I have a Spektrum DX3E transmitter designed for radio control ground vehicles, with a matching Spektrum SR300 receiver for mounting on the vehicle. I want radio control equipment like this to be one of many options for controlling a Micro Sawppy rover, and my DX3E will be my example RC equipment for developing corresponding ESP32 software. Before I dive into the software, though, there is a minor hardware modification I wanted to make.
There are several conventions for radio control servo plugs, which look superficially similar to generic 0.1″ pitch wire connectors but aren’t quite identical. From my past experience I knew of the “Futaba” style, with a tab to help with proper alignment. I didn’t have many of those on my radio control toys. Most of my old equipment conformed to the “JR” style, which lack the tab but have tiny bevels to prevent plugging a servo into the receiver backwards. Commodity micro servo plugs do not have this bevel, and neither will Micro Sawppy ESP32 plug. While it is theoretically possible to manually cut the necessary bevel in a generic 0.1″ pitch three-position connector, I have several connectors in mind for experimentation and that would quickly get tedious. So for my own experimentation purposes, I decided to cut off the wedges that enforce bevel direction on the receiver instead. This is not necessarily something I recommend for others. If they only have a single device, it’ll probably be better to cut bevels.
I didn’t want to cut off those wedges with with the receiver intact, because a slip of the blade might damage its circuit board. So I’ll take it apart, which gives me a chance to look inside as well, something I always enjoy. There were no elaborate security measures, merely four small Philips head screws. Once they were removed, the case comes apart easily. In my case, a few grams of dirt fell out as well. Results of my RC cars going off track due to pilot error.
Here is the top side of the receiver. Marked with the year 2008, it reminded me how long it’s been since I played in this hobby. Looking over the components, I was not surprised by capacitors to buffer power input and the oscillator to maintain accurate frequency. There is a large IC clearly in charge of the operation, but it is unmarked. We do see an array of five pins marked J1 that looks like a debug header, but I’m not terribly interested in poking into this chip right now. The output signals pins were a surprise. I had expected some sort of a transistor array to let the main IC toggle signals on and off at the same output voltage as the input voltage. However, all I see are little resistors (R2 – R5) implying they are merely there to limit current draw on IC output pins. This is worth following up.
The back side of the circuit board confirms power and ground pins are connected in parallel across all output pins, with the four signal pins separate as expected. I see a lot of surface imperfection here. It looks like corrosion which might be reaction to the dirt that has been trapped in here. It may also be something from the factory, possibly excess soldering flux that was not cleaned up. I also see a sticker marked ST104M but I have no idea what that represents. Maybe a firmware revision number?
The circuit board was interesting, but for today they were merely a side show. I just wanted it out of the way as I cut into the enclosure. With the PCB removed I could confidently wield my blade, and the little wedges were quickly removed.
The receiver reassembled easily, and a quick test confirmed I could now plug in and use generic micro servos (or other devices) without interference from those now-gone little wedges.
Commodity TT gearmotors became the center of my attention once I decided to switch to using DC motors for driving wheels on my little Sawppy rover project. Where did this form factor come from? Why do people call them TT? Why are most of them yellow? I don’t have answers to those historical questions, but I will see if I can build a little rover with them.
The adventure starts with buying a batch and taking one apart to see what’s inside. I’m not sure if the commodity TT gear motor market has diversified implementation like the micro servo market. If this experiment with TT motors go well, I expect I’ll buy more batches in the future for more little rovers and I’ll open those up to look for differences. Right now I could only speak to this one.
Externally, we see three mounting points. Two mounting holes go through the entire gearbox, next to the two screws holding the gearbox together. A third mounting hole is on a thin tab at the end opposite from the motor. There are two attachment points to the output shaft, which appears to be symmetric and have identical detent patterns. Turning the output shaft by hand, I can see the other output shaft moves in sync, but that doesn’t necessarily mean it is a single piece.
While the output shafts appear symmetric, the rest of the gearbox almost but not quite symmetric. The motor is offset by a little over a millimeter away from the camera in these pictures. On the side facing the camera, we see a little nub above the axle, whereas its opposite side is smooth.
The motor is held in place by a band of clear elastic plastic held by hooks molded into the gearbox exterior. In this particular unit, the clear plastic has partially melted into the yellow plastic and had to be peeled off with pliers before I could stretch them for removal. Once the clear plastic is removed, the motor can slide out. (To release just the motor, it is not necessary to remove the two screws seen in this picture.)
The motor looks very much like a commodity form factor used in many battery-powered toys. In disassembly and hacking circles I frequently see it referred to as “Mabuchi motor”. But just like “JST connector” this is not precise enough. Mabuchi Motor Company has a large product line, most of which aren’t this thing. I found references to this sized motor as FA-130, but with such commoditization I’m certain the majority aren’t genuine Mabuchi products. There’s certainly no Mabuchi logo on this particular motor.
What’s important for the purposes of project creation is that this is a common form factor. And thanks to its use in products like the Tamiya Mini 4WD product line, we can get motors with a wide range of performance characteristics. Same external motor dimensions, but different tradeoffs for torque vs. max speed, etc. At least that’s the theory, I won’t know for sure until I try buying one of those Mini 4WD Hop-Up motors and try installing it in one of these gearboxes.
With the two screws removed, I could open up the gear box and see the gears inside. Pulling the gear train apart, I find four separate components.
My first observation is that all the gears appear to have different diameters. I’ve seen a few TT gearbox modding guides that claim I could select different gear ratios by flipping some gears around, but I don’t see how that is possible when the gears are all different diameters. I’m either overlooking something, or this unit is the wrong variant for that mod to work.
My second observation is that the output shafts poking out on both sides of the gearbox are indeed part of a single piece shaft. There are no ball bearings here but at least they are supported on both sides of the shaft. However, since the output shaft is very clearly asymmetric, I should pay attention to which side is used as the main weight bearing member. Looking at this teardown, I have a clear preference for the side further from the camera in these pictures. That side of the shaft has far more support, in the form of a plastic tube approximately 8mm long. The side closer to the camera (and laid flat against the surface in these pictures) has only a thin wall of plastic for support.
I wonder if there’s a situation where the opposite is true? Perhaps when torque is a concern and we want to be closer to the final output gear, in order to minimize torque imposed on the shaft? I don’t think that’s likely at this power level, but I’ll keep an eye open for the possibility.
I didn’t need to take apart this DC gearmotor to use it, but having seen its insides I feel more confident approaching the task of mechanically adapting it to rover duty. In the meantime, I have a parallel adventure of learning how to drive these motors electrically.
After a service life of over two and a half years, this Monoprice PowerCache 220 was retired due to its degraded battery and malfunctioning thermal protection system. I bought a Paxcess Rockman 200 to replace this old workhorse, which is now long out of warranty and has also been discontinued. Can I fix it? Should I fix it? I won’t know until I take it apart and see what I can find out.
The first step is removing side panels. They are held by hex-drive socket head fasteners that appear to be large durable machine bolts.
