Notes on Siglent SDS1104X-E Oscilloscope User’s Guide

I have some basic ideas on how to use an oscilloscope, but I’ve never had one of my own until I bought one during this year’s Amazon Prime Day sale. Given its complexity and cost, I thought it would be a good idea to invest some time into Reading The Fine Manual. This did not start well, as there was only a Quick Start Guide in the box, featuring this particular gem:

These symbols may appear on the product: (But we won’t tell you what they mean!) Thanks, guys. Despite such minor mistakes, the quick start guide seems fine if perfunctory. I was moderately annoyed that they used the same manual for two-channel and four-channel versions of this scope, so I would occasionally look at something that made no sense until I realize it was about the two-channel. That annoyance aside, I learned valuable things like adjusting probe compensation as part of unpacking and initial setup (they were all slightly under-compensated but easily resolved with the procedure) but most of the other descriptions assumed I already knew how to use an oscilloscope. I was worried until I saw a note saying I could find more information in the User Manual.

Okay! A real User Manual exists, even if it isn’t in the box. I went hunting online and found my answer on Siglent NA (North America?) document repository where I could find the User Manual (and many other guides) in PDF format under the SDS1000X-E-Series section. It has the same annoyance of using one manual for both 2- and 4-channel versions, but now with a lot more useful detail.

  • One valuable thing I learned and need to keep in mind is that most knobs on this oscilloscope are like the quadrature encoder knob I took apart: there is a button press in addition to rotation. If I’m poking around looking for a feature, it might be a knob press.
  • I like the idea of the “Auto Setup” button. It is advertised to looks at the channel’s signal and choose an appropriate vertical and horizontal scaling. Sounds like a counterpart to “auto ranging” capability on a multimeter, I hope it will turn out to be as useful as it sounds.
  • These scopes came with probes that have a switch to toggle between 1X and 10X attenuation. It appears the probe has no way to communicate its current setting to the scope, I have to tell the scope. Something to keep in mind and check when things make no sense.
  • When I zoom out to a longer timescale, there’s a threshold where the cheap DSO-138 would automatically switch to showing data in a horizontal scrolling display. After reading this user’s guide I know it is called “Roll Mode” (Page 34) here and it’s something I can choose to toggle on/off with a button, independent of timescale.
  • I frequently try to adjust display timescale on the DSO-138 so I could zoom in and out to look at various features. Now, I have an actual zoom function (page 35) so I can keep the longer timescale waveform on screen simultaneously with a short timescale subset of the same wave.
  • DSO-138 would frequently fail to show fast blips. If I need to see peaks of very brief signals, I can choose to display “Peak Detection” mode. (page 46).
  • Typically having multiple channels mean multiple lines all graphed against time, but setting “Acquire” to “XY” (page 49) allows graphing one channel versus another instead of time. There will be some vector graphics fun with Lissajous curves in the near future.
  • It seems like half of the manual goes into depth on what each of the trigger modes do. I will need to re-read this section several times. Eventually I should be able to recognize which situations are best fit for certain trigger modes.
  • I was very excited to read about Video Trigger: it sounds like the oscilloscope knows what NTSC composite video signals should look like and can trigger on specific parameters or fields. Once I master this mode, I foresee it becoming extremely valuable for debugging my ESP32 composite video output library.
  • I had no idea “Measurements” (page 130) are something oscilloscopes can do now. So instead of reading the screen to see how much time is represented by an on-screen grid division, and calculating the period of a waveform, and from there calculating the frequency… now the scope has measurement tools to do all that math for us. Wow, fancy!

Judging by what I’ve learned from this User’s Guide, I’m very happy with the potential usefulness of my oscilloscope purchase. I hope it will prove to be actually useful as I learn to harness its abilities.

Finally Bought a Real Oscilloscope

An oscilloscope has been on my workbench wish list for years. I had been limping along with a degraded DSO-138 kit, occasionally wishing for something with more channels, or more bandwidth, or just the ability to measure voltage levels accurately. The key word being occasionally. I haven’t felt that I would use an oscilloscope enough to justify the expense. But when this year’s Amazon Prime Day rolled around, the memory of deciphering multi-channel signals was fresh on my mind, and I clicked “Buy” on a Siglent Technologies SDS1104X-E Oscilloscope. (*)

I had actually been eyeing a Rigol DS1054z(*), which had become a very popular entry-level oscilloscope for hobbyists. It is sold far and wide including my favorite vendor Adafruit, and its popularity meant plenty of online resources. From basic beginner’s “Getting Started” guides to hacks for unlocking features. Ah yes, those features. They were a big part of why I hadn’t bought the Rigol: it really sours me on a company when they would hold features for ransom even though all of the hardware is already present. Sure, I could visit questionable websites and generate codes to unlock those features without paying for them, but just the idea of buying from a company that would do such a thing turned me off.

While the Siglent oscilloscope did have a few paid upgrade features, they all involved additional hardware not already onboard. This made the concept more palatable for me. For reference, they were:

  • WiFi capability. The scope comes with an Ethernet port for network connectivity. Wireless comes at extra cost for the software upgrade in addition to the cost of a supported wireless adapter. I prefer wired Ethernet so I did not care.
  • AWG (arbitrary waveform generator) capability requires extra hardware in the form of Siglent SAG1021I. (~$175 *) So far, my waveform generation needs have been very basic. So basic, in fact, that I wrote a HTML app to cover my needs. I don’t think I’ll miss this feature.
  • MSO (multi-signal oscilloscope) capability requires a Siglent SLA1016 (~$330 *) which adds sixteen additional digital channels for logic analysis. Between the four channels already on board the oscilloscope (which already has logic analyzer functionality without paying to unlock as would a Rigol) and eight channels on my Saleae, I think I’ll be fine without the MSO add-on.

