Status Update: Of Phones and Fire

Things might be on a bit of a hiatus for the next little while. My trusty Sony Xperia Z5 Compact literally went up in flames a few hours ago, and I need to find a replacement very soon, as well as recover any data that wasn’t saved to my SD card. Thankfully, apart from a sore throat and burning eyes from battery smoke, I am doing fine (as well as my house).

IMG_4711

My Sony Xperia Z5 Compact… after the lithium-ion battery fire.

Once things settle down, I’ll hopefully have a juicy story about lithium-ion battery fires and (failed) eMMC data recovery.

UPDATE (May 18, 2018): I upgraded to a Samsung Galaxy S9 a couple days ago. The eMMC chip I desoldered from the Z5 Compact is effectively bricked, as it only identifies itself but no data can be read – I suspect that the intense heat must have “baked” the NAND flash and result in too many uncorrectable bit errors that the firmware couldn’t recover from. There goes my progress in Angry Birds 2 (among other data)…

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Recovering Cookie Clicker saves from an offline installation/backup of Google Chrome

Update (August 29, 2018): Turns out cleaning out your cookies/cache will erase your Cookie Clicker save. Who would’ve thought…

Cookie Clicker saves: You don’t realize the importance of saving your progress until you lose your save data. A few days ago I opened Chrome to my always-running instances of Cookie Clicker, but found that all of my progress was deleted (and it was showing a “Don’t forget to back up your save” message just to add insult to injury).

My heart sank when I realized that one of my runs, over three years old, had suddenly vanished into thin air. I tried restoring Google Chrome’s data via a Shadow Copy; no dice. I tried using my Windows Home Server 2011 backups, but realized that it would take over an hour to restore my Chrome folder. After much frustration, I decided to retrieve and examine Chrome’s Local Storage folder and see whether I could retrieve my save files that way – and it worked! Here’s how to recover your own Cookie Clicker saves…

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eMMC Adventures, Episode 2: Resurrecting a dead Intel Atom-based tablet by replacing failed eMMC storage

As seen on Hackaday!

Recently, I purchased a cheap Intel Atom-based Windows 8 tablet (the DigiLand DL801W) that was being sold at a very low price ($15 USD, although the shipping to Canada negated much of the savings) because it would not boot into Windows – rather, it would only boot into the UEFI shell and cannot be interacted with without an external USB keyboard/mouse.

The patient, er, tablet

The tablet in question is a DigiLand DL801W (identified as a Lightcomm DL801W in the UEFI/BIOS data). It uses an Intel Atom Z3735F – a 1.33GHz quad-core tablet SoC (system-on-chip), 16GB of eMMC storage and a paltry 1GB of DDR3L-1333 SDRAM. It sports a 4500 mAh single-cell Li-ion battery, an 8″ 800×1200 display, 802.11b/g/n Wi-Fi using an SDIO chipset, two cameras, one microphone, mono speaker, stereo headphone jack and a single micro-USB port with USB On-The-Go support (this allows the port to act as a USB host port, allowing connections with standard USB devices like keyboards, mice, and USB drives).

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eMMC Adventures, Episode 1: Building my own 64GB memory card with a $6 eMMC chip

As seen on Hackaday!

There’s always some electronics topic that I end up focusing all my efforts on (at least for a certain time), and that topic is now eMMC NAND Flash memory.

Overview

eMMC (sometimes shown as e.MMC or e-MMC) stands for Embedded MultiMediaCard; some manufacturers create their own name like SanDisk’s iNAND or Hynix’s e-NAND. It’s a very common form of Flash storage in smartphones and tablets, even lower-end laptops. The newer versions of the eMMC standard (4.5, 5.0 and 5.1) have placed greater emphasis on random small-block I/O (IOPS, or Input/Output operations per second; eMMC devices can now provide SSD-like performance (>10 MB/s 4KB read/write) without the higher cost and power consumption of a full SATA- or PCIe-based SSD.