Once freed by a hex wrench, however, we see it was an illusion. Underneath the big beefy top is a short self-tapping screw fastened to the plastic. I don’t recall ever seeing a self-tapping fastener with a hex-drive socket head before today.
Once the tough-looking (but actually not) fasteners have been removed, the side panels could slide downwards roughly 1cm, then they can be freed.
With the sides removed, we’ll need to remove the rear fasteners. This is fairly straightforward, none are hiding behind labels. They are all self-tapping Philips screws in clearly visible recessed round holes.
Once those screws are removed, rear half of the enclosure can be lifted to expose the remaining attachment point: a wire harness for the cooling fan mounted in the rear enclosure.
It was easy to unplug the fan (looked like a JST-XH polarized connector) to get a clear look at the interior. Most of the available volume is allocated to a large sealed lead-acid battery. The battery is surrounded by a few pieces of foam padding, probably so it wouldn’t rattle around as the unit is carried around..
This PCB is dominated by large components we would expect to see in a power control application.
Attached to the aluminum heat sinks are power control MOSFETs.
The Golden Rule of Teardowns: Whenever an identifier is visible, put it into a web search to see what comes up. Unfortunately we’ve got nothing for SGD005-INV. In time, the search engines will find this page and send people here. I apologize in advance to those who come to this page seeking information I don’t have.
I was pleasantly surprised to see an easily replaceable fuse. It looks like a standard blade-style fuse popular in automotive applications. I feel it is on the lenient side as 35A * 12V = 420 Watts. I agree if this fuse blows, something has gone very very wrong, but I’m not convinced it’ll blow early enough to protect the rest of the device.
I had expected unpopulated debug points like the RX TX and GND visible towards the right, but the connection to the left actually had populated headers and that was a surprise.
I was encouraged by what I’ve seen so far. It all looks nice and tidy. If I can figure out the thermal problem, I should be able to restore this to full function with a new sealed lead-acid battery. Either way, the degraded battery needed to be removed. This was when I learned the foam padding was glued to the battery. I had hoped they could be easily transferred to a replacement battery, but sadly not.
Once the battery was removed it became much easier to move things around to get a better look. The temperature sensors are likely thermistors, and they have been held into a channel on the heat sink with some kind of glue that dried into a white blob. I had hoped maybe a sensor is misplaced, or dislodged, or unplugged, but it was none of those obvious problems. With those easy fixes ruled out, my prospect for repair dropped.
And once I flipped up the power PCB, my willingness to figure out the temperature problem also dropped. While one side was nice and tidy, the back side is a mess. I see lots of extra solder tinned to various areas on the circuit board, presumably to increase electric current capacity by some amount. And there’s some kind of white residue left all over the board presumably from soldering flux.
A quick web search found that this “heaps of solder” approach is not unusual for lowest-bidder circuit boards. Supposedly it is not terribly effective, but it does provide some benefit for nearly zero additional cost and thus sometimes chosen over any other “right way” approaches to solve the problem.
Not knowing the design constraints placed upon the engineers behind this product, I shouldn’t criticize. After all, it has worked well for over two and a half years. However, it doesn’t make me terribly fond of the device and given that the trivial fixes have been ruled out, repairing it has dropped very low on my priority list. Heck, let’s just say it has been removed from the priority list entirely.
Focus thus shifted from “evaluation for repair” to “satisfy curiosity and evaluate parts salvage.” Looking around the messy circuit board some more, I see the brains of the operation: the STM32F030K6 is a 32-bit ARM Cortex-M0 microcontroller, a cousin of the chip used in the “blue pill” development boards. Unsurprisingly, it is right next to the populated debug header pins I noticed earlier, though the traces don’t seem to go directly into the chip.
Looking past the power control PCB, I see another circuit board. Ah, yes, we would certainly need another board for the front panel status display, and on/off buttons.
Unplugging a few wiring harnesses gave us a better look.
The brains of this operation is a less powerful 8-bit chip, the STM8L052C6.
To give myself a little more room to work, all connectors to the power control PCB has been removed.
But it’s still too cramped, so I also removed the handle. This is a very sturdy handle that is also comfortable to hold. Attached with not just six screws but also molded-in channels to take up weight from the front and rear enclosure halves. Usually when I tear down retired products for salvage, the non recyclable plastic is sent to the landfill. But this time I’m looking at a sturdy enclosure with a handle and think there may be a second life for them.
Finally the control PCB is freed.
Not too many immediate candidates for salvage on the back side.
But the front is a different story. Multiple buttons and LEDs, plus four jacks. Two of them are common 5.5mm OD / 2.1mm ID barrel jacks, the other two are less common but matches the size used by Lenovo for some devices. Piezo buzzer, USB ports, all kinds of good stuff. I doubt I’ll find another use for the LCD panel, though.
I’m still very wary of 110V AC, but these sockets are so easy to salvage I might as well do so. I’m amused at the fact the grounding prong is left unconnected. A portable power source is not connected to ground, so of course there’s nothing to connect them to, but it’s still funny to see.
The 12V “cigarette lighter” socket is very likely to find another use. I wanted to salvage this connector but it was not obvious how. It took me a while to figure out what I was looking at, the answer is that the entire outer base is the “nut” holding the socket in place. In order to remove it from the panel, I had to turn the whole exterior counter-clockwise. And before I could do that, I had to break away most of the solidified orange adhesive.
Nonstandard size meant I had to dig through the tool box for pliers and vise grips of the right sizes to grip without crushing the thin metal exterior can. But eventually it was freed, and the socket could be removed from the panel.
Using earlier pictures as reference, I plugged all the electrical connectors back where they were. Then the mechanical components were laid out for this final roll call without the battery.
Out of all the electronics, I believe the cooling fan will be the first to find a use somewhere, followed by the 12V socket. But I’m actually more intrigued by the enclosure. It is sturdy, already designed to carry something heavy, has provision for cooling, has a big confidence-inspiring handle, and soft rubber feet cushions impact when I set down the box. I think I will cut away the front panel and replace it with something 3D-printed or laser-cut, and the rest of the… whatever it will be… can be installed inside the box. There are lots of potential here.
I have a few UPS (Uninterruptible Power Supply) units to keep my electronics running through short blinks in household electricity, something more likely in a heat wave as neighborhood air conditioning units demand power from the grid. Historically I’ve preferred UPS made by APC as they’ve worked well for me, but over the past few years I’ve heard grumblings from unhappy APC users. The claim is that quality of their consumer line has gone down since their acquisition by Schneider Electric in a misguided effort to compete on price. I can confirm the price premium is less than it used to be, but it still exists. And as to the quality… all I can say is that my units are still working. I’ll post an update if any of the newer APC units fail.
I saw some of the complaints were of dead lead-acid batteries after some years, but I do not consider that a failure on APC’s part. Just like the lead-acid batteries in our cars, batteries are wear items expected to need replacement after some number of years. The guidelines for mission-critical UPS is to replace the battery modules after 2-3 years of active service, but that is being cautious. Batteries on long term standby (like those in a UPS) can last much longer. It’s just a matter of luck.
