Rethinking Your Jellybean Op Amps

January 6, 2025 by Dan Maloney 44 Comments

Are your jellybeans getting stale? [lcamtuf] thinks so, and his guide to choosing op-amps makes a good case for rethinking what parts you should keep in stock.

For readers of a certain vintage, the term “operational amplifier” is almost synonymous with the LM741 or LM324, and with good reason. This is despite the limitations these chips have, including the need for bipolar power supplies at relatively high voltages and the need to limit the input voltage range lest clipping and distortion occur. These chips have appeared in countless designs over the nearly 60 years that they’ve been available, and the Internet is littered with examples of circuits using them.

For [lcamtuf], the abundance of designs for these dated chips is exactly the problem, as it leads to a “copy-paste” design culture despite the far more capable and modern op-amps that are readily available. His list of preferred jellybeans includes the OPA2323, favored thanks to its lower single-supply voltage range, rail-to-rail input and output, and decent output current. The article also discussed the pros and cons of FET input, frequency response and slew rate, and the relative unimportance of internal noise, pointing out that most modern op-amps will probably be the least thermally noisy part in your circuit.

None of this is to take away from how important the 741 and other early op-amps were, of course. They are venerable chips that still have their place, and we expect they’ll be showing up in designs for many decades to come. This is just food for thought, and [lcamtuf] makes a good case for rethinking your analog designs while cluing us in on what really matters when choosing an op-amp.

Would An Indexing Feature Benefit Your Next Hinge Design?

November 27, 2024 by Donald Papp 2 Comments

[Angus] of Maker’s Muse has a video with a roundup of different 3D-printable hinge designs, and he points out that a great thing about 3D printing objects is that adding printable features to them is essentially free.

These hinges have an indexing feature that allows them to lock into place, no additional parts needed.

A great example of this is his experimental print-in-place butt hinge with indexing feature, which is a hinge that can lock without adding any additional parts. The whole video is worth a watch, but he shows off the experimental design at the 7:47 mark. The hinge can swing normally but when positioned just right, the squared-off pin within slots into a tapered track, locking the part in place.

Inspired by a handheld shopping basket with a lockable handle, [Angus] worked out a design of his own and demonstrates it with a small GoPro tripod whose legs can fold and lock in place. He admits it’s a demonstration of the concept more than a genuinely useful tripod, but it does show what’s possible with some careful design. Being entirely 3D printed in a single piece and requiring no additional hardware is awfully nice.

3D printing is very well-suited to this sort of thing, and it’s worth playing to a printer’s strengths to do for pennies what one would otherwise need dollars to accomplish.

Want some tips on designing things in a way that take full advantage of what a 3D printer can achieve? Check out printing enclosures at an angle with minimal supports, leveraging the living hinge to print complex shapes flat (and fold them up for assembly), or even print a one-piece hinge that can actually withstand a serious load. All of those are full of tips, so keep them in mind the next time you design a part.

Hacker Tactic: Building Blocks

October 24, 2024 by Arya Voronova 12 Comments

The software and hardware worlds have overlaps, and it’s worth looking over the fence to see if there’s anything you missed. You might’ve already noticed that we hackers use PCB modules and devboards in the same way that programmers might use libraries and frameworks. You’ll find way more parallels if you think about it.

Building blocks are about belonging to a community, being able to draw from it. Sometimes it’s a community of one, but you might just find that building blocks help you reach other people easily, touching upon common elements between projects that both you and some other hacker might be planning out. With every building block, you make your or someone else’s next project quicker, and maybe you make it possible.

Sometimes, however, building blocks are about being lazy.

Continue reading “Hacker Tactic: Building Blocks” →

Supercon 2023: Aleksa Bjelogrlic Dives Into Circuits That Measure Circuits

September 11, 2024 by Lewin Day 10 Comments

Oscilloscopes are one of our favorite tools for electronics development. They make the hidden dances of electrons visually obvious to us, and give us a clear understanding of what’s actually going on in a circuit.

