Having a few machine tools at one’s disposal is a luxury that not many of us are afforded, and often an expensive one at that. It is something that a large percentage of us may dream about, though, and with some commonly available tools and inexpensive electronics a few people have put together some very inexpensive CNC machines. The latest is the Minamil, which uses a rotary tool and straps it to an economical frame in order to get a functional CNC mill setup working.
This project boasts impressively low costs at around $15 per axis. Each axis uses readily available parts such as bearings and threaded rods that are readily installed in the mill, and for a cutting head the build is based on a Dremel-like rotary tool that has a similarly low price tag. Let’s not ignore the essentially free counterweight that is used.
For control, an Arduino with a CNC shield powers the three-axis device which is likely the bulk of the cost of this project. [Paul McClay] also points out that a lot of the material he needed for this build can be salvaged from things like old printers, so the $45 price tag is a ceiling, not a floor.
The Minamil has been demonstrated milling a wide variety of materials with excellent precision. Both acrylic and aluminum are able to be worked with this machine, but [Paul] also demonstrates it in its capacity to mill PCBs. It does have some limitations but for the price it seems that this mill can’t be beat, even compared to his previous CNC build which repurposed old CD drives.
[Petteri Aimonen] presents for us a modular differential probe, as his entry into the 2021 Hackaday Prize.
This project shows a simple and well polished implementation of a differential-to-single-ended preamplifier, which allows a differential signal to be probed and fed to an oscilloscope via a BNC cable.
PCB Spark gap for primary ESD protection
It implements a classic instrumentation amplifier, where we have two amplifier stages. The first gives us the options for a gain of either 1 or 10, if we need it, with the second stage having a gain of 2.
The remaining circuit is a power supply to generate the necessary dual-rail supplies to feed the opamps. There is a lot of filtering on those output rails as well as on the USB power input side to try keep all that switched-mode power supply noise out of the signal path.
There are a couple of interesting design choices including the use of PCB material for the long removable probe arms, that integrate PCB spark gaps to offer a first defence against ESD reaching the more delicate parts of the system.
Why This Is Useful
There are two main classes of signals we electronics engineers care about: single-ended and differential-mode.
With the first kind, the signal is carried on a single wire, which is defined as being referenced to the common system ground. Current flows along the wire and returns to its source along the path of least resistance, at least at low frequencies. At higher frequencies, the path of least inductance is more relevant. This is all well and good, so long as you design the PCB correctly.
Coupling from adjacent wires due to mutual capacitance and inductance, as well as noise in the reference ground all conspire to mangle the signal we want to pass down the wire.
As the frequencies increase, and especially if you’re dealing with sharp edges, with all that extra odd-harmonic power, things start to get bad real fast. The way we deal with this is by utilising differential-mode signalling. This is where instead of a single wire, referenced to some notion of ground, we send the signal down a pair of wires, where the voltage difference between the wires forms the signal. Any external noise that leaks into the pair, will (hopefully!) affect both wires equally, forming what we call a common-mode component. When you look at the difference, this common mode noise disappears. (Our own [Bil Herd] covered this some time ago.)
When probing a circuit, it pays to have the right kind of probe as well as an understanding of the effect the probe will have on the circuit in operation. If you have a single-ended signal and you want to view it on your scope, your choice is either a passive or active probe. Usually some kind of passive probe will be most available. These commonly come in 50 Ω and 1 MΩ versions, and you need to be careful to use the correct probe type for your application.
For probing differential signals, it is possible to use a pair of probes, one for each signal wire, and then utilise the scope’s math difference function to show the signal. This is quite often a desperate measure, and what you really want is a differential front-end in hardware. You need a differential active probe.
The circuit may be simple, but don’t underestimate how much tweaking it needs to have good performance – a little slip with the PCB layout, as the author describes, caused some annoying resonances which can be hard to track down.
The project is still under active development, with the author showing the process as the project progresses, but its looking pretty good already, if you ask us.
Sources can found on his GitHib, which uses all Open Source tools, so its pretty accessible too.
Well, this hack has us tickled pink. We love the idea of buying some really cheap piece of technology and doing something amazing with it, and this is a textbook example of that. [davedarko] found the cutest little calculator watch on Ali Express and is working on making a new PCB for it. The plan is to use an ARM processor and Arduino and add a few extras like 24-hour mode and a pink (or potentially RGB) backlight. The new brain will be an ATSAML22G18A, which has an on-board LCD controller and exactly one I/O pin to spare without charlieplexing the buttons.
One of [davedarko]’s primary goals is to keep the LCD and figure out how to talk to it. The first order of business was reverse engineering the watch’s LCD controller by sussing out the secrets from beneath the black blob of epoxy. This was an eye-opening experience as [davedarko] had never worked directly with LCDs before. A strange reading made him bust out the oscilloscope. Long-ish and informative story short, [davedarko] found out that it uses a bias of 1/2 for generating the wave necessary to multiplex the segments and keep the signal alternating. This is definitely one to watch!