One thing that made me frown was that the AWG and MSO addons connect by something Siglent called “SBus”. Proprietary expansion ports are nothing new, but they chose to use a HDMI connector for the purpose. With a warning that plugging in actual HDMI devices would damage the oscilloscope. Gah! I see the economic advantage of using an existing high bandwidth connector already produced at high volume, but the resulting user experience sucks. Since I don’t plan on making any SBus upgrades, I will try my best to ignore that not-HDMI port.

This oscilloscope cost more than a Rigol DS1054z, though it is technically cheaper because many of Rigol’s paid add-ons were on the Siglent without extra charge. The Prime Day discount closed the price gap enough for me. Once it arrived, I dug into the manual eager to learn about my first real oscilloscope.

(*) Disclosure: As an Amazon Associate I earn from qualifying purchases.

Windows SFC (System File Checker) Revived Explorer

On a computer running Microsoft Windows operating system, the executable application explorer.exe is very important. It handles the start bar and is the starting point for almost every activity on the system. Its core position means if Explorer breaks for any reason, it’s very hard to do anything else on that system! Yet its complexity and wide span of responsibilities also means having wide exposure to things that go wrong. Countering this risk, Explorer has recovery measures built-in as well. If it freezes up, there’s a watchdog time to restart the process. If it should crash, there are mechanisms to relaunch it. And if the relaunch immediately leads to a problem, it relaunches with gradually decreasing capability until it finds a configuration that is stable enough for the user to go in and figure out what went wrong.

This happened to my Windows machine. Something went wrong and Explorer went into a failing loop that restarted once every 10-15 seconds. This continued for several minutes (Explorer restarting a few dozen times) until it stabilized in a very reduced configuration that was unfortunately pretty difficult to use. The Start menu is missing, but at least Window+E shortcut key still worked to open File Explorer. That allowed me to launch diagnostics tools, though I had to use my phone to search for their paths on the system so I could find them in File Explorer.

The first stop to diagnose Windows problems is the Event Viewer, which I had to launch from File Explorer by double-clicking C:\Windows\System32\eventvwr.exe. Clicking the root node in the tree “Event Viewer (Local)” will show a summary of events. My system showed over four hundred “Error” events in the past hour, an obvious place to start looking. Expanding that tree took me to a list of those hundreds of Application Error logs, here is one example:

Unfortunately, the details of this Application Error were not scaled for high DPI displays and pretty unreadable in that screenshot, so here is a copy of the text shown inside that “General” tab:

Faulting application name: explorer.exe, version: 10.0.22000.832, time stamp: 0x8947d46c
Faulting module name: wintypes.dll, version: 10.0.22000.778, time stamp: 0xb903efeb
Exception code: 0xc0000005
Fault offset: 0x0000000000022b20
Faulting process id: 0x1f44
Faulting application start time: 0x01d8b13598ecfee1
Faulting application path: C:\Windows\explorer.exe
Faulting module path: C:\Windows\SYSTEM32\wintypes.dll
Report Id: d0fb6df2-0bad-45bd-aff3-dee9c438b3d2
Faulting package full name: 
Faulting package-relative application ID: 

Looks like explorer is pointing a finger at its dependency wintypes.dll. Unfortunately, there isn’t enough data here to tell us if the problem is in wintypes itself or a dependency in turn. But at least it is a narrower scope than explorer, whose scope covers damned near everything. A search for “wintypes corrupt” found many websites advertising “Download wintypes to fix your system!” But downloading replacements for Windows system executables off the internet is a recipe for security disaster and I’m not going to do that. There were a few promising diagnostics steps, the one that was eventually successful was this Microsoft community forums thread.

The repair procedure was to first run the Deployment Image Servicing and Management tool (DISM) to ensure my system has a valid copy of the system image. Followed by running the System File Checker tool (SFC) to scan through my Windows system files. SFC will compare what’s on my system against the system image archive. If a mismatch is found, SFC will replace the corrupted file with a clean copy from the system image. These are system-level administrative tools. In order to run them, I had to launch an administrator command prompt from File Explorer. (Right click on C:\Windows\System32\cmd.exe and select “Run as administrator”)

It took several minutes for those tools to complete. After SFC reported scan and repair was complete, I rebooted my system. And this time, Windows explorer started with full functionality. Success! I went back to take a look at the log file (C:\Windows\Logs\CBS\CBS.log) and searched for mentions of “repair”. I found these two lines:

2022-08-15 23:15:56, Info                  DEPLOY [Pnp] Corrupt file: C:\Windows\System32\drivers\bthmodem.sys
2022-08-15 23:15:56, Info                  DEPLOY [Pnp] Repaired file: C:\Windows\System32\drivers\bthmodem.sys

Huh. The Bluetooth communications driver caused me all this grief? It is indeed part of my Windows system, because I’ve been playing with Microsoft Phone Link and it connects to my Android phone over Bluetooth. I didn’t think a problem with this file would bring down Explorer, but now I know it can. I also don’t know how this file got corrupted to begin with, and that might be important to know if it should happen again. For now, I’m happy my computer is back up and running.

Cutra Wondercutter S Is Expensive but Also Really Cool

Cutting apart a well-sealed Makita battery cartridge was a big milestone for my Cutra Wondercutter S purchase. It was the first big project that would have been unreasonably difficult to do with any of the other tools I have on hand. With this milestone, I am confident the tool has a unique niche. Does it justify the cost? That’s a harder question whose answer will depend on usage and budget.

I bought my Wondercutter from Micro-Mark after doing a bit of window-shopping research on the item. I was simultaneously optimistic and skeptical that its capability will live up to its high price tag. When I opened up the box, I saw that a small piece of test material was included in the package for us to take our first Wondercutter cut. It is some sort of foamcore material, and it presented the best-case scenario. It was thick and durable enough to take effort cuting with my X-Acto #11 blade and even then, the cut wasn’t very clean. But Wondercutter sliced through like hot knife through butter on this material and also leaving a clean edge.