My luck ran out after five years, when my UPS started beeping at me with an error code. I bought the official replacement battery APCRBC123 (*) but I was curious: Superficially it appears to be two commodity 7Ah 12V modules connected together, are they actually that? Once the new module was installed and working, I took the old module outside to see if my suspicion was correct. The modules were held together by plastic sheets with adhesive backing, complete with convenient tabs where I could start peeling.
Once tape was removed (surprisingly cleanly) I could split the module apart and see it is indeed a pair of commodity form factor lead-acid batteries. Two of them, connected in series via a proprietary adapter in the middle.
So now I know: for the next replacement, it is possible to buy commodity batteries and rebuild the module myself. It wouldn’t have saved me much money this time: the APC module costs roughly in line with the average selling price of two 7Ah batteries. (*) Besides, who knows how long those zero review lowest-bidder batteries would last. But in a few years my new battery module will wear out and require another replacement. If there is a significant price premium on authentic APC replacement modules — or if they are no longer available at all — I have a fallback option.
(*) Disclosure: As an Amazon Associate I earn from qualifying purchases.
Since there’s currently a shortage of high quality webcams, an old and long discontinued HD 4310 has been repurposed for the current exploration. The fact it is not brand new also makes it less psychologically intimidating to tailor the device to suit. Since there’s no warranty left to worry about voiding, I’m going to open it up to see what I have to work with.
The two black circular depressions in the back were stickers, easily taken off to access screws underneath. Once the screws were gone, the plastic enclosure proved to be two pieces of plastic held by clips and could be pried apart with mild effort.
When the two halves popped apart, the buttons flew out as well. Though the three buttons are individually rigid, they are held together by a flexible strip. On the back shell, we could see a single screw holding the webcam stand in place. The stand slid out easily when that lone screw was removed.
Everything else seems to be mounted to a single circuit board, which was expected. Except for the single microphone, which was a mild surprise. The front exterior shape had two perforated grills that implied a pair of microphones. Also, I had expected those two microphones to be surface mounted to the circuit board, so it was a surprise to see only a single microphone that was not surface mount. It wasn’t even aligned with the perforated grill! I thought that would compromise sound quality, but I’m no audio engineer.
The circuit board was held by two more screws. Before I took them off, I considered the possibility that the front shell was part of the optical assembly. There’s a risk that when I pick up the camera I’ll scatter little lens mechanisms all over my work table. If this was a brand new unit I might have backed off, but it wasn’t, so I proceeded.
Fortunately the camera and lens assembly was an integrated unit and nothing flew out as the buttons did earlier. Once removed we could see the audio guide sending sound from one small part of the perforated front grill to the microphone. We could also see the three buttons up top, and the connector for USB.
I opened up my HP Stream 7 because I wanted to see if I could run it without the battery. The answer is no, but since I had it open anyway it is an opportunity to look over the mechanical design of this little tablet. The general electrical architecture is not surprising, similar to most tablets majority of interior volume was allocated to the battery and a PCB smaller than the battery held most of the electronics.
The mechanical engineering, however, showed evidence of more attention than I would have expected in an entry level design that must have been designed for cost. The rearmost removable plate to access microSD slot was nothing special, but as soon as I started looking at the next layer I was impressed by how rigid it was with only a few clips and screws. This attention to mechanical design carried across a few other elements.
This metal plate had two of the enclosure screws dedicated to holding it in place. This plate is immediately adjacent to the micro USB power port and the headphone jack. It reinforces the part of the PCB most likely to see mechanical stress, reducing the chances that a clumsy user would tear out these plugs by accident. Unfortunately while the mechanical engineers did great work, somebody dropped the ball on the electrical front. The headphone jack is so noisy as to be unusable, a trait highlighted in reviews so I know it’s not just this unit.
For the side buttons, I had expected to see sideways switches on the main PCB. I’ve seen those small surface mount buttons before and they are at risk of breaking if the mechanical design doesn’t redirect stress elsewhere. But they are cheap, so we keep seeing them, and they keep breaking off in poorly designed devices. But there’s no such cost-cutting shortcut for this stout tablet. Its buttons are on a separate PCB mounted such that it can take the force face-on instead of letting the force shear off a sideways switch. This adds parts count, and adds steps to assembly, which adds cost, in order to give us more durable buttons. I appreciate it.
Behind the switch is this puzzling field of copper pads and solder. Pads and solder like this are usually for surface mount electronics components, but this large field is completely devoid of hardware. I have no idea why this is here or what it does.
Lower down we see a SK hynix chip with “NAND” label, presumably the onboard flash memory storage. Adjacent to that chip is the microSD slot where the user can add more storage. Adjacent to those chips I see the crab I associate with RealTek audio chips. Two flexible PCBs round out the bottom. One of these is probably for touch and the other for display.
At the very bottom, a small speaker that is actually quite sizable for such a tiny tablet, but there are fundamental handicaps to sound quality at such sizes. I’m thankful for the speaker, but I would have much rather have had a better headphone jack.
Overall I feel the mechanical design on this tiny tablet is pretty good. Too bad its electrical and computational performance isn’t up to the mechanical design. And after this little detour through the world of hardware design, I return to trying the ESA ISS Tracker on other machines. Next on the list: Samsung 500T.
I dusted off my HP Stream 7 tablet to see if it might be suitable for an always-on status display. I encountered some battery power management issues and wanted to see if I could try running it without a battery. Every Windows x86 laptop I’ve ever owned was happy to run without battery power and since my current intent is for a wired 24×7 display screen, I didn’t need the battery anyway.
This experiment was made possible by the design of the device. Relative to almost every other piece of modern portable electronics, the HP Stream 7 is easy to open up. The back plate can be opened without tools, just follow the gap they designed and start prying plastic clips apart.
This was how users could access its microSD slot for adding more storage space. And given how the battery is clearly visible when the back is removed, I thought it was also to enable easy battery replacement. My assumption was wrong! The battery appears to be glued in place and WARNING: BATTERY IS NOT REMOVABLE printed on the battery. Curiously that was printed with a dot matrix printer, implying this specific battery is not always non-removable, perhaps it is removable from another device but that won’t help us here today anyway so let’s move on.
I don’t remember ever dropping this tablet, but one corner tells a tale of my neglect.
If I want to try running this device without battery, I will need to access its battery connector which is hidden underneath the next piece of plastic. That piece is fastened quite well by a large number of plastic clips, backed up by small screws. Together they created a pretty durable enclosure for this tablet while still being removable. There was nothing tricky about opening up this device. Once the second back plate was removed, the battery connector was accessible.
Once exposed the connector easily popped free. I pressed the power button and… nothing. Unlike laptops, this device refuses to run without a battery. This makes it less useful for the current project. Nevertheless, such ease of access to durable internals has raised my opinion of this tablet. And since I had it open, I might as well look around a little more.
