Happy Holidays

I’ve been a bit more of a Grinch this year than I am usually at Christmas/Festivus/Hanukkah/Kwanzaa/etc. I think part of it is my worries about the economy and the rest is because I think the buying of presents is good intentioned, but kind of a waste. Once I get past my own soapbox, I often find that I end up with some thoughtful gifts from the ones I love. Let’s get to the part where I am thankful for the gifts I did get:

  1. A book — My gf was kind enough to listen to me complain about being an analog engineer and not having one of the most important books on my bookshelf. She got me Troubleshooting Analog Circuits by Bob Pease. Up until the past few months I never knew who Bob Pease was until an experience co-worker turned me onto his and Jim Williams’ writings. I admire both of them for their extensive experience in the field of Analog Engineering and their friendly, down-to-earth writing style (something I try to emulate). The “Troubleshooting” tome is well known as a guide on how to specifically move towards pinpointing issues in an analog circuit. I look forward to reading it and applying it. I also hope to post a book wishlist/review list in the near future.
  2. Tools — My parents understood that people trying to fix up a house and make it more energy efficient require tools to do so; they got me some great tools. I’m sure those tools will help me fix all the mistakes I make in the house too. I have also decided that Lowe’s/Home Depot/Etc are the Toys R’ Us of the “older kids”.
  3. A Chord Organ — This is a gift from previous owner of the house I bought to me…because they left it in the attic. It turns out this is a “Magnus Serenade”, and so far it has been pretty hard to find any information on it.  I believe that it is a simple chord organ, similar to the other Magnus models. The idea is that you activate reeds or sets of reeds with keys or buttons (respectively) and then an electronic blower forces air across them to produce a sound. Really it’s like a big accordion (without the back pain). I haven’t had a chance to pull it out of the attic to try it out yet, but if it does not work, it will give me another opportunity to work on old musical instruments. The video I’ve included below is a similar model of chord organ…not the best sound, but definitely unique.

Magnus_Serenade_1 Magnus_Serenade_2

I hope everyone had a great holiday and I look forward to continuing to post in 2009!

A Quick Thought on the Economics of Renewable Energy

I glanced at my natural gas bill today while cleaning up the house and was a little shocked at myself. I pride myself on being better than most on conservation (at least cognizant of it) and my usage was quite high. That was last month and I can only imagine this month will get worse. And yes, I do live in a rental house right now (with an energy efficient house in my near future), but that’s the case for a lot of people, especially lower income. So I got to thinking, what will stop people from using so much energy in their frosty, great northern homes?

The answer is, of course, money. It always has been. But now we’re in a climate where the costs are beginning to rise so fast that people who sat dormant before will begin to take action. In fact, this will also likely move people in all economic groups to take action; the most important of these being the middle- to lower-income groups. Why? Because costs like heating are a larger percentage so there will be a more voluminous cry from the masses for cheaper energy (not that we don’t love our green friends, pushing the renewable energy agenda and buying recycled elephant dung paper as Christmas gifts for family). Hopefully more people clamoring for energy efficient devices and alternative fuels will push us towards a tipping point (which I incorrectly identified as a singularity), where renewables become the norm and cost of energy will drop due to the abundance of natural energy, waiting to be converted. So as prices continue to increase–and the temporary drop in gas prices is undoubtedly temporary–the push from most people will be towards a more sustainable future.

How about you? Have you felt the need to push for more conservation lately solely on energy costs? Let me know in the comments.

Photo by nothern green pixie

Designing For The Long Term

I was at the gym the other day and glanced over at a fellow gym-goer on their cellphone. I did a triple take as the phone was a flip phone that was maybe 4 inches wide and 5 inches high on each flap of the flip (making a 10 inch phone when completely extended).  On my third glance at this monstrosity of a phone I realized it was in fact a Blackberry that he had pulled out of it’s case/holder but the case looked like the bottom half of a flip phone. It got me thinking about design longevity.

I think back on the cell phones of the past and recent past and remember how clunky and awkward they were. That was maybe 5 years ago and those phones have long been sitting at the back of peoples’ desk drawers or hopefully donated to causes that recycle phones. I am amazed that these phone manufacturers continually get away with phones that will be obsolete in 5 years maximum. Why don’t we expect more from our mobile devices (in terms of longevity)? Do we really think your phone will last more than 3 years?

