Sony KP-53S35 Power Board “G”

After high voltage transformer was freed, I looked over the rest of this board. Aside from a big “G” next to the Sony logo, I didn’t find a designation marked on it. I’m calling this the power board just because this is where the AC power cable came into the television. Power enters through a connector in the lower-left corner of this picture. Accordingly, most of the larger components are clustered near that area, implying power handling duties. Many also had thin sheets of metal attached, either as heat sink or as shielding or possibly both.

Power Board top before

Near the center of the board is a curious connector – it just has a wire that loops back into itself. What could be the purpose of such a thing?

Power board curious connector

A big beefy 20W resistor with very low resistance of 0.82 ohms hint at a shunt, possibly for measuring current flow.

Power board 20W resistor

Enough looking, time to pull off the interesting looking parts, meaning pretty much every component which is not a resistor or a capacitor. I first started with the ICs on the board as I wanted them to practice free-form circuit building. I doubt my first attempts will look good, so I might as well start by creating circuits around chips that are likely nonfunctional due to excessive heat used to remove them. I had the heat gun hot enough and close enough so solder melted in under 30 seconds. That heat can’t be good for the chip!

Power board ICs removed

Emboldened by success removing these little chips in short order, attention turned to the big convergence control modules STK392-110.

STK392-110 convergence control amplifiers

Sadly their big heat sinks were very good at their job of dissipating heat so I couldn’t reach melting point of solder holding them to the board. I turned to removal via mechanical means, which is a fancy way of saying “ripping that sucker out of there.” I first removed the screws fastening the heat sink to the chip, then started pulling and rocking the heat sink. The metal leg on the right side held strongly to the circuit board and broke the board. The other side, however, is different.

Power board mechanical removal

The left side of the heat sink seemed to have popped free of its leg which is soldered to board. It looks like a little drilling will be enough to intentionally separate the heat sink from its attachment bracket, and that worked to ease removal of the second heat sink.

Power board drill to separate

Once the heat sinks were removed, the heat gun could free the STK392-110 modules. I reunited chip and heatsink for whatever their future holds.

Then the heat gun were pointed at the rest of power-handling components. Transformers, rectifiers, etc. They are relatively durable components and are likely to have survived the heat of their removal if I ever dare to use them for a future project.

Power board misc parts

And here’s the aftermath: a heat-charred and distorted circuit board still home to many uninteresting resistors and capacitors. It will be dropped off at electronic recycle.

Power board back after


Sony KP-53S35 Power Amplifier Parts

A 21-year old Sony KP-53S35 TV we disassembled occupies a sweet spot for this curious electronics learner. It’s old enough that there are still discrete components we can look at, and new enough that information for those components can be found online. Here are two examples:

A Philips TDA6106Q is the most sophisticated looking component on the circuit board attached to the business end of the CRT. Datasheet says it is an amplifier, taking input voltage signal (0 to 8V) and amplifying it to a much higher voltage. (0 to 250V) It can handle signals almost up to 6 megahertz. The output pin of this chip can be traced to pin 8 of the tube. Best guess: this is how beam intensity is modulated to create a picture as the beam swept across the screen.

Philips TDA6106Q IC

Components with big heat sinks always draw attention – they tend to be the most powerful components on the board. Either because they are doing a lot of complicated work, or that they are handling a lot of power. The circuit board with the power supply and high voltage transformer also had a pair of these STK392-110 units. The fact there were only two was curious: almost everything in a rear projection television comes in threes, one for each tube, what purpose would a pair of something serve?

STK392-110 convergence control amplifiers

Looking up STK392-110 gave us the answer on both fronts: they are high power amplifiers used for the purpose of controlling color convergence. The high power (over 100W) explains the heat sinks, and convergence control explains why there’s only two of them. If we’re working to make sure all three colors converge at the same places on screen, we could leave one color alone and just adjust the other two.

This seems to be a commodity part used by many rear projection televisions, and their high power handling meant they do burn out. As a consequence there are replacement modules still available for purchase at very affordable prices. Unfortunately the market is large enough for there to be counterfeit items as well.

Lissajous Curve Is An Ideal CRT Learning Project

Lissajous curve with shorter exposure

It was satisfying to see our CRT test rig showing Lissajous curves. [Emily] and I both contributed components for this cobbled-together contraption, drawing from our respective bins of parts. While the curves have their own beauty, there were also good technical reasons why it makes such a great learning project for working with salvaged cathode ray tubes. Mainly for things we don’t have to do:

Focus: We weren’t able to focus our beam in our first work session. We couldn’t count on sharp focus so we appreciate that Lissajous curves still look good when blurry. Thankfully, we did manage better focus for better pictures, but it was not required.

Modulation: To create a raster image, we must have control over beam brightness as we scan the screen. Even if doing arcade vector graphics, we need to be able to turn the beam off when moving from one shape to another. In contrast Lissajous curves are happy with an always-on dot of constant brightness.

Deflection: To create a raster image, we’d need a high level of control over the tube’s deflection coils. We’d need to create a constant horizontal sweep across the screen, as well as scanning vertically. HSYNC, VSYNC, all that good stuff. In contrast driving deflection coils for Lissajous curves require far gentler and smoother coil changes.

Geometry: Unlike modern flat panel displays, CRT can have geometry distortions: pincushion, trapezoidal, tilt, they’re all annoying to adjust and correct in order to deliver a good raster image. Fortunately, a Lissajous curve suffering from geometry distortions still look pretty good and allow us to ignore the issue for the time being.