Earlier this year I brought a failed dimmable Cree LED light bulb to SGVHAK for a teardown. We determined the LEDs were fine and the problem was in its power supply but we couldn’t figure out exactly where. I stashed the board aside, intending to someday pull the LED modules off for potential reuse elsewhere. That “someday” has finally rolled around.
I deployed the heat gun I’ve used to remove many components from PCBs before. It is usually just for fun, or for removing hardy components like switches, transformer coils, and power connectors. This would be the first time I tried removing a silicon component with intention of reuse.
Out of eight modules, two were damaged when I tried to remove them. These LED modules were composed of two parts: a substrate to which the set of 10 LEDs were mounted, and a diffuser/cover module over them. And much to my chagrin – they weren’t bonded very tightly to each other. Here are pictures of one of the damaged modules. One LED was clearly torn off and embedded in the cover, or else I would have been tempted to power it up just to see if it works. (The LEDs are not powered in the picture, they appear bright via reflected ambient light.)
I considered trying to repair that module, by adding a blob of solder to bridge the gap where the damaged LED used to live. But it proved beyond my skill level to work at such sub-millimeter scales. Here is one of the successfully removed modules next to a ruler showing millimeters.
There are three solderable contacts at the bottom of each module where I expected just two. So they would be positive, negative, and… something else? To try to figure out which pad did what, I soldered a small wire (trimmed from the end of a resistor) to each pad. This turned out to be even more difficult than its small size suggested. The first wire wasn’t too bad, but when I tried to solder on a second wire I understood the challenge. This module is so small there’s very little heat dissipation between adjacent pads. As soon as I heat up one solder joint, it is hot enough to melt solder on remaining pads too. This was really designed for SMD soldering by machine, where the solder is supposed to all melt at once. Soldering one at a time by hand was hard.
Once soldered, I connected power to two of the three pins. It appears the center solder point is not for power. My best guess is that it is for heat dissipation and apparently a wire soldered to the pad does not offer enough dissipation to tolerate abuse. As a test I cranked up the power (over 30V and over 40mA). That heated up the LED enough to melt the solder and escape, falling off the wires onto my workbench.
Which meant another opportunity to practice patience while soldering. This time I didn’t bother soldering to the center pad, and I didn’t crank the power up as high.
These LED modules give a dull glow at 24V, drawing less than 10 mA while doing so. They start growing brightly at roughly 27V, drawing approximately 20mA. I’ll need to provide better heat dissipation, connected to that center pad, before I push through power any higher again.
Once I extracted the optical assembly carriage of a Panasonic UJ-867 optical drive, the next step is to interface it with a Pololu A4988 driver board. And just as with the previous optical drive stepper motor, there are four visible pins indicating a bipolar motor suitable for control via A4988. However, this motor is far smaller as befitting a laptop computer component.
The existing motor control cable actually passed through the spindle motor, meaning there were no convenient place to solder new wires on the flexible connector. So the cable was removed and new wires soldered in its place.
Given the fine pitch of these pins it was very difficult to avoid solder bridges. But it appeared to run standalone so I reinstalled into the carriage. Where it still ran – but was very weak. Hardly any power at all. When I tilted it up so the axis of travel is vertical, the carriage couldn’t win its fight against gravity. Since the job is only to move an optical assembly, I didn’t expect these carriages exert a great deal of force. But I’ve seen vertically mounted slot loading optical drives. I thought it should at least be able to fight against gravity.
A Dell laptop charger delivers 19.2V. I’m not sure how many volts this motor intended to run at, but 12V seemed reasonable. Then I increased current beyond the 50mA of the previous motor. Increasing both voltage and amperage seemed to help with more power, but it remained too weak to overcome gravity.
As I’m tilting the metal carriage assembly in my hand, I started noticing it was warming. Oh no! The motor! I checked the temperature with my finger, which was a mistake as it was hot enough to be painful to human skin. I shut down my test program but it was too late, the carriage never moved again.
Lessons learned: don’t get too overzealous with power and check temperature more frequently.
The Panasonic UJ-867 is a slot loading optical drive. This particular unit was salvaged from a dead Dell XPS M1330 previously featured when I pulled its power port, and disassembled its battery, plus trying to use its AC power adapter to charge a Neato vacuum. A web search indicated this drive was better known as a drive used in certain models of Apple MacBooks. An optical drive typically has a carriage for its laser assembly driven by a stepper motor, and that carriage is my target for further stepper motor experimentation.
When the lid was removed, the age of this device was clear: it still held a disk! The Windows edition of Norton AntiVirus confirms this was not from a MacBook. The year also spoke to the vintage of this drive.
With the disk removed, we can see all the mechanical linkages. This was far more than I had expected, because I had never taken apart a slot-loading drive before. Many of the pieces were involved in the slot loading mechanism, which is in the “disk inserted” position. (The Norton disk was not properly ejected – I removed the lid and popped it off!) Various mechanisms in this position block fasteners making it difficult to take apart.
Tracing through the mechanical bits, I guessed this motor is the heart of the drive loading and ejection mechanism. It is a simple DC motor so I should be able to put power on these pins to move the mechanism to their eject state. However, there are a few parts nearby that I might bump into if I powered from the top, so to be safe I soldered some pins from the bottom.
Applying power to this motor did indeed run through the ejection sequence, even though I’ve already removed the disk. Now it became fairly straightforward to take apart the drive.
Almost all of the pieces are specifically tailored to this usage, making reuse unlikely. But I do enjoy seeing the eject motor gearbox run. This is a distraction, though. The optical carriage was the goal and that was removed for the next step: connecting it to my Arduino + A4988 test breadboard.
The plastic enclosure yellowing from age is not a surprise, but its heft was: it was far heavier than it looked. Judging by the collection of debris this machine had gathered, it had been left outdoors for some time. It was not a surprise when it failed to power on. Which is fine as we had no use for a fax machine and little interest in fixing it, but we were curious what was inside one of these anachronisms.
Most of this device’s mass came from a single beefy cast aluminum frame inside the machine. Select portions have been machined to precise tolerances. Why was this necessary? Emily hypothesized the robust frame was necessary to hold optical scanning components in precise alignment. The optical path was more complex than we had expected. Illumination came from a wide LED strip sitting under what looks like a glass rod slice lengthwise. It began to emit visible yellow-green light at roughly 15 volts (while drawing less than 200mA) and we cranked it as high as 20 volts (just under 500mA) but no further as we didn’t know the strip’s limits.
That light bounced off a few front surface mirrors before reaching the document, whose reflected light is picked up by yet more mirrors and finally a lens assembly that focused onto a sensor. A web search for TCD102D only found the first page of this device’s data sheet. But it was enough to tell us it was a line of 2048 photodiodes designed specifically for this purpose of scanning a line of a document scrolling past sensor optics.