My most recent phone just passed away after 2 years. In my case I MAYBE dropped my phone in a bowl of soup, but I think it just got one of the external speakers; really I think the kiss of death was something a bad battery (which was not contaminated with soup). But even if it lasted another year and THEN died, would I have been upset? I don’t think I or most people would be because we have come to expect consumer products to have a shorter life span.

How do we design electronics for the long term? There are a bunch of great examples of electronics that have been built to last:

  1. Military designs –Aside from the humongous budgets that most contractors have for their military products, the specs on military designs can be equally large in scope. Translation: The military gets high quality products that were expensive but are built to last. These products are often ahead of the technology curve (thanks to the money available), so the technology often goes obsolete later too. The final piece is that the harsh environments encountered by military personnel requires gadgets that are sturdy enough to last for a long time; the ones that function in the field can continue to do so for a long time. A good example would be this emergency radio which was recently torn down by EETimes after an eBay purchase. The 1950s internals reveal high quality workmanship with components that match.
  2. Space designs — Although NASA’s budget has been cut back since Bush has taken office, this research intensive organization has produced some of the finest inventions for human kind. Not only that, they have a mandate to create equipment that can last for long periods of time. My favorite example is the Voyager 1 satellite, currently exiting our solar system and headed further than any other human instrument has ever been. Not only that, but this advanced spacecraft started taking up close pictures of Jupiter and Saturn before I was even born (first passed Jupiter in 1979). The fact that this machine is still functional, still running tests and still capable of sending back data until 2025 (est.) is mind boggling. Not only that, but the spacecraft has not had the advantage and protection of the earth’s ionosphere, so it has been taking much more direct cosmic radiation than normal electronics.
  3. Power companies — These terrestrial behemoths don’t have to worry about cosmic radiation quite as much as the NASA folks, but they often have materials carrying hundreds of amperes of current over long distances. Unfortunately, these systems are in need of some updating (especially to accommodate new renewable energy resources onto the grid), but once they are built, I’m sure they will hold up. Usually power companies achieve longevity in their equipment by using high quality, high strength materials that are designed with enough overhead to manage higher loads that they expect to see (i.e. A copper wire that is designed to carry 1000A of current, but only carries 600A on a regular basis).
  4. Nuclear Facilities — Some of the remnants of the Cold War include the control systems that decided whether missiles would fire or not. These are still some computers operational today in Russia that (we hope) are still making logical decisions. While I don’t agree with these computers in the first place, I sure hope they continue to hold up, otherwise it will prove to be a doomsday device. Proper shielding from radiation and free radicals help to prevent aging damage to electronics from fissile material, in addition to starting with high quality, military-grade products.
  5. Autos — While the auto industry might be falling on its face currently, the designers in Detroit used to help drive new technologies in many other walks of life. Looking at cars that have lasted since the 50s and beyond, we see examples of simple yet elegant electrical designs that were meant to last. Cars have not always had the GPS systems of today (which I’m guessing will have a much shorter lifespan), but have had electronics powering the wiper blades and the spark plugs for a long time. These systems in vintage cars require some maintenance and the occasional fuse replacement, but on the whole are sturdy enough to continue powering well-cared for vintage vehicles.

So these industrial/military and some commercial applications obviously present the need for longevity in finished products. However, designers need to consider many different parameters of a system in order to produce the best product for the long term.

