A Compact SMD Reflow Hotplate Powered By USB-PD

January 9, 2024 by 10 Comments

When it comes to home-lab reflow work, there are a lot of ways to get the job done. The easiest thing to do perhaps is to slap a PID controller on an old toaster oven and call it a day. But if your bench space is limited, you might want to put this compact reflow hotplate to work for you.

There are a lot of nice features in [Toby Chui]’s build, not least of which is the heating element. Many DIY reflow hotplates use a PCB heater, where long, thin traces in the board are used as resistive heating elements. This seems like a great idea, but as [Toby] explains in the project video below, even high-temperature FR4 substrate isn’t rated for the kinds of temperatures needed for some reflow profiles. His search for alternatives led him to metal ceramic heaters (MCH), which are commonly found in medical and laboratory applications. The MCH he chose was rated for 20 VDC at 50 watts — perfect for powering with USB-PD.

The heater sits above the main PCB on a Kapton-wrapped MDF frame with a thermistor to close the loop. While it’s not the biggest work surface we’ve seen, it’s a good size for small projects. The microcontroller is a CH552, which we’ve talked about before; aside from that and the IP2721 PD trigger chip needed to get the full 60 watts out of the USB-PD supply, there’s not much else on the main board.

This looks like a nice design, and [Toby] has made all the design files available if you’d like to give it a crack. Of course, you might want to freshen up on USB-PD before diving in, in which case we recommend [Arya]’s USB-PD primer.

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A Very 21st Century Receiver For A Very 20th Century Band

January 9, 2024 by 24 Comments

The FM broadcast band has been with us since the middle of the 20th century, and despite many tries to unseat it, remains a decent quality way to pick up your local stations. It used to be that building an FM broadcast receiver required a bit of RF know-how, but the arrival of all-in-one receiver chips has made that part a simple enough case of including a part. That’s not to say that building a good quality FM broadcast receiver in 2024 doesn’t involve some kind of challenge though, and it’s one that [Stefan Wagner] has risen to admirably with his little unit.

Doing the RF part is an RDA5807MP single chip radio, but we’d say the center of this is the CH32V003 RISC-V microcontroller and its software. Twiddling the dial is a thing of the past, with a color display and all the computerized features you’d expect. Rounding it off in the 3D printed case is a small speaker and a Li-Po pouch cell with associated circuitry. This really is the equal of any commercially produced portable radio, and better than many.

Even with the all-in-one chips, there’s still fun in experimenting with FM the old way.

37C3: The Tech Behind Life With Quadraplegia

January 9, 2024 by 21 Comments

While out swimming in the ocean on vacation, a big wave caught [QuadWorker], pushed him head first into the sand, and left him paralyzed from the neck down. This talk isn’t about injury or recovery, though. It’s about the day-to-day tech that makes him able to continue living, working, and travelling, although in new ways. And it’s a fantastic first-hand insight into how assistive technology works for him.

If you can only move your head, how do you control a computer? Surprisingly well! A white dot on [QuadWorker]’s forehead is tracked by a commodity webcam and some software, while two button bumpers to the left and right of his head let him click with a second gesture. For cell phones, a time-dependent scanner app allows him to zero in successively on the X and Y coordinates of where he’d like to press. And naturally voice recognition software is a lifesaver. In the talk, he live-demos sending a coworker a text message, and it’s almost as fast as I could go. Shared whiteboards allow him to work from home most of the time, and a power wheelchair and adapted car let him get into the office as well.

The lack of day-to-day independence is the hardest for him, and he says that they things he misses most are being able to go to the bathroom, and also to scratch himself when he gets itchy – and these are yet unsolved problems. But other custom home hardware also plays an important part in [QuadWorker]’s setup. For instance, all manner of home automation allows him to control the lights, the heat, and the music in his home. Voice-activated light switches are fantastic when you can’t use your arms.

This is a must-watch talk if you’re interested in assistive tech, because it comes direct from the horse’s mouth – a person who has tried a lot, and knows not only what works and what doesn’t, but also what’s valuable. It’s no surprise that the people whose lives most benefit from assistive tech would also be most interested in it, and have their hacker spirit awakened. We’re reminded a bit of the Eyedrivomatic, which won the 2015 Hackaday Prize and was one of the most outstanding projects both from and for the quadriplegic community.

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How To Refrigerate With Urine

January 9, 2024 by 13 Comments

It’s often said that the best science experiments are the ones which do not require any special devices or ingredients, which makes the use of what naturally comes out of one’s body clearly one of the winners. It’s also the beginning of yet another [Hyperspace Pirate] chemistry video that’s both fascinating and unforgettable — this time introducing a considerable collection of urine, and the many uses of the urea in it, including its use for refrigeration.