For the output side of this device, there was a roll of thermal paper and a thermal image print head that worked much like the sensor in reverse: a line that heats a sheet of paper rolling past it to create an image. Digging below them both, we find the mechanical pieces making paper scroll. There was a stepper motor driving rollers for source document, and another stepper motor driving rollers feeding thermal paper for output.
Beyond the two stepper motors, few components had prospect for reuse though some (like the front surface mirrors) were kept for novelty. Unfortunately this disassembly also evicted an insect from its now-demolished home.
The biggest win was a lens assembly that formerly sat in front of the linear CCD. It has the right optical properties to be used as a small macro lens for an equally small cell phone camera. Emily plans to design and 3D print a bracket to hold this lens at the proper location and distance so we should see more close-up shots of small electronics components in the future.
And now, something a little different from the usual fare. Today’s teardown project has no electronics in it whatsoever. It is an exploration into an entirely different category of home consumer merchandise: furniture.
This old couch had been in service for several decades and long overdue for retirement. The default option was to treat it as bulk waste and call for pickup, but let’s see what we can learn from its deconstruction.
We start with seat bottom cushion which were easily removed. Some coins were found but there were little else of value trapped within. Too bad – we once found a lost cell phone in here, but not today.
Unlike the bottom cushions, this couch’s back cushions were attached and had to be cut off for disassembly.
Each armrest cushion were held by four of these rivet-like structures, two inside and two outside of each armrest. It was easiest to cut fabric around each rivet than trying to unfasten them.
Those armrest cushions were the final pieces of soft padding material. Everything that remained are fabric and rigid structure.
Fabric panel cutting started with the bottom-most sheet. This sheet is not typically visible, made of a thin and partially transparent material that is also very tear-resistant.
This sheet was fastened by staples. The decision was made to cut instead of pull to avoid staples flying everywhere possibly puncturing tires and feet.
Seat springs were visible once that bottom fabric panel was cut away. We’ll be back for those springs later. For now focus is still on removing pieces of fabric so we proceed to cut back panel.
We can see more of the wooden frame once the back panel was removed. These wood beams were surprisingly irregular in their dimension. Each segment might be a little wider or thicker than its neighbors. Not that a great deal of precision was necessary – pieces were held to each other with copious amounts of staples. This construction method does not demand dimension accuracy. It’s possible this flexibility allowed the couch to be built using scrap wood left from manufacturing other things.
Cutting off the back panel also exposes these metal strips. These were used to cover up fabric seams. When installed properly, they are not visible and thus preferable to staples.
With the removal of each fabric panel, the couch looks less and less like a couch.
Returning to the bottom, a bolt cutter helps cut off the springs. With the first cut I discover they are bent in a direction to support weight. This discovery was accompanied by reinforcement that it’s always good to stay back when cutting metal things to minimize chances of injury.
By this point all loose fabric panels have been cut free, as has metal springs. Most of the remaining parts are wood and fabric glued to panels of wood. It is time for the reciprocating saw to make its entrance.
A reciprocating saw made quick work of wood pieces. A few cuts, and the couch back is gone.
After a few more cuts, the couch is no longer recognizable as a couch at all. These easily managed pieces can now be disposed as regular household landfill and do not require special bulk waste procedures.
As a change of pace from tearing down consumer electronics, today’s teardown is a simple single-pole, single-throw household light switch. This specific switch has been in service for many years and failed with the following symptoms: mechanically, the switch now moves freely without the tactile feedback it formerly had. Electrically, the switch is always closed leaving the attached ceiling light fixture illuminated. These switches are simple and failures are rare, so it was interesting to find out what the weakest point was in such a simple thing.
The top mounting bracket appears to be made from stamped sheet metal, and held to its body with a few bent metal fingers. A pair of pliers released those fingers and we could see the next layer.
We see a sheet of something that feels like paper. The most obvious purpose is for electrical insulation, but it may have some fire resistant properties as well. This sheet was easily removed.
As soon as that sheet was removed, we had our first hint: a loose spring sitting in the lower left corner which probably should be sitting somewhere else.
Lifting the switch lever showed us the nub that used to be that spring’s home. The spring served as an elastic connector between the the plastic lever flipped by the user and the metal contact beneath which closes the electrical connection. When the spring broke, there is no longer any physical connection between these two parts, and the metal contact stayed closed due to gravity.
The spring broke off leaving approximately 2mm on the swinging metal contact. There’s a chance that, if we removed the small tail, we could reassemble the switch and it will work again. However, by this time a replacement had already been purchased from the local Home Depot for $0.88 USD and installed. The replacement is not exactly identical due to literal decades separating them, but the basic principles are the same. It’s amazing all of the following could be manufactured, built, shipped and stocked locally for retail sales all for just $0.88.
3 ~1mm thick metal pieces for electrical contacts.
2 thin sheets keeping the two static electrical contacts inside body.
Now that we have a better understanding of how a NEC VSL0010-A vacuum fluorescent display (VFD) works, figuring out its control pinout with the help of an inkjet power supply, we returned to the carcass we salvaged that VFD out of. Now that we knew each pins’ function, we picked those that supplied 2.5V AC for filament power to track. We expect they are least likely to pass through or be shared by other devices. We traced through multiple circuit boards back to the main power transformer output plug. We think it’s the two gray wires on the left side of this picture, but our volt meter probes are too big to reach these visible contact points. And the potential risk of high voltage made us wary of poking bare wires into that connector as we did for the inkjet power supply.
Our solution came as a side benefit of decision made earlier for other reasons. Since we were new to VFD technology, our curiosity-fueled exploratory session was undertaken with an inexpensive Harbor Freight meter instead of the nice Fluke in the shop. Originally the motivation was to reduce risk: we won’t cry if we fry the Harbor Freight meter, but now we see a secondary benefit: With such an expensive device, we also feel free to modify these probes to our project at hand. Off we go to the bench grinder!
A few taps on the grinding wheel, and we have much slimmer probes that could reach in towards those contacts.
Suitably modified, we could get to work.
We were able to confirm the leftmost pair of wires, with gray insulation, is our 2.5VAC for VFD filament. The full set of output wires from this transformer, listed by color of their insulation, are:
Gray pair (leftmost in picture): 2.6V AC
Brown pair (spanning left and right sides): 41V AC
Dark blue pair: (center in picture) 17.2V AC
Black pair (rightmost in picture): 26.6V AC
There was also a single light-blue wire adjacent to the pair of dark blue wires. Probing with volt meter indicated it was a center tap between the dark blue pair.
Once determined, we extracted the transformer as a single usable unit: there was a fuse holder and an extra power plug between it and the device’s AC power cord. We’re optimistic this assembly will find a role in whatever project that VFD will eventually end up in. 2.6V AC can warm filament, rectified 26.6V AC should work well for VFD grid and segments. And with proper rectification and filtering, a microcontroller can run off one of these rails. It’ll be more complex than driving a LED display unit, but it’ll be worth it for that distinctive VFD glow.