I then tried it on materials that I expect to work with. A scrap sheet of 3mm acrylic took more effort to cut than the test material, but it did cut just the same. The sight of acrylic melted along the cutting edge was accompanied by the smell of heated acrylic. Some of the cutting action must have been from heat melting the acrylic and not just the ultrasonic cutting action. This sample indicated the Wondercutter is no substitute for a laser cutter for clean sharp edges. But I don’t have a laser cutter, so a Wondercutter will work in a pinch for quick acrylic cuts at home.

The next tests were done on various failed prints from my 3D printer. Printed PLA cut more easily than acrylic, with similar sight and smell of melting. PETG was more difficult to cut and, thanks to its higher temperature resistance, there was only minimal melting. Another characteristic of cutting PETG is that I could occasionally feel vibration through my fingers, like a dental cleaning session which can be unpleasant. Printed support materials were easier to cut than solid shapes, as they are intentionally printed to be weaker. For this purpose, using a Wondercutter is faster than my X-Acto blade, but by itself is not necessarily enough to justify the expense. I’ve read that the Wondercutter is great for cutting resin support structures, so I look forward to that if I ever get into resin-based 3D printing.

The final test was done on a circuit board. Some Wondercutter vendors claimed it can cut circuit boards, though neither Cutra nor Micro-Mark mentioned it either way. This was a no-go. While the blade could make its way through FR4 fiberglass, cutting progress came to a literal screeching halt as soon as the blade touched a copper trace. It damaged the blade, so I had to replace it. Thankfully there is a pack of 40 replacement blades in the box. I hope it didn’t damage the transducer.

With this bit of testing under my belt, I start pulling out the Wondercutter for various teardown projects. The first big win was cutting the ultrasonic transducer mount free from an oil diffuser. It went much faster than an X-Acto blade and less messy than a Dremel cutting wheel. Some smaller jobs were sprinkled here and there, like cutting the battery tray free from various devices so I could use them in my own projects. Or the plastic-encased bearing assembly of an evaporator fan. The Makita battery project is similar to the oil diffuser transducer: much faster than an X-Acto blade, and less dangerous than a Dremel cutting wheel. The Wondercutter is an expensive investment an order of magnitude more expensive than a Dremel and two orders more than an X-Acto blade. But every once in a while, I find myself in need of its capabilities and glad that I now have it.

Sanyo CCB Close Enough to SPI For Logic Analyzer

I’m examining the control signals for a Sanyo LC75853N LCD driver chip, which uses a Sanyo proprietary protocol they call CCB. (Computer Control Bus.) It’s popular enough that I could find CCB reference material online, but it’s not popular enough to be natively understood by Saleae’s Logic Analyzer software. Beyond Saleae’s set is a list of Community Shared Analyzers but Sanyo CCB didn’t make the cut there, either. Those additional analyzers were written using Saleae’s Protocol Analyzer SDK so there is the option to write one for CCB. For the purpose of initial experimentation, though, their default SPI analyzer is close enough.

Before we even try using the SPI analyzer, we can look at the raw data. CCB transmits the peripheral address before raising CE. Here I can see 0x42 hexadecimal, or 0b01000010 binary. (The white binary numbers were not part of Saleae software, I drew it in afterwards.) In an unfortunate bit of coincidence, this binary value is symmetric so it alone couldn’t tell us if CCB transfer least-significant bit first or most-significant-bit first. According to spec, it is least-significant-bit first. Seeing this gave me the confidence I’ve wired up everything correctly for further probing.

The clock pulses measured out to be in the ballpark of 400kHz, which I can probably work with. But more importantly, I was relieved to see that the clock pulse widths varied somewhat between transmitted bits. This is encouraging because it meant the protocol is graceful under irregular clock pulses, making it more likely I can successfully communicate using CCB in software. Which is great because I don’t have dedicated CCB communication peripheral hardware.

The next step was to activate SPI analyzer with the following parameters. The biggest difference between CCB and SPI is the behavior of CE line, and thankfully Saleae’s SPI analyzer can be configured to ignore CE. (“Enable” set to “None”.) I set the SPI analyzer options to the following values to decode all the values regardless of CE status:

SPI Analyzer OptionValue
Significant BitLeast Significant Bit First
Bits per Transfer8 Bits per Transfer
Clock StateClock is High when inactive
Clock PhaseData is Valid on Clock Trailing Edge
Enable Line(Doesn’t matter when “Enable” is “None”)

Now the software can decode data for us. This time, the decoded values 0x42, etc. in this image was drawn by the software.

This was the start of the very first data transmission after I applied power to the tape deck. Which is why CLK started as low even though it is normally high when inactivity. When Enable is set to None, I see all the data regardless of CE status.

First question to answer: the B in CCB is “Bus”. How many devices are on this bus? Taking advantage of the difference between CCB and SPI, I can tell the SPI analyzer to decode just the CCB address by saying CE is Active Low:

SPI Analyzer OptionValue
Enable LineEnable is Active Low

The decoded values on LCD-DI were all 0x42, which tells me the LCD control chip is the only peripheral on this bus, which makes things simpler. I won’t have to worry about reading data intended for the wrong device. And once I decided I didn’t have to worry about different addresses anymore, I can switch the SPI Analyzer over to Active High CE. This will cause the analyzer to ignore addresses (since I expect them to all be 0x42) transmitted while CE is low and decode just the data.

SPI Analyzer OptionValue
Enable LineEnable is Active High

Within the ~3/4 second of the faceplate getting power, something is transmitted repeatedly approximately once every 5 milliseconds. Zooming in, I see they are three consecutive CCB transmissions to address 0x42:


Next: compare this captured data to the LC75853N datasheet to see if they make sense.

Clothes Iron Assistant for Hot Air Rework Station

I’ve been gradually building up my skills and tools working with surface-mount technology components. After the most recent episode of frustration trying to rework components without a hot-air rework station, I went ahead and bought a simple starter unit on Amazon. (*) This is quite similar to the hot-air rework station I got to play with earlier, and I’m operating under the assumption that something simple is far better than nothing at all. It is certainly less destructive than the blunt hammer of a paint removal heat gun. Using my new hot air rework station, I was able to salvage more red LEDs from my pile of salvaged electronics and install them on the Mr. Robot Badge. The job is a lot easier once I had the right tool! The result is not quite perfect, because my salvaged LEDs are slightly different shade of red and a touch dimmer, but it is running and it’s all red.

