A set of three linear actuators set atop a green with yellow grid cutting mat. The electric actuator on the top of the image is silver and has a squarish tube. It is slender compared to the other two. A black, hydraulic actuator sits in the middle and is the largest of the three. A silver pneumatic actuator at the bottom of the image is the middle sized unit.

Linear Actuators 101

August 28, 2025 by 16 Comments

Linear actuators are a great help when you’re moving something along a single axis, but with so many options, how do you decide? [Jeremy Fielding] walks us through some of the high level tradeoffs of using one type of actuator over another.

There are three main types of linear actuator available to the maker: hydraulic, pneumatic, and electric. Both the hydraulic and pneumatic types move a cylinder with an attached rod through a tube using pressure applied to either side of the cylinder. [Fielding] explains how the pushing force will be greater than the pulling force on these actuators since the rod reduces the available surface area on the cylinder when pulling the rod back into the actuator.

Electric actuators typically use an electric motor to drive a screw that moves the rod in and out. Unsurprisingly, the electric actuator is quieter and more precise than its fluid-driven counterparts. Pneumatic wins out when you want something fast and without a mess if a leak happens. Hydraulics can be driven to higher pressures and are typically best when power is the primary concern which is why we see them in construction equipment.

You can DIY your own linear actuators, we’ve seen tubular stepper motors, and even a linear actuator inspired by muscles.

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Animatronic Eyes Are Watching You

August 28, 2025 by 9 Comments

If you haven’t been following [Will Cogley]’s animatronic adventures on YouTube, you’re missing out. He’s got a good thing going, and the latest step is an adorable robot that tracks you with its own eyes.

Yes, the cameras are embedded inside the animatronic eyes.That was a lot easier than expected; rather than the redesign he was afraid of [Will] was able to route the camera cable through his existing animatronic mechanism, and only needed to hollow out the eyeball. The tiny camera’s aperture sits nigh-undetectable within the pupil.

On the software side, face tracking is provided by MediaPipe. It’s currently running on a laptop, but the plan is to embed a Raspberry Pi inside the robot at a later date. MediaPipe tracks any visible face and calculates the X and Y offset to direct the servos. With a dead zone at the center of the image and a little smoothing, the eye motion becomes uncannily natural. [Will] doesn’t say how he’s got it set up to handle more than one face; likely it will just stick with the first object identified.

Eyes aren’t much by themselves, so [Will] goes further by creating a little robot. The adorable head sits on a 3D-printed tapered roller bearing atop a very simple body. Another printed mechanism allows for pivot, and both axes are servo-controlled, bringing the total number of motors up to six. Tracking prefers eye motion, and the head pivots to follow to try and create a naturalistic motion. Judge for yourself how well it works in the video below. (Jump to 7:15 for the finished product.)

We’ve featured [Will]’s animatronic anatomy adventures before– everything from beating hearts, and full-motion bionic hands, to an earlier, camera-less iteration of the eyes in this project.

Don’t forget if you ever find yourself wading into the Uncanny Valley that you can tip us off to make sure everyone can share in the discomfort.

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PVDF: The Specialized Filament For Chemical And Moisture Resistance

August 28, 2025 by 18 Comments

There’s a dizzying number of specialist 3D printing materials out there, some of which do try to offer an alternative to PLA, PA6, ABS, etc., while others are happy to stay in their own niche. Polyvinylidene fluoride (PVDF) is one of these materials, with the [My Tech Fun] YouTube channel recently getting sent a spool of PVDF for testing, which retails for a cool $188.

Some of the build plate carnage observed after printing with PVDF. (Credit: My Tech Fun, YouTube)
Some of the build plate carnage observed after printing with PVDF. (Credit: My Tech Fun, YouTube)

Reading the specifications and datasheet for the filament over at the manufacturer’s website it’s pretty clear what the selling points are for this material are. For the chemists in the audience the addition of fluoride is probably a dead giveaway, as fluoride bonds in a material tend to be very stable. Hence PVDF ((C2H2F2)n) sees use in applications where strong resistance to aggressive chemicals as well as hydrolysis are a requirement, not to mention no hygroscopic inclinations, somewhat like PTFE and kin.

In the video’s mechanical testing it was therefore unsurprising that other than abrasion resistance it’s overall worse and more brittle than PA6 (nylon). It was also found that printing this material with two different FDM printers with the required bed temperature of 110°C was somewhat rough, with some warping and a wrecked engineering build plate in the Bambu Lab printer due to what appears to be an interaction with the usual glue stick material. Once you get the print settings dialed in it’s not too complicated, but it’s definitely not a filament for casual use.

