The aim of the device is to automate the motion of a laser pointer to make playing with the cats a hands-free operation. A pan-tilt servo mechanism has a low-power red laser pointer fitted, and the assembly is hooked up to a NodeMCU microcontroller. Based on the ESP8266, it allows the system to be controlled remotely over WiFi. Various sweeps can be automatically commanded from a smartphone, or the servo position can be controlled manually.
Test footage confirms that [Tobi’s] pets do indeed find the device to be worthy prey. It’s a popular build for cat lovers, and readily achievable with off-the-shelf parts. If you’ve built your own hardware to keep these proud hunters out of trouble, be sure to hit up the tip line.
As somebody who loves technology and wildlife and also needs to develop an old farmhouse, going down the bat detector rabbit hole was a journey hard to resist. Bats are ideal animals for hackers to monitor as they emit ultrasonic frequencies from their mouths and noses to communicate with each other, detect their prey and navigate their way around obstacles such as trees — all done in pitch black darkness. On a slight downside, many species just love to make their homes in derelict buildings and, being protected here in the EU, developers need to make a rigorous survey to ensure as best as possible that there are no bats roosting in the site.
Perfect habitat for bats.
Obviously, the authorities require a professional independent survey, but there’s still plenty of opportunity for hacker participation by performing a ‘pre-survey’. Finding bat roosts with DIY detectors will tell us immediately if there is a problem, and give us a head start on rethinking our plans.
As can be expected, bat detectors come in all shapes and sizes, using various electrickery techniques to make them cheaper to build or easier to use. There are four different techniques most popularly used in bat detectors.
Heterodyne: rather like tuning a radio, pitch is reduced without slowing the call down.
Time expansion: chunks of data are slowed down to human audible frequencies.
Frequency division: uses a digital counter IC to divide the frequency down in real time.
Full spectrum: the full acoustic spectrum is recorded as a wav file.
Fortunately, recent advances in technology have now enabled manufacturers to produce relatively cheap full spectrum devices, which give the best resolution and the best chances of identifying the actual bat species.
DIY bat detectors tend to be of the frequency division type and are great for helping spot bats emerging from buildings. An audible noise from a speaker or headphones can prompt us to confirm that the fleeting black shape that we glimpsed was actually a bat and not a moth in the foreground. I used one of these detectors in conjunction with a video recorder to confirm that a bat was indeed NOT exiting from an old chimney pot. Phew!
Leaving no stone unturned in his quest for alternative and improbable ways to generate lift, [Tom Stanton] has come up with some interesting aircraft over the years. But this time he isn’t exactly flying, with this unusual Coandă effect hovercraft.
If you’re not familiar with the Coandă effect, neither were we until [Tom] tried to harness it for a quadcopter. The idea is that air moving at high speed across a curved surface will tend to follow it, meaning that lift can be generated. [Tom]’s original Coandă-copter was a bit of a bust – yes, there was lift, but it wasn’t much and wasn’t easy to control. He did notice that there was a strong ground effect, though, and that led him to design the hovercraft. Traditional hovercraft use fans to pressurize a plenum under the craft, lifting it on a low-friction cushion of air. The Coandă hovercraft uses the airflow over the curved hull to generate lift, which it does surprisingly well. The hovercraft proved to be pretty peppy once [Tom] got the hang of controlling it, although it seemed prone to lifting off as it maneuvered over bumps in his backyard. We wonder if a control algorithm could be devised to reduce the throttle if an accelerometer detects lift-off; that might make keeping the craft on the ground a bit easier.
As always, we appreciate [Tom]’s builds as well as his high-quality presentation. But if oddball quadcopters or hovercraft aren’t quite your thing, you can always put the Coandă effect to use levitating screwdrivers and the like.