MMC and eMMC storage is closely related to the SD card standard everyone knows today. In fact, SD hosts will often be able to use MMC devices without modification (electrically, they are the same, but software-wise SD has a slightly different feature set; for example SD cards have CPRM copy protection but lack the MMC’s TRIM and Secure Erase commands. The “e” in eMMC refers to the fact that the memory is a BGA chip directly soldered (embedded) to the motherboard (this also prevents it from being easily upgraded without the proper tools and know-how.

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Performance analysis/review of Kentli PH5 Li-ion 1.5V AA battery

In my previous blog post, I tore down the Kentli PH5 battery – a Li-ion battery that has an internal 1.5-volt regulator that allows for terrific voltage stability… up to a point. In terms of data collection, so far I have collected 55+ runs of data logs (248 MB of text files!) and still do not quite have all the data I want. As for the data that I do have, I will be disseminating them with as much thoroughness as possible.

Updated (May 1, 2018):

The battery’s self-discharge rate experiment has come to its conclusion – click here to read it.

I forgot to add a diagram of my test setup – here’s a Visio diagram of the hardware used to test the battery’s performance… Click here to see the full-sized diagram.

ph5 cycle test setup diagram

 

Voltage vs. load current

As expected, the voltage output of the PH5 remains quite stable, up until roughly 2.1 amps where the voltage sags noticeably until the regulator goes into overcurrent protection mode.

A maximum load capacity of 2.1 amps seems to be a bit… limiting. That said, I have not done tests on the PH5’s transient load capacity, as it would require more automated control than what I currently have available.

Another issue with having such a flat discharge curve is that any device that performs fuel gauging using voltage alone will report 100% capacity, until it suddenly shuts down. This could be a big problem for digital camera users, as they will have no indication that their batteries are running low, until the device abruptly stops working. If the camera was writing an image to its memory card when the battery died, it could cause the image to be corrupted, or worse, damage the file system on the card!

Voltage vs. state-of-charge

Unless you are running the battery at a high discharge rate, the output voltage will be flat at 1.5 volts before abruptly brickwalling and dropping to zero immediately at the end of discharge. At a high load (in the case of the graph below, at 2 amps), the voltage remains flat until the very end of the discharge cycle (99% depth of discharge for my test run), where it quickly tapers off and drops to zero.

Capacity vs. load

This is the big one, and it took a lot of work to get this data, especially at low loads (48+ hours of continuous logging is just asking for Murphy’s Law to come into play). I used almost 50 discharge runs to create the graph below.

This is where things get… interesting. I was expecting the capacity to peak at low currents then taper off as the load current increases. Instead, I noticed a definite ‘hump’ in capacity around the 250 mA mark (reaching a maximum of 1700 mAh / 2550 mWh), and only after that point did I see the expected downward slope in capacity, reaching 1200 mAh (1800 mWh) at the 2 amp mark.

This data brings forth some very interesting conclusions. The PH5’s capacity is inferior to its Ni-MH counterparts (even the relatively crappy ones), and at higher discharge rates it has similar capacity to that of an alkaline at the same load, albeit with much better voltage stability than the Ni-MH or alkaline chemistries.

Other findings

Although I won’t go into too much detail for the next few points (I haven’t gotten quite enough data to be presentable), there are some other issues with the battery that I think should still be mentioned.

One issue is the amount of heat the battery gives off at high loads. At 2.1 amps, I had to use a fan to blow cool air onto the DC-DC converter just to prevent it from entering its over-temperature shutdown mode. Although the converter itself can tolerate elevated temperatures, the Li-ion cell inside will not; the uneven heating that the cell will encounter could potentially degrade its lifespan in the long run.

Another problem is efficiency. At 1 amp, the DC-DC converter is about 75% efficient, and is only 65% efficient at 2 amps. I have not tested the converter’s efficiency at lower loads yet, but I doubt it will achieve more than 85-90% efficiency.

A potential issue with this battery is self-discharge. The buck converter remains active all the time, unless the converter or the Li-ion protection circuit enters a protective shutdown state. I have not had a chance to fully charge an unmodified battery in order to perform a long-term self-discharge test, but I will create another blog post for that, if/when the time comes. Update (May 3, 2018): See the top of the page for the link to the self-discharge test results.