One of the reasons LED has overtaken VFD in electronics is reduced power requirements. Not just in raw wattage of power consumed, but also the varying voltage levels required to drive a VFD. The NEC VSL0010-A VFD whose pinout we just probed ran on 2.5V AC and ~30V DC. In contrast, most LED can run at the same 5V or 3.3V DC power plane as their digital drive logic, vastly simplifying design.
We didn’t have a low voltage AC source handy for probing, so we used 2.5V DC. We expected this to have only cosmetic effects. One side of our VFD will be brighter than the other, since one side will have a filament-to-grid/element voltage difference of 30V but the other will only have 27.5V.
But putting 2.5V DC on the filament occupied our only bench power supply available at the time. What will we use for our 30V DC power source? The answer came from our parts pile of previously disassembled electronics, in this case a retired HP inkjet printer’s power supply module labeled with the number CM751-60190.
According to the label, this module could deliver DC at 32V and 12V. Looking at its three-conductor output plug, it was easy to come to the conclusion we have one wire for ground, one wire for 32V, and one wire for 12V. But that easy conclusion would be wrong. Look closer at the label…
We do indeed have a ground wire in the center, but there is only one power supply wire labelled +32V/+12V. It actually delivers “32 or 12” volts, not “32 and 12” volts. That last pin on the left has an icon. What did that mean? Our hint comes from power output specifications: +32V 1095mA or +12V 170mA. We deduced this meant the icon is a moon, indicating a way to toggle low-power sleep mode where the power supply only delivers 12V * 170mA = 2 watts vs. full 32V * 1095mA = 35 W.
With that hypothesis in hand, it’s time to hook up some wires and test its behavior.
When “sleep mode” pin is left floating, voltage output is 32VDC. When that pin is grounded, voltage output drops to 12VDC. Since we’re looking for 32VDC to drive our VFD grid and elements, it’s easy enough to leave sleep wire unconnected and solder wires to the remaining two wires to obtain 32V DC for our VFD adventures.
Vacuum Fluorescent Display (VFD) technology used to be the dominant form of electronics display. But once LEDs became cheap and bright enough, they’ve displaced VFDs across much of the electronics industry. Now a VFD is associated with vintage technology, and its distinctive glow has become a novelty in and of itself. Our star attraction today served as display for a timer and tuner unit that plugs into the tape handling unit of a Canon VC-10 camera to turn it into a VCR. A VFD is very age-appropriate for a device that tunes into now-obsolete NTSC video broadcast for recording to now-obsolete VHS magnetic tape.
Obviously, in this age of on-demand internet streaming video, there’s little point in bringing the whole system back to life. But the VFD appears to be in good shape, so in pursuit of that VFD glow, salvage operation began at a SGVHAK meetup.
We have the luxury of probing it while running, aided by the fact we can see much of its implementation inside the vacuum chamber through clear glass. The far right and left pins are visibly connected to filament wires, probing those pins saw approximately 2.5V AC. We can also see eight grids, each with a visible connection to its corresponding pin. That leaves ten pins to control elements within a grid. Probing the grid and element pins indicate they are being driven by roughly 30V DC. (It was hard to be sure because we didn’t have a constant-on element to probe…. like all VCRs, it was blinking 12:00)
This was enough of a preliminary scouting report for us to proceed with desoldering.
Now we can see its back side and, more importantly, its part number which immediately went into a web search on how to control it.
The top hit on this query is this StackExchange thread, started by someone who has also salvaged one of these displays and wanted to get it up and running with an Arduino. Sadly the answers were unhelpful and not at all supportive, discouraging the effort with “don’t bother with it”.
We shrugged, undeterred, and continued working to figure it out by ourselves.
If presented with an unknown VFD in isolation, the biggest unknown would have been what voltage levels to use. But since we have that information from probing earlier, we could proceed with confidence we won’t burn up our VFD. We powered up the filament, then powered up one of the pins visibly connected to a grid and touched each of the remaining ten non-grid pins to see what lights up. For this part of the experiment, we got our 32V DC from the power supply unit of a HP inkjet printer.
We then repeated the ten element probe for each grid, writing down what we’ve found along the way.
We hope to make use of this newfound knowledge in a future project, and we hope this blog post will be found by someone in the future and help them return a VFD to its former glowing glory.
When [Emily] found her Neato vacuum in a thrift store, it had an advantage over mine in that hers still have the company of its charging dock. This is our first look at a Neato robot vacuum charging dock and a chance to determine how one worked. We wanted to have some idea of what to expect when we put it to work charging newly installed replacement batteries.
The charging dock is designed to sit against a wall. The two metal strips are obviously for supplying power, as they line up with the two metal wires at the back of a Neato vacuum. When the dock is plugged in, a volt meter reports 24V DC between those two plates, top plate positive and bottom plate ground. Each of the plate is mounted on a piece of spring-loaded plastic that allows approximately 3-5mm of horizontal movement. A Neato vacuum can press its wires against these plates to draw power.
Above the plates is a black plastic window, we expect something behind that window to communicate with the Neato so a hungry robot vacuum knows where to go to feed itself. How does it work? We hypothesized there are infrared emitters and receivers behind that panel, functioning like a consumer electronics remote control, to talk to a Neato vacuum.
The orange tab on top looked very inviting as a way to open the dock. A bit of fiddling later, the dock was open. It was surprisingly simple inside. There was an AC power supply delivering 24V DC. It has a standard power cable on the input side, which can be routed to exit either side of the dock. This way a user can swap as needed to point towards the nearest power outlet, and possibly swap for a longer standard power cable if necessary to reach an outlet. The output wires of the power supply lead to the two metal plates, and that’s it.
Surprisingly, there’s nothing visible behind the black plastic window. The IR emitters and receivers we expected were absent, as were any circuit boards with components to communicate with the vacuum. So this charger dock location beacon must work passively. Now we’re reallyinterested in finding out more. How does it work?
The black plastic window were held in place with a few clips. They stood between us and knowledge and were quickly dispatched. We were afraid the black plastic might be glued in place, but fortunately that was not the case and it popped off for us to see underneath.
We see a pattern laid out with two types of surfaces. The white segments are highly reflective much like the stripes on high visibility orange safety vests. The black segments are presumed to provide a contrast against the white parts. We found out earlier that a Neato lidar data stream returns both distance and intensity of reflections it saw. The distance is useful for navigation, but using just distance information the charger would be an unremarkable flat surface. This is where intensity comes into the picture: these surfaces behind the black plastic window will create a distinct pattern in reflection intensity, something a Neato robot vacuum can seek to find its charging dock.
Disassembling this passive system tells us two things:
The engineers are Neato are quite clever
We now know enough to try creating our own charging docks. Userful when we have Neato vacuums found at thrift stores without their charger.
This SGVHAK teardown project came courtesy of an electronics waste bin. A nondescript box with a USB cable, it has three moving parts on top of a heavy base. The center piece takes up majority of width, and two far smaller pieces sitting on either side. Each piece can be pressed down and we can feel a tactile click of a switch. It has a respectable heft and doesn’t look damaged or even worn. It feels rather beefy and unlikely to physically break.
