Programming Tiny Blinkenlight Projects With Light

August 1, 2024 by Dan Maloney 18 Comments

[mitxela] has a tiny problem, literally: some of his projects are so small as to defy easy programming. While most of us would probably solve the problem of having no physical space on a board to mount a connector with WiFi or Bluetooth, he took a different path and gave this clever light-based programming interface a go.

Part of the impetus for this approach comes from some of the LED-centric projects [mitxela] has tackled lately, particularly wearables such as his LED matrix earrings or these blinky industrial piercings. Since LEDs can serve as light sensors, albeit imperfect ones, he explored exactly how to make the scheme work.

For initial experiments he wisely chose his larger but still diminutive LED matrix badge, which sports a CH32V003 microcontroller, an 8×8 array of SMD LEDs, and not much else. The video below is a brief summary of the effort, while the link above provides a much more detailed account of the proceedings, which involved a couple of false starts and a lot of prototyping that eventually led to dividing the matrix in two and ganging all the LEDs in each half into separate sensors. This allows [mitxela] to connect each side of the array to the two inputs of an op-amp built into the CH32V003, making a differential sensor that’s less prone to interference from room light. A smartphone app alternately flashes two rectangles on and off with the matrix lying directly on the screen to send data to the badge — at a low bitrate, to be sure, but it’s more than enough to program the badge in a reasonable amount of time.

We find this to be an extremely clever way to leverage what’s already available and make a project even better than it was. Here’s hoping it spurs new and even smaller LED projects in the future.

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The BAPPR Keeps Your Addressable LED System Cool

July 27, 2024 by Alexander Rowsell 17 Comments

We all love a nice strip or grid of addressable LEDs. It can add flair or an artistic touch to many projects, and it can make gaming computers look extra 1337. However, providing enough current to a long strip of addressable LEDs can sometimes be difficult. Often a separate voltage rail is needed to supply enough juice. At the same time, continually sending out data to animate them can often use 100% of the microcontroller’s CPU power, especially if the serial bus is being bit-banged. A crash or badly timed interrupt can leave the system in a weird state and sometimes with the LEDs not displaying the correct colours. Or you might just want to enter a power-saving mode from time to time on your main MCU? Well, the BAPPR is designed to address all of these problems.

[TheMariday] created the BAPPR and made it fully open-source. It’s a switch-mode power supply that can accept anywhere from 7 V to 17 V and converts it into a strong 5 V rail for typical addressable LEDs. It also has a “smart” mode where it monitors the data line going to the LEDs to see if there is activity. If for some reason the system stops sending data, the BAPPR can intervene and shut off the power to the LEDs, which can help prevent strange colour combinations from being displayed while the system recovers. Once data starts flowing again, power is restored and the light party can resume.

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You Can Use LEDs As Sensors, Too

July 23, 2024 by Lewin Day 63 Comments

LEDs are a wonderful technology. You put in a little bit of power, and you get out a wonderful amount of light. They’re efficient, cheap, and plentiful. We use them for so much!

What you might not have known is that these humble components have a secret feature, one largely undocumented in the datasheets. You can use an LED as a light source, sure, but did you know you can use one as a sensor?

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Simple Version Of Pong Played On A Row Of LEDs

July 15, 2024 by Tom Nardi 5 Comments

As far as video games go, Pong is already about as simple as it gets. But if even two dimensions is a bit more than you’re looking to tackle, [mircemk] shows how you can distill the core gameplay of this iconic title to its absolute minimum using an Arduino and a row of LEDs.

While [mircemk] brings their usual design aesthetic and flash to the project, this one could truly be done as a parts bin build. All you really need is a microcontroller with enough I/O pins (here, an Arduino Nano is used), a couple of buttons, and the aforementioned LEDs. A 16×2 LCD and a buzzer have been added to improve on the user interface a bit, but even that isn’t strictly required.

To play, each user holds their button and gets ready to hit it as soon as the LED closest to them lights up. Again, [mircemk] spruces this build up by offering both integrated buttons on the front panel of the game, as well as a pair of external “controllers” so you don’t have to crowd around the main unit. In this incarnation the score is shown on the LCD, but swapping that out for a pair of seven-segment LEDs could give the whole thing a bit more of a retro flair.