Conclusion

Overall, I’m on the fence when it comes to this battery. Its innovative design does provide unparalleled voltage stability, but its low capacity even at moderate discharge rates dampens the fun significantly. Additionally, the 2.1 amp discharge limit could prove to be a bottleneck for some high-drain applications; this, coupled with the cell’s tendency to shut down abruptly when the internal cell runs empty could potentially cause file system corruption for digital cameras that have not been designed to handle such sudden power interruptions.

Also, the batteries are very costly. At about $10 per cell, you may want to think twice about replacing all your current disposable and rechargeable batteries with these newfangled Li-ion ones. Don’t forget the charger either, as a special charger is required to make contact with a recessed terminal on the top of the battery.

Overall, this cell is… interesting. Just don’t expect a miracle in a steel can.

Pros:

  • Excellent voltage stability, even at high loads
  • Li-ion chemistry allows for a very lightweight cell, even with the addition of a DC-DC converter
  • High output voltage could allow some devices to run more efficiently

Cons:

  • Low capacity – provides a mere 1200 mAh (1800 mWh) @ 2 amps, and up to 1700 mAh (2550 mWh) @ 250 mA (even alkaline batteries can do better than this)
  • Abrupt shutdown when the battery is overloaded, overheated, or over-discharged
  • Runs hot at high loads (and therefore is fairly inefficient)
  • 1.5 MHz converter and unshielded inductor can cause excessive EMI (electromagnetic interference) in sensitive devices
  • Expensive! Costs approximately $10/cell
  • Requires proprietary charger

Bottom Line: This is a niche product and should not be considered a universal replacement for alkaline or Ni-MH AA batteries.

Ramble: Fixstars’ 6TB SATA SSD – is it a thing?

If you know me personally, you’ll know that I absolutely love SSDs. Every PC I own has one, and I can’t stand to use a computer that runs off an HDD anymore. Naturally, when I read about a 6 TERABYTE SSD coming out, it piqued my curiosity.

Photo is owned by Fixstars and is not my property. Retrieved from http://www.fixstars.com/en/news/wp-content/uploads/2015/05/SSD-6000M.png

Official SSD-6000M promotional photo, taken from Fixstars’ press release

A Japanese company by the name of Fixstar has recently announced the world’s first 6TB SATA-based SSD. Although 2.5″ SSDs in such a capacity range already exist, they’re SAS (Serial Attached SCSI) based which limits them primarily to server/datacenter usage. According to Fixstars’ press release, their SSD-6000M supports sequential read speeds of 540 MB/s, and sequential write speeds of 520 MB/s, which is on par with most modern SATA III (6 Gbps) SSDs on the market today.

Concerns

However, after reading a bit online, I’m beginning to have some concerns about the drive’s real-world performance. One thing that is rather worrying is that the company has only mentioned sequential I/O speeds and has said nothing on random I/O or read/write latency; although SSDs do have much better sequential speeds than their mechanical spinning counterparts, they really shine when it comes to random I/O (which makes up much of a computer’s typical day-to-day usage). In the early, early days of SSDs, manufacturers cared only about sequential I/O and it resulted in some SSDs that were absolutely terrible when it came to random I/O (fun fact: I once had an early SSD, the Patriot PS-100, and its performance was so bad that it actually turned me off of SSDs for a few years, so I know how bad such unoptimized SSDs can perform).

Construction

The SSD appears to be made up of 52 eMMC (embedded MultiMediaCard) chips in a sort of RAID 0 configuration and an FPGA (field-programmable gate array) as the main controller. In layman’s terms, this SSD is literally made up of a bunch of SD cards “strapped” together with a chip so that it appears as one single drive. In that sense, one can make a similar solution using a board like this, which parallels multiple microSD cards to act as a single ‘SSD’.

Image retrieved from Amazon (http://ecx.images-amazon.com/images/I/51y0QqWL5sL.jpg)

The consumer equivalent of the SSD-6000M: SD cards and a controller chip. You can even get them from Amazon.

Conclusion

I’m wary of how well this SSD is going to take off. It could end up being a tremendous success, but it’ll certainly be out of the reach of the consumer market – either by its potentially poor random I/O performance, or its price (apparently it will cost well over $6000 USD).

