2026-01-12 20:00:32
Living without standard utility hookups like electricity, Internet, water, and sewer comes with a whole host of challenges, all of which are most commonly solved by spending lots of money. For electricity, a solar array or a generator is fairly common. The Internet can similarly be accessed via a satellite link if wires aren’t available. For water, most people will drill a well, but that gets similarly expensive. [Cranktown City] recently bought an off-grid home and needed a way to get water to it on a budget, so he built this water trailer instead.
The trailer started off as a standard single-axle utility trailer. The weight rating was probably around 3,500 pounds or 1588 kg. A few support structures were welded in. The supports serve double duty as a frame for two IBC totes, which can hold about 550 gallons or 2082 liters of water. The trailer also got upgraded wiring, including some extra wires to support a backup camera. The two totes were then plumbed together with a ball valve for an outlet. That valve was mated to a motor that can be remotely activated from within a truck to dump the water out into a cistern.
On the cistern side, [Cranktown City] welded up a door with a linear actuator and a remote control. When he’s ready to dump the water into the cistern, he can easily back up the trailer using the backup camera, open the door to the cistern remotely, and then activate the ball valve on the trailer to start filling the reservoir. It’s a clever solution to bringing water to his off-grid property at a fraction of the cost of a drilled well. We’ve seen some other unique ways to live off-grid as well, like this hydroelectric generator, which might offset the cost of an expensive solar array.
2026-01-12 17:00:13
If you’ve got a decent CRT monitor, you can usually adjust the settings to make sure the image scans nicely across the whole display. But what if you could rotate the whole image itself? [Jeri Ellsworth] has shown us how to achieve this with an amusing mechanical hack.
The trick behind this is simple. On a standard CRT, the deflection yoke uses magnetic coils to steer the electron beam in the X and Y axes, spraying electrons at the phosphors as needed. To rotate the display as a whole, you could do some complicated maths and change how you drive the coils and steer the electron beams… or you could just rotate the entire yoke instead. [Jeri] achieves this by putting the whole deflection yoke on a custom slip ring assembly. This allows it to receive power and signal as it rotates around the neck of the tube, driven by a stepper motor.
Amusingly, [Jeri] even found a super nifty way to drive the stepper. There are no microcontrollers or fancy driver logic here—instead, the quadrature output from a rotary encoder outputs a perfectly legible pulse train which can drive the stepper as needed. [Jeri] notes this provides a nicely instantaneous response. There’s still work to be done, too. The project is due to get a 3D-printed housing, a homing system, and some improvements to the DIY slip ring setup.
If [Jeri’s] name sounds familiar, that’s because she’s built many a grand project over the years. You might have seen her work on the C64 DTV or the breadbin keytar.
I have big plans for spinny CRT
— Jeri Ellsworth (@jeriellsworth.bsky.social) 2026-01-05T10:42:52.953Z
[Thanks to Neonsystem95 for the tip!]
2026-01-12 14:00:30
It used to be a rite of passage to be able to do the math necessary to design various bipolar transistor amplifier configurations. This doesn’t come up as often as it used to, but it is still a good skill to have, and [Void Electronics] walks us through a common emitter amplifier in a recent video you can see below.
The input design parameters are the gain and the collector voltage. You also have to pick a reasonable collector current within the range for your proposed device that provides enough power to the load. You also pick a quiescent voltage which, if you don’t have a good reason for picking a different value, will usually be half the supply voltage.
The calculations are approximate since the base-emitter voltage drop will vary by temperature, among other things. But, of course, real resistors won’t have the exact values you want, or even the exact value marked on them, so you need a little flexibility, anyway.
There are other ways to approach the design. But most design guides will make the same assumptions: Ic=Ie, base current is negligible, and similar simplifying assumptions.
At the end, the circuit winds up on a breadboard so you can see how close the predicted performance is to the design.
We’ve covered biasing bipolar devices a number of times. We’ve even modeled circuit variations in a spreadsheet.
2026-01-12 11:00:52
Variable capacitors may be useful, but the air gap that provides their capacitance is their greatest weakness. Rather than deal with the poor dielectric properties of air, some high-end variable capacitors replace it with a vacuum, which presents some obvious mechanical difficulties, but does give the resulting capacitor a remarkable quality factor, high-voltage performance, and higher capacitance for plate area than their air-gapped brethren. [Shahriar] of [The Signal Path] managed to acquire a pair of these and took a detailed look at their construction and performance in a recent video.
The vacuum capacitors don’t use quite the same parallel plate design as other variable capacitors. They instead make the plates out of interlaced concentric metal rings mounted in a vacuum tube. Both sets of rings are connected to terminals, one fixed and one capable of being pulled in or out on a threaded rod surrounded by an accordion-pleated copper seal. A nut on the outside pulls the rod out, and the interior vacuum pulls it in toward the other set of plates. Unfortunately, since the mobile terminal needs to be mechanically connected to some adjustment mechanism (such as someone’s hand), it can’t really be at a floating voltage. The mobile terminal needs to be grounded for safety. Alternatively, for automatic control, one of the capacitors had a chassis with a motor, gearing, and a positional encoder.