A label on the bottom of the device lets us know it is version 14 of the Infinity IN-USB-2 foot pedal. Which explains its mass and durability: this box was designed to sit under a desk and be stepped on. A box sitting out of sight explained its raised side pedals allowing its user to find them by feel.
A few screws on the bottom held a plate in place, easily removed. We see a few springs for the pedals, and two pieces of metal that gave the device its heft.
There were a few visible plastic clips holding individual pedals in place, but they were only the first line of defense – unclipping them allowed individual pedal to move a little further but did not release them. There were also a few hinge pins that could be removed, but again it allowed additional movement but did not release.
The two shiny metal weights were held by tenacious stretchy glue. We could pry them up far enough to see they weren’t obviously hiding screws, but we were wary to apply addition force as it threatened to break apart the plastic housing.
Without an obvious way forward for nondestructive disassembly, we decided to pause and reassemble the pedal to see if it can be useful intact before we risk destroying it. My computer was running Ubuntu at the time, which gave us a starting point with the dmesg tool to see what kind of greeting it has to say to my computer.
[ 459.086214] usb 1-4.4.3: new low-speed USB device number 17 using xhci_hcd [ 459.192673] usb 1-4.4.3: New USB device found, idVendor=05f3, idProduct=00ff [ 459.192679] usb 1-4.4.3: New USB device strings: Mfr=1, Product=2, SerialNumber=0 [ 459.192683] usb 1-4.4.3: Product: VEC USB Footpedal [ 459.192687] usb 1-4.4.3: Manufacturer: VEC [ 459.196360] input: VEC VEC USB Footpedal as /devices/pci0000:00/0000:00:14.0/usb1/1-4/1-4.4/1-4.4.3/1-4.4.3:1.0/0003:05F3:00FF.0012/input/input28 [ 459.196980] hid-generic 0003:05F3:00FF.0012: input,hiddev1,hidraw9: USB HID v1.00 Device [VEC VEC USB Footpedal] on usb-0000:00:14.0-4.4.3/input0
So far everything looks in line with the manufacturer’s name we found earlier. It also tells us the device conforms to USB HID (Universal Serial Bus Human Interface Device) specification. The final line also hinted us to a newly visible device under the path/dev/hidraw9.
$ ls -l /dev/hidraw9 crw------- 1 root root 240, 9 Mar 17 13:32 /dev/hidraw9
This path is owned by root, so further experimentation requires taking ownership of that path to see what we can do with it.
$ sudo chown $USER /dev/hidraw9
Now we can try treating it as a file with the cat command. Every time we press or release a pedal we get some kind of visual feedback but we don’t understand it.
We then tried treating it as a serial port using minicom but that didn’t get us much further. It vaguely resembles the garbage that might occur if a baud rate setting is incorrect, but changing baud rate in minicom didn’t do anything. Probably because it’s not a serial port!
Since the device was classified as a USB HID v1.00 Device, the next thought was to try communicating with it via some sort of HID API for developers. But USB HID is not a trivial thing and after a half hour of following and reading links to documentation I was no closer to talking to the pedal in a “proper” way. So I tabled that approach and returned to treating it as a file. It’s pretty trivial using Python’s file APIs to open it up for reading.
>>> hr9 = open('/dev/hidraw9','r')
Reading a few bytes at a time, we figured out the device sends two bytes upon every action. First byte is a bitfield indicating pedal status, and the second is always zero. The leftmost pedal corresponds to the least significant bit 0x1, then center pedal 0x2 and right pedal 0x4. So if both right and center pedals were both pressed, it would give 0x6. Here’s a simple Python loop that reads two bytes at a time and outputs to command line.
>>> while True: ... hr9.read(2)
The output if I press and release the left, then repeat for center and right pedal.
Not every action will trigger data events. There’s a small time window where separate events are collapsed together for a single notification. If I’m quick enough on the press and on release, I can push the right and left pedals simultaneously for a single 0x05 report, then release simultaneously for a 0x00 report, without any intermedia reports of 0x04 or 0x01.
This is a very promising set of experiments indicating that, if it should be necessary, we can write code to make use of this pedal in Linux without digging through all of HID API.
With that knowledge under our belts, experimentation then moved to Windows 10, which immediately recognized it as a USB HID and even shows us the name. However, it doesn’t do much without further help.
Searching for answers on the web, we learned this device was designed for people transcribing audio recordings into text. The pedals allow them to control sound playback (pause, play, rewind, etc.) without taking their typing hands off the keyboard. I’m sure this is a productivity boon for its target audience, but that wasn’t us. Fortunately, the manufacturer has also released a piece of software call Pedalware which will allow this pedal to be used outside its designed scenario, like emulating keyboard keys or mouse buttons. I thought it sounded interesting enough to try.
And this is where we started getting a hint why this device has been retired… this piece of hardware’s associated software is old. Pedalware’s installer demands Windows 7 or earlier and refused to run under Windows 10.
At this point, Windows 10 backwards compatibility module kicked in and offered the option of running in compatibility mode. I accepted.
That was enough to get Pedalware up and running on my Windows 10 computer. Now I can assign an arbitrary keyboard or mouse action to each of three pedals.
This worked fine in everyday web browsing and productivity applications. It is, however, too slow for gaming purposes. The aforementioned time window seen under Linux, which collapsed multiple events into a single event, manifests here as well resulting in foot click actions getting lost in high-speed gaming action.
But that’s fine, the device was never intended to be a gaming peripheral. The real problem comes from its driver software becoming unreliable as a computer goes into low-power standby. When the computer resumes, the pedal doesn’t always come back into action. And once it gets stuck, the only way to get it back is a full reboot.
This was a sign of the times when this device was designed. I remember when many peripherals would not gracefully handle a computer going to sleep, which meant I typically leave my computer running in the Windows XP/Vista/7 days. Computers have gotten more power efficient over these years but it’s still better to put them to sleep. Also, modern USB peripherals are much better about resuming from sleep.
But this pedal does not, and that’s probably why it was retired. Fortunately, my work does not require a predictably functional foot pedal, so I’ll keep it around and try using it on the occasions when it works.
I brought an old LED light bulb to a SGVHAK meetup for an educational dissection. This bulb has illuminated my front porch for several years, hooked up to a light-sensitive fixture that turns on the bulb when dark, and turn it off when the sun is up. However, when illuminated this bulb has started flickering. At first it was a mild pulse that I didn’t mind very much as I don’t usually need the light myself anyway. But after a while, the blinking started getting annoying and even the bright pulses were too dark for the light to serve its intended purpose. This bulb was retired, and now we take it apart to see what’s inside.
Looking inside the cooling vents, we can see there are two circuit boards mounted at right angles to each other. Obviously there will be LEDs soldered to these boards, with a power supply at its base. Since all the LEDs pulsed together, we expect there to be a power supply failure and hope we might be able to see what component caused the problem.
