Remote MQTT Temperature Sensor Shows How It’s Done

March 13, 2022 by Donald Papp 7 Comments

First of all, there are definitely simpler ways to monitor remote temperatures, but [Mike]’s remote MQTT temperature sensor and display project is useful in a few ways. Not only does it lay out how to roll such a system from scratch, but it also showcases system features like solar power.

After all, if one simply wants to monitor temperature that’s easily done, but once one wishes to log those temperatures and use them to trigger other things, then rolling one’s own solution starts to get more attractive. That’s where using someone else’s project as a design reference can come in handy.

[Mike’s] solution uses two Wemos D1 boards: one with a DS18B20 temperature sensor for outdoors, and one with a small OLED screen for an interior display. The external sensor relies on a rechargeable 18650 cell and a solar panel for a hassle-free power supply, and the internal sensor (of which there can be many) has a cute enclosure and is powered by USB. On the back end, a Raspberry Pi running an MQTT gateway and Node Red takes care of the operational side of things. The whole system has been happily running for over two years.

What is MQTT? It is essentially a messaging protocol, and takes care of the whole business of reliably communicating data back and forth between IoT devices. It scales very well and doesn’t need to be hard or intimidating; our own [Elliot Williams] can tell you all about implementing it.

Make Your Own Tabletop Game Organizers With Online Tool

February 19, 2022 by Donald Papp 3 Comments

There is a vibrant cottage industry built around selling accessories to improve the storage and organization of tabletop games, but the more DIY-minded will definitely appreciate [Steve Genoud]’s deckinabox tool, which can create either 3D-printable designs, or ones more suited to folded paper or cardstock. Making your own organizer can be as satisfying as it is economical, and [Steve]’s tool aims to make customization simple and easy.

The tool can also generate models for folded paper or cardstock.

The interface for customizing the 3D-printable token tray, for example, begins with a simple filleted receptacle which one can split into additional regions by adding horizontal or vertical separators. The default is to split a given region down the middle, but every dimension can of course be specified. Things like filleting of edges (for easier token scooping) and other details are all handled automatically. A handy 3D view gives a live render of the design after every change.

[Steve] has a blog post that goes into some added detail about how the tool was made, and it makes heavy use of replicad, [Steve]’s own library for generating browser-based 3D models in code. Intrigued by the idea of generating 3D models programmatically, and want to use it to make your own models? Don’t forget to also check out OpenSCAD; chances are it’s both easier to use and more capable than one might think.

One Tool Twists Wires, And Skewers Shish Kebabs

February 11, 2022 by Chris Lott 19 Comments

Twisting stranded wire with your fingers in preparation for tinning and/or soldering is almost a reflex for folks making electronic assemblies. But what if the wires are too close to get your fingers around, or you have the fingers of a sumo wresters? Well [DIYDSP] has a solution for you (see video below the break) that’s easy to make from a shish kebab skewer that’s probably rolling around your kitchen drawer. The reason that [DIYDSP] wanted to twist such closely spaced wires was to solder a length of 0.1 in O.C. stranded ribbon cable directly onto a PCB pin header pattern.

The method is very simple. Drill a long hole in the factory-cut flat end, followed by using a countersink bit to give a conical taper to guide the wires in. [DIYDSP] found that a 1/16 inch (1.6 mm) drill bit was a bit too large to grip the types of wires he was using, and finally settled on a 0.6 mm bit. If you are using larger wires, you should experiment to get the right size, or just build a handful of these of differing diameters since they’re so easy to make — just mark them clearly so you don’t accidentally grill shish kebabs with them on the BBQ.

The resulting tool is not unlike the business end of a hand-held wire-wrap tool, but works different principle and is a fraction of the cost. If you do any amount of interconnect wiring with stranded wires, then you should check out this video and whip up a couple of these to throw in your tool box.

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A Guide To Milling PCBs At Home

February 9, 2022 by Chris Lott 31 Comments

If you keep up with various retro vacuum tube projects, you probably have run across [UsagiElectric] aka [David]’s various PCBs that he makes on his own Bridgeport EZ-Track 3-axis milling machine — massively oversized for the job, as he puts it. In a recent video, [David] walks us through the steps of making a sample PCB, introducing the various tools and procedures of his workflow. He points out that these are the tools he uses, but the overall process should be similar no matter what tools you use.

Logisim to validate logic designs
TINA-TI, Texas Instrument’s version of the TINA SPICE simulator
DesignSpark PCB for schematic entry and PCB layout
FlatCAM, a computer-aided PCB manufacturing tool

For this video, [David] makes a half-adder circuit out of four vacuum tubes plus a seven-segment VFD tube to show the combined sum and carry outputs. Momentary switches are used to generate the two addends. Using this example, he proceeds to design, simulate, build and demonstrate a working circuit board. We like his use of the machined pin socket inserts for building a vacuum tube socket directly into the board.

Now this process isn’t for everyone. First of all, a Bridgeport mill is a pretty good sized, and heavy, tool. That said, these procedures should adapt well to other milling machines and engravers. We should point out that [David] is making boards mostly for vacuum tubes, where circuit trace width and spacing distances are generous. If you’re planning to make home PCBs for a 273-pin PGA chip, this isn’t the technique for you.

