A view of the schematics for each major component.

Simulating The Commodore PET

August 26, 2025 by John Elliot V 2 Comments

Over on his blog our hacker [cpt_tom] shows us how to simulate the hardware for a Commodore PET. Two of them in fact, one with static RAM and the other with dynamic RAM.

This project is serious business. The simulation environment used is Digital. Digital is a digital logic designer and circuit simulator designed for educational purposes. It’s a Java program that runs under the JVM. It deals in .dig files which are XML files that represent the details of the simulated hardware components. You don’t need to write the XML files by hand, there is a GUI for that. Continue reading “Simulating The Commodore PET” →

Google Will Require Developer Verification Even For Sideloading

August 26, 2025 by Maya Posch 115 Comments

Do you like writing software for Android, perhaps even sideload the occasional APK onto your Android device? In that case some big changes are heading your way, with Google announcing that they will soon require developer verification for all applications installed on certified Android devices – meaning basically every mainstream device. Those of us who have distributed Android apps via the Google app store will have noticed this change already, with developer verification in the form of sending in a scan of your government ID now mandatory, along with providing your contact information.

What this latest change thus effectively seems to imply is that workarounds like sideloading or using alternative app stores, like F-Droid, will no longer suffice to escape these verification demands. According to the Google blog post, these changes will be trialed starting in October of 2025, with developer verification becoming ‘available’ to all developers in March of 2026, followed by Google-blessed Android devices in Brazil, Indonesia, Thailand and Singapore becoming the first to require this verification starting in September of 2026.

Google expects that this system will be rolled out globally starting in 2027, meaning that every Google-blessed Android device will maintain a whitelist of ‘verified developers’, not unlike the locked-down Apple mobile ecosystem. Although Google’s claim is that this is for ‘security’, it does not prevent the regular practice of scammers buying up existing – verified – developer accounts, nor does it harden Android against unscrupulous apps. More likely is that this will wipe out Android as an actual alternative to Apple’s mobile OS offerings, especially for the hobbyist and open source developer.

Avocado Harvester Is A Cut Above

August 26, 2025 by Bryan Cockfield 7 Comments

For a farmer or gardener, fruit trees offer a way to make food (and sometimes money) with a minimum of effort, especially when compared to growing annual vegetables. Mature trees can be fairly self-sufficient, and may only need to be pruned once a year if at all. But getting the fruit down from these heights can be a challenge, even if it is on average less work than managing vegetable crops. [Kladrie] created this avocado snipper to help with the harvest of this crop.

Compounding the problem for avocados, even compared to other types of fruit, is their inscrutable ripeness schedule. Some have suggested that cutting the avocados out of the trees rather than pulling them is a way to help solve this issue as well, so [Kladrie] modified a pair of standard garden shears to mount on top of a long pole. A string is passed through the handle so that the user can operate them from the ground, and a small basket catches the fruit before it can plummet to the Earth. A 3D-printed guide helps ensure that the operator can reliable snip the avocados off of the tree on the first try without having to flail about with the pole and hope for the best, and the part holds the basket to the pole as well.

For those living in more northern climates, this design is similar to many tools made for harvesting apples, but the addition of the guide solves a lot of the problems these tools can have which is largely that it’s easy to miss the stems on the first try. Another problem with pulling the fruits off the tree, regardless of species, is that they can sometimes fling off of their branches in unpredictable ways which the snipping tool solves as well. Although it might not work well for avocados, if you end up using this tool for apples we also have a suggestion for what to do with them next.

Battery Repair By Reverse Engineering

August 26, 2025 by Tyler August 28 Comments

Ryobi is not exactly the Cadillac of cordless tools, but one still has certain expectations when buying a product. For most of us “don’t randomly stop working” is on the list. Ryobi 18-volt battery packs don’t always meet that expectation, but fortunately for the rest of us [Badar Jahangir Kayani] took matters into his own hands and reverse-engineered the pack to find all the common faults– and how to fix them.

[Badar]’s work was specifically on the Ryobi PBP005 18-volt battery packs. He’s reproduced the schematic for them and given a fairly comprehensive troubleshooting guide on his blog. The most common issue (65%) with the large number of batteries he tested had nothing to do with the cells or the circuit, but was the result of some sort of firmware lock.

It isn’t totally clear what caused the firmware to lock the batteries in these cases. We agree with [Badar] that it is probably some kind of glitch in a safety routine. Regardless, if you have one of these batteries that won’t charge and exhibits the characteristic flash pattern (flashing once, then again four times when pushing the battery test button), [Badar] has the fix for you. He actually has the written up the fix for a few flash patterns, but the firmware lockout is the one that needed the most work.