The question few of us ever ask is, how do they work? Most specifically—how do you design a circuit that’s intended to measure another circuit? Aleksa Bjelogrlic has pondered that very idea, and came down to explain it all to us at the 2023 Hackaday Supercon.

Continue reading “Supercon 2023: Aleksa Bjelogrlic Dives Into Circuits That Measure Circuits” →

Mobile Coffee Table Uses Legs To Get Around

September 10, 2024 by Bryan Cockfield 22 Comments

For getting around on most surfaces, it’s hard to beat the utility of the wheel. Versatile, inexpensive, and able to be made from a wide array of materials has led to this being a cornerstone technology for the past ten thousand years or so. But with that much history it can seem a little bit played out. To change up the locomotion game, you might want to consider using robotic legs instead. That’s what [Giliam] designed into this mobile coffee table which uses custom linkages to move its legs and get itself from place to place around the living room.

Continue reading “Mobile Coffee Table Uses Legs To Get Around” →

Better Battery Design Through Science

August 2, 2024 by Bryan Cockfield 6 Comments

Before the age of lithium batteries, any project needing to carry its own power had to rely on batteries that were much less energy-dense and affordable. In many ways, we take modern lithium technology for granted, and can easily put massive batteries in our projects by the standards of just a few decades ago. While the affordability of lithium batteries has certainly decreased the amount of energy we need to put in to our projects to properly size batteries, there’s still a lot of work to be done if you’re working on a bigger project or just want to get the maximize the efficiency and effectiveness of your DIY battery pack.

The main problem with choosing a battery, as [ionworks] explains, is that batteries can’t be built for both high energy and high power, at least not without making major concessions for weight or cost. After diving in to all of the possible ways of customizing a battery, the battery guide jumps in to using PyBaMM to perform computational modeling of potential battery designs to hopefully avoid the cumbersome task of testing all of the possible ways of building a battery. With this tool virtually all of a battery’s characteristics can be simulated and potential problems with your setup can be uncovered before you chose (or start production of) a specific battery system.

While customizing a battery pack to this extent might not be a consideration for most of us unless the project is going to be big enough to run something like an electric car or a whole-house generator, it’s a worthwhile tool to know about as even smaller projects like ebikes can benefit from choosing the right cell for the application. Some of the nuances of battery pack design can be found in this guide to building packs from the standard 18650 cells.

Header: Lead holder, CC BY-SA 3.0 .

Hacker Tactic: Single-PCB Panels

July 17, 2024 by Arya Voronova 35 Comments

Ordering a PCB? Two of them? Three? Five? For about eight years now, I’ve been regularly ordering large numbers of different PCBs, and, naturally, have developed a toolkit to make things smoother. One trick is PCB panelization, and you should really know about it.

You might’ve encountered PCB panels already. Perhaps, if you order PCBA at a fab, you will get your board returned in a whole new form-factor, with rails on the sides that you have to snap off before your PCB is usable. Those rails are used so that your PCBs are easier to handle during assembly, but that’s far from the only reason why you would make a panel.

If you need multiple pieces of a PCB, your fab may say that building 50 pcs is classified as “large batch” and that takes longer than 30 days, which delays your entire PCB order. I’ve been there, five years ago, running out of time right before Chinese New Year. The fix was simple – I made a 2×2 panel and ordered that in quantity of 10-15. Panelization might be a little more expensive, or maybe even cheaper, but, most importantly, it will be faster.

In a few hours’ time, I sat down, figured out that KiCad has built-in features for panelization, and ordered panels instead of separate PCBs. Thanks to that, I made the Chinese New Year deadline that year and could successfully restock my store, letting me earn a fair bit of money instead of keeping a popular product out-of-stock – ultimately, helping my family stay up on rent that month.

Panelization lets you hack around many PCB ordering and assembly limitations, and I’ve only gotten started – there’s way way more! For now, let’s sort out panelizing multiples of the same PCB. As long as your boards are using KiCad (or KiCad-converted from Eagle/EasyEDA/Altium/gerbers), there’s no better software than KiKit.

Continue reading “Hacker Tactic: Single-PCB Panels” →