Then I saw this on Twitter:

Hey, I have one of those “SMT stations” too! In my pile of household appliances awaiting teardown is a retired clothes iron. Something is wrong with its temperature regulation circuit. It would heat up to the requested temperature then turn its heater off. But then it would cool far more than acceptable before it would start heating back up again, and it never heats all the way back up to the requested temperature before turning off again. In short, it was no longer useful as a clothes iron and I thought I’d take it apart eventually. Due to my confusion when looking at a simple coffee maker circuit, I’m not optimistic I could fix the iron, it was just to see if I could learn anything.

But now I have something else I can do with it instead of taking it apart. Reading the rest of the above Twitter thread, I confirmed my understanding that unmodified clothes irons do not get hot enough to melt solder by themselves. What they can do is assist the hot air gun by keeping the working area warm. This helps the hot air rework station work better by reducing the amount of heat dissipated away uselessly.

So I set up my own “SMT station” and placed upon it the mainboard from an old retired Roomba Red. The proprietary CPU (or at least customized enough to have an iRobot logo on it) was too big for me to remove with the hot air station alone, but with the iron keeping the entire circuit board warm, I was able to melt the solder and remove the chip intact. There’s a small chance this chip is still usable, not that I plan to do anything with it.

Also, the same temperature regulation problem that made me retire this iron also made it bad at maintaining circuit board temperature. I can work around it by unplugging the iron and plugging it back in to reactivate that initial heating period. Far from ideal, but good enough for today’s learning exercise.

Then I revisited my previous hot air experiment failure: the CPU from the mainboard of an Acer Aspire convertible Windows tablet. This time I was successful! Sort of.

It was far more difficult to remove than the Roomba CPU. I damaged a corner of the module with my tweezers by yanking too hard, it’s been bent upwards so definitely destroyed. But this was great practice and I’ll keep at it as I do my teardowns. Eventually I’d like to reach a point where I can salvage and reuse something more complex than a LED.

Window Shopping: Cutra Wondercutter Ultrasonic Knife

During an online video meetup with some makers, I learned that consumer-level ultrasonic knives exist. One member of the meetup was taking theirs apart for some reason I’ve now forgotten, I just remembered his quick demo of the handheld cutting blade cutting through a 3mm thick sheet of acrylic. It wasn’t exactly “hot knife through butter” (maybe cold knife through refrigerated butter) but certainly far superior to what I could do with my X-Acto #11 blade.

I had known of ultrasonic tools in the medical field, specifically dental tools. I also had some idea they existed in the realm of industrial manufacturing equipment. But something I could conceivably buy for my own workbench? That’s news to me. Unfortunately, the person on the video wasn’t able to give me much information to go on, so I started searching for “ultrasonic knife” from my usual list of tool vendors. Unsurprisingly, I got a hit at McMaster-Carr: Item #3415N11 Fast-Cutting Ultrasonic Precision Knife. Visually, this looks like the same device I saw being disassembled at the meetup. But McMaster-Carr didn’t give me very much information on this device, not even some things I consider basic like make and model for further evaluation.

A search for “Ultrasonic Knife” on Amazon would give me several multi-thousand-dollar industrial machines, and also this listing. (*) Titled “The Wondercutter S” it looks right, but this listing felt odd for several reasons. The brand is listed as “MICRO-MAKE” but there’s nothing else by that brand name. There is also a logo on the device absent from the McMaster-Carr listing. It is stylized so I couldn’t quite decipher it to letters, but it is definitely neither “Wondercutter” or “MICRO-MAKE”. This listing didn’t give me the confidence I needed to commit several hundred dollars, despite Amazon Prime guarantees.

Continuing online search, I also got a hit at Home Depot which was a mild surprise. I had not associated the big orange DIY home improvement store with high tech tools. From this listing I got a brand name “CUTRA” which explains the stylized logo I couldn’t read earlier.

Now that I have a brand name, I found its company site and their own product site. It appears to be a Korean company and I finally got the specifications I could sink my teeth into. There were also a lot of demonstrations videos on what this device could do, the one that got my attention was cleaning up supports for 3D printing. I’ve never enjoyed cleaning up supports, and I’ve had a few dangerous close calls with my trusty X-Acto blade doing so. A couple of hundred dollars is a significant investment, but if it saves me a single hospital visit that would make the item worthwhile.

From this site I also learned that Wondercutter was crowdfunded as an Indiegogo project back in 2017. Well, I definitely missed the early bird backer special of $258 USD! I just have to pay retail now. Elsewhere on the site I saw I could order direct from Korea, but they have signed an official distributor for United States: Micro-Mark. Now this is a name I know from my scale plastic model days! I used to be a very good Micro-Mark customer buying Tamiya paints (they’ve all since dried out) and small model-building hand tools (I still use some of them).

Well, at least this explains the mystery branding of “Micro-Make” on that Amazon listing, it was a typo of Micro-Mark. There is actually a Micro-Mark storefront on Amazon (*), but with only a subset of the full catalog. For example, they sell replacement Wondercutter blades (*) but they don’t sell the Wondercutter itself on Amazon. Why would they leave it open for an imposter vendor to take away potential Amazon sales? That’s a curious business decision. Micro-Mark claims to be the exclusive distributor for North America, and I can see they are listed as vendors on sites like Walmart. But I’m not sure what’s the point of going through Walmart (or Home Depot or Amazon) if Micro-Mark is actually the distributor. It seems to make more sense to order one direct from Micro-Mark’s own website.

(*) Disclosure: As an Amazon Associate I earn from qualifying purchases.