There is a long way to go before we know enough to drive these tubes at their maximum potential. For one thing, it is running at a tiny fraction of its maximum brightness level. The tube’s previous life in a rear projection television was a hard one, visible in the above picture as a burned-in trapezoid on its phosphor layer. Driven hard enough to require liquid cooling, it would be so bright to be painful to look at and that’s when the beam is scanning across the entire screen. A Lissajous curve covers only a small fraction of that screen area. Concentrating a full-power beam in such a small area would raise concerns of phosphor damage. As pretty as Lissajous curves are, I don’t want them permanently burned into the phosphor. But we don’t have to worry about it until we get beam power figured out.

CRT Test Rig Produced Lissajous Curves

Last night’s CRT exploration adventures with [Emily] produced beautiful Lissajous curves on-screen that looked great to the eye but were a challenge to capture. (Cameras in general have a hard time getting proper focus and exposure for CRT phosphors.) Here’s a picture taken with exposure time of 1/200th of a second, showing phosphor brightness decay in a simple curve.

Lissajous curve with shorter exposure

Due to this brightness decay, more complex curves required a longer exposure time to capture. This picture was taken with a 1/50th second exposure but only captured about half of the curve.

Lissajous curve with longer exposure

Our test setup was a jury-rigged nest of wires. Not at all portable and definitely unsafe for public consumption. It required a space where everyone present are mature adults who understand high voltage parts are no joke and stay clear. (And more pragmatically, if an accident should occur, there will be other people present to call for immediate medical attention.)

CRT Test Rig angled view

Our beam power section consisted of two subsystems. The first is a battery that supplies low power (8 volts and less than 1 watt) to heat the filament. Using a battery keeps it electrically isolated from everything else. The second subsystem supplies high voltage to drive the CRT, and we keep a respectful distance from these parts when powered on.

CRT Test Rig beam power system

Connected to the tail end of the tube is the connector we freed from its original circuit board, wired with a simplified version of what was on that board. Several pins were connected to ground, some directly and others via resistors. The two wires disappearing off the top of the picture are for the heated filament. Two wires for experimentation are brought out and unconnected in this picture. The red connects to “screen grid” (which we don’t understand yet) and the black connected to an IC which we also don’t understand yet.

This is a rough exploratory circuit with known flaws. Not just the two wires that we haven’t yet connected to anything, but also the fact when we connected its ground to transformer’s ground, the tube flared bright for a fraction of a second before going dark. We only got a dot when connecting transformer ground to the filament heater negative, which was unexpected and really just tells us we still have a lot to learn. On the upside, something in this circuit allowed our “focus” wire to do its job this time, unlike our previous session.

CRT Test Rig tube wiring

But that’s to be figured out later. Tonight’s entertainment is our beam control section, which sits safely away from the high voltage bits and we can play with these while our tube is running.

CRT Test Rig beam control system

Controlling vertical deflection is an old Tektronix function generator. This is a proper piece of laboratory equipment producing precise and consistent signals. However, its maximum voltage output of 20V is not enough to give us full vertical deflection. And since we only had one, we needed something else to control horizontal deflection.

That “something else” was a hack. The big black box is a “300W” stereo amplifier, procured from the local thrift store for $15. Designed to drive speaker coils, tonight it is driving a CRT control yoke’s horizontal deflection coil instead. It was more than up to the task of providing full deflection. In fact, we had to turn the volume down to almost minimum for tonight’s experiments. A cell phone running simple tone generator app provided input signal. Not being a precision laboratory instrument, the signal generated was occasionally jittery. But enough for us to have fun producing Lissajous curves!


Gathering High Voltage Components of Sony KP-53S35

Now that we got a blurry dot on screen of picture tubes we removed from a Sony KP-53S35 rear projection television… it is encouraging for us to keep going and see how much further we can go. There are two main avenues of investigation: (1) How to make a better and tighter beam, and (2) how to control direction of that beam.

To help experiments on making a better and tighter beam, we’re going back to the harvested pile of parts. A control box with three knobs labeled “focus” seems promising. It also has three other knobs labeled “screen” whose purposes we’re not sure about. This box had been mounted with the knobs facing forward such that a technician can access these knobs while looking at the screen.

HV Subsystem 3 - focus and screen adjust front

The back side of this box has a few wires. Most significantly, a pair of wires went to each of three picture tubes. In this picture, we still see the wire pairs for the green and blue tubes attached. The empty spots are for the red tube, removed before this picture was taken. The yellow, brown, and upper left corner black wire is unknown. The red wire in the lower left is connected to the high voltage transformer.

HV Subsystem 2 - focus and screen adjust back.jpg

Pulling the camera back shows the system in a little more context.

HV Subsystem 1 - wires

Close-up pictures were then taken for each of the three picture tube PCBs for future reference.

Our earlier experiment used a transformer purchased off Amazon intended for something else – we had hoped its voltage would be close enough, and it was. Now for the best beam we want to get the correct voltage by using the original transformer which generated the voltages for these tubes. It lives on one of the two main circuit boards that had lived at the bottom of the television. This board is where the power cord connected, so it has the power supply and everything relating to high voltage. The transform is still attached to an unit that distributes voltage to the three picture tubes.


The transformer isn’t expected to be terribly delicate, so the cheap hot air gun will be deployed. But before that, a picture of its PCB footprint was taken for possible future reference.