The respective cooling effect of a variety of compounds in solution. (Credit: Hyperspace Pirate)
The respective cooling effect of a variety of compounds in solution. (Credit: Hyperspace Pirate)

As icky as this may sound, it doesn’t even rank in the top ten of quaint things people have historically done with urine, so extracting urea from it is rather benign. This is performed by adding sodium hydroxide to the starting component after heating, which creates gaseous ammonia (NH3) which was then condensed into its liquid (dissolved) form. In order to create the target compound – being ammonium nitrate – nitric acid (HNO3) had to be created first.

For this the older, but cheaper and easier Birkeland-Eyde process was used. This uses high-voltage electrical arcs to break down the nitrogen and oxygen in the air and cause the formation of nitric oxide (NO), that subsequently reacts with atmospheric oxygen to form nitrogen dioxide (NO2). Running the NO2 through water then creates the desired HNO3, which can be combined with the ammonia solution to create ammonium nitrate. The resulting solution was then evaporated into solid ammonium nitrate, to use it in an aluminium cooling cylinder, with freshly added water.

This is the simplest way to use the cooling effect of such solutions (pictured), but the benefit of ammonium nitrate over the original urea seems minimal. The low efficiency of this cooling approach means that the next use of urine will involve a much more efficient vapor-absorption cycle, which we’re sure everyone is squeezing their legs together for in anticipation.

We’ve been covering the refrigeration experiments [Hyperspace Pirate] has been conducting for some time now. If you’re into the science of making things cold check out how seashells can be turned into dry ice, or what goes into building a home cryocooler.

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Another Tesla Coil Starts

January 8, 2024 by 5 Comments

Everyone interested in electronics should build at least one Tesla coil. But be careful. Sure, the high voltage can be dangerous, but the urge to build lots of coils is even worse. [Learnelectronics] shows how to build a slayer exciter using a 3D-printed core, and lots of wire of course. You can see the coil, an explanation of the design, and a comparison to a cheap kit in the video below.

Of course, you hear about Tesla coils, but it is really more of a Tesla transformer. The 3D-printed core holds the many turns of the secondary coil. The larger Tesla coil, amusingly, upset the camera which made it hard to get close-up shots.

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A Picture Frame For Your Eyes Only

January 8, 2024 by 2 Comments

We can think of all kinds of reasons you’d want to display a picture that only you and the family can see, and we don’t even have to work blue to do it. Whether as a joke, or as a serious way to hide a special image, this magical picture frame by [Placitech] is just the thing.

You might recognize this as using PDLC switchable “smart” film. Whenever power is applied, the panel goes from frosty opacity to near-crystal clarity in an instant. The trick here is to to image recognition and only allow certain faces to unlock the picture.

The brains of this operation is an ESP32-CAM module, which does all the heavy lifting of getting the image in the first place, handling it, and deciding via code who is eligible to flick the switch. Everything is housed in a nice 3D printed frame that [Placitech] designed.

Be sure to check out the build video after the break, and files are available via [Placitech]’s Discord if you’d like to build this yourself.

There’s a lot you can do with PDLC panels, as evidenced by this amazing dress.

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Putting The C In C64

January 8, 2024 by 42 Comments

Older CPUs and some fairly modern microcontrollers are not made to readily support C compilers. Among those are the 1802, some 8-bit PICs, and the 6502 at the heart of the Commodore 64. That’s not to say you can’t make a C compiler for any of them, but the tricks required to handle the odd word sizes, lack of stack manipulation, or whatever other reason C isn’t a good fit tends to make compiled code bloated and possibly slower. [Dr. Mortal Wombat] took a different approach. The oscar64 compiler takes C source code and compiles it to a virtual machine code or native machine code for cases where performance might be important.

Turns out, the penalty for using native code isn’t as much as predicted, at least in some cases, The performance penalty for using the interpreter, however, can be significant in many common cases. The 6502 has a small stack that is hard to address, and indexing into a user-maintained stack is slow. The word size problem also produces lots of code as you have to break 16-bit operations into multiple 8-bit ones. The compiler aims to be C99-compliant, including floating point, recursion, multiple dimensions for arrays, and pointers to structures.

There are a few things left to hammer out. The linker doesn’t support external libraries, and the floating point code doesn’t understand NaN. On the other hand, many C++ features are available, like namespaces, reference types, templates, and more. The compiler can target several Commodore machines from the C128 to the PET. It also works with some Nintendo and Atari systems and can create various cartridge formats.

If you are writing code for any kind of 6502, it is probably worth checking out. Compiling C for the 6502 is no small feat, but then, so it is targeting PowerPoint. Don’t have a C64? Build one.

Image: [MOS6502], CC-BY-SA 3.0