Schematics Lecture Notes

Here are the lecture notes for today's discussion on schematics and bills of materials.

Lab 1

Build a battery-powered circuit that flashes an LED.

That's the whole lab assignment. It's up to you to design a schematic, find parts, choose a construction technique, and make sure the customer (your professor) is satisfied. Feel free to ask questions, but you must demonstrate a working circuit by the end of class today.

Difficulty setting:

Teardown highlights from iFixit 2015

Part of the homework this weekend is to read some teardowns at iFixit and send me an email with a link to your favorite one, with a short explanation of why it's your favorite. Here are the replies that I've received so far:

• Pebble Smartwatch

I liked the teardown of the Pebble smartwatch. It was cool to see how much they packed into such a small space, especially with a large portion of it being the battery (which was only 130 mAh, but supposedly able to last a whole week). The craziest thing was that the screen had to be pried off and ended up being destroyed in the process. This was because in this version of the watch (the Kickstarter version), everything was held tightly together with adhesives. Newer versions utilize screws and are supposed to be more easily serviceable.

• iPhone 1 and iPhone 6

Comparing and contrasting the original iPhone with the latest version was actually pretty interesting. It was crazy to see how much some of the components stayed the same and how much others had changed. Although the iPhone 6 is jam packed with more features and components to go with these features, it was quite a bit more organized, as all the components were smaller. I think the main reason that this was possible was because the antenna and logic board had shrunk considerably. I wonder if that’s due to new technology or better sourcing of components?

• Tracking Device

I thought the tracking device looked like something that could be interesting to take apart. I mean, that’s what you do when you find FBI super-secret spy gadgets on your car. The tracker looked a lot bigger than I was expecting, and I was hoping for some military-grade stuff (…there is some mil spec velcro-ing going on though). Some cool parts of the teardown are the huge magnets, and the battery that’s supposed to last 10-20 years. I like that the screws were coated in thread lock to keep people from doing teardowns, and that the FBI was hand-soldering the board components. I also appreciated step 10 about the FBI finding you if you find their tracking device.

• Amazon Echo

Echo is all about audio (both input and output), and the components inside reflect that. Amazon advertises the omnidirectional microphone on Echo strongly, and those are found at the top of the device. 6 microphones ring the perimeter of Echo, and one sits in the center. This purportedly allows Alexa to hear you no matter where you are in a room. These microphones may be Amazon-custom, as the part number doesn't appear anywhere else on the internet except in reference to the Echo. Many of the other components are specialized towards audio as well, including an audio codec, an amplifier, a digital media processor and a regulator. (Interestingly, all of the above were TI components.) The remaining components include a wifi/BT chip, flash memory, RAM, and a general processor.

• FitBit Flex

I really enjoyed this teardown because I personally own this device and have thought many times about how to actually open and get into the device. Seeing that the way that iFixit approached this issue was using a saw was quite amusing. I was surprised by seeing that only half of the small device was taken up by a battery while with personal experience, the battery lasts about a week. It is crazy to see that the device was able to pack so much stuff into such little space.

• Dell Latitude D620

I thought it would be cool to see a teardown of a Dell Latitude, because that is the type of laptop we are given as Olin students. Right off the bat, I was kind of surprised by how the author approached the problem. Instead of attacking the screws in the back of the laptop, he pried the nameplate off from the keyboard, and then lifted the keyboard. I also didn't fully understand everything about how the insides of a computer work, so it was cool to learn about how the CMOS battery keeps time even when power isn't supplied. I was also surprised to see how messy some of the thermal paste heat sinking was, because everything else fit together very elegantly. The teardown process was very delicate, to the point that loosening a screw too much can damage the logic board of the computer. For a lot of the teardowns I read, the process has to go perfectly for there to be any chance of reassembling the device again.