It seems that the bulk of [David]’s vacuum tube PCBs are single-sided, and reasonably so. They use wire links here and there to jump over traces. Adapting this process to double-sided PCBs is doable, but more complex. Are you milling double-sided boards in your lab? If so, let us know about it in the comments below.

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A graph visualising approximation errors - the specific principle pictured is described well by the linked article

Time And Accuracy In Las ATMegas

January 31, 2022 by Arya Voronova 4 Comments

Do you ever have to ensure that an exact amount of time passes between two tasks in your microcontroller code? Do you know what’s the difference between precision and accuracy? Today, [Jim Mack] tells us about pushing timers and interrupts to their limits when it comes to managing time, while keeping it applicable to an ever-popular ATMega328P target! Every now and then, someone decides to push the frontiers of what’s possible on a given platform, and today’s rules is coding within constraints of an Arduino environment. However, you should check [Jim]’s post out even if you use Arduino as a swearword – purely for all of the theoretical insights laid out, accompanied by hardware-accurate examples!

This will be useful to any hacker looking to implement, say, motor encoder readings, signal frequency calculations, or build a gadget processing or modifying audio in real time. To give you a sample of this article, [Jim] starts by introducing us to distinctions between precision and accuracy, and then presents us with a seemingly simple task – creating exactly 2400 interrupts a second. As much as it might look straightforward, problems quickly arise when clock crystal frequency doesn’t cleanly divide by the sampling frequency that you have to pick for your application! This is just a taste of all the examples of hidden complexity presented, and they’re accompanied with solutions you can use when you eventually encounter one of these examples in your hacker pursuits. In the end, [Jim] concludes with links to other sources you can study if you ever need to dig deeper into this topic.

Keeping our projects true to the passage of time can be an issue, and we’ve been at it for ages – calibrating your RC oscillator is a rite of passage for any ATTiny project. If you ever decide to have an interrupt peripheral help you with timing issues, we’ve gone in-depth on that topic in the past, with a three-part series describing the benefits, the drawbacks and the edgecases of interrupts. Going for a more modern target? Our piece on using interrupts with STM32 is a great path for trying out tools of the modern age.

View of a well-organized workspace in front of a window view to outdoors

How To Optimize Your Workspace: Analyze How You Work

January 24, 2022 by Donald Papp 27 Comments

[Jay Carlson] has shared some fantastic guidance on how to optimize one’s home workspace, and you just might want to emulate some of his layout, especially if you routinely juggle multiple projects. He makes the important point that different people have different needs, so one size does not fit all. Optimizing one’s workspace must first take into account what kind(s) of work one does, and many of his tips and tricks are pretty broadly applicable.

A rack of trays, each with a project — Looking online for these? A common industry term is “bun rack”. This one is “half-height” in size.

[Jay] works on embedded systems, and often switches between many different jobs and projects. Get your notepads ready, because there are plenty of great takeaways.

For example, to get a good top-down camera view of what’s on the workbench, he uses a camera mounted on an articulated arm (the kind that usually has a lamp attached to the end.) This makes the camera easy to deploy and easy to stow, and he can effortlessly save footage or share video with colleagues online.

Another great tip is using what most of us would call cafeteria trays and a matching rack. With each tray devoted to a different project or version of hardware, it makes switching between jobs as simple as sliding in one tray and pulling out another. It’s also a highly space-efficient way to store a lot of in-progress hardware. [Jay] gives a detailed walkthrough of his workspace and explains every decision, it’s well worth a read.

It’s always better to save space, as long as doing so doesn’t negatively impact the work itself. If you’re looking for space-saving tips, be sure to check out this tiny workshop’s space-saving hacks for more ideas.

Cables Too Long? Try Cable Management Via DIY Coiling

January 23, 2022 by Donald Papp 34 Comments

Annoyed by excessively-long cables? Tired of the dull drudgery and ugly results of bunching up the slack and wrapping it with a twist-tie? Suffer no longer, because the solution is to make your own coiled cables!

[Dmitry] is annoyed with long, unruly cables and shared a solution he learned from the DIY keyboards community: coil them yourself with a piece of dowel, a hair dryer, and about 10 minutes of your time. However, it’s just a wee bit more complicated than it may seem at first glance.

The process begins with wrapping a cable around a mandrel, then heating it as uniformly as possible to thermoform the jacket, but the instructional video (embedded below) says that all by itself that isn’t quite enough to yield lasting results. After heating the cable and letting it cool, the coils will be formed but it will not hold the new shape very well. The finishing touch is to “reverse” the direction of the coils, by re-wrapping it backward around the mandrel, inverting the coils upon themselves. This process is awkward to explain, but much simpler to demonstrate. This video by [DailySetupTech] explains this process around the 2:30 mark. That final step is what yields a tightly-wound, springy coil.

The nice part about using this process as a cable management technique is that it is possible to coil only a portion of a cable, leaving the exact amount of uncoiled slack required for a given application. Keep it in mind the next time some cables need managing. And if you don’t want to coil a cable but still need it out of the way, you might find this design for a DIY cable chain made from a tape measure useful.

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