When life gives you lemons, you make lemonade. At least that’s what the [Sprice Machines] thought when they decided to turn a house into the set of a 9-minute long Rube Goldberg machine to make lemonade. (Video embedded below.) The complex chain reactions runs across multiple rooms, using everyday objects like brooms and even a vibrating smartphone to transfer energy across the complex contraption.
While the team professionally builds Rube Goldberg machines for clients, the Lemonade Machine looks surprisingly organic, like something a family might decide to do for fun over a long weekend (although there area few moments that make you question just how they were able to perfectly time every sequence in the chain reaction). Even though the actual lemonade making only takes up a small fraction of the machine, watching marble runs, weights dashing across a clothesline, and random household items repurposed into energy transfer mechanisms is really entertaining.
Transformers are deceptively simple devices. Just coils of wire sharing a common core, they tempt you into thinking you can make your own, and in many cases you can. But DIY transformers have their limits, as [Great Scott!] learned when he tried to 3D-print his own power transformer.
To be fair, the bulk of the video below has nothing to do with 3D-printing of transformer coils. The first part concentrates on building transformer cores up from scratch with commercially available punched steel laminations, in much the same way that manufacturers do it. Going through that exercise and the calculations it requires is a great intro to transformer design, and worth the price of admission alone. With the proper number of turns wound onto a bobbin, the laminated E and I pieces were woven together into a core, and the resulting transformer worked pretty much as expected.
The 3D-printed core was another story, though. [Great Scott!] printed E and I pieces from the same iron-infused PLA filament that he used when he 3D-printed a brushless DC motor. The laminations had nowhere near the magnetic flux density of the commercial stampings, though, completely changing the characteristics of the transformer. His conclusion is that a printed transformer isn’t possible, at least not at 50-Hz mains frequency. Printed cores might have a place at RF frequencies, though.
In the end, it wasn’t too surprising a result, but the video is a great intro to transformer design. And we always appreciate the “DIY or Buy” style videos that [Great Scott!] does, like his home-brew DC inverter or build vs. buy lithium-ion battery packs.
Automakers continue to promise that fully autonomous cars are around the corner, but we’re still not quite there yet. However, there are a broad range of driver assist technologies that have come to market in recent years, with lane keeping assist being one of them. [raja_961] decided to implement this technology on an RC car, using a Raspberry Pi.
A regular off-the-shelf RC car is used as the base of the platform, outfitted with two drive motors and a third motor used for the steering. Unfortunately, the car can only turn either full-left or full-right only, limiting the finesse of the steering. Despite this, the work continued. A Raspberry Pi 3 was fitted out with a motor controller and camera, and hooked up to the chassis. With everything laced up, a Python script is used along with OpenCV to run the lane-keeping algorithm.
[raja_961] does a great job of explaining the lane keeping methodology. Rather than simply invoking a library and calling it good, instead the Instructable breaks down each stage of how the algorithm works. Incoming images are converted to the HSL color system, before a series of operations is used to pick out the apparent slope of the lane lines. This is then used with a PID algorithm to guide the steering of the car.
It’s a comprehensive explanation of a basic lane-keeping algorithm, and a great place to start if you’re interested in learning about the technology. There’s plenty going on in the world of self-driving RC cars, you just need to know where to look! Video after the break.
We know not everyone who likes to build circuitry wants to dive headfirst into the underlying electrical engineering that makes everything work. However, if you want to, now is a great time. Many universities have most or all of their material online and you can even take many courses for free. If you want an endless pool of solved study problems, check out autoCircuits. It can create many different kinds of electronics problems and their solutions.
You can get a totally random circuit, or choose if you want to focus on DC, AC, two-ports, or several other types of problems. You can also alter the general form of the problem. For example, for a DC analysis, you can have it assign circuit values so that the answer is a value such as 45 ohms, or you can have it just use symbols so that the answer might be i4=V1/4R. You even get to pick the difficulty level and pick certain types of problems to avoid. Just be fast. After the site generates a problem, you have 10 seconds to download it before it is gone forever.