• Occulus Rift VF Development Kit

Earlier this semester I was asked questions about the workings of this headset. Seeing the teardown, I was able to actually visualize the connections between the screen, speakers, camera modules, and housings in a way I couldn’t the day of those questions. If I could go back and do it again, I would have looked for something like this as preparation, but as they say, hindsight is 20/20. Another aspect I really appreciated was seeing the ease with which boards could be removed and parts could be identified. It seems to me like this represents a pretty decent way of doing a visual/digital project where you’re more likely to suffer with ribbon cables and wiley wires.

• Blendtec Total Blender

My favorite teardown was the Blendtec Total Blender. Partly due to their hilarious videos but also because it wasn’t another microprocessor wrapper. Most of the tear downs of modern electronics are basically computers (which I have some experience assembling and disassembling) with a few extra components. The most impressive portion of the blender was of course the giant motor, but also the sensors that are required to maintain the motor and keep users safe. I hope by the end of the semester I can comment more on the electronic design.

• FitBit Flex

I chose the Fitbit Flex because I have been interested in wearable devices for a while, and I thought it was quite interesting to see what was going on inside of one. I was surprised by how much of the interior was taken up by the vibrator, considering I had originally assumed that there would be more space required for the various components that take measurements from our body. It was also unfortunate that it was so destroyed in the process.

• Nintendo Wii U

The Wii U is interesting because it has both a main station and a complex controller that have to communicate with one another with minimal lag time. The main console is impressively small and has interesting ways to fit the heat sink in the small space. The controller is even more interesting since the circuit board has to take in several inputs (including analog sticks, buttons, and even a large touch screen) which are ergonomically organized.

• Steam Machine

Most of the components are off-the-shelf making them easy to upgrade. The controller has a microcontroller that can handle the user’s configured functions of the several buttons. Not only does the box contain the standard video card, hard drive, CPU cooler and power supply, but it also is prepped for another hard drive to store games on. It already contains an impressive 1 TB platter drive common in laptops, in addition to an 8 GB SSD. Unsurprisingly, the heatsink fan is huge, 80 mm, but surprisingly quiet. The on button on the console is quite large. It was surprising how much space was taken up by LED’s just to illuminate the circumference of the button but I guess this device is not built to be very compact. This device is built to be highly modular, high speed processing and have a lot of memory.

• Nexus 7

My favorite teardown was of the Nexus 7. I've had to remove the back cover of my Nexus 7 several times to repair the speakers and headphone jack, but left the other components largely untouched. It was interesting to see more of what was under the battery. I found the L shape of the motherboard particularly interesting because I had always assumed that it was rectangular. It's also amazing to me how densely packed some portions of the motherboard appear to be.

• Chromecast

I elected to review the Chromecast because my hall elected to buy one last semester for our communal television. Compared to a lot of teardowns that I read, this one had the most fun banter: the writers commented on how the model number, H2G2 - 42, is a reference to Hitchhiker's Guide to the Galaxy. I also thought it was interesting how they did not provide solutions for fixing the Chromecast (presumably because it is effectively impossible to repair). The teardown revealed a relatively large heat sink, but didn't explain which components would get hot. I hope by the end of EE Proto I can come back and figure it out myself.

• Nintendo 3DS

What I found most surprising is how easy it is to take apart (relatively speaking) Usually Nintendo products, or game consoles in particular, are items that you'd figure are not meant to be easily repaired. But, the 3DS seems to have a ton of just simple screws, and only requires a bit of heat. Compare to some of the other consoles, and you'd be in for something much more involved. I also enjoy seeing how many cameras are employed to take the 3D pictures. As a proud owner of a few 3DS's myself, I get such a simple joy out of taking 3D pictures, and being able to tuck 4 cameras in is pretty great. Plus, it takes some pretty cool pictures.

• Kindle Voyage

I had never before thought about what went into the making of an E-reader since its display is so reminiscent of newspaper ink. Aside from the humor and gadgets (a plastic card) used in this teardown, which I found delightful, I really loved learning about the multitude of sensors and ICs in this package. The PagePress force sensor reacts to an increase in pressure to trigger a page turn which is activated in tandem with a piezo haptic vibrator. IC packages streamline memory, power management, and wireless connection among additional functions. Best of all, e-paper still maintains its display even after batteries are removed!

