An ESP32 Clock With A Transforming LED Matrix

October 29, 2019 by Tom Nardi 5 Comments

Over the years we’ve seen countless ways of displaying the current time, and judging by how many new clock projects that hit the tip line, it seems as though there’s no end in sight. Not that we’re complaining, of course. The latest entry into the pantheon of unusual timepieces is this ESP32-powered desk clock from [Alejandro Wurts] that features a folding LED matrix display.

The clock uses eight individual 8 x 8 LED arrays contained in a 3D printed enclosure that hinges in the middle. When opened up the clock has a usable resolution of 8 x 64, and when its folded onto itself the resolution becomes 16 x 32.

This variable physical resolution allows for alternate display modes. When the hardware detects that its been folded into the double-height arrangement, it goes into a so-called “Big Clock” mode that makes it easier to see the time from a distance. But while in single-height mode, there’s more horizontal real estate for adding the current temperature or other custom data. Eventually [Alejandro] wants to use MQTT to push messages to the display, but for now it just shows his name as a placeholder.

The key to the whole project is the hinged enclosure and the reed switch used to detect what position it’s currently in. Beyond that, there’s just an ESP32 an some clever code developed with the help of the MD_Parola library written for MAX7219 and MAX7221 LED matrix controllers. [Alejandro] has published the code for his clock, which should be helpful for anyone who’s suddenly decided that they also need a folding LED matrix in their life.

Now if the ESP32 LED matrix project you have in mind requires full color and high refresh rates, don’t worry, we’ve got a solution for that.
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The Basics Of Persistence Of Vision Projects

October 29, 2019 by Lewin Day 6 Comments

Persistence of Vision (POV) is a curious part of the human visual system. It’s the effect by which the perception of an image lingers after light has stopped entering the eye. It’s why a spinning propeller appears as a disc, and why a burning sparkler appears to leave a trail in the air. It’s also commonly used as a display technology, where a series of flashing LEDs can be used to create messages that appear to float in the air. POV displays are a popular microcontroller project, and today, we’ll explore the basic techniques and skills required in such builds.

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24 Hours Of Temperature Data At A Glance

October 25, 2019 by Tom Nardi 7 Comments

In an era where we can see the current temperature with just a glance at our smartphones, the classic “Time and Temp” gadget sitting on the desk doesn’t have quite the same appeal. The modern weather fanatic demands more data, which is where this gorgeous full-day temperature display from [Richard] comes in.

The display, built inside of a picture frame, shows the temperature recorded for every hour of the day. If the LED next to the corresponding hour is lit that means the value displayed is from the current day, otherwise it’s a holdover from the previous day’s recordings. This not only makes sure all 24 LED displays have something to show, but gives you an idea of where the temperature might be trending for the rest of the day. Naturally there’s also a display of the instantaneous temperature (indoor and outdoor), plus [Richard] even threw in the current wind speed for good measure.

In the video after the break, [Richard] briefly walks us through the construction of his “Thermo Logger”, which reveals among other things that the beautiful panel art is nothing more exotic than a printed piece of A4 paper. The video also features a 3D model of the inside of the device which appears to have been created through photogrammetry; perhaps one of the coolest pieces of project documentation we’ve ever seen. We’ll just throw this out there: if you want to ensure that your latest build makes the front page of Hackaday, pop off that back panel and make some decent quality 3D scans.

Given the final result, it should come as no surprise to find that this isn’t the first incredible weather display that [Richard] has built. We previously covered another weather monitoring creation of his that needed two seperate display devices to adequately display all the data it was collecting.

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Light Emitting Logic Gates Built From Scratch

October 24, 2019 by Sharon Lin 44 Comments

What’s the weirdest computer you can think of? This one’s weirder.

[Dr. Cockroach] figured out a way to create an inverting NOT gate from just one LED and two resistors (one being a photo-resistor). The Dr. has since built AND, NAND, OR, NOR, XOR and XNOR gates, as well as a buffer, incorporating light into every logic gate.

Traditional inverters – NOT gates – are already made with diodes (typically not light-emitting), resistors (typically not light-dependent), and bipolar transistors. The challenge was to reduce the number of transistors. The schematic from the very first test shows the slight modifications [Dr. Cockroach] made to incorporate light into the logic gate using a 910 Ohm, output LED, and an LED and LDR in parallel.