HV Subsystem 5 - transformer footprint



Cheap Seats At The Hot Air Gun Show

At a recent SGVTech meetup, newcomer Amir had lots to offer. One item that I picked up on was his assertion that a cheap Harbor Freight heat gun can be a low-cost alternative to fancy electronics hot air rework stations. I have one of those cheap hot air guns in my garage! Designed for home improvement projects like paint stripping, it is a big crude tool. I wouldn’t use it to assemble surface mount devices or anything I actually care about until I get a better idea of what I am doing. I’ll learn to handle it by disassembling parts that are either robust, or that I don’t care about.

The very next week, I got the chance to put that idea to the test when [Emily] and I felt inspired to try lighting up a CRT. The original driving electronics are no longer functional due to us crudely tearing them out of the TV, but the tube and a few associated accessories are still intact. To help us play with the tube, we thought it might be a good idea to remove a CRT socket to make it easier to access our tube’s pins. This is the ideal situation for testing the heat gun – a big socket should be robust enough to take the heat of a clumsily applied hot air gun much better than something delicate. This TV is also old enough to predate ROHS and lead-free solder, so we expect the solder to flow relatively easily.

I aimed the hot air gun at the solder joints at low setting. After a minute of inactivity, I turned it up to high. About a minute after that, we could see solder starting to melt. A few more seconds after that, all solder on the socket melted enough for us to remove it.

CRT socket removed from PCB

This was much faster and easier than individually undoing solder joints using a soldering iron and a solder removal tool. And the mission was successful: our newly freed socket made it easier to probe terminals and to make experimental connections with alligator clips.

CRT pin probing with socket

Old TV Picture Tubes Lights Again

When we tore apart an old rear projection television a few weeks ago, I did not expect those picture tubes would ever light up again. We took everything apart quickly within the narrow time window, so we didn’t have time to be careful to keep the electronics driving those CRTs intact. Those electronics are in pieces now, and in that writeup, I said the tubes were beautiful glass work and I hoped to display them as such in the future.

Well, there has been a change in plans.

On the same day as that teardown, [Emily] was gifted an old non-functioning camcorder. She has since taken that apart, too. The first component to see reuse was its tiny black and white viewfinder CRT. And as she dug deeper into the world of old CRTs, [Emily] came across this YouTube video by [Keystone Science] going over the basics of a cathode-ray tube and shared it with me. We were inspired to try lighting these tubes up again (without their original electronics) at yesterday’s SGVTech meetup.

The first step was to straighten out the pins at the rear end of our salvaged CRTs – they got a bit banged up in transport. A quick web search failed to find details on how to drive these tubes but probing with a meter gave us a few candidates for exploration.

Probing CRT pins

  • A pair of wires had around 8 ohms of resistance, highest of all wire pairs that gave a reading. This is likely the heating filament.
  • A few other wire pairs gave readings we didn’t understand, but several of them had some relation to a common pin. The common pin was thus our best candidate for cathode pin.

We knew the anode is connected to the side of the CRT, so now we have all the basics necessary to put a blurry dot on screen. A bench power supply was connected to the eight ohm load, and a few seconds later we can see a dull glow. Then a high voltage transformer was powered up across our anode and candidate cathode.

RPTV picture tube and transformer

After a bit of debugging, we have our blurry green dot! We proceeded to power up the other two tubes, which gave us a blue dot and a red dot. The colors look good to us, but apparently they’re not quite the right colors because during our TV disassembly we saw some color filters on the red and green tubes. (The blue tube had no color filter.)

During the course of the evening, the quality of our dot varied. Most of the time it was a blur approximately 5mm in diameter. On one occasion it bloomed out to 3cm diameter and we didn’t know what had caused it. Likewise, we had a pinpoint bright dot for a few seconds not correlating to any activity we could recall. As far as driving a CRT, we know enough to be respectful of the high voltage involved, but obviously we still have a lot more to learn. It’s just as well we don’t know how to focus the dot, because in the absence of sweep, a constant bright focused dot would likely burn a hole in the center of the screen’s phosphor layer.

A first step towards moving the beam was to put some power on the magnetic deflection yokes. These coils of wire were hooked up to a function generator, and we were able to get movement along one axis. Its maximum output of +/- 20V could only deflect a small fraction of the screen size, but it was something.

We didn’t have a second function generator on hand, but we got movement along another axis using magnets. They were taped to a shaft that was then put into a cordless drill. Holding the spinning drill near the control yoke induced movement along the other axis. Combined with the function generator, it allowed us to make a few curves on screen.

RPTV Red curves

Tinkering projects with visual results are always rewarding. With this success, there might yet be life ahead for these tubes as something other than pretty glass. A search found a hobbyist’s project to drive a CRT for an XY vector arcade monitor. That project page also linked to an excellent description of vector CRTs as used in old Atari arcade machines. Lots to learn!

Sawppy Post-Faire Cleanup

When I work on Sawppy, I test and run indoors. At DTLA Maker Faire Sawppy ran all over, both indoors and out. Most of the time people were playing with Sawppy on a piece of artificial turf at Maguire Gardens. This is an outdoor space where people would walk their dogs, raising obvious sanitation concerns running Sawppy on my home carpet after the event.

Well, after a long day of work, who doesn’t enjoy kicking off their shoes and soaking their feet? I could give Sawppy the same royal treatment. All six wheels were removed and soaked in a tub filled with a mixture of water and household bleach. A retired toothbrush was used to scrub off dirt particles clinging to the wheel. Hopefully this removed most of the contaminants Sawppy might have picked up during the event.