• PlayStation 3 Slim
• Nest Thermostat
• Canon PowerShot S500
• Google Glass

I selected Google Glass because my friends bought one last month and I'm amazed by its powerful features. Users can take pictures, surf Internet and send message by just blinking their eyes a couple of times. I’m curious about how engineers manage to consolidate camera, smartphone, signal processing techniques and wireless transmissions into such a small volume. I thought it would be cool to see a teardown of the Google Glass and I’m eager to know the latest technologies that being used in this amazing gadget.

Gear Teardowns

Assignment for Monday, January 26:

1. Get a toolkit (if you don't already have one).
2. Read Chapters 1 and 2 in "Troubleshooting Analog Circuits" by Bob Pease.
3. Discuss the autopsy/teardown candidates with your lab partner (see exhibits A through Z in the administrative handout).
4. Review the some teardowns at iFixit and send me an email with a link to your favorite one, with a short explanation of why it's your favorite. Be sure to venture beyond the lists of "Recent" and "Popular". For some examples, see
   • Teardown highlights from 2014.
   • Teardown highlights from 2013.
5. Watch the following video (a teardown of an Anritsu spectrum analyzer from Mike's Electric Stuff; see his YouTube channel for more videos).

Good stuff.

New Term 2015

Today is the first day of EE Proto 3.0. We even have a permanent catalog number (no longer a "special topics" number). Stay tuned for new activities.

Teardown highlights from iFixit

Part of the homework this weekend is to read some teardowns at iFixit (each student was assigned 12 to read) and send me an email with a link to your favorite one, with a short explanation of why it's your favorite. Here are the replies that I've received so far:

• Nvidia Shield and iPod Touch 5th Generation 16 GB

No one is going to buy the Nvidia Shield. But, the teardown is interesting as an example of the intersection of mechanical and electrical design. (The joystick potentiometers are surprisingly cool.) It's also a fairly complicated teardown, and an example of taking things apart in a reasonably reversible way. Also it has fire.

Very few people are going to buy the 16GB iPod Touch. But, there are some fairly clever techniques used in the teardown. It also shows the power of teardowns as an analysis tool, finding the changes between this and the previous iPod model.

• AirPort Extreme A1521

Apple products are well-designed in a way which allows you to easily forget that there are even insides, so it was kind of nifty to break into this aesthetically beautiful fortress. In particular, any engineer reading this is likely floored at how much empty space they left – why would they bother leaving several inches between the ports and the fan? It’s a nice lesson in aesthetic design: not everything has to be built for efficiency, and it’s okay to let the non-engineers make things pretty.

• 2012 MacBook Air

Very impressive device. A neat feature is the "asymmetrical fan" that has different fan blade lengths in order to disperse sounds over a wide range of frequencies, reducing fan noise. Visually, the interior was very clean and crisp; most components, including the battery and PCB's were black. However, in classic Apple fashion, the 2012 MacBook Air was riddled with proprietary components, including pentalobe screws on the case in order to keep the casual observer's curiosity at bay.

• Nikon D600

I had never previously thought about the complexity of such an opto-electronic device and could not have imagined how complex and densely packed the device is. Step 15 reveals the absurd number of EMI shields and other busses that are crammed into the case. You wonder what all those bits of metal could possibly be for until you see in steps 19 and 22 how boards and different ICs are carefully scattered across every surface of the exposed camera frame. It was neat to see the 24MP image sensor exposed, and Chipworks has some more details and SEM images of its design.

• Pebble

The teardown of the Pebble E-Paper watch was pretty fascinating. The watch does not have any exterior screws, so the needed to pry the screen off of the front of the watch. They were actually unable to get the screen off without breaking it due to the amount of adhesive used in the design, which makes me wonder if this was an intentional decision to keep tinkerers out, or if it is just a result of being the first design they were able to come up with via their Kickstarter funds/timeline. Other than that, it was just a very thorough analysis which showed how compact of a design it is and identified all of the major ICs.

