US @ 1000+ units. That is a bit pricy.

I will take a closer look at it. I'm not familiar with iButton or the 1-Wire protocol. I still have not thought of a good way to get the data out of the EEPROM in my version, so I need to keep my options open.

I need to remember the entire point of this exercise was not to just develop a datalogger, but to learn by doing. Using an all-in-one, pre-developed system isn't going to help me learn.

Everything But the Kitchen Sink

I'm been giving thought to what would be a set of reasonable requirements for a temperature sensor/datalogger. Here are some of my first thoughts in general order of importance:

• Very Low Power Consumption
• Best powered by a 3V lithium battery
• Active: < 1mA, Sleep: < 50µA
• Long Recording Period
• At least one week to several months
• Reasonable Recording Intervals
  • Event recorded every 15-60 minutes
• Rugged Construction
  
• Wide Operating Temperature Range
  
• Small Form Factor
  
• Easy Downloading of Data
  
• Inexpensive (<$50US)
  

That all should be easy, NOT! Considering I sometimes still put diodes and transistors into my protoboard backwards this could take awhile. It's a good goal though. This may sound a little sad, but this project has be more excited that any software project I've been involved with for the last few years.

How Hot Was It?

A couple of years ago a new car came into the household and my workhorse Integra lost it's privilege of parking in the apartment's underground parking area. Now exposed to the elements I was surprised this summer when I found a couple of hard candy tins had become so hot, even out of the sunlight, that the hard candy had at one point melted into a near liquid and later resolidified.

The lowest melting point for a sugar I found was 85^oC (185^oF). That's at the low end. Common sucrose doesn't melt until nearly 150^oC (over 300^oF)! So my question is: How Hot Was It?!

I don't care about the candy, but I do care about my digital SLR camera. I couldn't find the recommended storage temperatures on the camera's spec sheet. I did find the Compact Flash cards are only rated to about 80^oC (176^oF), storage maximum, not operation. I suspect the camera is much more sensitive.

It's obvious storing the camera in the car during the summer is a bad idea. Yet when might it be a good idea? Could I keep some extra doses of my prescription medication in the car for those time I forget to take them with me? Would my chocolate truffles ever be safe in my car!?

This rather unimportant question kept running around in my head. How could I measure and store the temperature minimums and maximums? I once used a high/low mercury thermometer when I grew indoor plans. But with how I throw things around the car I'd end up crushing it and getting mercury in the upholstery. I could drive around with mercury vapors too! Weeee to dying brain cells.

So this is where the new training comes in. Could I build a temperature sensor/datalogger that would record the ambient temperature over a period of weeks or months? Sure I can! For the ignorant everything is easy!

Tomorrow I'll consider the requirements.

Welcome to BlinkingBoxes

Who am I and what is this about?

The name is Dave and after working in the Software/IT business for over 22 years I needed to make a change. Being a Web Engineer during the DotCom Crash also helped make the decision for me.

About two years ago I returned to school at a local community college, the College of San Mateo, to experiment and see if this aging dog could learn anything new. I tried some work in Graphic Design; it was fun but I couldn't see any future earning potential for myself. I also checked out a new program in Computer Forensics.

At the last moment one of the Computer Forensics classes was postponed until the following semester. I looked around and discovered that there was an opening in "D.C. Electronics". This triggered some good memories.

When I was a teenager I'd played around with building digital circuits. I enjoyed it and most likely would have continued the hardware work, except I lost my most valuable components in a power supply failure. At the time the value of the lost circuitry was maybe $150, but it was 1977 and I was 15. I couldn't recover from that large a loss. I dropped the electronics hardware and stuck to the software side using a Tandy TRS-80 microcomputer. This simple start eventually lead to my 22 year software career.

Now with the goal to explore, I took the "D.C. Electronics" course. The rest, as they say, is history. I continued with the classes and am now less than a year away from finishing the technical portion of an A.S. in Electronics Technology. Who knows, a BSEE could follow someday.

It's been very frustrating and amazingly rewarding. I've come to remember the joy of learning and getting in touch with yet another aspect of my inner geek.

Right now I'm so green I glow in the dark. My hope is to learn, talk about what I learn, develop electronics projects and ask questions. Then maybe I'll glow a little less brightly.