A Little Pick-Me-Up: Samsung 840 EVO SSD slowdowns, and how to fix it (for now…)

There’s been word going around that Samsung’s 840 EVO solid-state drives have an issue where they become really, really slow to read if the data on it has been sitting around for a few months, and I can confirm this is the case as well.

The first half of the drive (which holds a fair amount of static data) was being read at around 30 MB/s, with newer data being read at almost 500 MB/s. That’s a pretty big difference. One thing to note (I didn’t take a screenshot for this) is that although the overall read speed was significantly affected, the read latency was only somewhat slower; only about 10-20 microseconds of extra latency.

To temporarily fix this (at least until Samsung releases a firmware update in the middle of October), I used Hard Disk Sentinel to read and rewrite all of the data on the SSD. Because this involves accessing data that is normally locked by Windows, I made a custom WinPE (a slimmed-down, portable version of Windows that’s used for installation and recovery) image with Hard Disk Sentinel inside it. This allowed me to boot outside of the normal Windows setup, and perform the Read+Write+Read test to refresh all of the data stored on the SSD. Note that this will impart a lot of write activity to the NAND flash in the SSD (hence a chance for increasing wear), but modern SSDs aren’t as delicate as people might think.

HD Sentinel's Refresh Data Area test

Hard Disk Sentinel’s “Refresh Data Area” test

This took about 2 hours on my 250 GB SSD. Afterwards, another read test showed that the drive was working smoothly again.

Will I still buy a Samsung SSD? Absolutely. No data was lost and Samsung did the right thing by acknowledging the issue and also finding a way to fix it, as opposed to simply calling it a non-issue and sweeping it under the rug.

Looking inside a (fake) iPhone 5S battery

Considering how popular the iPhone is, there’s always going to be some counterfeits out there. I’ve been out buying various iPhone batteries to build a database of each generation’s characteristics, but one model has eluded me so far: the iPhone 5S. The iPhone 5C’s battery that I bought appears to be genuine (but with its own issues), but none of the iPhone 5S batteries I’ve bought so far (4 of them at the time of writing this blog post) were genuine. All of these fakes look like a genuine battery at first glance, but all of them share a few common traits.

Battery teardown

The fake battery sports the usual iPhone battery information, complete with some dot-matrix printed data and a data-matrix barcode. It’s labeled with a capacity of 1560 mAh and 3.8 volts nominal voltage.

Comparison between real and fake iPhone 5S battery

Comparison between real and fake iPhone 5S battery

The connector itself has two points for soldering the connector to provide durability. However, with the fake batteries, they are not soldered down. The two spots on the ends of the connectors are dark with a small point visible inside it (that point is the reinforcement pin on the connector). If this connector is installed in an iPhone, it will probably not come out without either damaging the battery’s connector, or worse, leave the plastic connector piece inside the phone, requiring tweezers to remove.

Connector lifted off with a hobby knife

Connector lifted off with a hobby knife

iPhone 5S and 5C battery pinout

iPhone 5S and 5C battery pinout

Removing the black protective tape reveals an iPhone 4 battery fuel gauge board. The connector is soldered to this board, with four solder points visible.

iPhone 4 battery PCB with soldered-on flat flex connector

iPhone 4 battery PCB with soldered-on flat flex connector

Pulling out the PCB  reveals another characteristic of these fake batteries: the positive terminal is cut short, with another metal section being clumsily spot-welded to the stub on the cell.

Note how the battery tab is poorly welded to the PCB.

Note how the battery tab is poorly welded to the PCB.

Battery fuel gauge data

The battery fuel gauge requires proper programming to accurately indicate the battery’s charge status. Because of this, each iPhone battery generation has its own specific configuration.

The fake iPhone battery retains the programming for the iPhone 4’s battery, which is a designed capacity of 1420 mAh, using a bq27541 fuel gauge running version 1.25 firmware. The data inside it is often that of a used/recycled battery as well.