[Shahriar] also tested the capacitors with an impedance analyzer and lock-in amplifier. They had fairly low capacitance (for the one he tested, 36 pF at maximum and 16 pF at minimum), but the dissipation factor was so low and the DC impedance so high that they couldn’t be meaningfully measured. He also tested one at 5000 volts and found almost no dissipation.
We recently saw another video going over a lesser-known feature of normal air-gap variable capacitors and another new non-standard variable capacitor design. On the opposite end of the fanciness spectrum might be this variable capacitor built out of aluminium cans.
2026-01-12 08:00:26
At the risk of starting a controversy: is there anyone who goes to the effort of setting up Home Assistant who wouldn’t really rather be living on the Enterprise-D? If such a person exists, it’s not [steve-gibbs5], who has not only put together a convincing LCARS dashboard on an Android tablet, but has also put together an easy-to-follow Instructable so you can too.
In case you’ve been monkishly avoiding television since the mid-1980s, LCARS is the high-tech touchscreen interface used on Star Trek: The Next Generation and its sequels. It’s an iconic, instantly-recognizable aesthetic, and we think [Steve] nailed it, even if he was taking design cues from Voyager, which is… not everyone’s favorite trek, to put it mildly. Though perhaps the haters are looking back on it a bit more fondly when compared to some more modern adaptations. Check it out in action in the video embedded below.
The secret to getting your Android tablet looking like a 24th-century terminal is an application called “Total Launcher“, which allows one to customize one’s homescreen to a very high degree. [Steve] shows us how he styled Total Launcher, but that custom home screen isn’t enough on its own. Those futuristic buttons need to do something, which is where a second app called Tasker comes in. Tasks in Tasker are linked to the LCARS interface and the smart home features — in [Steve]’s case, Amazon Alexa, but it looks like Google’s spyware or the open-source Home Assistant are equally viable options.
We saw Star Trek style on Raspberry Pi back in the day, but nothing says your smart home has to be Trek-themed. You could even control it via a dumb terminal if that’s more your style.
2026-01-12 05:00:51
EDM (Electrical Discharge Machining) is one of those specialised manufacturing processes that are traditionally expensive and therefore somewhat underrepresented in the DIY and hacker scenes. It’s with great delight that we present EnderSpark, a solution to not one but two problems. The first problem is how to perform CNC operations on hard-to-machine materials such as hardened metals (without breaking the bank). The second problem is what to do with all those broken and forgotten previous-generation Creality Ender 3D printers we know you have stashed away.
To be honest, there isn’t much to a cheap 3D printer, and once you ditch the bed and extruder assembly, you aren’t left with a lot. Anyway, the first job was to add a 51:1 reduction gearbox between the NEMA 17 motors and the drive pullies, giving the much-needed boost to positional accuracy. Next, the X and Y axes were beefed up with a pair of inexpensive MGN12H linear rails to help them cope with the weight of the water bath.
The majority of the work is in the wire feeder assembly, which was constructed around a custom-machined aluminium plate.
It’s not lost on us how the original RepRap bootstrapping concept could be applied here: a basic frame made externally in a low-cost material, then using the machine to cut a much thicker, stronger copy for its own upgrade. The main guide nozzle is an off-the-shelf ruby part surrounded by a 3D printed water-cooling jacket. To maximise power transfer from the wire into the electrically conductive workpiece material, the top part of the wire feeder, including the wire itself, is one electrode, and the entire bottom part of the frame is electrically isolated from it. The bottom part pulls the ‘consumed’ stock wire through the nozzle above and keeps it under tension, sending it onward to the waste spool.
Electrically speaking, the project is based on stock Ender electronics, with an additional power driver stage to send capacitor-discharge-derived pulses down the wire from the 48V power supply, up to 10A, generating the needed tiny sparks as the wire is advanced into the electrically grounded workpiece. Industrial machines operate around twice this voltage, but safety is a big issue with a DIY machine. Not to mention 48V and water don’t make the best of friends. Speaking of water, it needs to be de-ionised to reduce dielectric loss, but ionic contamination will build up over time, so it needs to be regularly changed.
Software-wise, the machine is running on G-code, so all that is needed is a custom plugin for Fusion 360 to turn the extracted toolpath (they’re using the Wazer water cutter profile as a basis) into G-code, with knowledge of the material. There aren’t too many variables to play with there.
In the future, a few things are being considered. Adding closed-loop control of the pulse energy would be straightforward, but controlling the horizontal feed rate would be a little trickier to implement with a pure G-code approach. We’ll keep an eye on the project and report back any advances!
If you’re thinking you’ve seen this sort of thing before, you’re right. Here’s another DIY EDM machine, and another, and finally, a Kickstarter we covered a while back that converts any 3D printer into a wire EDM.
Thanks [irox] for the tip!