  1. Communication protocol — This item applies most directly to cell phone makers and is a decent excuse for their short life products (but does not excuse everything about them). Unfortunately for phone users (and fortunately for phone makers), wireless protocols are always changing in order to try and achieve the highest bandwidth, usually through higher frequencies or different transmission methods. So once a technology changes for good, older phones become obsolete (and the phone makers happily sell you a new shiny one). This problem also exists when looking to the internals of products; to prevent obsolescence due to outdated protocols, they should be standard to the industry in which the product will be used, simple enough to incorporate into a new standard (and included legacy support) and well documented. Nothing is worse than having a 20 year old device that works fine but can no longer transmit information. An example might be an industrial test fixture on an old computer that only has a 5.25 inch floppy drive. The test fixture might work great, but getting data off that computer is no longer viable so the entire setup is obsolete. A tried and true method for machines to communicate has always been serially and with good reason. While a newer communication protocol might require myriad signals that are not available on an older product, most improvements to a serial signal are often speed (increasing the frequency of the oscillator driving the serial line) or encoding. Since devices can be re-programmed to send a new encoding or you could slow down the device on the receiving end, serial communications seem to be a viable solution for lots of applications.
  2. Long term drift of components — Designing for 10’s of years often requires attention to detail and deep pockets. The most important first step is to watch for this parameter on a data sheet for any critical component (marked as “long term drift”, often given as a percentage change over a specified period). But beware, many vendors simply leave this data off of their spec because they either do not think it is relevant, do not want to display poor data or because they don’t know what it means. In any of these situations it is critical to demand this data or to perform testing yourself in order to create lasting products.
  3. Susceptibility to thermal stress — Size matters when it comes to handling thermal stress; this is partially why older electronics hold up so well. The smaller components on a device get, the less heat they can dissipate (assuming similar materials in a larger package). A good example would be resistors. A 0603 resistor (.6mm x .3mm) can only dissipate 1/10 of a watt while a standard through-hole component can dissipate 1/4 watt on average. This is a trade-off that must be made in any system designed for portability, but could result in lower product lifetime (especially in high heat or high current situations).
  4. Standard packaging — The chip industry is a highly competitive environment where silicon designs are always being touted as the next best thing. Unfortunately for older products, this can often mean that components such as op-amps or a buck converter will no longer be produced. It’s a symptom of being in a dynamic industry and has to be dealt with. The best way to combat obsolescence is to create projects that have standards designed in to them. Thinking about creating a great new analog circuit with a non-standard pin-out in a device package that is so obscure that you have trouble finding it in catalogs?  Why not try making some other compromises on your circuit board and squeezing in a proven SOIC-8 with a pin-out similar to 4 other op-amps. You’ll be happy you do in about 4 years when that op-amp you’re using goes obsolete.

There are probably other ways to help design a product with a long life span, but these are a good start. A common theme is to pay more for higher quality components, which might not be preferred in certain situations. However, designing products for the long term can help save money year after year by not having to replace products or maintain sold products so spending a little more up front could pay off in the end. Some newer consumer electronics industries create new products each year either to drive demand or to fulfill needs after older devices break (which they may have produced).  In the process, they try to drive cost down by using the cheapest parts available; this can cause failures and unhappy customers. To design a long term product, costs and long term design considerations must be balanced.

What’s the longest period you’ve ever had a piece of functioning electronics? What kinds of changes did you see over the years? Have you ever created a low cost design that lasted more than 5 years? Let me know in the comments.

Circuit Board Design (And How It Has Changed)

Products today mostly use Printed Circuit Boards (or PCBs) to successfully route signals from one component in a circuit to the next. There are multiple layer circuit boards with printed metal “wires” that run between the various elements in a circuit. However, this was not always the case. In the good ol’ days, there were different variations and precursors to the PCB. Some of these included point to point wiring (just soldering a wire between say a resistor and a capacitor), wire wrap boards (think of a point-to-point board on a grid with more wires than you’d know what to do with), acid etched copper on dielectric (think of a 1 layer PCB with very large and rounded signal traces) and many others. These kinds of boards had many many different methods but also had less restrictions than modern designs. In fact,  Paul Rako from EDN recently wrote a great article on prototyping using some of these older methods. He references many techniques of the greats like Bob Pease and Jim Williams and their rapid prototyping techniques. It’s an information rich article and I would highly suggest checking it out. OK, back to the party.

So what has changed when moving from older boards and circuit designs to newer circuit boards?