Sawppy kicks off shoes

It was also a good time to perform an inspection to see how Sawppy held up mechanically. In addition to the set screw mentioned yesterday, a few chassis mounting screws have fallen out and need to be replaced. I designed plenty of redundancy in these mounts so there was little risk of Sawppy falling apart.

Sawppy lost fasteners

After a few hours of soaking, the wheels were hung up to dry like old socks. What has six rover wheels but is not a rover? This laundry rack.

Sawppy laundry

(Cross-posted to

Sawppy at DTLA Mini Maker Faire

Yesterday Sawppy went on an adventure to the downtown Los Angeles Mini Maker Faire. There Sawppy found a receptive and appreciative audience. There were a lot of enchanted kids, interested parents, and other makers who might be building their own Sawppy rovers.

The morning started out with Sawppy sitting on a table alongside a few different builds of JPL open source rover. Eric’s build is on the left in black and white, Santa Susana High School build is on the right with purple printed parts.

Taking Sawppy around and talking to individuals about Sawppy was a lot of fun and something I’ve done in other contexts before. I have hopes for a few of the contacts to develop into something cool for Sawppy’s future. What’s new this time was that I also signed up to give a short 15-minute presentation about Sawppy and that took more work and preparation. Thanks to the 2-minute “lightning talk” opportunities at Hackaday LA the past few months I’m less nervous about public speaking than I used to be, but I still got pretty stressed about it. I’m sure it’s a matter of practice and the more I can take advantage of such opportunities the better I’ll get.

Roger Sawppy

Outside of the presentation, Sawppy and I spent most of our time on the astroturf across the walkway from the officially assigned display area. It was a hilly part of the park which meant there were no tables or booths set up there, and it was a good place to demonstrate rover suspension in action. I had a spare phone set up to be Sawppy control and handed the control to anyone who wanted to pilot Sawppy for a bit.

Sawppy on lawn.jpg

Most were content to run around the turf. Some of the little ones tried to run Sawppy into their siblings. A few ran into the bushes beyond the turf for a more rugged demonstration of Sawppy chassis. A perpetual favorite is to have Sawppy climb over shoes.

Sawppy running over feet

Thanks to refinements to improve robustness over the past few months, Sawppy came out of the experience with only a slightly wobbly left rear wheel that was easily repaired by tightening the set screw on the left rear steering servo coupler. A great improvement over earlier outings!

(Cross-posted to

Xbox 360 Steering Wheel Teardown

I just bought the top-of-the-line Xbox One X in order to play Forza Horizon 4 in 4K HDR. I’ve also reclaimed my old Xbox 360 Halo 4 Edition, which I loaned out to a friend’s family but the children had lost interest in the older console. I got the console itself back, plus my old game library and all accessories. This all started when I went looking for my old Kinect sensor bar, but that’s a story for another time.

Physically, the biggest thing in this package was the Xbox 360 Steering Wheel. Built to offer realism through force-feedback and take severe physical punishment, it was big and beefy and takes up entirely too much space. A problem that almost certainly drove its retirement and replacement by a much smaller controller. Since it is not compatible with my new console, where I can play all four Forza Horizon games, I see no reason to keep it around in running condition.

Which means it is time for some fun!

I brought it to our weekly maker meetup where we can tear into this relic of the past. The big wheel is set aside for now.

Xbox 360 Steering Wheel 1 - wheel intact

We’ll start with the pedals. These are designed to sit on the floor and take the force of frantic game players stepping hard on them. They are made of extremely sturdy plastic with surprising heft.

Xbox 360 Steering Wheel 2 - pedal intact

It was straightforward to open up, where we can see it is fairly simple inside.

Xbox 360 Steering Wheel 3 - pedal open

All the force gets dissipated by heavy duty springs and metal brackets into the beefy plastic, leaving only the rotational motion to be read by simple position encoders which are likely just inexpensive potentiometers.

Xbox 360 Steering Wheel 4 - pedal electronics

That done, we start tearing into the wheel itself. Most of the visible screw holes are at the bottom, where it is curved to fit on our laps. Unlike the pedal unit, these screws are “security screws” with a post in the middle of the Torx shaped fastener. It proved to be a minor annoyance but easily overcome with brute force as we don’t care about putting it back together.

Xbox 360 Steering Wheel 5 - wheel lap mount

After the “lap desk” layer was removed, we repeat the process for the actual enclosure.

Xbox 360 Steering Wheel 6 - wheel enclosure

A lot of destroyed fasteners and plastic later, the innards of the steering wheel is visible. As expected, it is mostly empty space. To the left is a control board with three wire bundles leading to the rest of the wheel. There’s one controlling the motor to provide force feedback, one to a sensor to read steering wheel angle, and a wiring harness going through the center of the steering shaft to the wheel-mounted controls.

Xbox 360 Steering Wheel 7 - wheel innards

Here’s a closeup of the force feedback motor and gearbox. Mechanically, this area takes the brunt of forces players would apply to the steering wheel. So I expect I can reuse this robust assembly in a physically demanding project in the future.

Xbox 360 Steering Wheel 8 - ffb gearbox

However, it proved to be tricky to remove. The four obvious screws release the metal plate, but that is only part of the assembly. There had to have been fasteners coming in the opposite direction, but none were clearly visible. By process of elimination, we eventually figured out the screws were hidden under a stealthy sticker that matched its surrounding color and shape so well we didn’t realize it was a sticker.

Xbox 360 Steering Wheel 9 - cleverly hidden screws

After that discovery, it was trivial to remove the motor gearbox assembly.

