The video begins with the removal of the round CRT tube. Once it’s extracted from the set, it’s placed in a round garbage can which serves as a handy work stand for the unique device. It’s all delicate work as it’s very easy to damage a picture tube, particularly an old one. Removing the discoloration is quite a job—the problem is caused by adhesive holding the front layer safety glass on, which has going bad over the years. It requires lots of heat to remove. In doing this repair, [bandersentv] notes he’s also giving up the safety of the original extra glass layer on the front of the tube. Worth noting if you’re worried about a given tube’s integrity.
Of course, cleaning the tube is just part of the job. [bandersentv] then gave us a second video in which he returns the tube to its original home and gets the TV back up and running. The quality is surprisingly good given what poor shape the tube was in to begin with.
As far as hobbies go, ham radio tends to be on the more expensive side. A dual-band mobile radio can easily run $600, and a high-end HF base station with the capability of more than 100 watts will easily be in the thousands of dollars. But, like most things, there’s an aspect to the hobby that can be incredibly inexpensive and accessible to newcomers. Crystal radios, for example, can be built largely from stuff most of us would have in our parts drawers, CW QRP radios don’t need much more than that, and sometimes even the highest-performing antennas are little more than two lengths of wire.
For this specific antenna, [W3CT] is putting together an inverted-V which is a type of dipole antenna. Rather than each of the dipole’s legs being straight, the center is suspended at some point relatively high above ground with the two ends closer to the earth. Dipoles, including inverted-Vs, are resonant antennas, meaning that they don’t need any tuning between them and the radio so the only thing needed to match the antenna to the feed line is a coax-to-banana adapter. From there it’s as simple as attaching the two measured lengths of wire for the target band and hoisting the center of the antenna up somehow. In [W3CT]’s case he’s using a mast which would break the $8 budget, but a tree or building will do just as well.
The video on the construction of this antenna goes into great detail, so if you haven’t built a dipole yet or you’re just getting started on your ham radio journey, it’s a great place to get started. From there we’d recommend checking out an off-center-fed dipole which lets a dipole operate efficiently on multiple bands instead of just one, and for more general ham radio advice without breaking the bank we’d always recommend the $50 Ham series.
A decade ago, [Jouke Waleson] bought a Dutch ‘model 1950’ PTT (The Dutch Postal Service) rotary-dial telephone of presumably 1950s vintage manufactured by a company called Standard Electric, and decided it would be neat to hack it to function as a Bluetooth hands-free device. Looking at the reverse, however, it is stamped “10.65” on the bottom, so maybe it was made as recently as 1965, but whatever, it’s still pretty old-tech now.
A well-specified transformer?
The plan was to utilise ESP32 hardware with the Espressif HFP stack to do all the Bluetooth heavy lifting. [Jouke] did find out the hard way that this is not a commonly-trodden path in hackerland, and working examples and documentation were sparse, but the fine folks from Espressif were on hand via GitHub to give him the help he needed. After ripping into the unit, it was surprisingly stuffed inside there. Obviously, all the switching, even the indication, was purely electromechanical, which should be no surprise. [Jouke] identified all the necessary major components, adding wires and interfacing components as required, but was a bit stumped at the function of one funky-looking component that we reckon must be a multi-tap audio transformer, oddly finished in baby pink! After renovating some interesting cross-shaped mechanical indicators and wiring up some driving transistors, it was time to get on to the audio interface. Continue reading “Bakelite To The Future – A 1950s Bluetooth Headset”→
Volumetric displays are simply cool. Throw some LEDs together, take advantage of persistence of vision, and you’ve really got something. [Nick Electronics] shows us how its done with his neat little volumetric lamp build.
The concept is simple. [Nick] built a little device to spin a little rectangular array of LEDs. A small motor in the base provides the requisite rotational motion at a speed of roughly 6000 rpm. To get power to the LEDs while they’re spinning, the build relies on wire coils for power transmission, instead of the more traditional technique of using slip rings.
Face it, we’ve all at some time or other looked at our hot glue guns, and thought “I wonder if I could use that for 3D printing!”. [Proper Printing] didn’t just think it, he’s made a working hot glue 3D printer. As you’d expect, it’s the extruder which forms the hack here.
