The physical design of the card is heavily inspired by [Frank Zhao]’s card; both use an ATtiny85 and the V-USB package to handle the USB protocol and communications. Instead of typing words into a text editor like [Frank]’s, [ch00f]’s card draws the ch00ftech logo in MS Paint or other image editor.
There was a problem with simply emulating the mouse to draw a logo on the screen, though; because different computers have different mouse settings for acceleration, the ch00ftech logo was nearly always distorted. [ch00f] fixed that by emulating an absolute input device, basically turning his business card into a single-function pen tablet.
The logo was traced by hand and put into a few arrays in the firmware. Surprisingly, the logo didn’t take up much space – only 4k of the tiny85’s flash is used. There’s a lot more space for a more complicated drawing, but for now the simple ch00ftech logo (video after the break) will do.
On a business trip, [ch00ftech] visited a Shenzhen electronics market and documented the trip. Some of the attractions included multiple Apple stores of questionable authenticity, stores selling PC components with no manuals, drivers, or packaging, and a variety of LEDs and lasers.
[ch00ftech] showed off the loot from the trip, including breadboards, perf boards, LED matrices, and an RFID reader all for very low prices. There’s also the Class 4 laser pointer that cost about $120 and has a power output of “between 500 mW and 8000 mW.” Given the 500 mW power restriction on lasers sold in the US, it’s fair to say that this thing should be handled with care. Hopefully the included safety classes actually block the specific wavelength of the laser.
The staff in these stores were very knowledgeable and knew part numbers and inventories by memory. One of the biggest surprises was just how low the prices were. While Radio Shack has started to carry some more parts for hackers, it seems that nothing stateside can compare these Chinese electronics markets.
[ch00f] was searching for an idea to build for his father this Christmas, and cast his gaze across those novelty phone charging cables that have “flowing” LEDs along their length. Not one to stick to the small scale, he set out to create a flowing LED effect for a Tesla EV charger.
The basic components behind the build are a current transformer, a NeoPixel LED strip, and an ATtiny44 to run the show. But the quality of the build is where [ch00f]’s project really shines. The writeup is top notch — [ch00f] goes to great lengths showing every detail of the build. The project log covers the challenges of finding appropriate wiring & enclosures for the high power AC build, how to interface the current-sense transformer to the microcontroller, and shares [ch00f]’s techniques for testing the fit of components to ensure the best chance of getting the build right the first time. If you’ve ever gotten a breadboarded prototype humming along sweetly, only to suffer as you try to cram all the pieces into a tiny plastic box, you’ll definitely pick something up here.
Digital cameras are great, because you can take thousands of pictures without running out of film. But there’s something to be said for having a tangible image you can hold in your hand. The Polaroid cameras of yesteryear were great for this, but now they’re hard to find and the price per photograph is ludicrously expensive.
Over the past few years, a few people have sought a way to create printed photographs at a lower cost. One of the best ways to do this is to find something much cheaper than Polaroid film — like thermal paper.
[Fabien-Chouteau]’s thermal printing camera isn’t the first — you’ve got the Gameboy Camera/Printer and a few others to thank for that. But it’s a great example of the form. The camera combines an Adafruit thermal receipt printer with an OpenMV camera, both easily sourced, if not exactly cheap. It even adds a ST7735 LCD for live display of the camera’s image, just like consumer-grade cameras!
It’s not just a slapped together kludge of parts bin components, however. While the thermal printer is only capable of printing black or white pixels, its resolution is much higher than the image from the camera. This allows the camera to use a 3×3 block of printed pixels to represent a single pixel from the camera, and with some fancy dithering techniques, can emulate shades of grey quite effectively. It’s tricks like this that really add polish to a project, and make a big difference to the picture quality at the end of the day.
It’s not the first thermal printer camera we’ve seen – [Ch00f]’s woodgrain instant camera build highlighted the issues of careful camera selection when pursuing this type of build.
Would you use your tech prowess to cheat at the Pinewood Derby? When your kid brings home that minimalist kit and expects you to help engineer a car that can beat all the others in the gravity-powered race, the temptation is there. But luckily, there are some events that don’t include the kiddies and the need for parents to assume the proper moral posture. When the whole point of the Pinewood Derby is to cheat, then you pull out all the stops, and you might try building an electrodynamic suspension hoverboard car.
Fortunately for [ch00ftech], the team-building Derby sponsored by his employer is a little looser with the rules than the usual event. Loose enough perhaps to try a magnetically levitating car. The aluminum track provided a perfect surface to leverage Lenz’s Law. [ch00ftech] tried different arrangements of coils and drivers in an attempt to at least reduce the friction between car and track, if not outright levitate it. Sadly, time ran out and physics had others ideas, so [ch00ftech], intent on cheating by any means, tried spoofing the track timing system with a ridiculous front bumper of IR LEDs. But even that didn’t work in the end, and poor [ch00f]’s car wound up in sixth place.
So what could [ch00ftech] had done better? Was he on the right course with levitation? Or was spoofing the sensors likely to have worked with better optics? Or should he have resorted to jet propulsion or a propeller drive? How would you cheat at the Pinewood Derby?
Fail of the Week is a Hackaday column which celebrates failure as a learning tool. Help keep the fun rolling by writing about your own failures and sending us a link to the story — or sending in links to fail write ups you find in your Internet travels.
Like [Brad], we’ve seen a number of PCB rulers out there. [Brad] was looking to take the idea and run with it. His DigiRule is a ruler with a logic gate simulator. What he built is a mash-up between PCB rulers, and the concept of electronic business cards.
All told it simulates seven logic gates, four flip-flops, and includes a four-bit counter. On one end of the ruler a CR1220 battery feeds the 18F43K20 which is performing the logic operations using buttons and LEDs. Of course the truth tables are printed on the back silk-screen, but playing with the lights is a lot more fun. We do find it fairly amusing that the centimeters on the bottom of the ruler are notated in binary.
The James Bond franchise is well-known for many things, but perhaps most important to us hackers are the gadgets. Bond always had an awesome gadget that somehow was exactly the thing he needed to get out of a jam. [hw97karbine’s] latest project would fit right into an old Bond flick. He’s managed to build a single-shot pellet gun that looks like a pen.
[hw97karbine] started out by cutting the body from a tube of carbon fiber. He used a hacksaw to do the cutting, and then cleaned up the edges on a lathe. A barrel was cut from a piece of brass tubing with a smaller diameter. These two tubes will eventually sit one inside of the other. A custom front end cap was machined from brass. One end is ribbed and glued into the carbon fiber tube. The barrel is also glued to this end of the front cap, though it’s glued to the inside of the cap. The other end of the cap has 1/8″ BSP threads cut into it in order to allow for attachments.
A rear end cap is machined from Delrin. This piece also has a Delrin piston placed inside. The piston has a small piece of rubber used as a gasket. This piston valve is what allows the gun to operate. The rear cap gets glued into place and attached to a Schrader valve, removed from an automotive tire valve stem.
To pressurize the system, a bicycle pump is attached to the Schrader valve. This pushes the piston up against the barrel, preventing any of the air from escaping. The piston doesn’t make a perfect seal, so air leaks around it and pressurizes the carbon fiber tube. The Schrader valve prevents the air from leaking out of the pen body. A special machined button was threaded onto the Schrader valve. When the button is pressed, the air escapes; the sudden pressure imbalance causes the piston to shoot backwards, opening up a path for the air to escape through the barrel. This escaping air launches the projectile. The whole process is explained better with an animation.
Now, the question left in our mind: is this the same pressure imbalance concept that was used in that vacuum pressure bazooka we saw a couple years back?