Disappointing Budget Keyboard Protector

I bought an Apple M1-powered MacBook Air laptop and bought a laptop cover to protect it against scratches and mild impacts. The hinge mechanism of this machine presents a challenge for case makers: there’s not much clearance to work with. Letting the lid open past 90 degrees is a tradeoff between protection and adding stress to the laptop joint. The first case I tried(*) had a very noticeable “bump” that my lid had to push past, and I worried about long term durability of the hinge under that stress. I then tried a different vendor (*), whose back corner (where the hinge is) is thinner and potentially more fragile but it put far less stress on the laptop hinge joint. Even though I could feel a bit of a bump as I open the lid, I decided to stay with this case which has worked very well over the past three months.

The same could not be said of the keyboard protector membrane that came bundled with the case. Historically I had not used such things and its inclusion did not factor in my case purchase decision. But since I got it anyway, I thought I would give it a try.

The good news: it is very good at its primary purpose of protecting the keyboard from small particles, like food crumbs that get dropped when I use the laptop while eating.

The neutral news: I had been worried about how it would change the keyboard feel. I’m a touch typist and particular about how my keyboard feel as I type. (I never got a “butterfly keyboard” MacBook for this reason.) And while the keyboard tactility definitely feels different, I did not find it objectionable. At least, at first.

Now we come to the bad news, part one. After a few months, the membrane material starts exuding some kind of liquid. There doesn’t seem to be any odor and there’s very little of it, but it starts leaving blackened blotches where the liquid touches the keyboard and made the membrane more transparent than other areas. This looks bad and I worry about getting that stuff on my fingers. The membrane never gets tacky enough to stick to my fingers, but it still doesn’t feel good to the touch.

The bad news, part two, is in the flexible nature of the material. After using it for several months, the material has started to stretch. If I try to keep the shape aligned with the keyboard, the stretched portions would bulge up which looks bad. Plus when the laptop lid is closed, these bulges touch the screen and leave behind little spots of the aforementioned liquid.

If I smooth out the bulge so the membrane lies flat, its shape no longer align with the keys. This is especially obvious in the arrow keys in the corner, where the designated bumps for arrow keys are now 2-3mm further to the right than the actual keys themselves.

Due to this unsightly shape, black spots, and sticky sensation, I’m going to throw away this membrane. It was a low-cost test so no big loss. But if I ever get serious about putting protectors on my keyboard I know to either (1) look for higher quality material or (2) budget for frequent replacement.

Backlight LED Tester

I have successfully salvaged LED backlight diffuser assemblies from three different LCD screens. It gave me the confidence to attempt pulling the backlight out of other LCD screens in my pile of less-used and broken electronics, in the expectation that diffuse white light sources will be more useful than low resolution displays. But before I start merrily tear more panels apart, I wanted to address one particular pain point: deciphering mystery LED strings.

Only one of the three examples so far gave me an easy time, where the LED backlight power planes were clearly marked with + and -. The other two had multi-conductor cables that required a little decoding to find a common anode and cathodes for individual strings, and sometimes a few conductors remained mysterious. I had been doing this work by spending a lot of time probing with a multimeter, then soldering wires to test points, and cautiously putting power on those lines with a bench power supply. This has worked so far, but I knew there was room to make this process faster for future panels.

Enter the dedicated LED backlight tester.

I wanted something that could put current-limited power over a set of probes. This would let me probe LED strings directly in a single-step versus my current multi-step workflow of multimeter, then soldered wires, then bench power supply. I considered buying a set of probes that I can connect directly to my bench power supply, but a quick search for dedicated LED testers found them quite affordable and I made the jump to try one.

Looking over several options on Amazon, I decided to try a SID LED KT4H(*) because it advertised a few extra features I thought might be useful enough to worth the extra cost. It has household AC input so I don’t have to worry about a separate power supply or batteries. Separate numerical displays for voltage and amperage allows me to read both metrics simultaneously. Simple dials for current and voltage limits make the user interface simpler than designs that use infuriating combinations of unintuitive button presses. There’s a switch to toggle between two current limits: the one set by the dial, and 1mA for testing purposes. This is much better than turning the current limit knob back and forth. And finally, it can also test the other side of the system: whether the device’s constant current supply is putting out any power at all.

The package also included a convenient carrying case, in the form of a generic First Aid Kit zippered fabric bag. Not the fanciest branding, it gave me a chuckle, but it should be quite sufficient.

The probes had sharp tips more than precise enough to hit the kind of test points I had been probing with my meter.

For a quick familiarization run, I used this tester on a single 5mm through-hole LED and saw it light up dimly in the 1mA test mode and brightly with current limit set at 20mA. Then I moved on to illuminate the recently-liberated backlight from an AU Optronics B101EAN01.5. A nice feature is that the current limit ramps up gradually: there is a slow (2-4 seconds) ramp-up as the device seeks the correct voltage level to deliver 20mA. In comparison to my bench power supply which will snap to a voltage almost instantly. I’m optimistic the slower ramp-up will prove valuable.

Before I could put this tester to work, though, life threw me a curveball and I had a broken clothes dryer to fix. The LED backlights will have to wait a bit.

(*) Disclosure: As an Amazon Associate I earn from qualifying purchases.

Hot Air Station Amateur Hour

A hot air station is one of the standard tools for working with surface-mount electronics, mostly in the context of rework to fix problems rather than initial assembly. In addition to manuals for individual pieces of equipment, there are guides like this one from Sparkfun. My projects haven’t really needed me to buy one, though that’s debatable whether that’s a cause or an effect: perhaps I design my projects so I don’t need one, because I don’t have one!

Either way I knew some level of dexterity and skill are required to use the tool well, and the best way to get started is to start playing with one in a non-critical environment. Shortly before the pandemic lockdown, I had the opportunity when Emily Velasco offered to bring her unit to one of our local meetups for me to play with. I had a large collection of circuit boards removed from tearing down various pieces of equipment. I decided to bring the mainboard from an Acer Aspire Switch 10, which was a small Windows 8 laptop/tablet convertible that I had received in an as-is nonfunctional state. I was able to get it up and running briefly but I think my power supply hack had provided the wrong voltage. Because a few months later, it no longer powered up.