The output is initially 4.5V for logic 1 and 1.5V for logic 0. Adding two 1N914 diodes and an AND gate ahead of the inverter create a two-input NAND gate. With the two diodes reversed and a 910 Ohm resistor removed, a NOR gate is created.

The next step was to build a S-R latch using the NAND gates and inverters, which holds some basic memory. From there, with some size reductions, a Master-Slave J-K Flip Flop, similarly using NAND gates and inverters, can be built. The current state of the project is a working sequencer and counter. You can even see a smooth sine wave propagating through the LED chaser, which is typically built with ICs or transistors but in this case is built simply with LEDs, LDRs, resistors, and capacitors.

The upcoming plan is to use the gates to build a processor that only uses diodes, resistors, and capacitors. While it’s probably not going to be nearly as fast as any processors we have today, it should be interesting (and educational!) to be able to visually track the flow of data from one logic gate over to the next. Continue reading “Light Emitting Logic Gates Built From Scratch” →

Painting With Light: The Homemade Pixelstick

October 16, 2019 by Sharon Lin 2 Comments

Light painting has long graced the portfolios of long-exposure photographers, but high resolution isn’t usually possible when you’re light painting with human subjects.

This weekend project from [Timmo] uses an ESP8266-based microcontroller and an addressable WS2812-based LED strip to paint words or custom images in thin air. It’s actually based on the Pixelstick, a tool used by professional photographers for setting up animations and photorealism shots. The equipment needed for setting up the light painting sticks runs in the order of hundreds, not to mention the professional camera and lenses needed. Nevertheless, it’s a huge step up from waving around a flashlight with your friends.

The LED Lightpainter takes the Pixelstick a few notches lower for amateur photographers and hobbyists. It directly supports 24-bit BMP, with no conversion needed. Images are stored internally in Flash memory and are uploaded through a web interface. The settings for the number of LEDs, time for the image row, and STA/AP-mode for wireless connections are also set by the web interface. The project uses the Adafruit NeoPixel, ArduinoJson, and Bodmer’s TFT_HX8357 libraries for implementing the BMP drawing code, which also allows for an image preview prior to uploading the code to the microcontroller. Images are drawn from the bottom row to the top, so images have to be transformed before updating to the LED painter.

Some future improvements planned for the project include TFT/OLED support, rainbow or color gradient patterns in the LEDs, and accelerometer or gyroscope support for supporting animation.

There aren’t currently too many galleries of DIY LED-enabled light paintings, but we’d love to see some custom modded light painting approaches in the future.

This isn’t the first LED light stick we’ve seen, if you’re interested in such things.

Hacking Pixmob Bands And Finding A Toolchain

October 15, 2019 by Lewin Day 16 Comments

The Pixmob band is an LED wrist strap, of the type often used at big concerts or other public events. Many have tinkered with the device, but as of yet, nobody was running custom code. It wouldn’t be easy, but [JinGen Lim] got down to work.

The wristbands are given out to concertgoers to create synchronized light shows in the crowd.

A teardown of a 2016 device revealed it consisted of an RGB LED, an IR sensor, a small EEPROM and a coin cell, which were all common parts. Unfortunately, the ABOV MC81F4204 microcontroller was a little more obscure. It’s a part that’s quite hard to find, and uses a proprietary programmer and an ancient IDE.

Searches online proved fruitless, and a working programmer remained outside [JinGen]’s grasp. Undeterred, he decided to simply walk into the company’s Korean headquarters and ask for help. As the part was end-of-life, they were unable to supply a programming device, but happily provided documentation for the chip that wasn’t publicly available. With this in hand, it was possible for [JinGen] to build his own programmer instead.

Booting up a copy of the ABOV IDE, with his newly-built programmer in hand, it was relatively easy to get the chip running custom code. Going the extra mile, [JinGen] even hacked the Arduino IDE to be partially compatible with the platform! A silicon error in the MC81F4204 design bricks the chips after only a few flash rewrites, so its never going to be the most useful platform, but it works nonetheless.

The Pixmob hardware has continued to evolve, and it’s unlikely modern units still use the same chip. Despite this, it’s a great example of what can be achieved by a little sleuthing and asking the right people the right questions. Others have attempted to hack similar products before, found at Disneyland and Coldplay concerts. You won’t catch this author at either, but if you’ve hacked something similar, be sure to reach out on the tip line!