This data can be (partially) read out directly from the iPhone with a tool such as iBackupBot, but more data can be read if the battery is read with another tool. I have the EV2400 from Texas Instruments to read this out on a PC, but this data can be read out with a USB-to-TTL serial port, a logic gate (a logic inverter) and a small MOSFET transistor.

I created a small tool that uses this circuit to interface with the fuel gauge and read out its data. Check it out here.

Using my tool, this is the report for one of these fake batteries. Note how it is identified as an iPhone 4 battery. Don’t be fooled by the calculated state of health. It’s not accurate for this battery as the fuel gauge still thinks it’s still inside an iPhone 4 battery pack.


**** START OF HDQ BATTERY LOG REPORT ****
HDQ Gas Gauge Readout Tool version 0.9 by Jason Gin
Date: 9/30/2014
Time: 0:52:24
Serial port: COM26

Battery Identification
========================
DEVICE_TYPE = 0x0541, FW_VERSION = 0x0125, DESIGN_CAPACITY = 1420 mAh
Battery's configuration matches that of a standard iPhone 4 battery.

Basic Battery Information
===========================
Device = bq27541 v.1.25, hardware rev. 0x00B5, data-flash rev. 0x0000
Voltage = 3804 mV
Current = 0 mA
Power = 0 mW
State of charge = 45%
Reported state of health = 0%
Calculated state of health = 99.3%
Cycle count = 14 times
Time to empty = N/A (not discharging)
Temperature = 27.9 °C (80.3 °F) (3009 raw)
Designed capacity = 1420 mAh
Heavy load capacity = 628/1410 mAh
Light load capacity = 673/1455 mAh

Advanced Battery Information
==============================
Capacity discharged = 0 mAh
Depth of discharge at last OCV update = ~778 mAh (8768 raw)
Maximum load current = -200 mA
Impedance Track chemistry ID = 0x0163
Reset count = 11 times

Flags = 0x0180
Flag interpretation:
* Fast charging allowed
* Good OCV measurement taken
* Not discharging

Control Status = 0x6219
Control Status interpretation:
* SEALED security state
* SLEEP power mode
* Constant-power gauging
* Qmax update voltage NOT OK (Or in relax mode)
* Impedance Track enabled

Pack Configuration = 0x8931
Pack Configuration interpretation:
* No-load reserve capacity compensation enabled
* IWAKE, RSNS1, RSNS0 = 0x1
* SLEEP mode enabled
* Remaining Capacity is forced to Full Charge Capacity at end of charge
* Temperature sensor: External thermistor

Device name length = 7 bytes
Device name: bq27541

**** END OF HDQ BATTERY LOG REPORT ****

Ramble: Engineers and hackers – never the twain shall meet?

Note: This is a vent post more than anything, and as such it won’t have much relation to the other things I write. If you want to stick to my main content, feel free to skip this blog post.

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Looking inside an iPhone 5 battery

In the wake of my previous teardowns of the iPhone 4 and 4S batteries, I went onto eBay and Amazon (realizing that they finally have Amazon Prime student rates up in Canada) and bought a few iPhone 5 and 5S batteries. Although I was primarily interested in trying to get the gas gauge information out of the batteries, I had a secondary reason. The Nexxtech Slim Power Bank (a subject of a separate blog post) uses a pair of 3.8-volt Li-ion polymer batteries, and they seemed to be be suspiciously similar in size to what is used in the iPhone 5. But enough of that, we’re here for the iPhone 5 battery in particular!

Battery Casing

The iPhone 5 battery measures 3.7 mm in thickness, 3.2 cm in width and 9.1 cm in length. This particular model, made by Sony, has a model ID of US373291H, with the six digits corresponding to the cell’s dimensions. This cell has a labeled capacity of 1440 mAh at a nominal 3.8 volts, with a maximum charge voltage of 4.3 volts. I tried to read the data matrix barcode on the cell but my barcode scanning app on my phone refused to recognize it. I might try to scan and sharpen the barcode later but it’s not something that’s of a high priority to me.

