Injection Molds From Your 3D Printer

Last time we checked in with [CrafsMan] he had bought a benchtop injection molding machine. This time, he shows off how to 3D print molds. If you have ever had to spend to make tooling for injection molding, you’ll appreciate being able to make molds relatively inexpensively.

To test his workflow, [CrafsMan] created a little 3D figurine and brought it into TinkerCad. From there he created a mold and used Lychee Slicer to print it using resin.

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AppCAD Does Transmission Lines

Broadcom and Agilent are perhaps not household words in every household, but among those who work with RF, they are common enough names. An Agilent developer wrote AppCAD to help with common RF design computations and now works for Avago who bought Broadcom. But whoever’s branding is on it, you can download the tool from Broadcom or check out the latest beta version. Then watch [IMASI Guy’s] video below on how to use part of it.

What can it do? According to the website:

  • S-Parameter Analysis and Plotting
  • Active Circuit Bias Design
  • Cascade Noise and IP3 Analysis
  • Transmission Line Analysis
  • Signals and Systems
  • Complex Math Engineering Calculator

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Live Energy Monitor Helps Plan Power-Hungry Appliance Use

There are a lot of good reasons to have a better understanding of one’s household power use, and that is especially true for those that do their own solar power collection. For example, [Frederick] determined that it would be more efficient to use large appliances (like a dishwasher or washing machine) when there was excess solar power available, but the challenge was in accessing the right data in a convenient way. His Raspberry Pi-based live energy monitor was the solution, because it uses an LED matrix to display live energy data that can be consulted at a glance.

Interestingly, this project isn’t about hacking the power meter. What this project is really about is conveniently accessing that data when and where it is best needed. [Frederick] has a digital power and gas meter with the ability to accept a small wireless dongle. That dongle allows a mobile phone app to monitor power usage, including whether power is being taken from or exported to the grid.

Since [Frederick] didn’t want to have to constantly consult his mobile phone, a Raspberry Pi using a Pimoroni Unicorn HAT HD acts as a glanceable display. His Python script polls the power meter directly over WiFi, then creates a live display of power usage: one LED for every 250 W of power, with the top half of the display being power used, and the bottom half representing power exported to the grid. Now the decision of when to turn on which appliances for maximum efficiency is much easier, not by automating the appliances themselves, but simply by displaying data where it needs to be seen. (This kind of thing, incidentally, is exactly the idea behind the Rethink Displays challenge of the 2021 Hackaday Prize.)

As for those of us without a digital power meter that makes it easy for residents to access power data? It turns out there is no reason a power meter’s wireless service interface can’t be sniffed with RTL-SDR.

DIY Fume Extractor Keeps Air Clean While You Solder

Soldering is a key skill to learn when building electronics, but it’s also a process that can put out a lot of fumes. The best way to deal with this is to use a fume extractor. Of course, you can always make your own, as [Open Green Energy] ably demonstrates.

The build relies on a 120mm case fan for suction, and it’s combined with a activated carbon filter to best capture the harmful fumes from the soldering process. The fan is neatly installed inside a 3D printed enclosure of custom design, which also includes a removable tray which holds the filter material. The fan is run from a DC power supply via a barrel jack, and a basic speed controller is installed to allow the fan to be turned up higher for more suction, or lower to reduce noise.

It’s a useful item to have around the home workshop, and it’s something that you could easily whip up at home with parts from the junk bin if you’re so inclined. The benefit of 3D printing is that you can easily alter the design to suit whatever parts you have on hand.

We’ve seen a few fume extractor builds over the years, from the simple and basic to the very fancy. Video after the break.

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One Giant Button To Mute Them All

The second round of this year’s Hackaday Prize is coming to a close, and we asked you to come up with ways of refreshing work-from-home life. Well here’s one we probably all could use — a large emergency mute button that can also turn off video with an extra click. You know, in case your kid or your roommate decides to walk around in their birthday suit.

[Colin Russell-Conway]’s software-agnostic mute button uses a Seeeduino Xiao and rotary encoder, plus three momentaries that give it a second function as a media controller. Two chunks of LED strip go blinky blinky when the mute is on, and are otherwise solidly lit and color-coded by videoconference type — blue for Zoom and Starleaf, green for Webex, and purple for Teams.

The companion app that [Colin] created is using the Windows Management Instrumentation (WMI) to check which program is control of the microphone. Whenever the mute button is pressed, the app makes note of the current program in focus, switches to the active videoconference, mutes it, and then switches back to reddit or twitch or whatever you had in focus when the kid started screaming for you from the bathroom. Check out the demo after the break.

Some of us like to celebrate a little when videoconferences are over. For those people, there is the pull-chain exit.

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The Story Behind Ohm’s Law

Do you ever wonder how much of what we do you could figure out from scratch? Tying your shoe might seem simple now, but kids have trouble mastering the skill, and dreaming it up for the first time is even harder. The same holds true for a lot of technology we use every day. Would you think up the computer mouse or even the computer if they didn’t already exist? Surely, though, one of the simplest and most useful math equations that is fundamental to electronics — Ohm’s law — would be easy to figure out, right? It is often the first thing you learn about electronics, but figuring it out that first time turned out to be quite difficult.

The fellow who discovered the relationship was Georg Ohm, a high school math and physics teacher from Köln. What you might not know is that the first time he published it, he got it wrong. But, lucky for us, he figured out his mistake and was able to correct it.

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Ball Balancing Wheel Puts A Spin On Inverted Pendulums

If you march sufficiently deep into the wilderness of control theory, you’ll no doubt encounter the inverted pendulum problem. These balancing acts have emerged with a number of variants over the years, but just because it’s been done before doesn’t mean there’s no space for something new. Here, [David Gonzalez], has taken this classic problem and given it an original own spin–literally–where the balancing act is now a ball balanced precariously upon a spinning wheel. (Video, embedded below.) Mix in a little computer vision for sensing, a dash of brushless motor control, a bit of math, and you have yourself a closed-loop system that’s bound to turn a few heads.

[David’s] implementation is a healthy mix of classic control theory with some modern electronics. From the theory bucket, there’s a state-space controller to drive both the angle and angular velocity of the ball to zero. The “state” is a combination of four terms: the ball angle, the ball’s angular velocity, the wheel angle, and the wheel’s angular velocity. [David] weights each of these terms and sums them together to create an input value to adjust the motor velocity driving the wheel and balance the ball.

From the electronics bin, [David] opted for an ESP32 running Arduino, the custom Janus Brushless Motor Controller running SimpleFOC, and a Maix Bit Microcontroller with an added camera running MicroPython to compute the ball angle. Finally, if you’re curious to dig into the source code, [David] has kindly posted the firmware on Github.

We love seeing folks mix a bit of control theory into an amalgamation of familiar electronics. And as both precision sensors and motor controllers continue to improve, we’re excited to see how the landscape of projects changes yet again. Hungry for more folks closing the loop on unstable systems? Look no further than [UFactory’s] ball balancing robot and [Gear Down for What’s] two wheeled speedster.

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