Using the hot air rework station, I started with small SMD components. A few capacitors, transistors, things of that nature. I could take them off, and put them back on. I have no idea if they remained functional, that will be a future test at some point.

The USB ports and mini HDMI port on this device were surface mounted and I tried them next. I could remove them with the hot air rework station, but I couldn’t reinstall them. I got close so I believe this is a matter of practice and improving my technique.

Those connectors had relatively few large connection points, I tried my luck with larger chip packages on board. These were memory modules and flash storage modules, fairly large chips with electrical connections underneath where no soldering iron could reach them. My success rate here is similar, of being able to pull them off but not put them back on. I was less optimistic I could get this to work with practice, since these are ball grid array (BGA) modules and I would have to re-ball them to reinstall properly.

The largest chip on the board was the Intel CPU. I suspect there are heat dissipation measures in circuit board copper layers, similar to how a DRV8833 handles cooling with PowerPAD. Whatever is going on, I could not remove the CPU at all with this hot air rework station.

This was a fun introductory hot air play session, I look forward to more opportunities to learn how to use hot air once we can safely hold hacker meetups again. Here’s the final dissected cadaver:

Hot air rework session end

Jumper Wire Headaches? Try Cardboard!

My quick ESP32 motor control project was primarily to practice software development for FreeRTOS basics, but to make it actually do something interesting I had to assemble associated hardware components. The ESP32 development kit was mounted on a breadboard, to which I’ve connected a lot of jumper wires. Several went to a Segger J-Link so I had the option of JTAG debugging. A few other pins went to potentiometers of a joystick so I could read its position, and finally a set of jumper wires to connect ESP32 output signals to a L298N motor control module. The L298N itself was connected to DC motors of a pair of TT gearboxes and a battery connector for direct power.

This arrangement resulted in an annoying number of jumper wires connecting these six separate physical components. I started doing this work on my workbench and the first two or three components were fine. But once I got up to six, things to start going wrong. While working on one part, I would inadvertently bump another part which tugs on their jumper wires, occasionally pulling them out of the breadboard. At least those pulled completely free were clearly visible, the annoying cases are wires only pulled partially free causing intermittent connections. Those were a huge pain to debug and of course I would waste time thinking it was a bug in my code when it wasn’t.

I briefly entertained the idea of designing something in CAD and 3D-print it to keep all of these components together as one assembly, but I rejected that as sheer overkill. Far too complex for what’s merely a practice project. All I needed was a physical substrate to temporarily mount these things, there must be something faster and easier than 3D printing. The answer: cardboard!

I pulled a box out of my cardboard recycle bin and cut out a sufficiently large flat panel using my Canary cutter. The joystick, L298N, and TT gearboxes had mounting holes so a few quick stabs to the cardboard gave me holes to fasten them with twist ties. (I had originally thought to use zip ties, but twist ties are more easily reused.) The J-Link and breadboard did not have convenient mounting holes, but the breadboard came backed with double-sided adhesive so I exposed a portion for sticking to the cardboard. And finally, the J-Link was held down with painter’s masking tape.

All this took less than ten minutes, far faster than designing and 3D printing something. After securing all components of this project into a single cardboard-backed physical unit, I no longer had intermittent connection problems with jumper wires accidentally pulled loose. Mounting them on a sheet of cardboard was time well spent, and its easily modified nature makes it easy for me to replace the L298 motor driver IC used in this prototype.

A Canary Corrugated Cardboard Cutter Convert

One of the bonus motivations for building my cardboard companion minion was a test run of the Canary Corrugated Cardboard Cutter (*). After my experience in that project, I am now a big fan of this tool.

I learned of the Canary cutter via CRASHSpace, a longstanding maker community in the greater LA area. As they are on the opposing side of downtown LA it is not trivial for me to visit. But now that everything is virtual, I actually have more interaction with members of that community than I would have otherwise.

One of the recent discoveries started by watching Barb Noren‘s session “Tinkering @ Home” for Virtually Maker Faire 2020. One of the topics was their Tinkering Toolkit and the Canary cutter in that kit caught my eye. Given the popularity of home delivery in these times, many of us are going through a large number of corrugated cardboard boxes. We could throw them in the recycle bin, but Barb Noren asserts that is a waste: they are useful raw material for projects! And the Canary cutter is how reDiscover Center can set children loose on cardboard, as young as seven years old, under adult supervision.

I’ve built many projects with corrugated cardboard, using X-Acto blades for fine detail and large box cutter knives for large cuts. And yes, I’ve had my share of accidental cuts and so I was immediately interested in the idea of a much safer cutting tool. I was willing to trade off some cutting effectiveness if it would gain me more safety. And after asking Barb a few questions about it at a virtual CRASHSpace event, I ordered one of my own to try.

When my Canary cutter arrived, I saw a well built tool with a plastic handle for manipulating the metal cutting blade, which was edged with fine serrations. It looked fine but did not inspire great expectations. That attitude changed as soon as I took a test cut. I had expected the serrated teeth to tear rough edges in the cardboard, and I had expected the less-scary blade to also be less effective than a sharp blade at cutting.

I was wrong on both counts.

The Canary cutter cut through corrugated cardboard amazingly quickly, with less effort than box cutter blades, and left a pretty clean edge. Yes, if I compare it side-by-side with something cut by a sharp knife I can see a difference, but when we’re working with corrugated cardboard we’re not exactly working with precision tolerances anyway. And the serrated edge cuts enough clearance that the blade does not get stuck, which my box cutter knives tend to do. Freeing a stuck sharp knife is the major cause of my crafting injuries, so just by eliminating that scenario, things became a whole lot safer.

However, it is still a cutting knife that demands respect, as I’ve already managed to draw my own blood once. But it is much less dangerous than putting big box cutter knives in the hands of children. Since Barb’s session video, reDiscover Center has posted another video about using the Canary cutter.