  1. Speed — There’ s no denying that the boards of today are faster than those of yesteryear. The extremes are apparent in the RF industry which is/was doing well because of the cell phone becoming the hottest platform to develop for (PCs are still around of course but the excitement is in the cell phone industry).  When frequencies get into the GHz range and you’re trying to guide signals instead of wire them, you know that your boards will be finicky. Additionally, the speed increase is not limited to the RF industry as many new designs have at least some component of a clocked digital system on them. Even pushing into the MHz range can be difficult with older board techniques. Wiring point to point is not as viable with high speed signals, especially when you have upwards of 32 wires between two components (a data line).
  2. Size/Type of components – This is another symptom of newer industries. As products go increasingly mobile, parts begin to shrink out of necessity or because the cost of making the older, larger parts becomes prohibitive. As such, the boards have made a large change going from through-hole components (like the capacitors in the picture at the top of this site), to Surface Mount Technology. This has affected the construction of final boards (SMT usually requires machine placement for quick and reliable boards). This also means that the amount of power a board containing only SMT parts can absorb (when the board is considered as one entity) is reduced as the smaller SMT parts cannot handle as much current without blowing up.
  3. Number of connections — I’ve included a picture of wire wrap from the Wikimedia commons site below. Notice anything about it? It’s ridiculous! And I would encourage you to go to the Wikipedia page and look into some of the other types of wire wrapped boards. Now let’s look at a common package today, the Ball Grid Array (BGA). This type of package uses little solderballs on the bottom of the package to adhere to the board. It is glued on at first and when you reflow (heat up to make the solder melt), the balls fall into place on whatever PCB you have produced (assuming you have made the PCB correctly).  BGAs start around 144 pins (maybe 196?) I believe and go to upwards of 1000 pins per part. Can you imagine trying to hook up 1000 wires like below? I don’t think so.
  4. RoHS — Lead is bad for the environment, for your health and for any children who decide to ingest it. In fact, the only people who speak the wonders of lead these days are cranky analog engineers such as myself, trying to solder something (I’m a 6 out of 10 on the cranky scale). Why do we love lead? Because Lead-Tin (Pb-Sn) solder is much easier to work with due to the lower melting temperature and higher thermal capacity.  So as RoHS becomes more widespread, with the Silver-Tin (Ag-Sn) solder that is more difficult to work with, it become another element of board design that must change.

So obviously some stuff has changed. Some is for the better, some not so much. Let’s look at board problems encountered in modern day printed circuit boards in order to see the problems encountered as circuit boards have become more inexpensive and repeatably made:

  1. Capacitance in the board — Printed circuit boards are constructed from a non-conducting material so that signals do not leak from one lead to another. However, in constructing the perfect insulator, they also created a material with a significant (but not huge) dielectric constant. This means if two signals are routed over top of one another (acting like plates), then the sandwich of the signal and the dielectric will act like a capacitor. Not only that, but as you increase the frequency of a signal (with speeds upwards of GHz), the capacitor looks more and more like a shorted wire! This phenomenon is known as “cross-talk” and can affect myriad high-speed or high voltage situations.
  2. Inductance in the leads of a chip — Before the BGAs mentioned in point 3 above, there were packages (usually square) with leads coming out the sides known as Quad Flat Packs (QFPs). The leads coming out of them vary in thickness, but usually get thinner as there are more leads on a chip. As the leads get thinner and longer, the inductance of those leads goes up. We remember that inductors are the “opposite” of capacitors in that they allow low frequency signals to pass and block high frequency signals. In a system that is mostly high frequency signals (think digital), the inductance of the leads can have a serious affect on how well a signal propogates from one element on a circuit board to the next. BGAs have started to reduce this problem, but the cost of dealing with BGAs can be quite prohibitive for smaller operations.
  3. Timing — In a high speed system that requires signals to depart a component at a certain time and arrive at a different component a short (predictable) while later, there are many things that can prevent the signal from arriving undisturbed. We’ve already seen the capacitive and the inductive effects mentioned above, but what about resistance?  Although everything has some amount of resistance, the lines in a board routing one component to the next can have an affect on the overall performance of a circuit. If one of these lines is longer than another than there will be a noticeable difference in the resistance of that line. Most importantly, when comparing the impedance (sum of the resistance and the frequency dependance of the impendance and capacitance) of two different lines going between components (say a processor and a RAM chip), differences can cause the signals to arrive at different times in different conditions. The rise times, the fall times, the over shoot, the under shoot, and the general shape of a signal can all be affected by the characterisitcs of the connection. It is useful to remember that every connection really acts like an RLC filter circuit, the only difference being how much resistance, inductance and capacitance are present and how they will affect the final signal.
  4. Ground/Power Plane — Other advantages a circuit board brings, especially multilayer circuit boards, is the ability to route a plane of power or a grounding plane underneath a portion of a design. If we think of a PCB as a large sandwich, the grounding plane would be like a slice of cheese, running underneath many of the different components of a circuit but not necessarily connected to them. If you design a circuit to have “vias” then an example component on the very top of a circuit board can connect down to the plane and access the power, ground or whatever signal happens to be running underneath there. This technique can be quite useful if you have many different op-amps in a certain area that will require positive and negative power supplies. Or if you have a large connector that requires a majority of pins to be grounded, a grounding plane can be useful to quickly connect many signals to the same net. However, as with any system, there are real-world consequences to deal with; in this case, we have to deal with electrons acting like electrons. With grounding planes, all of the pins on a board that are tied to ground will technically be at ground, however if one pin happens to have a large current going into the ground, then that area might have a slightly higher potential (voltage) than other ares of the grounding plane. This could have some definite effects in sensitive electronic situations and should be considered when designing a new PCB.
  5. Heat/Warping — A major downside to PCBs is the rigidity of the material; worse, when it heats up, it can often warp and become unusable. This could also be a problem in acid etched and wire wrap boards (the warping), but since the connections are often either larger traces or wires, the chances that the warping would break the connection are lower. Worse yet, the example above (dumping current into a ground plane) can create its own heat and warp a board without even being in a heated environment. Thermal budgets become important in any new PCB design and you should be mindful of them. Some SPICE programs even allow you to check out what the heat/power dissipation will be before putting the components on a board.
  6. Low Power — Unfortunately for high power circuit manufacturers, PCBs require extra care when they contain high voltages or high currents. Newer boards are often optimized for power savings, so high power situations are not as much of a priority for the tools that create PCBs. There are often constraints in the layout programs to ensure proper safety requirements, but other steps might be necessary, like separating high power lines from one another so they do not spark or create noise on other lower power lines.

Printed circuit boards allow for reliable products that can quickly be deployed to customers or used in a lab situation to test new circuit configurations. As long as you are mindful of the pitfalls of PCBs listed above, you can create circuit designs that can do just about anything imaginable.  If you have any suggestions on how to create better PCBs or circuits in general, please leave your thoughts in the comments.

Update: Wurlitzer 200A–Still in pieces

I thought I would update on my hobby subject for tonight since I mostly worked on my Wurlitzer 200A electric piano instead of writing the post I meant to. I’m just now getting back into working on my electric piano after previously having zapped something on the board and not being able to get it working since. When I messed up last time I was actually trying to replace the capacitors and transistors that had dried up; I had thought these were causing considerable hum in the circuit. However, since deconstructing the piano I found a modification to the wiring scheme between the two speakers and the output headphone jack located at the bottom of the board. I found that on the headphone jack someone had wired in a simple RC circuit, presumably for filtering the headphone output. However, the small wiring scheme they used and meant to ground to the chassis had been disconnected, possibly by me. This floating output circuit could have been the problem all along! Only time will tell but I will feel silly if that was indeed the culprit.

Still, I always prefer a silly mistake that is found and easily corrected (with damage only to my ego) , as opposed to a difficult error that cannot be fixed or worse, found. See the pictures below of the destruction that has befallen my piano and hope that I can get humpty-dumpty back together again.

The main board, removed from the chassis. With new electrolytic caps.

The piano with the chassis and the board removed. The speaker assembly and the transformer are all bolted to the main chassis, which is convenient when you want to work on the action of the keys (how the hammer hits the tone bars).

The slew of new components I got in from my online order…and now may not need?

It’s not the wand, it’s the magician. In this case, the wand is a piece of junk soldering iron from Radio Shack. Maybe Santa will bring me an industrial voltage controlled soldering iron.