Xbox 360 Steering Wheel 11 - ffb gearbox extracted

The main board was also removed for examination. The electronics people in the room looked over the board and noted the main processor has a Microsoft logo on it. We had expected to find name and designation for a microcontroller we might reprogram, but this is a custom chip.

Xbox 360 Steering Wheel 10 - mainboard

Teardown proceeded to the wheel unit itself, where we found another surprise: The big motor isn’t the only one providing tactile feedback. The bottom left and right corners of the steering wheel also housed vibration motors.

Xbox 360 Steering Wheel 12 - wheel vibration motors.jpg

The two motors appeared identical, but they had different sized weights affixed to their output shafts to produce different tactile sensations for users’ palms.

Xbox 360 Steering Wheel 13 - wheel vibration motors extracted

The shifter paddles in the back of the wheel also had to take some punishment, as people can pull on those pretty hard. Again, a lot of mechanical design dissipated any over exuberant energy into sturdy plastic pieces and metal springs, leaving just a simple mechanical motion to press on small push buttons on the back side of the wheel circuit board.

Xbox 360 Steering Wheel 14 - paddle shift buttons

Remainder of the in-wheel PCB was unremarkable with standard buttons.

Xbox 360 Steering Wheel 15 - wheel PCB

The physical wheel we hold in our hand, however, was interesting. Its weight led to speculation that it might have metal weights inside or possibly be formed from a steel tube. We put it through a metal-cutting bandsaw and found that it was solid heavy plastic all the way through. Three layers are visible: The crudely formed center (dark gray) which is likely just a C shape. Then a more precisely formed plastic layer was formed over it (lighter gray) which probably also formed the center of the wheel housing all the buttons and PCBs. Then finally, a soft rubbery rim was formed over that, with a dimpled texture for grip.

Xbox 360 Steering Wheel 16 - solid rimThis steering wheel controller was a lot of fun in its prime. It felt great in the hand making its best effort at realism. The robust construction took all manners of abuse (from children and grownups alike) without any sign of damage. This wheel was definitely not flimsy! I appreciated seeing all the work that went into making such a robust gaming peripheral.

Now all the potentially reusable parts like motors, springs, gearboxes, and electronics have been harvested and put away, consuming far less storage volume than the entire wheel and pedal assembly. The remaining (beefy) plastic is on their way to a landfill.

A Photo Studio Under The Desk

A conversation about Pixelblaze digressed into photography and how I had taken some of the pictures I used. Some on this blog, some on, and some elsewhere. It was a quick little project and today I’ll walk through it, illustrated with some pictures.

The problem I wanted to solve is one shared by many other makers: how to take good pictures to show off projects to the world. The dream solution is to have a full-blown photo studio where I have control over lighting. Cast on a neutral backdrop so all the focus is on the subject, free of background distractions. In reality, few of us can set aside the room required by a serious photo studio. Especially makers: every square foot consumed by a photo studio is a square foot not used for making!

My solution was to put a tiny photo studio under a computer desk. Most of the time the desk will be used for normal desk duties, home of my Luggable PC among other equipment. When I sit at the desk, I put my legs under the table.

Under Table Photo Studio 1 - Computer desk

Aside from the curtain rods sticking conspicuously out the side, all the elements of my tiny photo studio can be stowed out of the way. The white fabric is a curtain from IKEA, mounted to the rod closest to the camera and draped over the far side rod.

Under Table Photo Studio 2 - Stowed with chairs

Bolted under the desk is a cheap LED light fixture from Costco. The segment of curtain draped between the two rods serve to diffuse light from this fixture.

Under Table Photo Studio 3 - light fixture

The curtain rods are suspended under the table using simple 3D-printed brackets held onto existing table leg brackets.

Under Table Photo Studio 4 - curtain rod bracket

When it’s time to take some pictures, the chairs are moved out of the way.

Under Table Photo Studio 5 - stowed no chairs

A few magnets salvaged from hard drives hold folded-up fabric to the far side table leg brackets. Moving magnets aside allows the extra fabric to drop to the floor. The segment of curtain between the far side rod and the floor serve as the backdrop.

Under Table Photo Studio 6 - released

Remainder of the curtain can now be unfurled to serve as the photo studio floor. Sometimes I take the few minutes necessary to smooth wrinkles out of the fabric, sometimes I don’t.

Under Table Photo Studio 7 - unfurled

When the light fixture is turned on, it’s showtime!

Under Table Photo Studio 8 - lights camera action

This little photo studio under the computer desk is where I took most of the pictures illustrating Sawppy assembly. The animated GIF illustrating Luggable PC Mark I assembly. Plus many other pictures on this blog, most recently the picture of Supercon goodie bag contents.


Fun With Tiny CRT

When we took apart the big old rear projection television, the same family also had an old VHS camcorder from the 1980s slated for disposal. [mle_makes] took it off their hands and merrily started taking it apart for fun components. First component to be brought to our weekly SGVHAK meetup was the viewfinder’s tiny CRT. I brought the box of Sony KP-53S35 salvaged RPTV parts on the same day so we could place the two picture tubes side by side with a ruler between them.

Tiny CRT 1 - Side by side with RPTV tube

While the big tube had 21 years of TV watching burned in to the surface, the little CRT looks to be in good shape. (Also, the RPTV tube was likely driven far harder to generate the necessary brightness.) And since the little tube was part of a battery-powered device (12 volt lead-acid!) the picture tube flickered to life with a DC power supply.

