We like to build things using real parts. But we do think the more you can model using tools like LTSpice, the less time you can spend going down dead ends. If you need to model a common component like a resistor or even an active device, most simulators have great models and you can tweak them to have realistic parasitic effects. But what if the component you want isn’t in the library or doesn’t have the fidelity you want? [FesZ] wanted to model photovoltaic cells and had to build his own model. The resulting two videos are well worth watching.
Building your own models in Spice isn’t necessarily very difficult. However, knowing exactly what to add to model different real-world effects can be challenging. The videos do a good job of showing how to mutate a simple diode into one that produces current when exposed to light.
[M Caldeira] needed to test a tube and didn’t have a spare to do the old swap test. He also didn’t have a tube tester handy. Drawing inspiration from a 2015 video, he managed to cobble up an ad hoc tube tester using stuff around the workbench. You can see a video of the process below.
To duplicate his effort, you are going to need a few meters. Good thing they are relatively cheap these days. Usually, a tube tester has a way to adjust all the different parameters for the tube, but there’s no reason you can’t just set those parameters using your testbench power supplies.
Reference mics are vital tools for audio work. They’re prized for their flat frequency response, and are often used for characterizing the audio response of a room or space. OpenRefMic aims to be an open source design for producing reference mics without paying exorbitant retail prices.
The heart of the build is a preamplifier that runs off standard 48 V phantom power, and is responsible for both biasing the electret microphone element and acting as a buffer for the mic signal. It’s designed specifically to work with the PUI AOM-5024L-HD-F-R mic capsule, chosen for its good performance and low noise characteristics. However, other electric mics should work, too. The hardware is wrapped up in a 3D printed case which can readily be made on most basic printers. It’s complete with a press-fit grille that holds the mic capsule in place.
The prime goal of the project is low noise; the project creator, [loudifier], notes that most commercial reference mics focus first on flat frequency response and then reducing noise. OpenRefMic performs well in this area, and its lack of a perfectly flat frequency response is countered with calibrated equalization. It also works with regular pro-grade XLR cables and phantom power, rather than needing fancy laboratory-spec cables and interfaces.
Industrial machines have all kinds of moving parts that require regular lubrication in order to prevent wear and damage. Historically, these would require regular visits from maintenance personnel to keep them greased up and slippery. Automatic lubricators eliminate that job by regularly dosing machines with fresh grease, and [Big Clive] decided to see what makes them tick.
The device can be set to deliver a full load of grease over a period of 1-12 months.
The simplest models merely use a spring to slowly force grease out over time. Changing the spring changes the rate at which grease is dispensed. Chemical versions exist too. A chemical pill is selected and inserted into a chamber with liquid, which releases gas over time. As gas is released, it creates pressure which forces a plunger down, dispensing grease over time.
Perhaps the fanciest versions are the electronic models, however, which have a dial on the back for selecting the rate of grease delivery. Turning the dial changes a resistance that is connected across two zinc-air cells which are sealed. Apparently, when current is forced through these cells and they’re excluded from oxygen, the cells liberate hydrogen gas, according to a patent [Big Clive] found. This then forces down the plunger, dispensing the grease. Turning the dial changes the resistance, changing the rate at which grease is dispensed.
The quest for labor saving in industry has produced multiple designs of automated lubricator, all of which are fantastically simple and optimised for purpose. It shows just how much can be achieved with a few components and some creative thinking, where one’s first impulse might be to reach for a timer or microcontroller to do the job.
We’ve seen a lot of camera slider builds here at Hackaday, and for good reason: having one really lets you take your project documentation, especially videos, to the next level. It’s one of those force multiplier builds — after you’ve completed it, it can help you make all your future projects just that much better. But we’re also no strangers to seeing these projects become overly complex, which can often make it difficult for others to replicate.
While some decent lasers are out there for under $400 USD, they tend to be a little small. What if you wanted something a little nicer but didn’t want to jump to the $2,000 category? The answer for [Owen Schafer] was to build it with parts he had lying around and a few strategic purchases.
While he was initially planning on using a diode laser, doing anything more than engraving is tricky. He purchased a cheap 40 W CO2 laser tube, but it meant that he needed water cooling, mirrors, and more complex stuff that a diode doesn’t need. The frame is aluminum extrusion held together with 3D printed plates. Given there was a powerful laser bouncing around with mirrors, a plywood box formed the enclosure.
The stepper controller is an Arduino Mega running the Marlaser firmware, though [Owen] admits perhaps a laser cutter-specific driver board would have been better as he spent many hours trying to get the Arduino to do what he wanted. Air ventilation is a tube with a fan that vents out a nearby window. Water cooling is just a bucket of water with a pump in it. A simple nylon hose connected to a compressor with a maximum airflow valve provides an air assist while cutting. Finally, we’re happy to report that [Owen] bought safety glasses specific to his laser to protect his eyes and researched how to ground the high voltages generated.
Like other metal detectors, this one uses two coils of wire with an oscillator circuit and some transistors. The unique part of this build, though, is how the detector alerts the user to a piece of metal. Normally there would be an audible alert as the frequencies of the circuit change when in the presence of metal, but this one uses a smartphone to analyze the frequency information instead. The circuit is fed directly into the headphone jack on the smartphone and can be calibrated and used from within an Android app.
Not only can this build detect metal, but it can discriminate between different types of metal. [mircemk] notes that since this was just for experimentation, it needs to be calibrated often and isn’t as sensitive as others he’s built in the past. Of course this build also presumes that your phone still has a headphone jack, but we won’t dig up that can of worms for this feature. Instead, we’ll point out that [mircemk] has shown off other builds that don’t require any external hardware to uncover buried treasure.