We love timepieces around here and have seen all kinds of hacks, especially on Casio watches. Want dark mode? Done. Enable the hidden countdown timer? We’ve got that, too. And have you ever wondered just how water-resistant the F91W is?
The 68000 chip was ubiquitous in the computing world well past its heyday in the 1980s. It was used as the basis for many PCs and video game consoles, and even in embedded microcontrollers. Now, one of its niche applications is learning about the internal functions of computers. 68000 builds are fairly common when building homebrew computers from scratch, but projects like these can be complicated and quickly get out of hand. This 68000 project, on the other hand, gets the job done with the absolute minimum of parts and really dives into the assembly language programming on these chips. (Google Translate from Spanish)
[osbox68] built this computer by first simulating its operation. Once he was satisfied with that, the next step was to actually build the device. Along with the MC68008 it only uses two other TTL chips, a respectable 32 kilobytes of ram, and additionally supports a serial port and an expansion bus. A few 74-series chips round out the build including a 74HC574 used for debugging support. With a custom PCB to tie everything together, it’s one of the most minimal 68000 builds we’ve seen that still includes everything needed to be completely functional.
After all, including the TTL and 74XX chips the entire circuit board only uses 10 integrated circuits and a few other passive elements for a completely functional retro computer. [osbox68] also includes complete schematics for building a PCB based on these chips to make construction that much easier. Of course, emulating an old microcontroller instead of using TTL components can save a lot of real estate on a PCB especially if you’re using something like an FPGA.
Some might look at a cheap inkjet printer and see a clunky device that costs more to replace the ink than to buy a new one. [Abhishek Verma] saw an old inkjet printer and instead saw a smooth gantry and feed mechanism, the perfect platform to build his own DIY vinyl cutter.
The printer was carefully disassembled. The feed mechanism was reworked to be driven by a stepper motor with some 3D printed adapter plates. A solenoid-based push/pull mechanism for the cutting blade was added with a 3D printed housing along with a relay module. An Arduino Uno takes in commands from a computer with the help of a CNC GRBL shield.
What we love about this build is the ingenuity and reuse of parts inside the old printer. For example, the old PCB was cut and connectors were re-used. From the outside, it’s hard to believe that HP didn’t manufacture this as a vinyl cutter.
We’re always fans of interesting clock builds around here, whether it’s a word clock, marble clock, or in this case a clock using a unique display method. Of course, since this is a build by Hackaday’s own [Moritz v. Sivers] the display that was chosen for this build was a custom thermochromic display. These displays use heat-sensitive material to change color, and his latest build leverages that into one of the more colorful clock builds we’ve seen.
The clock’s display is built around a piece of thermochromic film encased in clear acrylic. The way the film operates is based on an LCD display, but using heat to display the segments. For this build, as opposed to his previous builds using larger displays, he needed to refine the method he used for generating the heat required for the color change. For that he swapped out the Peltier devices for surface mount resistors and completely redesigned the drivers and the PCBs around this new method.
Of course, the actual clock mechanism is worth a mention as well. The device uses an ESP8266 board to handle the operation of the clock, and it is able to use its wireless capabilities to get the current time via NTP. All of the files needed to recreate this are available on the project page as well, including code, CAD files, and PCB layouts. It’s always good to have an interesting clock around your home, but if you’re not a fan of electronic clocks like this we can recommend any number of mechanical clocks as well.
If the last year and its supply chain problems have taught us anything, it’s the value of having a Plan B, even for something as commoditized as PCB manufacturing has become. If you’re not able to get a PCB made commercially, you might have to make one yourself, and being able to DIY a dual-layer board with plated-through vias might just be a survival skill worth learning.
Granted, [Hydrogen Time]’s open-source method, which he calls “Process 01”, is something that he has been working on for years now. And it’s quite the feat of chemistry, which may require you to climb a steep learning curve, depending on how neglected the skills from high school or college chemistry are. But for as complex as Process 01 is, it’s actually pretty straightforward, and the first video below covers it in extreme detail. It starts with a drilled double-sided copper-clad board, which after cleaning is given a bath in palladium chloride. A follow-up dunk in stannous chloride leaves a thin film of palladium metal over all surfaces, even the via walls. This then acts as a catalyst for electroless copper plating in a solution of copper sulfate, followed by an actual electroplating step to thicken the copper plating.
After more washing, photoresist is applied to define the traces as well as to protect the now-plated vias, the board is etched, and a solder mask layer is applied. The boards might not be mistaken for commercial PCBs, but they’re pretty darn good, and as [Hydrogen Time] states, Process 01 is only a beginning. We expect this will be improved and streamlined as time goes by.
Fair warning, though — some steps require a fume hood to be performed safely. Luckily, we’ve got that covered. Sort of.