Viewed from the top, we are reminded how much of a space savings modern LCDs gave us. Both of these tubes are far longer than their picture’s diagonal size.

Tiny CRT 2 - Length comparison with RPTV tube

The little tube’s image was remarkably crisp and bright when viewed in person, a fact extremely difficult to capture in a photograph. The 525 scan lines of a NTSC signal meant this little tube was pushing 600 dpi of resolution!

Tiny CRT 3 - tape measure

All of these images on the tube were generated from an old video conference camera, which had a composite video output port that was wired to the tube’s control board. Here’s one of the test setups, using a scrap piece of paper and a simple smiley face drawn on it with a Sharpie marker.

Tiny CRT 4 - camera test setup

The best picture taken of the tube was when I narrowed the aperture to get a longer field of depth, so the camera is free to focus on something other than the actual picture and still get halfway decent results. (I think it is focused on the edges of the glass here.) An admirable amount of paper texture was conveyed on this tube.

Tiny CRT 5 - camera test image

A few weeks after this initial tiny CRT demo, it became the centerpiece of this Freeform Mini CRT Sculpture on

My Volt Was A Good Car, But I Do Not Miss It

This week General Motors put out a press release full of corporate euphemisms that boiled down to this: several car models that aren’t selling well enough are getting axed. The press release was careful not to use the word “layoff” but it’s hard to imagine that workers will continue to be paid if there are no cars to be made. Obviously this got a lot of people upset, especially in light of the 2008 government bailout and more recent corporate big tax breaks. But here I’m going to focus on one specific car: the Chevrolet Volt.

The Volt was still in development when financial markets melted down in 2008. It expressed a potential high-tech future for General Motors. I saw it as one of the most convincing arguments against the “let GM die” school of thought. It was a much more interesting piece of engineering than what was found in a Toyota Prius and a sensible stepping stone on the transition to an electrified future for cars. And putting my money where my mouth was, I signed for a 2012 Chevrolet Volt on a three year lease. I took this picture when I took delivery, a day after Christmas 2011.

Roger Leases 2012 Chevrolet Volt

For three years it served as an efficient commuter vehicle taking me to and from work and everyday errands. The gasoline-fueled electric generator meant I could take it out on a few road trips and not worry about being stranded by lack of charging. 75% of its 30,000 leased miles were powered by electricity, a hearty endorsement of the “Voltec” architecture that maximized advantages of an electric power train using a minimally sized battery pack.

When my lease expired in December 2014, a Volt was at the top of the list if I needed another commuter car. But circumstances never motivated me to get another, and now it is likely I never will.

But I think that’s perfectly OK. Why?

First: the Volt was always designed to be a transition from gasoline to electric propulsion. It more than met its objectives, exceeding my expectation in many ways. But time moves on and that electric future is here. If I were to get a commuter car in the final days of Volt production, it would be evaluated against all-electric vehicles. Including the Chevrolet Bolt, which incorporated many of the lessons GM learned from making the Volt.

Second: the Volt was a sensible efficient commuter vehicle, not one to stir emotion or attachment. It handled far better than any Toyota Prius I’ve rented, but nowhere near the fun of my Mazda RX-8. When I returned the car at the end of my lease, I set down the keys, signed the paperwork, and walked away without looking back.

It was a good car that made sense for its time. It did its job reliably and efficiently, and I couldn’t ask for more from a commute appliance. But its niche is shrinking. So despite how bad the decision might look to history, GM made their business decision to look forward.

Amazon Machine Learning School Now Open

AWS logoWhen I was learning about artificial intelligence in school, knowledge was found in the form of advanced textbooks and academic journals. It takes a certain amount of dedication to understand and digest that information. Now, a few decades later, leading edge research can be found on the internet. But even better: many educational resources for people outside those academic fields of study are also available online.

These resources have just grown again, as Amazon opened up their AWS Machine Learning course to the world. Formerly a part of internal employee training, it now helps people get up to speed outside the company as well. (And naturally help convert them to become paying AWS customers.)

There are different courses for different audiences, from developers to business professionals. And they cover different parts of AWS services. When I get around to taking these classes (the to-do list never seems to grow shorter…) I’ll likely dive into the developer track for visual recognition algorithms. If I feel good about my grasp of the code, I’ll see if I can integrate an Amazon DeepLens unit into my robotics projects.

This set of AWS courses is the latest addition to a long list of web-accessible resources for learning latest tools for AI. It’s great that I don’t need to enroll in school to see how the field has evolved since the time I was at UCLA.

Sawppy Will Be At DTLA Mini Maker Faire

The Downtown Los Angeles (DTLA) Mini Maker Faire, hosted at the Los Angeles Public Library central location, is coming up this weekend and my rover Sawppy will be among the many maker projects at the event.

DTLA Mini Maker Faire Website

Sawppy will be one of several rovers present. JPL’s Open Source Rover team should be there with their original build, SGVHAK will be there with the beta build rover I contributed to, which inspired my Sawppy and they’ll all be hanging out together.

The JPL team will also be giving a brief presentation in the KLOS Children’s Theater upstairs about their rover project, followed by an even briefer presentation by me on building Sawppy. Both of these talks are listed on the workshop schedule though (as far as I know) there is no hands-on workshop activity planned. Sawppy will be present and running for people to see up close, but no assembly (and certainly no disassembly!) is planned. I may bring an extra corner steering unit for people to play with, and they’ll be welcome to take that apart and put it back together, but not much beyond that.