• Xbox One Kinect

The Xbox Kinect is a really interesting piece of technology. Of course, it has a lot of neat signal processing going on, but the really interesting part is the sensor suite. This particular teardown actually focuses more on the IR blaster and camera assemblies since these are the functions that make the Kinect function. As the teardown points out, these assemblies are very sensitive and taking them apart was about "like a game of Operation." I find this to be a pretty bold move by Microsoft, considering that the purpose of this product is for people to jump around and swing their arms every which way. Not just do they need to worry about damage due to customer abuse, but I would imagine they also needed to develop a very specific and accurate assembly procedure to forego any damage during production.

• Samsung Galaxy Note 10.1

I though the Galaxy Note 10.1 teardown was very interesting from both a mechanical and hardware standpoint. By reading the teardown, it is very apparent that the Samsung engineers designed the Note so that parts can be easily removed and taken apart. Unlike most electronics that are held together mainly by adhesives and press fits, the engineers at Samsung took the time to design the Note around screws and snaps. Similar the LCD screen can actually be removed from the glass unlike most devices. Therefore if the screen cracks, instead of replacing both the screen and the LCD display, just the screen has to be replaced. A cool feature about the hardware was that the EMI shielding (which are easily removed by screws) also serve as the Note’s heat sinks.

• Keithley 199 Scanner Multimeter

I like it because, unlike the variety of modern phones or simple devices included in my section, this teardown really goes into details on components and what can be fixed. Additionally, it has some real depth that the modern devices just can't match which makes the actual dissembly much more interesting.

• Orange

Just kidding.

• HTC One

A few years ago I ended up repairing a few iPhone 3G's and 3GS and remember the difficulties with doing it. I thought it was interesting to see how much more difficult it's become since then to repair these things, to the point where the HTC One essentially has to be broken to even get inside of it. Beyond the continuing of this accessibility trend, it's always fascinating to see how much the cram into so little space and techniques I didn't know about to help with that, like copper shielding on almost all of the components for heat dissipation and grounding.

• Nexus Q

My favorite teardown was of the Nexus Q, a strange failed hardware project of Google's. The guide was well written with a healthy dose of humor. The writer took the time to identify ICs and speculate on their significance. There were small interesting factoids included along the way, such as the country of origin of various parts. I also thought the geometry of the device itself was interesting. The casing is a sphere. The board layout had to be done in a way such that big components jutting out perpendicularly (like capacitors) were placed in the center, so that the whole thing could be sandwiched together between two shells.

• Apple A7

At the very heart of the iPhone5 is its A7 processor, and this teardown stripped away another black box to see the silicon itself. The nature of the teardown for a teeny-tiny chip meant that all the heavy lifting had to be done with in lab rather than a work bench. The nanometer scale that the transistors had to be measured on gave a new gravity to this impressive device. The ability to cram so many functions into such a tiny space is truly astounding.

• Macintosh 128K

The engineering of the Macintosh 128k is interesting because most of the pieces are slid together and held together with screws, so taking it apart is not very difficult. It is also an interesting tear down because it shows how technology has progressed in 30 years. The logic board is cool because there are no surface mounts, there are only through holes making it look very different than the boards we see today. I thought that the fact that the buttons of the keyboard were soldered directly to the board is funny because in current keyboards, the keys just pop off, and I think it’s just an advancement that I don’t really think about but is pretty important.

• Compaq iPaq Pocket PC 3765

The Compaq iPaq Pocket PC 3765 is interesting to me because it was one of the few popular hand-held personal assistants that existed before smart phones combined their capability with cell phone service. I surprised by how easy the device was to take apart. Just a few screws in back and some snapping mechanisms hold the casing in place. They point out that though the company responsible for the product is Compac, both the processor and the control board are branded with HTC. I think that's particularly interesting since HTC makes so many smart phones now.