A Dremel hot glue gun supplies the hot end, whose mains heater cartridge is replaced with a low voltage one with he help of a piece of brass tube. He already has his own design for an extruder for larger diameters, so he mates this with the hot end. Finally the nozzle is tapped with a thread to fit an airbrush nozzle for printing, and he’s ready tp print. With a much lower temperature and an unheated bed it extrudes, but it takes multiple attempts and several redesigns of the mechanical parts of the extruder before he finally ended up with the plastic shell of the glue gun as part of the assembly.
The last touch is a glue stick magazine that drops new sticks into a funnel on top of the extruder, and it’s printing a Benchy. At this point you might be asking why go to all this effort, but when you consider that there are other interesting materials which are only available in stick form it’s clear that this goes beyond the glue. If you’re up for more hot glue gun oddities meanwhile, in the past we’ve shown you the opposite process to this one.
Out of curiosity, I redrew the Supercon Vectorscope badge schematics in KiCad last year. As you might suspect, going from PCB to schematic is opposite to the normal design flow of KiCad and most other PCB design tools. As a result, the schematics and PCB of the Vectorscope project were not really linked. I decided to try it again this year, but with the added goal of making a complete KiCad project. As usual, [Voja] provided a well drawn schematic diagram in PDF and CorelDRAW formats, and a PCB design using Altium’s Circuit Maker format (CSPcbDoc file). And for reference, this year I’m using KiCad v8 versus v7 last year.
Importing into KiCad
This went smoothly. KiCad imports Altium files, as I discovered last year. Converting the graphic lines to traces was easier than before, since the graphical lines are deleted in the conversion process. There was a file organizational quirk, however. I made a new, empty project and imported the Circuit Maker PCB file. It wasn’t obvious at first, but the importing action didn’t make use the new project I had just made. Instead, it created a completely new project in the directory holding the imported Circuit Maker file. This caused a lot of head scratching when I was editing the symbol and footprint library table files, and couldn’t figure out why my edits weren’t being seen by KiCad. I’m not sure what the logic of this is, was an easy fix once you know what’s going on. I simply copied everything from the imported project and pasted it in my new, empty project.
While hardly necessary for this design, you can also import graphics into a KiCad schematic in a similar manner to the PCB editor. First, convert the CorelDRAW file into DXF or SVG — I used InkScape to make an SVG. Next do Import -> Graphics in the Kicad schematic editor. However, you immediately realize that, unlike the PCB editor, the schematic editor doesn’t have any concept of drawing layers. As a work around, you can instead import graphics into a new symbol, and place this symbol on a blank page. I’m not sure how helpful this would be in tracing out schematics in a real world scenario, since I just drew mine from scratch. But it’s worth trying if you have complex schematics.
Note: this didn’t work perfectly, however. For some reason, the text doesn’t survive being imported into KiCad. I attribute this to my poor InkScape skills rather than a shortcoming in KiCad or CorelDRAW. Despite having no text, I put this symbol on its own page in sheet two of the schematic, just for reference to see how it can be done.
Just like last year, the footprints in the Circuit Maker PCB file were imported into KiCad in a seemingly random manner. Some footprints import as expected. Others are imported such that each individual pad is a standalone footprint. This didn’t cause me any problems, since I made all new footprints by modifying standard KiCad ones. But if you wanted to save such a footprint-per-pad part into a single KiCad footprint, it would take a bit more effort to get right.
Recreating Schematics and Parts
After redrawing the schematics, I focused on getting the part footprints sorted out. I did them methodically one by one. The process went as follows for each part:
Start with the equivalent footprint from a KiCad library
Duplicate it into a local project library
Add the text SAO to the footprint name to avoid confusion.
Position and align the part on the PCB atop the imported footprint
Note and adjust for any differences — pad size and/or shape, etc.
Update the part in the project library
Attach it to the schematic symbols in the usual manner.
Delete the imported original footprint (can be tricky to select)
Some parts were more interesting than others. For example, the six SAO connectors are placed at various non-obvious angles around the perimeter. I see that [Voja] slipped up once — the angle between connectors 4 and 5 is at a definitely non-oddball angle of 60 degrees.
With all this complete, the PCB artwork consists of all new footprints but uses the original traces. I needed to tweak a few traces here and there, but hopefully without detracting too much from [Voja]’s style. Speaking of style, for those interested in giving that free-hand look to hand-routed tracks in KiCad, check the options in the Interactive Router Settings menu. Choose the Highlight collisions / Free angle mode and set the PCB grid to a very small value. Free sketch away.