(Cross-posted to

Highland Park Railroad Open House

HPRR01 - WelcomeHighland Park Society of Model Railroad Engineers is my local railroad club. I appreciate the detailed work that goes into a model railroad layout but I haven’t decided to spend the time and money required to do a good job at it myself. Still, when they hold an open house, I go and admire the work they’ve put in. This is a train layout that has been worked on by club members for most of the last seven decades!

The club house appears to be literally a house – a former residential building that has now been completely taken over by the club. Roughly half of the available square footage inside are train tracks, with the remainder used for support equipment, workshops, and general club space.

HPRR02 - Layout Partial

“Does your train of thought have a caboose?” Generally speaking… mine do not.

HPRR03 - Safety and Caboose

The general theme is 1940s-1950s America, conveniently covering the final transition period from steam locomotives to modern diesel electric and all electric trains. Since this club is in the Los Angeles area, there are trains inspired by local history, like some Red Cars.

HPRR04 - Red car

A scratch built reproduction of Angel’s Flight climbs the side of a mountain rather being in the middle of a city like the real thing.

HPRR07 - Angel's Flight

A steam locomotive was set up as if it’s on museum display.

HPRR08 - Highland Pacific locomotive display

And behind the museum piece, an impressive train station.

HPRR09 - Union Station

One of several train yards in the layout, anchored by a big turntable.

HPRR11 - Turntable

Another train yard featured a group of train enthusiasts taking pictures. I wonder if the figurines are modeled after specific members of the club who would go on such trips.

HPRR15 - Train phtographers

Many little towns dot the layout.

HPRR16 - Town

Some of the town buildings have storefronts inside.

HPRR17 - Town detail

This bridge painting crew is having a bad day.

HPRR12 - Bridge painters

Locomotives running on the layout are under command of train engineers at these stations, coordinated by a dispatcher.

HPRR10 - Train engineers

Behind the scenes, a massive panel of relays manage the layout.

HPRR05 - Relay panel

Wire-wrapping was already a technology on its way out when I started learning electronics, but given the age of the club, it’s not surprising that some wire wrapping is still present.

HPRR06 - Wire wrapping

The power conversion and distribution panel.

HPRR14 - Power supply

Venturing underneath the train tracks is not for the faint of heart or the easily confused, but it’s far more spacious and less cluttered than I had expected.

HPRR13 - Underneath

One of the many objectives of the open house is to recruit new members to the club. While I’m very appreciate the work, I think I’ll stick with software and robots rather than get into model trains.

Still, I’ll probably stop by on the next open house.

Sony KP-53S35 Teardown

SonyTD 01 - Final serviceThis Sony KP-53S35 rear projection television is over 21 years old and we’re going to pull it apart. The aim is to get parts for future projects that are difficult (or unreasonably expensive) to buy on their own. Plus a few auxiliary items because it’s easy to get them at the same time. The “shopping list” sorted by size are:

  • A large Fresnel lens that’s a core part of the main screen.
  • The large front-surface mirror reflecting picture onto screen.
  • Lens assemblies on picture tubes.
  • Speakers.
  • Caster wheels.

SonyTD 02 - Tag.jpg

Since this might get messy, the doomed TV was moved out to the driveway for dissection. The rear service panel is the obvious place to start. [mle_makes] has taken apart many RPTVs and was recruited as expert guide to the process. [amybaldwindev] has not taken many things apart before and is here to learn.

SonyTD 03 - Back panel

With the service panel removed, we can see the heart of the TV: picture tube and electronics driving them. The rest of a RPTV is basically empty space.

SonyTD 04 - Back panel removed

Next to be removed was the large rear mirror. I was a little disappointed to find this was an ordinary rear-surface mirror, not a front-surface mirror as I had hoped for. Still, it has many future project possibilities.

SonyTD 05 - Mirror removed

The largest two circuit boards were mounted on a tray that could slide out for servicing, giving us a better look at the heart of the machine. Aside from some beefy-looking heat sinks, there is little desire for whatever’s on these non-HDTV circuit boards. They’ll be stashed away and likely disposed in electronics waste disposal in the future.

SonyTD 06 - Tubes and electronics

Old age made the circuit boards uninteresting, but old age made the picture tubes novel. They were removed next, and their focusing lens assemblies removed.

SonyTD 07 - Tube lens removal

With the lens assemblies removed, we can see the picture tube behind a liquid cooling assembly. We knew to expect three tubes: one each for red, green, and blue. And it wasn’t too surprising to see color imparted by colored lenses. What’s puzzling is the fact the red and green tubes got colored lenses…. but the blue one did not. Do these tubes emit blue by default?

SonyTD 08 - Tube no lens front

The three tubes are different in other ways: The red and green tubes had an extra circuit board on their control yokes, but the two boards are clearly different. In contrast, the blue tube had no circuit board on its control yoke at all.

SonyTD 09 - Tube no lens rear

Here’s how the three tubes (and their control yokes) were mounted in the case, which may be useful if they are to ever light up again.

RPTV Picture tube and coil orientation

The coolant (most likely ethylene glycol) in the chamber in front of all three tubes were drained into a glass jar for safe disposal. (Or potential reuse.) Once drained, the cooling assembly was removed to expose the picture tube face. Visible on each face is a burned-in rectangle representing 21 years of TV watching. Due to the geometry of the optical path, the tubes on either side had a trapezoidal pattern (visible here) and the center tube has a rectangular pattern.