Battery Teardown and Pinout

The board itself is rather interesting. The protection MOSFETs used to switch the battery’s power are chip-scale packages and are glued down with epoxy, same with the gas gauge itself. This means that I can’t easily replace it with a rework station if the need arises. The board includes the gas gauge, thermistors, protection circuitry and still has room for a polyfuse for extra over-current protection.

iPhone 5 battery PCB layout

iPhone 5 battery PCB layout

The pinout of the iPhone 5 battery is pretty much the same as of the iPhone 4 and 4S. You have Pack-, NTC Thermistor, HDQ and Pack+. In this particular model of battery, the gas gauge is a bq27545 (labeled SN27545), but has basically the same feature set as the iPhone 4/4S’ bq27541. With this information, I soldered to the small terminals on the connector (the actual connectors for this battery haven’t arrived yet since it takes so long to receive items from China on eBay), and hooked it up to my trusty Texas Instruments EV2400 box.

iPhone 5 battery pinout

iPhone 5 battery pinout

Battery Data

iphone 5 firmware versionAnd once again, we’re presented with an obscure firmware revision. The latest bq27545-G1 firmware is only version 2.24, but this chip has version 3.10. After forcing GaugeStudio to accept this gauge as a -G1 version, we’re once again presented with a sealed chip. Let’s try to unseal it with the default key…

... aaaaand nope. No dice with 0x36720414, unlike last time.

Nope. No dice with 0x36720414, unlike last time.

… and I get the dreaded “Unseal Key” prompt. Cue the dramatic Darth Vader “NOOOOO” here. Maybe Apple read my previous post and decided to change the default keys this time (Hey Apple, if you read this, make the iPhone 6’s gas gauge have the default keys again)! This means that not only can I not access any of the juicy details of this battery, but I cannot update its firmware to a more… conventional version either. I could try brute-forcing it, but trying to hack a key with a 32-bit address space over a 7 kbps bus… uh, no. That’s not going to happen. I’d probably have better luck reverse-engineering Apple’s battery code but I doubt they have any facility to do in-system firmware updates for the gas gauge.

Data captured from GaugeStudio

Data captured from GaugeStudio

Now for some rather… interesting details of what we can access. The design capacity of this battery, according to the gas gauge, is 1430 mAh, same as the iPhone 4S and also 100 mAh less than what’s written on the label. That, and the full charge capacity of this battery is 1397 mAh out of the gate. The gauge seems to be an insomniac (it won’t enter Sleep mode even when the battery is not hooked up to any load), and it seems to have less features despite having a higher firmware version (I’m sure the internal temperature isn’t 131 degrees C…), and the Pack Configuration register doesn’t bring up any sensible data.

Battery… conspiracy?

One thing that I haven’t confirmed is whether or not this battery had been tampered with before I received it. I bought this particular battery from eBay and it was listed as new. It had some adhesive residue but no obvious sign of being peeled off from another iPhone. The cycle count is set to 1, and because the gas gauge is sealed, I can’t read any other data like the lifetime data logs. There is a chance that this battery isn’t new and that the seller had somehow changed the data memory and sealed the chip with a non-default key, but I need to wait until some other batteries arrive in the mail and perhaps try reading out batteries taken out directly from some iPhone 5s. Until then, it’s only speculation as to why this chip is sealed with a different key.

The next victims specimens: an iPhone 5S battery, a “new” iPhone 4 battery, and an Amazon Kindle battery.

Review, teardown and analysis of Charging Essentials USB wall outlet

(UPDATE: March 2, 2015 – I’ve picked up a pair of the newer tamper-resistant versions of this wall outlet. A review and teardown on that unit is coming up; stay tuned!)
(UPDATE 2: May 29, 2016 – Scratch that on the first tamper-resistant model; it had the same performance as the one mentioned here. Also, Costco has released a 3.1A version of this outlet, and is currently under review.)

About a week ago I bought a set of wall outlets from Costco that integrate two USB charging ports into a standard Decora-type receptacle. It’s marketed to replace your traditional AC adapter, allowing other appliances to be plugged in while charging your portable electronics.

