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182 Articles

TinyTacho: Rotational Speed Measurement Without The Bulk

November 26, 2020 by 10 Comments

An electronic tachometer is a straightforward enough device, in which the light reflections from a white spot on a rotating object are detected and counted over time, measuring the revolutions per minute (RPM). It’s a technique that has its roots in analogue electronics where the resulting pulses would have fed a charge pump, and it’s a task well suited to a microcontroller that simply counts them. But do you need an all-singing, all-dancing chip to do the job? [Stefan Wagner] has done it with a humble ATtiny13.

His TinyTacho is a small PCB with an IR LED and photodiode on one end, a small OLED display on its front, and a coin cell holder on its rear. The electronics may be extremely simple, but there’s still quite some effort to get it within the ATtiny’s meagre resources. Counting the revolutions is easy enough, but the chip has no I2C interface of its own and some bitbanging code is required. You can find all the design files and software you need in a GitHub repository, and he’s put up a video of the device in action that you can see below the break.

Tachometers are a popular project hereabouts, and we’ve featured a lot of them over the years. Perhaps the best place to direct readers then is not to another project, but to how to use a tachometer.

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The Most Annoying Among Us Tasks Created In Real Life

November 22, 2020 by 12 Comments

Among Us is a hit game of deception and intrigue. Those who have played it know the frustration of trying to complete some of the intentionally difficult tasks onboard the Skeld. [Zach Freedman] decided to recreate some of these in real life.

[Zach] built what are arguably the three most frustrating tasks from the game. There’s the excruciatingly slow upload/download station built out of an old Samsung tablet and an NFC tag, and the reactor start console created using a Raspberry Pi 3B, Teensy 3.2, and a custom mechanical keyboard. But perhaps most annoying of all is the infamous card reader. Built with another Teensy, it requires the user to swipe their ID card at just the right speed, except that speed is randomly generated for every swipe. Also, the machine fails 20% of good swipes just because. Perhaps what we love most is the way [Zach] recreated the classic VFD look by putting an OLED display behind bottle-green plastic and using a 14-segment font.

It’s a fun homage to a wildly successful indie game, and we could imagine these props would be a hit at a makerspace party. We’ve featured other Among Us themed builds before, too. Video after the break.

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The 10,000 Pixel Per Inch Display Is Now Possible

October 28, 2020 by 54 Comments

A good smartphone now will have about 500 pixels per inch (PPI) on its screen. Even the best phones we could find clock in at just over 800 PPI. But Stanford researchers have a way to make displays with more than 10,000 pixels per inch using technology borrowed from solar panel research.

Of course, that might be overkill on a six-inch phone screen, but for larger displays and close up displays like those used for virtual reality, it could be a game-changer. Your brain is good at editing it out, but in a typical VR headset, you can easily see the pixels from the display even at the highest PPI resolutions available. Worse, you can see the gaps between pixels which give a screen door-like effect. But with a density of 10,000 PPI it would be very difficult to see individual pixels, assuming you can drive that many dots.

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Smoothing Big Fonts On Graphic LCDs

October 25, 2020 by 36 Comments

Here’s a neat little trick: take the jaggies out of scaled fonts on the fly! This technique is for use on graphic displays where you might want to scale your fonts up. Normally you’d just write a 2×2 block of pixels for every area where there would have been one pixel and boom, larger font. Problem is, that also multiplies each empty area and you end up with jagged edges in the transitions that really catch your eye.

[David Johnson-Davies] entered big-brain mode and did something much cleverer than the obvious solution of using multiple font files. Turns out if you analyze the smoothing problem you’ll realize that it’s only the angled areas that are to blame, horizontal and vertical scaling are nice and smooth. [David’s] fix looks for checker patterns in what’s being drawn, adding a single pixel in the blank spots to smooth out the edge incredibly well!

The technique has been packaged up in a simple function that [David] wrote to play nicely in the Arduino ecosystem. However, the routine is straightforward and would be quick to implement no matter the language or controller. Keep this one in your back pocket!

Now if all you have on hand is an HD44780 character LCD, that one’s arguably even more fun to hack around on just because you’re so limited on going beyond the hard-coded font set. We’ve seen amazing things like using the custom character slots to play Tetris.

Parking Assistant Helps Back Up The Car Without Going Too Far

September 27, 2020 by 24 Comments

Sure, [Ty Palowski] could have just hung a tennis ball from the ceiling, but that would mean getting on a ladder, testing the studfinder on himself before locating a ceiling joist, and so on. Bo-ring. Now that he finally has a garage, he’s not going to fill it with junk, no! He’s going to park a big ol’ Jeep in it. Backwards.

The previous owner was kind enough to leave a workbench in the rear of the garage, which [Ty] has already made his own. To make sure that he never hits the workbench while backing into the garage, [Ty] made an adorable stoplight to help gauge the distance to it. Green mean’s he’s good, yellow means he should be braking, and red of course means stop in the name of power tools.

Inside the light is an Arduino Nano, which reads from the ultrasonic sensor mounted underneath the enclosure and lights up the appropriate LED depending on the car’s distance. All [Ty] has to do is set the distance that makes the red light come on, which he can do with the rotary encoder on the side and confirm on the OLED. The distance for yellow and green are automatically set from red — the yellow range begins 24″ past red, and green is another 48″ past yellow. Floor it past the break to watch the build video.

The humble North American traffic signal is widely recognized, so it’s a good approach for all kinds of applications. Teach your children well: start them young with a visual indicator of when it’s okay to get out of bed in the morning.

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Transparent OLED Hitting The Market With Xiaomi’s Mi TV LUX Transparent Edition

August 21, 2020 by 46 Comments

One of the major advantages of OLED over LCD panels is that the former can be made using far fewer layers as the pixels themselves are emitting the light instead of manipulating the light from a backlight. This led some to ask the question of whether it’s possible to make an OLED panel that is transparent or at least translucent. As Xiaomi’s new Mi TV LUX OLED Transparent Edition shows, the answer there is a resounding ‘yes’. Better yet, for a low-low price of about $7,200 you can own one of these 55″ marvels.

Transparent OLED technology is not new, of course. Back in 2018 LG was showing off a prototype TV that used one of the early transparent OLED panels. In the video that is embedded after the break, [Linus] from Linus Tech Tips goes hands-on with that LG prototype while at LG in South Korea, while including a number of crucial details from an interview from one of the engineers behind that panel.

As it turns out, merely removing the opaque backing from an OLED panel isn’t enough to make it transparent. In order for an OLED panel to become transparent, the circuitry in the pixel layer and TFT layer need to be aligned as best as possible to allow for many, many tiny holes to be punched through the display.

Looking at [Linus]’s experiences with the LG prototype, it does appear that this kind of technology would be highly suitable for signage purposes, while also allowing for something like an invisible television or display in a room that could be placed in front of a painting or other decoration. Once displaying an image, the screen is bright enough that you can comfortably make out the image. Just don’t put any bright lights behind the TV.

Anyone else anxious waiting for sub-10″ versions of these panels?

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