SonyTD 10 - Tube burn in

These large powerful high-voltage tubes are not going to be used for their designed purpose in the future, but the glass work is beautiful and I hope to find an aesthetic way to display them. All the components were stripped off the glass vessel.

SonyTD 11 - Bare tube

It’s a bit of a shame, as the wiring in the control yoke has aesthetics of their own.

SonyTD 12 - Control yoke

With all the components packed away, it was time to break down the cabinet. It is mostly built from injection-molded polystrene and should be recyclable.

SonyTD 13 - Plastic frame

This is where a reciprocating saw (the Harbor Freight knockoff of a Sawzall) became very handy.

SonyTD 14 - Breaking down

At the end of the day, a big bulky RPTV has disappeared. Its desirable components were packed for reuse, hazardous components were packed for safe disposal, and the remaining cabinet pieces broken up for household waste/recycling.

Yet to come: giving these salvaged parts new life.

Entering the Wide World Of ESP32

Espressif Logo

As a thanks for participating in the ESP32 mesh network project by Morgan and Ben, people whose badges became nodes on the network were generously gifted the ESP32 module mounted to each of our badges. Unfortunately, I managed to damage mine before the big stage demo so sadly I didn’t put in the honest work to earn that ESP32. Still, I now have a damaged ESP32 that I can try to fix.

Before I start trying to fix it, though, I should have a better idea on how to tell if a ESP32 is up and running. The only mechanism I had before was to run the badge mesh network app and see if there’s any response, but I want to know more about how a ESP32 works in order to better tell what’s broken from what’s working. Also – since I’ve desoldered my ESP32 from the carrier board, it is not nearly as easy to test it against the badge.

I’ve read about a lot of projects built using the ESP32 on Hackaday, so I know it’s popular for and it would be cool to add it to my own project toolbox. Given its popularity, I thought it wouldn’t be a problem to find resource on the internet to get started.

I was right, and wrong. There is no shortage of information on the internet, the problem is that there’s too much information. A beginner like myself gets easily disoriented with the fire hose of data presented by

Do I start with Espressif’s own “ESP-IDF” development framework?

Do I start with an Arduino-based approach to ESP32 development?

Do I start with Amazon’s tutorial for how to use an ESP32 with AWS?

How about other individual tinkerer’s adventures on their own blogs? Here’s one person’s initial report poking around an ESP32, including using an oscilloscope to see how quickly it can change output based on input. And here’s another Hello World, and there are many more blogs covering ESP32. (Soon including this one, I suspect.)

It’s going to take a while for me to get oriented, but it should be fun.

Adafruit Feather System

I received a Adafruit Hallowing in the Supercon sponsor gift bag given to attendees. While reading up about it, I came across this line that made no sense to me at the time.

OK so technically it’s more like a really tricked-out Feather than a Wing but we simply could not resist the Hallowing pun.


I can tell the words “Feather” and “Wing” has some meaning in this context that is different from their plain English meaning, but I didn’t know what they were talking about.

But since this is Adafruit, I knew somewhere on their site is an explanation that breaks down whats going on in detail. I just had to follow the right links to get there. My expectations were fully met – and then some – when I found this link.

So now I understand this is a counterpart to the other electronics hobbyist programming boards and their standardized expansion board form factor. Raspberry Pi foundation defines their HAT, Arduino defines their Shield, and now Adafruit gets into the game with feathers (a board with brains) and wings (accessories to add on a feather.)

Except unlike Raspberry Pi or Arduino, a feather isn’t fixed to a particular architecture, or a particular chip. As long as they operate on 3.3 volts and can communicate with the usual protocols (I2C, SPI), they can be made into a feather. Adafruit make feathers out of all the popular microcontrollers. Not just the SAM D21 at the heart of Hallowing, but also other chips of the ATmega line as well as recent darling ESP32.

Similarly, anyone is welcome to create a wing that could be attached to a feather. As long as they follow guidelines on footprint and pin assignment, it can fit right into the wings ecosystem. Something for me to keep in mind if I ever get into another KiCad project in the future – I can build it as a wing!


V-USB For Super Basic USB On AVR Chips

One of the gifts to Supercon attendees was a Sparkfun Roshamglo badge. While reading documentation on writing software for it, one detail that stood out about this Arduino-compatible board was the lack of a USB-to-serial bridge. Such a component is common on Arduino boards. The only exceptions I’m aware of are the Arduino Leonardo line using the ATmega32u4 chip which has an integrated USB module.

The ATtiny84 on the Roshamglo is far too humble of a chip to have an integrated USB functionality, so that deviation from standard Arduino caught my interest. In fact, not only does the board lack a serial-to-USB bridge, the ATtiny84 itself doesn’t even have a UART peripheral for serial communication with a serial-to-USB bridge. Now we’re missing not one but two things commonly found in Arduino-compatible boards.

What’s the magic?

vusb-teaserThe answer is something called V-USB, a software-only implementation of basic USB fundamentals. It is not a complete implementation, most notably it does not handle all the error conditions a full implementation must gracefully handle. But it does enough USB to support the Micronucleus boot loader. Which creates a very basic way to upload Arduino sketches to an ATtiny84 without an USB serial interface engine (SIE), or even a UART, on the ATtiny84 chip.

Yes, it requires its own custom device driver and upload tool, but there are instructions on how to make all that happen. The point is minimizing hardware requirements – no modification on the host computer, and minimal supporting components for the ATtiny84.

It looks like a huge hack, and even though SparkFun cautions that it is not terribly reliable and won’t work on every computer, it is still impressive what the V-USB people have done under such limits.