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The Browser Wasn’t Enough, Google Wants To Control All Your Software

August 28, 2025 by 164 Comments

A few days ago we brought you word that Google was looking to crack down on “sideloaded” Android applications. That is, software packages installed from outside of the mobile operating system’s official repository. Unsurprisingly, a number of readers were outraged at the proposed changes. Android’s open nature, at least in comparison to other mobile operating systems, is what attracted many users to it in the first place. Seeing the platform slowly move towards its own walled garden approach is concerning, especially as it leaves the fate of popular services such as the F-Droid free and open source software (FOSS) repository in question.

But for those who’ve been keeping and eye out for such things, this latest move by Google to throw their weight around isn’t exactly unexpected. They had the goodwill of the community when they decided to develop an open source browser engine to keep the likes of Microsoft from taking over the Internet and dictating the rules, but now Google has arguably become exactly what they once set out to destroy.

Today they essentially control the Internet, at least as the average person sees it, they control 72% of the mobile phone OS market, and now they want to firm up their already outsized control which apps get installed on your phone. The only question is whether or not we let them get away with it.

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Receiving Radio Signals From Space Like It’s 1994

August 28, 2025 by 18 Comments

For certain situations, older hardware is preferred or even needed to accomplish a task. This is common in industrial applications where old machinery might not be supported by modern hardware or software. Even in these situations though, we have the benefit of modern technology and the Internet to get these systems up and running again. [Old Computers Sucked] is not only building a mid-90s system to receive NOAA satellite imagery, he’s doing it only with tools and equipment available to someone from this era.

Of course the first step here is to set up a computer and the relevant software that an amateur radio operator would have had access to in 1994. [Old Computers Sucked] already had the computer, so he turned to JV-FAX for software. This tool can decode the APT encoding used by some NOAA satellites without immediately filling his 2 MB hard drive, so with that out of the way he starts on building the radio.

In the 90s, wire wrapping was common for prototyping so he builds a hardware digitizer interface using this method, which will be used to help the computer interface with the radio. [Old Computers Sucked] is rolling his own hardware here as well, based on a Motorola MC3362 VHF FM chip and a phase-locked loop (PLL), although this time on a PCB since RF doesn’t behave nicely with wire wrap. The PCB design is also done with software from the 90s, in this case Protel which is known today as Altium Designer.

In the end, [Old Computers Sucked] was able to receive portions of imagery from weather satellites still using the analog FM signals from days of yore, but there are a few problems with his build that are keeping him from seeing perfectly clear imagery. He’s not exactly sure what’s wrong but he suspects its with the hardware digitizer as it was behaving erratically earlier in the build. We admire his dedication to the time period, though, down to almost every detail of the build. It reminds us of [saveitforparts]’s effort to get an 80s satellite internet experience a little while back.

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The (Data) Plot Thickens

August 28, 2025 by 35 Comments

You’ve generated a ton of data. How do you analyze it and present it? Sure, you can use a spreadsheet. Or break out some programming tools. Or try LabPlot. Sure, it is sort of like a spreadsheet. But it does more. It has object management features, worksheets like a Juypter notebook, and a software development kit, in case it doesn’t do what you want out of the box.

The program is made to deal with very large data sets. There are tons of output options, including the usual line plots, histograms, and more exotic things like Q-Q plots. You can have hierarchies of spreadsheets (for example, a child spreadsheet can compute statistics about a parent spreadsheet). There are tons of regression analysis tools, likelihood estimation, and numerical integration and differentiation built in.

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Acoustic Coupling Like It’s 1985

August 27, 2025 by 20 Comments

Before the days of mobile broadband, and before broadband itself even, there was a time where Internet access was provided by phone lines. To get onto a BBS or chat on ICQ required dialing a phone number and accoustically coupling a computer to the phone system. The digital data transmitted as audio didn’t have a lot of bandwidth by today’s standards but it was revolutionary for the time. [Nino] is taking us back to that era by using a serial modem at his house and a device that can communicate to it through any phone, including a public pay phone.

As someone in the present time can imagine, a huge challenge of this project wasn’t technical. Simply finding a working public phone in an era of smartphones was a major hurdle, and at one point involved accidentally upsetting local drug dealers. Eventually [Nino] finds a working pay phone that takes more than one type of coin and isn’t in a loud place where he can duct tape the receiver to his home brew modem and connect back to his computer in his house over the phone line like it’s 1994 again.

Of course with an analog connection like this on old, public hardware there were bound to be a few other issues as well. There were some quirks with the modems including them not hanging up properly and not processing commands quickly enough. [Nino] surmises that something like this hasn’t been done in 20 years, and while this might be true for pay phones we have seen other projects that use VoIP systems at desk phones to accomplish a similar task.

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