The outlet is made by Omee Electrical Company, but curiously enough this particular model, the OM-USBII, wasn’t listed on their site. The packaging itself bears the name Charging Essentials, with a logo that looks like a USB icon that’s had one Viagra too many. The packaging states that the outlet has:

  • “Two 5VDC 2.1A ports for more efficient charging in less time”
  • “Smarter USB charging with special chip designed to recognize and optimize the charging requirements of your device”
  • “Screw-free wall plate snaps into place for a more clean, modern appearance”

The second note is of particular importance to me. If it’s true, that means it might be using some USB charge port controller like TI’s TPS251x-series chips. But I’m not one to have blind faith in what’s written on the packaging. Let’s rip this sucker apart!

The outlet has a snap-on coverplate which may look sleek but could hamper removal of this outlet later on if needed. I was curious as to why one couldn’t just use a regular screw-on coverplate, and it turns out it’s because the mounting flange doesn’t have any tapped screw holes; you physically can’t use screws on this because the manufacturer didn’t want to go to the effort to make holes that can accept screws!

The casing is held together with four triangle-head screws in a weak attempt to prevent opening of the device. I had a security bit set on hand so this posed no hindrance to me. Upon removing the cover, the outlet seems rather well built. However, after removing the main outlet portion to reveal the AC-DC adapter inside, I quickly rescinded that thought.

The converter seems relatively well-built (at least relative to some crap Chinese power supplies out there). Some thought was put into the safe operation of this device, but there’s almost no isolation between the high and low voltage sides, and the DC side of this adapter is not grounded; the “ground” for the USB ports floats at 60 volts AC with respect to the mains earth pin. The Samxon brand caps are also pretty disappointing.

As for the USB portion of this device, I had to remove some hot glue holding the panel in place. After a few minutes of picking away at the rubbery blob, I was able to pull out the USB ports.

… and I found LIES! DIRTY LIES! There is no USB charge port controller, contrary to what the packaging claims. It just uses a set of voltage dividers to emulate the Apple charger standard, which could break compatibility with some smartphones. Ugh, well let’s put it back together and take a look at it from the performance side of things. At least the USB ports feel pretty solid…

To measure the voltage-current characteristic of the outlet, I rebuilt my bq27510-G3 Li-Ion gas gauge board so it had better handling of high current without affecting my current and voltage measurements. The reason I used this is because the gauge combines a voltmeter and ammeter in one chip, and by using the GaugeStudio software, I could create easy, breezy, beautiful V-I graphs.

Using a Re:load 2 constant-current load, I slowly ramped up the load current while logging the voltage and current data to a CSV file for analysis in Excel.

overall vi graphThis charger’s… okay. It has surprisingly good regulation up to 2.3 amps, but after that point the AC-DC converter basically brickwalls and the voltage plummets to 3 volts. That said, this also means that this outlet is not a set of “two 2.1A USB ports”. You can charge one tablet but you won’t be able to charge a tablet along with another device simultaneously.

Bah, I’ve had it with this wall outlet. Looks like this one’s gonna be returned to Costco in the next few days. This outlet may be adequate for some people, but for me it’s a disappointment.

Pros:

  • Solid USB ports
  • Good voltage stability (up to 2.3 amps, enough to charge ONE tablet)
  • Apple device compatibility

Cons:

  • Annoying coverplate design
  • Does not meet rated current output, will not charge 2 tablets or 1 tablet + another device
  • Does NOT have a “smart charging chip” despite being stated on packaging, some devices (eg. BlackBerry) will refuse to charge from these ports
  • Power supply for USB seems cheap
  • USB port is not grounded – if a short-circuit happens inside the power supply it can be a shock hazard to you

KitchenAid induction cooktop service manual

In preparation for a future post in which I do some failure analysis on my KitchenAid KICU509XBL induction cooktop, I dug up the service manual I had laying in one of my document drawers and have scanned it into a PDF. Download the PDF file here.

Since Googling for the cooktop’s error/failure codes didn’t turn up anything useful, I’ll post them here so that people can find it more easily (note that I’ve paraphrased it from what’s listed in the PDF itself):

Failure types:

  1. Power control board: Affects only one burner, with the rest remaining functional.
  2. Usually from the power control board, but could be some exceptions: Affects all burners associated with that control board, but any burners that aren’t using said board will still work.
  3. User interface board: Entire cooktop will be unusable.