I’m pretty amazed at how well the Canary cutter worked. This reduces the barrier of entry for corrugated cardboard projects in the future. As the above video stated, it is not suitable for all cuts. We’d still need to have scissors and our old friend the X-Acto blade for fine detail, but for large cuts the Canary cutter is pretty amazing. Anyone who wants to unleash their creativity on corrugated cardboard should get one. (*)

Naturally, with my hands on such a fun new tool, I didn’t stop at just one project and found another cardboard project to start on.

(*) Disclosure: As an Amazon Associate I earn from qualifying purchases.

Old School Engraving With Gravoply

There’s a certain aesthetic I associate with older labels, signs, and equipment control panels. They have two contrasting colors and a three dimensional feel. It has mostly faded away by now, replaced by crisp flat printing with multiple solid colors or even full color halftone. I hadn’t thought much about those old panels until I had the opportunity to look over some dusty retired equipment for making them.

This particular material was “Gravoply” and it is still available for order. We can specify from a wide selection of colors, though the core (rear) color selection is a little more limited than selection for surface (front) color. The dimensional feel is a function of how they are used to create signage: a rotary engraving tool cuts away the surface layer and expose the core layer to produce a display with two contrasting colors.

This rotary tool was held in a pantograph to trace templates on Gravoply. Laying out a particular design meant working with individual letter templates in a simplified version of how past typesetters did their jobs. While in concept a pantograph could allow arbitrary scaling, it appears scaling is limited in this particular implementation. Otherwise there wouldn’t need to be multiple sizes of letter templates.

Gravoply Templates

This technique is unforgiving of mistakes. If the rotary tool went off track, it would cut portions of surface material that was not intended to be cut away. When this happens, the user has no choice but to start over. Which was the explanation for why these pieces haven’t been used in years: they moved away from this system as soon as a cost effective and less frustrating alternative was available.

Visiting the web site of Gravograph today, I see their products on the front page are computer motion controlled machines,. Though they still make pantographs for doing things the old fashioned way, materials for mechanical removal like Gravoply are typically cut with small CNC vertical mills. Plus they also have material designed for engraving by laser. Technology has moved on, and the company behind Gravoply has evolved with it.

I found the pantograph an interesting mechanism and I might ask to use it in the future for the sake of getting some hands on time with a mechanical anachronism. But I’m not likely to actually create something significant using a pantograph, at least not as long as I have a CNC engraver at my disposal.

Valuable Resource: Searchable FCC ID Database

I love taking things apart, and it’s an extra bonus if I can take something apart without destroying it. And to do that, it’s useful to have information about the innards before applying tools. Manufacturers aren’t in the habit of providing free information for what they refer to as the “non user serviceable parts inside.” However, if they want to legally sell a device that involves wireless communication, they have to submit certain information to regulatory authorities. In the United States, this is the FCC (Federal Communications Commission) and every wireless device is required to have a FCC ID and submit information to be filed with that ID.

The information presented are tailored for FCC purposes, but they are also useful for the curious consumer who want to take apart what they’ve bought. Breakdown of exterior components are common, as are pictures of disassembled device’s interior. It’s one of the many resources I consulted for my recent Hackaday how-to writeup describing how to repurpose a portable Bluetooth speaker for fun electronics projects.

As far as I can tell, the web site FCC is not run by the government agency otherwise I assume the domain would have been under which it is not. I couldn’t find an “About Us” page describing why the site exists, but it is a simple straightforward bare bones site. Full of useful information and lacking in useless fancy eye candy and also lacking in annoying ads. I don’t know how the site owners make money to support the site, but I hope it is working out for them and I appreciate having this resource available.

Second Caliper Battery Hack Prioritizes Simplicity

One of my early 3D printing projects was motivated by the wasteful battery usage of a cheap Harbor Freight digital caliper. I didn’t want to replace its LR44 battery all the time, and I didn’t want to directly modify the caliper in any way, so I ended with an overly complex tray to hold a AAA battery in place of the default LR44 battery.

The main goal was to avoid the wastefulness of burning through LR44 batteries, and that goal was a success. I was able to use cheaper AAA batteries and use them for longer. In fact, this caliper was able to run on AAA batteries that were too weak for much else, giving them a very useful secondary life. However, my battery tray suffered poor reliability of electrical contact points. In actual usage it was too easy to move a component just enough to break electrical connection, resetting the caliper and losing whatever measurement I had at the time. After a few frustrating episodes, I broke off the plastic head substituting the LR44 battery and soldered wires directly.

Caliper printed battery tray cracked

After years of use, the battery tray I designed and 3D printed finally cracked. And this time around I decided to go for simplicity instead: a commodity AA battery tray held to the back side of my caliper with double-sided foam tape.

Caliper commodity battery tray back mounted

Wires from this battery tray were soldered directly to the battery tabs inside my caliper for reliable operation. I could no longer lay this caliper down flat on a table, but I don’t think that will be a significant concern. I’ll know for sure after some usage and if it proves to be a problem I will re-evaluate.

In the meantime, I have a replacement battery tray allowing me to run my caliper on weak AA batteries already destined to be thrown away. And since this tray is a mass produced commodity item, using it was cheaper and it was faster to install than my previous solution.

Moral of the story: sometimes 3D printing is not the answer.

Drilling Into Half Inch Diameter Tubes

It didn’t take long before my new old drill press was put to work doing something that was difficult without the tool: I needed to drill a total of eight holes through three half inch diameter aluminum tubes, perpendicular to the tube’s axis.

Because the surface is curved at the point where drilling starts, it takes a skilled hand to perform the task via freehand held drill and workpiece. I did not have such skills in my hands. Putting the workpiece in a vise helps, but still difficult for me to keep a hand held drill on center. What I needed was a way to hold both the workpiece and the drill bit in rigid relation to each other, meaning a custom workholding solution bolted to the drill press table.

