Cinemas all over the world have become no-go zones with COVID-19 around, but watching the latest blockbuster on the small screen at home is simply not the same. You could bring the big screen home, but buying a quality projector is going to set you back a small pile of cash. Fortunately [Matt] from [DIY Perks] has an alternative for us, demonstrating how to build your own true 4K projector with parts bought off eBay, for a fraction of the price.
The core of the projector is a small 4K LCD panel, which is from a modified Sony smartphone. [Matt] disassembled the phone, removed the backlight from the LCD, which leaves it semi-transparent, and mounted it at a right angle to the rest of the phone body. The battery was also replaced with a voltage regulator to simulate a full battery. To create a practical projector, a much brighter backlight is needed. [Matt] used a 100W 10 mm diameter LED for this purpose. The LED needs some serious cooling to prevent it from burning itself out, and a large CPU cooler does the job perfectly. Two Fresnel lenses in series are used to turn the diverging light from the LED into a converging light source to pass through the LCD. An old 135 mm large format camera lens is placed at the focal point of light to act as a projection lens. The entire assembly is mounted on a vertical frame of threaded rods, nuts, and aluminium plates. [Matt] also used these threaded rods with GT2 pulleys to create a simple but effective moving platform for the projection lens that allows the focus of the projected image to be adjusted. The frame is topped off by a 45-degree mirror to project the image against a wall instead of the roof, and the frame is covered with aluminium panels.
There was a time when if you wanted a computer, you had to build it. And not by ordering parts from Amazon and plugging everything together in a case — you had to buy chips, solder or wire-wrap everything, and tinker endlessly. The process was slow, painful, and expensive, but in the end, you had a completely unique machine that you knew inside out because you put every bit of it together.
In some ways, it’s good that those days are gone. Being able to throw a cheap, standardized commodity PC at a problem is incredibly powerful, but that machine will have all the charm of a rubber doorstop and no soul at all. Luckily for those looking to get back a little of the early days of the computer revolution or those that missed them entirely, there are alternatives like the Gigatron. Billed as a “minimalistic retro computer,” the Gigatron is a kit that takes the builder back even further in time than the early computer revolution since it lacks a microprocessor. All the logic of the 8-bit computer is built up from discrete 7400-series TTL chips.
The Gigatron is the brainchild of Marcel van Kervinck and Walter Belgers. Tragically, Marcel recently passed away, but Walter is carrying the Gigatron torch forward and leading a thriving community of TTL-computer aficionados as they extend and enhance what their little home-built machines can do. Walter will stop by the Hack Chat to talk all things Gigatron, and answer your questions about how this improbably popular machine came to be.
Click that speech bubble to the right, and you’ll be taken directly to the Hack Chat group on Hackaday.io. You don’t have to wait until Wednesday; join whenever you want and you can see what the community is talking about. Continue reading “Gigatron Hack Chat”→
xorSprite() plots an 8×8 sprite, moveSprite() moves a given sprite by one pixel without any flicker, and hitSprite() checks a sprite for collision with any screen elements in a given color. That is all it takes to implement a simple game, and [David] makes them easy to use, even providing a demo program in the form of the rolling ball maze shown here.
If you think you need fancy parts to build a giant robot drawing machine, think again! [Cory Collins] shows you how he built his Big-Ass Wall Plotter v.2 out of stuff around the house or the hardware store, including electrical conduit, gang boxes, scrap wood, and skateboard bearings, alongside the necessary stepper motors, drivers, and timing belt. (You should consider having this trio of parts on hand as well, in our opinion.) With a span of 48″ (1.2 m) on a side, you probably don’t have paper that’s this big.
And while the construction is definitely rough-and-ready, there are a ton of details that turn this pile of parts into a beautifully working machine in short order. For instance, making the rails out of electrical conduit has a few advantages. Of course it’s cheap and strong, but the availability of off-the-shelf flanges makes assembly and disassembly easy. It also hangs neatly on the wall courtesy of some rubber cuphooks.
[Corey] uses the machine to make patterns for his paper sculptures that are worth a look in their own right, and you can see the machine in action, sped up significantly, in the video below. This is the perfect project if you have a DIY eggbot that’s out of commission post-Easter: it reuses all the same parts, just on a vastly different scale. Heck, [Corey] even uses the same Inkscape Gcodetools extension as we did in that project. Now you know what we’re up to this weekend.
[Greg06] started learning electronics the same way most of us did: buy a few kits, read a few tutorials, and try your hardest to put a few things together. Sound familiar? After a while, you noticed your skills started increasing, and your comfort level with different projects improved as well. Eventually, you try your hand at making your own custom projects and publishing your own tutorials.
[Greg06’s] robot has a quadruped based, housed within a 3D printed spherical body. The legs are retractable and are actuated by tiny servo motors inside the body. [Greg06] even included an ultrasonic distance sensor for the obstacle avoidance mechanism. Honestly, if it weren’t for the ultrasonic distance sensor protruding from the spherical body, you might think that the entire robot was just a little Wiffle ball. This reminds us of another design we’ve seen before.
If that weren’t enough, the spherical head can rotate, widening the range of the ultrasonic distance sensor and obstacle avoidance mechanism. This is accomplished by attaching another servo motor to the head.
Sometimes connectivity problems go away by power cycling a router. It’s a simple but inconvenient solution to a problem that shouldn’t exist, but that didn’t stop [Mike Diamond] from automating it for a few bucks in parts. The three-dollar router rebooter may be a simple device with only one job, but it’s well documented and worth a look.
The device is an ESP8266 board configured to try to reach Google periodically via the local wireless network. If Google cannot be reached, the board assumes a reboot is needed and disconnects the 12 V power supply from the router by using a relay. Then, after a delay, power is re-connected and all of one’s problems are over until the next time it happens. [Mike] used a relay module that has built-in screw terminals and a socket for the ESP8266-01, so it looks like the whole device can be put together without soldering a thing.
While the code for making this happen may sound trivial, [Mike] nevertheless delves into documenting it. It makes a great example of how to implement a simple event-driven finite state machine in a way that’s clear and concise. By structuring the code so that there is a finite number of specific states the device can be in (router power on, router power off, and testing connection) and by defining exactly how and when the device switches between those states, operation and troubleshooting becomes a much more manageable job. Another great example is this IoT Garage Door Opener project. If you’re programming devices that interface to physical things, these techniques are definitely good practice.
What does one do with tiny 1:35 scale remote controlled off-road vehicles? Build appropriately-tiny tracks for them to drive on, of course. That’s exactly what [David] did when he created his fantastic rock crawling track that he has dubbed the ‘4×4 Arena’, and what’s even better is that he used leftover foam inserts and acrylic paints and materials to do it, and didn’t have to spend a penny.
This isn’t [David]’s first track. He originally made a smaller rock-crawling track he called Rubble Wasteland for the tiny vehicles, and he liked it so much he expanded it considerably. The new track builds on the original and is three levels deep, sports tight cave-like passages, tunnels, tricky climbs, and and realistic terrain textures.
An enormous photo gallery is right here, and other than the first and final images, it’s roughly in chronological build order. If your curiosity has been piqued about the tiny 1:35 scale remote controlled vehicles that this track is built for, around gallery page nine is where pictures of what makes these tiny things tick begins.