Error codes:

  • F12: Type 1 – Insufficient current to a burner’s electromagnetic coil.
  • F21: Type 2 – Mains power supply frequency is out of range.
  • F25: Type 2 – Cooling fan is stuck or dead. The specific fan that has failed can be determined by which side the F25 error code is appearing on the user interface board.
  • F36, F37: Type 1 – A burner’s temperature sensor has failed.
  • F40: Type 1 or Type 2 – Power control board has failed.
  • F42: Type 2 – Mains power supply voltage has a problem, perhaps an open fuse on the EMI filter/mains input board.
  • F47: Type 2 – User interface board cannot communicate with the power control board, and/or its fuse is blown. (This failure code is what appeared on my particular cooktop.)
  • F56: Type 3 – The configuration data on the cooktop’s user interface board EEPROM is invalid.
  • F58: Type 2 – The configuration data on the cooktop’s power control board EEPROM is invalid.
  • F60: Type 3 – User interface board has failed.
  • F61: Type 2 – Power control board has failed, likely because it is not receiving enough voltage.
  • C81, C82: Type 2 – Cooktop is overheating.

EDIT (November 6, 2015): The F47 code, in my case, was because the power control board (which is responsible for driving the induction coils to heat up the cookware) had short-circuited somehow. Either way, it burnt out all of the transistors and the diode bridge, which then caused its fuse to blow, and at one point it tripped the main breaker in the house.

I suspect it was caused by using the largest element (the rear right burner) on the Boost/P setting, which overloaded the electronics and caused them to fail dramatically. After getting the board replaced (twice), KitchenAid said they do know about this issue to some extent, and repaired our cooktop free-of-charge despite being out of warranty for several months.

How NOT to cut monocrystalline solar cells

The notion of “free electricity” has had some allure for me for quite some time. Back in the middle of high school, with a relatively full pocket after a hard summer job operating rides at a local outdoor theme park, I thought “Hm… Calgary sure gets a lot of sun. Now what if I tried to harness its energy?”

Back in late 2011 I purchased a set of 44 6″ by 6″ monocrystalline solar cells (the good stuff) off eBay. These cells sat unused for years until I tried to build a small panel with one of the cells. I wanted to have a small portable panel that I could bring around to charge my phone (I shoehorned a Nokia BL-5C into my Samsung Galaxy S II and it still works better than my fake “Samsung” battery I bought off eBay for $7 or so).

Cell plan created in Publisher

Cell plan created in Publisher

I created a layout of the way to cut up the cells using Microsoft Publisher, as it has the ability to create shapes in a what-you-see-is-what-you-get manner. I divided the 6-by-6 inch cell into 12 subcells. One whole cell is rated for 4 watts in full sun (0.5 volts * 8 amps), so each subcell should produce ~667 mA or 333 mW. However, the corner cells will have 1.5 cm^2 less area because monocrystalline cells are manufactured from a round wafer, but the output difference isn’t of huge concern to me. Of course, the useful power output of the cells will be much lower than this, but designing for that’s all part of the fun (or pain, depending on how you look at things).

I used a diamond cutting disk designed for a Dremel or other rotary tool, and scored the top side of the solar cell. If things went as planned, I could “snap” the cell at that scored line and it should break cleanly.

Since at this point the cell was basically ruined (Most of the fragments are usuable, provided the silver conductive pad is present on the back of the cell), I decided to cut up some “usable” sections by scoring both sides (and with more depth). It worked… okay I guess. The yield was poor but I did have a few cells that split acceptably.

Overall, the panel’s usable area is much less than what I expected. With 12 subcells I can expect about 1-2.5 watts from this panel. Oh well, live and learn.

Next up is to acquire a proper glass-cutter with a flat working surface…

The Operation Failed Successfully: New series on this blog

I’ve created a new category for my posts, named “The Operation Failed Successfully” in a somewhat mocking term of the Windows error “The operation completed successfully.” It’s intended to be used in a similar manner as Hack A Day’s “Fail of the Week”, showcasing some… less successful ideas of mine.