Kritik sah

The vibrobot – a vibrating motor and battery attached to the head of a brush – isn’t truly a robot, since its movement can’t be controlled, but it’s whetted the interest of many future roboticists. With a clever control method , though, it is in fact possible to drive them in any desired direction while using only one motor. [Namaskar Mitro] based the design of this robot on this research paper ; if the vibrating motor is mounted at an angle above the base of the robot, it causes the bot to rotate, and if the motor is mounted off-center from the center of mass, the robot moves in a circle. Crucially, reversing the direction of the motor’s rotation reverses the direction of the robot’s rotation. By rapidly switching the direction of rotation, the bot can move in a series of short, shallow arcs which approximate a straight line. The robot which [Namaskar] built was based on an ESP-01F microcontroller, which let it be remote-controlled over Wi-Fi. It used a DRF8212 motor driver to cont...

Building your own sprinkler system controller isn’t that difficult on the face of it, but what happens when your system starts to grow, adding more distant areas? To tackle this, [Vinnie] leveraged the tried-and-true RS-485 differential pairs to communicate reliably with ever-more-spread-out valves on his farm’s irrigation system . The system uses a Raspberry Pi to control when each valve turns on and for how long. It does this via a custom RS-485 valve master board, whose code and design files are on GitHub . The master board communicates with the Pi over I2C and issues RS-485 commands while controlling the 12V line to the valves. Toggling the 12V supply is a smart move it lets [Vinnie] save power by not keeping the valves energized when idle. At the valves themselves lives a valve node board (also on the GitHub repo). Each node has a unique address so it knows when its name is called to open or close a valve. The valves are latching solenoids, ideal because they don’t require cons...

If you want to maximize the life of your lithium-ion batteries, proper storage voltage is critical. That is, don’t store them empty, and don’t store them completely full either. “Almost fully charged” is a sweet spot for occasional-use devices. Sadly, this is easier said than done. While many devices use integrated rechargeable batteries these days, most provide no method of limiting charge level. That’s where [DaverDavid]’s ChargeCap comes in . By sampling charge current and disconnecting when it drops to 50 percent of peak, charging is reliably stopped when the target device is 80 to 90 percent charged, regardless of cell count or capacity. ChargeCap sits between a USB charger and target device, disconnecting when it detects that recharging is 80 to 90 percent complete. This is particularly useful for maximizing the cell life of devices that see only intermittent use. The way ChargeCap does this is clever, and relies on the fact that all lithium-...

Fire arrow versus the recreated fire dart. (Credit: Tod’s Workshop, YouTube) The  Mary Rose was a carrack in the English Tudor Navy of King Henry VIII  that fought in multiple battles during the 16th century before it was sunk in 1545. After its wreck was located in 1971 and raised in 1982 the ship and all the items contained within the partially preserved hull became the focus of intense study. Among these items are the weaponry found, including the canons, but also massive darts that seemed to have been designed for an incendiary payload. Recently [Tod’s Workshop] collaborated with others to test these presumed incendiary darts . Although fire arrows have been around for a while, seeing what appears to be super-sized versions of these is somewhat unusual, but could make sense in taking out enemy ships of the time. The main questions are how you would even fire them, and how effective they would be. Were the darts thrown by hand from e.g. the crow’s nest, or fired ...

If you’ve watched a Saturn V launch, you’ve probably seen how a large rocket will often jettison a stage on the way up. There are several reasons for this — there is no reason to haul an empty fuel container, for example. However, you can probably imagine how the separation works. You release something — probably explosive bolts — and gravity pulls the old stage away from you as you climb on the next stage’s engines. But what about on the way back? The command module drops the service module before reentry. [Apollo11Space] has a video explaining just how complicated that was to pull off . You can watch it below. The main problem? The service module has almost everything you need: oxygen, a big engine, fuel, and electrical generation capability. If you’ve ever seen a real command module, they are tiny. Somehow, you need to get the command module prepared to be on its own for the amount of time it takes to land, and get the service module safely ...

If you’ve been interested in FreeCAD but haven’t known where to start, here’s a wonderful video tutorial for FreeCAD 1.1 by [Deltahedra] aimed squarely at how to model a 3D part from scratch while also following best engineering practices for part design. It focuses on a concise and meaningful workflow that respects your time and doesn’t make assumptions about skill level. It even starts by taking a few moments to explain how to navigate the interface, a courtesy many will appreciate. FreeCAD can do quite a lot, so a tutorial that focuses on a specific yet broadly-applicable task with a clear context is a great way to narrow the scope into something manageable, and be comprehensive without getting bogged down in minutiae. [Deltahedra] does this by exclusively using the part design workbench, demonstrating what to do to make a part step-by-step, and showing common mistakes that can happen and how to fix them if they occur. Beyond that, it’s left up to the...