This isn’t the first time [mircemk] has tackled 1D Pong — if you can spring for addressable LEDs, you can pull the whole thing off with significantly less wiring.

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Candle Powered Lantern Isn’t As Silly As You Think

July 6, 2024 by Adam Fabio 30 Comments

[Gilles Messier] at the Our Own Devices YouTube channel recently took a look at an interesting device — an electric lantern powered by a candle. At first glance, this sounds completely absurd. Why use a candle to power LEDs when you can use the light from the candle itself? This gadget has a trick up its sleeve, though. It lets candle light out and uses the heat from the candle flame to generate power for the LEDs.

The small Peltier “solid-state heat pump” module in the lantern acts as a thermoelectric generator, converting heat from the candle into electricity for the LEDs. The genius of the device is how it handles the candle “exhaust”. A bimetallic disk in the chimney of the lantern closes when the air inside the device is hot. The Peltier device converts the heat differential to electricity, causing the air inside the lantern to cool. Meanwhile, the candle is beginning to starve for oxygen. Once the air cools down a bit, the disk bends, allowing stale smoke out, and fresh air in, allowing the candle to burn brightly again. Then the cycle repeats.

[Gilles] does a deep dive into the efficiency of the lantern, which is worth the price of admission alone. These lanterns are pretty expensive — but Peltier modules are well-known by hackers. We’re sure it won’t be too hard to knock together a cheap version at home.

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Baffle The Normies With This Binary Thermometer

June 8, 2024 by Dan Maloney 9 Comments

We think it’s OK to admit that when someone puts a binary display on a project, it’s just a thinly veiled excuse to get more blinkenlights into the world. That and it’s a way to flex a little on the normies; you’ve gone pretty far down the tech rabbit hole to quickly decipher something like this binary-display thermometer, after all.

Don’t get us wrong, we think those are both perfectly valid reasons for going binary. And all things considered, a binary display for a thermometer like [Clovis Fritzen]’s is much simpler to decode than, say, a clock. Plus, it seems a bit that this build was undertaken at least partially as an exercise in Charlieplexing, which [Clovis] uses to drive the six-bit LED display using only three lines of GPIO from the Digispark ATtiny85 board running the show.

The temperature sensor is a DHT11, whose output is read by the microcontroller before being converted to binary and sent to the six-bit display. The 64-degree range is perfect for displaying the full range of temperatures most of us would consider normal, although we’d find 63°C a touch torrid so maybe there’s a little too much resolution on the upper end of the scale. Then again, switching to Fahrenheit would shift it toward the hypothermia end of the scale, which isn’t helpful. And you can just forget about Kelvin.

Old Dot-Matrix Displays Give Up Their Serial Secrets

June 4, 2024 by Dan Maloney 11 Comments

If there’s one thing we like better around here than old, obscure displays, it’s old, obscure displays with no documentation that need a healthy dose of reverse engineering before they can be put to use. These Plessey dot-matrix displays are a perfect example of that.

We’re not sure where [Michael] scored these displays, but they look fantastic. Each 8-pin DIP has two 5×7-matrix, high-visibility LED displays. They bear date codes from the late 80s under the part number, GPD340, but sadly, precious little data about them could be dredged up from the Interwebz. With 70 pixels and only six pins after accounting for power and ground, [Michael] figured there would be a serial protocol involved, but which pins?

He decided to brute-force the process of locating them, using a Pico to sequentially drive every combination while monitoring the current used with a current sensor. This paid off after only a few minutes, revealing that each character of the display has its own clock and data pins. The protocol is simple: pull the clock and data pins high then send 35 bits, which the display sorts out and lights the corresponding pixels. The video below shows a 12-character scrolling display in action.

Plessey made a lot of displays for military hardware, and these chunky little modules certainly have a martial air about them. Given that and the date code, these might have come from a Cold War-era bit of military hardware, like this Howitzer data display which sports another Plessey-made display.

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