Here’s the bulb intact, before teardown began.
Here’s the label on the bulb. This was not a bargain basement device, it was a dimmable bulb and it was also designed to be usable in damp environments as the front porch is occasionally exposed to rain. It was also exposed to outdoors wildlife, including some insects who have climbed inside and sadly died there, too.
It was nicely sealed with no obvious way to take apart the plastic housing nicely, so out came a beefy cutter and we start cutting from top vents.
Once the top vents were clipped open, we could perform some literal debugging of our device by pouring the dead carcasses out. They look like honeybees.
Aside from debugging, the opened top also lets us see more details inside. Sadly, there were no visible mechanisms for easy release, so cutting continues at waist-level vents.
Once those portions were cut away, we could see more of internals. There were fewer LED surface mount packages than we had expected.
At this point I ran out of convenient places to cut with a hand tool, so cutting moved on to a band saw.
Once the band saw cut through all around the base of transparent plastic bulb exterior, we were able to free its internals for a closer look. Surprisingly, the circuit boards connect to each other and to the base with tiny spring-loaded connectors rather than a direct soldered joint. One hypothesis is the bulb was not only designed for humid environments, it was designed to sustain vibration as well. Another hypothesis was that humid environments also imply a larger temperature swing, where spring-loaded connectors can accommodate thermal expansion/contraction better than soldered joints.
Here is the main board’s topside. Nothing appeared obviously damaged. The big electrolytic capacitor immediately drew our attention, as that is the type of component most likely to fail with age. However, the usual signs were absent. No leaking electrolyte, no bulging of the body, and no breakage in the top. With the help of our multi meter, we could tell the capacitor has neither failed open or failed short. We also measured its capacitance, which won’t be a reliable number as the capacitor is still installed on the board: we’d be measuring capacitance of the capacitor as well as the board it is installed on. But the number was roughly in the ballpark of the rating printed on its side, so it looks clear on all counts.
Bottom side of the main showed no such obvious attention-getters. The small light colored surface mount component at the base might be a safety fuse, and it tested OK for continuity.
We explore the fewer-than-expected LED modules by trying to power up a single LED using a bench top power supply. At first it stayed dark and we thought maybe the LEDs were at fault instead of the power supply. But then we realised we weren’t giving it enough power: we were surprised it took over 24 volts before a single module would illuminate.
An explanation surfaced once we adjusted camera settings to see individual light sources inside the package: there are actually ten LEDs in each package, in a three + four + three configuration. This explains how it could be so bright with so few surface mounted modules!
At this point we’ve verified all the discrete components we understood and could test, we’ve removed dead bug remains that might have caused problems, and we cleaned up all the electrical connectors. Maybe that’s enough to bring this bulb back to life?
Sadly, the answer was no. We hooked it up to AC power and plugged it in: it is still dim and blinky. Obviously we failed to understand how this particular bulb works – the power supply circuitry was far more complex and sophisticated than we had expected. But still, it was fun to look inside a premium (for its day) LED bulb.
Tonight at #SGVHAK: This old LED light bulb dates back to the time when such dimmable units were $50 each. Something is wrong with its power supply. We couldn't figure out which specific component failed, but we had a lot of fun trying. pic.twitter.com/7zX1D8Vsm7
On the one hand, I love many Disney properties. On the other, I’m very clear Disney wrings every penny out of their fans. Disney Infinity was a video game where new characters and capabilities are acquired via purchase of physical figurines. Advancement in the game requires a steady stream of new figurine purchases. As much as I love both video gaming and Disney properties, that was too much of a money grab for me to put up with. Apparently enough people thought the way I did, because Disney shut it down for not making enough money.
Ironically, that announcement is why I now have a Disney Infinity starter pack: once the announcement was made, these kits went on the clearance rack for drastically reduced prices. I was not interested in paying their full price, but I can certainly spare $5 for a gaming peripheral with no future just so I could take it apart! It took a while for me to get around to this project, which finally happened at a recent SGVTech meetup.
This starter pack came with the system base, Merida, and Stitch. Based on how the game worked, we expected a RFID-based system. That implies RFID chips in the bottom of these figurines, and the USB-connected base has coils to read them. Expectations on these fronts were met but there were a few surprises on the way.
The plastic top of the base were held with a few clasps that were easily broken. Once removed, we could see three white PCBs each with what appears to be a surface mount LED on top, and a green PCB with connections to each of them and the USB cable.
When we flip over one of the white PCB, we could see it is a simple single layer design and its RFID coil is visible. The straight lines towards the middle are for driving the LED.
The control board is a more typical multi layer board. The biggest chip on board is from the STM32 family, specifically the STM32F072C8T6. Typing the numbers printed on top of next two larger chips into a web search didn’t return any useful results.
The LED on each white PCB appears to have four leads. When we saw four leads our first thought was an addressible LED with power, ground, data, and clock. Then we remembered this is a toy built to low cost: it’s more likely a RGB LED package with a common anode and three cathodes, one per color. Either that or the reverse with a common cathode and three color anodes. The ‘+’ labelled on its PCB hinted at a common anode design, which was confirmed with a quick test using a bench power supply putting power on some exposed pads.
Aside from the RGB LED, there’s not much of interest from these three white PCB I could pull off and reuse. The main green PCB was more sophisticated, and there were exposed pads on the bottom that hint at the possibility of reprogramming the STM32 for something fun, but that’s beyond my current skill level. (This guy can probably do something with it.) The part of the board with best potential for reuse is its USB connection. It gives me a USB-A connector for plugging into a computer, and the other end is a nice modular connector with 2mm pitch. This will be useful the next time I want to hack a standard USB cable onto a device.
Attention then turned to the other part of this system: the figurines. Once the clear plastic portion was removed, its RFID sticker is accessible. Sadly, Stitch’s arms did not survive the process of prying apart his base.
A closeup of RFID sticker showed most surface area is antenna, and that tiny black dot is a chip with the secret code to unlock a Stitch character in a Disney Infinity game. People online have tried to hack these bases with little success. Given that the revenue stream comes from selling figurines, there was a robust security scheme to protect the game against counterfeit tags. I was not interested in exploring the digital side in any case, this was strictly a physical teardown.
In her movie Brave, Merida was guided by little blue glowing wisps. In the figurine, a wisp floated by Merida’s foot. As a ghostly entity, it was fittingly cast in translucent plastic.
But there was an extra detail: the translucent plastic went all the way through the opaque parts of the stand, so it could pick up LED illumination from the USB base. When it glowed with a blue LED, the wisp would glow blue just like in the movie. This bonus showed the artists were thinking about how to best take advantage of this medium. Too bad such creative thoughts were infrequent (Stitch had no such attraction) and probably went unnoticed by most buyers.
The final piece – hexagonal tiles for some purpose or another – were unremarkable. Once the transparent and opaque pieces were pried apart, a similar RFID tag could be removed. I didn’t see any interesting possibilities for reuse.