[Badar] took the time to find the J-tag pins hidden on the board, and flash the firmware from the NXP micro-controller that runs the show. Having done that, some snooping and comparison between bricked and working batteries found a single byte difference at a specific hex address. Writing the byte to zero, and refreshing the firmware results in batteries as good as new. At least as good as they were before the firmware lock-down kicked in, anyway.

He also discusses how to deal with unbalanced packs, dead diodes, and more. Thanks to the magic of buying a lot of dead packs on e-Bay, [Badar] was able to tally up the various failure modes; the firmware lockout discussed above was by far the majority of them, at 65%. [Badar]’s work is both comprehensive and impressive, and his blog is worth checking out even if you don’t use the green brand’s batteries. We’ve also embedded his video below if you’d rather watch than read and/or want to help out [Badar] get pennies from YouTube monetization. We really do have to give kudos for providing such a good write up along with the video.

This isn’t the first attempt we’ve seen at tearing into Ryobi batteries. When they’re working, the cheap packs are an excellent source of power for everything from CPap machines to electric bicycles.

Thanks to [Badar] for the tip.

Continue reading “Battery Repair By Reverse Engineering” →

Automated Brewing

August 26, 2025 by Bryan Cockfield 6 Comments

There’s little more to making alcoholic beverages than sugar, water, yeast, and time. Of course those with more refined or less utilitarian tastes may want to invest a bit more care and effort into making their concoctions. For beer making especially this can be a very involved task, but [Fieldman] has come up with a machine that helps automate the process and take away some of the tedium.

[Fieldman] has been making beers in relatively small eight-liter batches for a while now, and although it’s smaller than a lot of home brewers, it lends itself perfectly to automation. Rather than use a gas stove for a larger boil this process is done on a large hot plate, which is much more easily controlled by a microcontroller. The system uses an ESP32 for temperature control, and it also runs a paddle stirrer and controls a screen which lets the brewer know when it’s time to add ingredients or take the next step in the process. Various beers can be programmed in, and the touchscreen makes it easy to know at a glance what’s going on.

For a setup of this size this is a perfect way to take away some of the hassle of beer brewing like making sure the stove didn’t accidentally get too hot or making sure it’s adequately stirred for the large number of hours it might take to brew, but it still leaves the brewer in charge for the important steps.

Beer brewing is a hobby with a lot of rabbit holes to jump down, and it can get as complicated as you like. Just take a look at this larger brewery setup that automates more tasks on a much larger scale.

Continue reading “Automated Brewing” →

Picture By Paper Tape

August 26, 2025 by Al Williams 14 Comments

The April 1926 issue of “Science and Invention” had a fascinating graphic. It explained, for the curious, how a photo of a rescue at sea could be in the New York papers almost immediately. It was the modern miracle of the wire photo. But how did the picture get from Plymouth, England, to New York so quickly? Today, that’s no big deal, but set your wayback machine to a century ago.

Of course, the answer is analog fax. But think about it. How would you create an analog fax machine in 1926? The graphic is quite telling. (Click on it to enlarge, you won’t be disappointed.)

If you are like us, when you first saw it you thought: “Oh, sure, paper tape.” But a little more reflection makes you realize that solves nothing. How do you actually scan the photo onto the paper tape, and how can you reconstitute it on the other side? The paper tape is clearly digital, right? How do you do an analog-to-digital converter in 1926? Continue reading “Picture By Paper Tape” →

Troubled USB Device? This Tool Can Help

August 26, 2025 by Heidi Ulrich 18 Comments

You know how it goes — some gadgets stick around in your toolbox far longer than reason dictates, because maybe one day you’ll need it. How many of us held onto ISA diagnostic cards long past the death of the interface?

But unlike ISA, USB isn’t going away anytime soon. Which is exactly why this USB and more tester by [Iron Fuse] deserves a spot in your toolbox. This post is not meant to directly lure you into buying something, but seen how compact it is, it would be sad to challenge anyone to reinvent this ‘wheel’, instead of just ordering it.

So, to get into the details. This is far from the first USB tester to appear on these pages, but it is one of the most versatile ones we’ve seen so far. On the surface, it looks simple: a hand-soldered 14×17 cm PCB with twelve different connectors, all broken out to labelled test points. Hook up a dodgy cable or device, connect a known-good counterpart, and the board makes it painless to probe continuity, resistance, or those pesky shorts where D+ suddenly thinks it’s a ground line.

You’ll still need your multimeter (automation is promised for a future revision), but the convenience of not juggling probes into microscopic USB-C cavities is hard to overstate. Also, if finding out whether you have a power-only or a data cable is your goal, this might be the tool for you instead.