Printed V vise jaw installed

It was built using a very cheap Harbor Freight vise. Its jaws were removable and I designed and 3D printed replacement jaws with a V profile to better hold a round object. The other benefit of 3D printed plastic jaws compared to metal jaws is the reduced chance of marring workpiece surface.

Printed V vise jaw gripping tube

The next step is to bolt this vise onto the drill press table. I saw mounting slots on both the table and the vise, and their slots were in the same pattern. I naively thought this was a standard form factor and they will easily line up.

When I put my vise on the table, I found that they did not.

Vise and drill press table slots do not align

Fortunately even though they did not actually line up, they left enough room for me to use a smaller bolt to try to make things work. In this case, my stockpile of 1/4″-20 bolts.

Vise and table has room for quarter inch-20

The slots are too wide for the typical 1/4″-20 washers I had on hand for this bolt, but again I could turn to my 3D printer for custom solutions that help me bolt the vise to the drill press at the location I needed.

Drill jig for 0.5 inch tube

It took some adjustment to bolt the vise exactly where it needs to be. (Tip: double check to make sure the drill press table isn’t itself moving!) But once everything was tightened down, the jig made drilling the holes I needed very simple.

Public Onshape CAD file for this project are available here.

Old Drill Press Is New Drill Press

When local fellow maker Emily upgraded to a big floor standing Delta drill press, her old benchtop drill press was up for grabs. “Free if you pick it up” were the terms of the sale, and I was glad I could pick it up before someone else did. Taking part in countless Emily projects in the past, it shall now play a role in my projects in the near future.

Its long history in the hands of many handy creators showed clearly, with many stock parts missing replaced by either scratch fabricated or adapted parts. This is not a problem at all, a drill press is fundamentally a fairly simple machine and none of the modifications changed its ability to do its core job. Besides, with a less-than-new machine, I feel less intimidated about adding my own modifications as necessary.

The first project on the list addressed a known existing mechanical problem: the drive belt occasionally rubs against the chassis when it is installed in the lowest and slowest of four pulley slots. I inherited a workaround from Emily which I was content to leave in place, but then I saw the set screws holding the pulley to the motor shaft.

Drill press motor pulley

I thought it might be worth a shot to try loosening the set screw and move the pulley a little higher. There might be a good reason why the pulley was in its location. I thought it was possible (likely) the motor was not original and had a shorter shaft, or something along those lines. But it was worth investigating.

I put my hex wrench on the set screw and discovered it is loose now. The reason this pulley is too low is because the set screw came loose and it fell down due to gravity. I moved the pulley a little bit higher, tightened the set screw, and we’re back in business without any rubbing between belt and chassis. This was a great start to what I hope will be a long illustrious career for this drill press, enabling my project ideas in the future.

SparkleCon Sidetrack: Does It Have A Name?

spool holder with two stage straightener 1600x1200

My simple afternoon hack of a copper wire straightener got more attention – both online and off – than I had expected. One of these came as a fun sidetrack to my Sparklecon talk about my KISS Tindie wire sculptures. As part of the background on my wire form project, I mentioned creating this holder. It kicked off a few questions, which I had answered, but I had the most fun with “Does it have a name?”

I gave the actual answer first, which was that I had only been calling it a very straightforward “wire spool holder with straightener” but I followed it up with an off-the-cuff joke “Or did you mean a name like Felicia?” I think I saw a smile by the person asking the question (hard to tell, he had a beard) and I also got a few laughs out of the audience which is great. I had intended to leave it at that, but as I was returning to my presentation another joke occurred to me: “Felicia will set you straight.”

Since my script was already derailed, I saw no reason to run with it: “Is there a fictional character who is a disciplinarian? That might be fitting.” and opened it up to the audience for suggestions. We got “Mary Poppins” which isn’t bad, but things went downhill from there. The fact is: the disciplinarian in a story is almost always a killjoy obstacle in our hero’s journey. Or worse, one of the villains, as in the suggestion of “Delores Umbridge” given by a woman wearing a Harry Potter shirt. My reaction was immediate: “No.” But two seconds later I remembered to make it a tad more positive: “Thank you, she is indeed a disciplinarian, but no.” Hopefully she doesn’t feel like I bit her head off.

After the talk, there were additional suggestions interpreting my second joke “Felicia will set you straight” in the sense of personal relationship preferences. This went down a path of politically conservative zealots who believe it is their public duty to dictate what people do in private. This direction of thinking never even occurred to me when I threw out the joke on a whim.

I think I’ll leave it at Mary Poppins.

SMD LED Under Macro Lens

Several recent posts focused on small things like a damaged ESP32 module. Trying to document these projects presented a challenge because it’s been difficult to take good clear pictures of fine detail. I did the best I could with what I had on hand, but the right tool for the job is a camera lens designed for macro photography. When one such lens for my Canon EF-M camera was on sale during the holiday shopping season, I could not resist.

Here’s the LED on the Introduction to SMD kit, with the entire image scaled down to 1024 pixels wide.

SMD intro kit scaled 1024

If I crop out the center of the original picture instead, this is what I see:

SMD intro kit LED 1024

A lot of detail are visible, certainly far better than what I could get before, but I think the focus could be a little sharper. I hope the lens is limited by operator skill rather than optical characteristics, because I could learn and improve my skill.

Here is a picture of the LED array from my recent freeform SMD experiment, again scaled down to 1024 pixels wide. The solder joints – which I could barely manage with the naked eye – look really uneven at this magnification. But wait – there’s more!

Freeform SMD 7 scaled 1024

Here’s the cropped-out center of that image. Tiny beads of solder look like monstrous blobs of invading space aliens, not at all attractive. But the wire inside the left side LED is clearly visible, and multiple diffractions of the right side LED can be seen. This picture represents a combination of two novice skills: freeform SMD soldering and macro photography. I’m pretty happy with the detail and clarity of these pictures, but not at the quality of these solder joints. That’s OK, it just means I have lots of room for improvement.

Freeform SMD 7 cropped 1024.jpg