Glitches
Actual jumper on assembled PCB
Circuit Maker PCB File
Schematics showing jumper
I used two photos of the actual board to check when something wasn’t clear. One such puzzle was the 3-pad SMT solder ball jumper. This was shown on the schematic and on the fully assembled PCB, but it was not in the Circuit Maker design files. I assumed that the schematics and photos were the truth, and the PCB artwork was a previous revision. There is a chance that I got it backwards, but it’s an easy to fix if so. Adding the missing jumper took a bit of guesswork regarding the new and adjusted traces, because they were hard to see and/or underneath parts in the photo. This redrawn design may differ slightly in appearance but not in functionality.
DRC checks took a little more iterating than usual, and at one point I did something to break the edge cuts layer. The irregular features on this PCB didn’t help matters, but I eventually got everything cleaned up.
I had some trouble sometimes assigning nets to the traces. If I was lucky, putting the KiCad footprint on top of the traces assigned them their net names. Other times, I had traces which I had to manually assign to a net. This operation seemed to work sporatically, and I couldn’t figure out why. I was missing a mode that I remember from another decade in a PCB tool, maybe PCAD?, where you would first click on a net. Then you just clicked on any number of other items to stitch them into the net. In KiCad it is not that simple, but understandable given the less-frequent need for this functionality.
You may notice the thru hole leads on the 3D render are way too long. Manufacturers provide 3D files describing the part as they are shipped, which reasonably includes the long leads. They are only trimmed at installation. The virtual technician inside KiCad’s 3D viewer works at inhuman speeds, but has had limited training. She can install or remove all through hold or SMT parts on the board, in the blink of an eye. She can reposition eight lamps and change the background color in mere seconds. These are tasks that would occupy a human technician for hours. But she doesn’t know how to trim the leads off of thru hole parts. Maybe that will come in future versions.
Project Libraries
I like to extract all symbols, part footprints, and 3D files into separate project libraries when the design wraps up. KiCad experts will point out that for several versions now this is not necessary. All (or most) of this information is now stored in the design files, alghouth with one exception — the 3D files. Even so, I still feel safer making these project libraries, probably because I understand the process.
KiCad can now do this with a built-in function. See the Export -> Symbols to New Library and Export -> Footprints to New Library in the schematic and PCB editors, respectively. These actions give you the option to additionally change all references in the design to use this new library. This didn’t work completely for me, for reasons unclear. Eventually I just manually edited the sch and pcb file and fixed the library names with a search and replace operation.
Hint: When configuring project libraries in KiCad, I always give them a nickname that begins with a dot. For example, .badge24 or .stumbler. This always puts project libraries at the top of the long list of libraries, and it makes it easier to do manual search and replaces in the design files if needed.
What about 3D files, you say? That isn’t built into KiCad, but have no fear. [Mitja Nemec] has you covered with the Archive 3D Models KiCad plugin. It was trivial to activate and use in KiCad’s Plugin and Content Manager.
All Done
In the end, the design passed all DRCs, and I could run Update PCB from Schematic... without errors. I went out on a limb and immediately placed an order for five PCBs, hoping I hadn’t overlooked something. But it’s only US$9.00 risk. They are on the way from China as I type this.
All the files can be found in this GitHub repo. If you find any errors, raise an issue there. I have not done this procedure for any of the SAO petals, but when I do, I will place a link in the repository.
If you’ve ever wondered what goes on in the ground facilities of a satellite TV operation, you could go banging on the doors or your local station. You’d probably get thrown out in short order. Alternatively, you could watch this neat little tour from [saveitforparts].
The tour takes us through a ground facility operated by the Canadian Broadcasting Corporation and Radio Canada in Montreal. The facility in question largely handles CBC’s French language content for the Canadian audience. We’re treated to a look at the big satellite dishes on the roof, as well as the command center inside. Wall to wall screens and control panels are the order of the day, managing uplinks and downlinks and ensuring content gets where it needs to go. Particularly interesting is the look at the hardcore hardware for full-strength transmission to satellites. The video also includes some neat trivia, like how CBC was the first broadcaster to offer direct satellite TV to customers in 1978.