• iPad mini Wi-Fi

The iPad mini teardown is interesting as Apple products are notorious for being designed to make it hard to open. The number of hidden screws and screws smaller than those in an iPhone 5It still surprises me how extensively glue is used to hold products together. Steve Jobs himself has mentioned that we "don't like to think of our products as glued together". The commentary on the choices for certain parts also make for an interesting read. The commentary on the design decisions like soldering the Lightning connector, or having the front glass and LCD assemblies separate, and how these decisions affect reparability gives me insights on to the implications of such decisions when building electronics. It is also cool to see that touchscreen still function after being taken off. Kind of like the electronic equivalent of a limb still moving after being detached.

Gear teardowns

Assignment for Monday:

1. Get a toolkit (if you don't already have one).
2. Read Chapters 1 and 2 in "Troubleshooting Analog Circuits" by Bob Pease.
3. Discuss the autopsy/teardown candidates with your lab partner (see exhibits A through Z in the administrative handout).
4. Review the assigned teardowns at iFixit and send me an email with a link to your favorite one, with a short explanation of why it's your favorite. For example explanations, see last year's favorites.
5. Watch the following video (a teardown of an Anritsu spectrum analyzer from Mike's Electric Stuff; see his YouTube channel for more videos).

Good stuff.

New Term

Tomorrow is the first day of EE Proto 2.0. Stay tuned.

Voltmeter wiring correction at the Museum of Science

Yesterday, the family and I spent the morning at the Museum of Science, and the kids wanted to revisit the Discovery Center (mentioned in this post). With mild trepidation, I approached the second floor to see the circuits display, and I was pleasantly surprised, thrilled actually, to see that the wiring error had been fixed!

Close-up of the meter connections...

The voltmeter and ammeter are no longer in series! Very nice. I admit that I didn't think it would be fixed, based on the rationalizations in the comments of the last post, but I am very happy to see that it has been. Score one for engineering education! (By the way, it is a fun exhibit; my daughter really liked it.)

Voltmeter wiring error at the Museum of Science

UPDATE: Fixed!

This post isn't really about EE Prototyping, but it is about electrical engineering education, so I will post it here.  I spent Mother's Day at the Boston Museum of Science with my wife and kids. The kids had a blast, and we all had a great time, except for one thing...

In the "Discovery Center" there was a fun little electricity demo that let you construct simple parallel and series circuits with some magnetic, conducting building blocks.  There was a light bulb block, a buzzer block, and an LED block (that glowed green when the current flowed in one direction and glowed red when the current flow in the other).  Neat exhibit.  The power supply was mounted above the desk with the circuit blocks, and it let you choose to power your circuit with two, four, or six AA batteries.  A large knob in the center of the panel selected the power source, and two analog meters displayed the voltage and current.

Here's the setting for 3V output (2 AA cells):

Here's the setting for 6V output (4 AA cells):

Here's the setting for 9V output (6 AA cells):

See the problem? The voltmeter and the ammeter are both wired in series.  As connected, this circuit couldn't possibly work!  Here's a clearer schematic:

WRONG. The ammeter measures the current through the batteries, but the voltmeter must measure the voltage ACROSS them.  The voltmeter should be connected in parallel with the batteries, not in series. The panel should be wired like this schematic:

Better yet, to emphasize that voltage is measured across the power source, and that current is measured through it, the panel should be redesigned to look like this schematic:

Of course, the orange wires in the display case are just representational, and the batteries shown aren't really connected to anything (there is a wall-powered power supply behind the panel), but this error in the connection of the voltmeter should be embarrassing.  This exhibit would be a good chance to discuss "across" variables and "though" variables to more advanced students, but the "artist" who designed the panel blew it.

So sad.

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UPDATE: See the responses in the comments below.

UPDATE UPDATE: Fixed!