The Engineering Case for Fusing Your LED Strips

Modern LED strips are magical things. The WS2812 has allowed the quick and easy creation of addressable RGB installations, revolutionizing the science of cool glowy things. However, this accessibility means that it’s easy to get in over your head and make some simple mistakes that could end catastrophically. [Thomas] is here to help, outlining a common mistake made when building with LED strips that is really rather dangerous.

The problem is the combination of hardware typically used to run these LED strings. They’re quite bright and draw significant amounts of power, each pixel drawing up to 60 mA at full-white. In a string of just 10 pixels, the strip is already drawing 600 mA. For this reason, it’s common for people to choose quite hefty power supplies that can readily deliver several amps to run these installations.

It’s here that the problem starts. Typically, wires used to hook up the LED strips are quite thin and the flex strips themselves have a significant resistance, too. This means it’s possible to short circuit an LED strip without actually tripping the overcurrent protection on something like an ATX power supply, which may be fused at well over 10 amps. With the resistance of the wires and strip acting as a current limiter, the strip can overheat to the point of catching fire while the power supply happily continues to pump in the juice. In a home workshop under careful supervision, this may be a manageable risk. In an unattended installation, things could be far worse.

Thankfully, the solution is simple. By installing an appropriately rated fuse for the number of LEDs in the circuit, the installation becomes safer, as the fuse will burn out under a short circuit condition even if the power supply is happy to supply the current. With the example of 10 LEDs drawing 600 mA, a 1 amp fuse would do just fine to protect the circuit in the event of an accidental short.

It’s a great explanation of a common yet dangerous problem, and [Thomas] backs it up by using a thermal camera to illustrate just how hot things can get in mere seconds. Armed with this knowledge, you can now safely play with LEDs instead of fire. But now that you’re feeling confident, why not check out these eyeball-searing 3 watt addressable LEDs?

Continue reading “The Engineering Case for Fusing Your LED Strips”

Reading out an EPROM – with DIP switches

We’re all too spoiled nowadays with our comfortable ways to erase and write data to persistent memory, whether it’s our microcontroller’s internal flash or some external EEPROM. Admittedly, those memory technologies aren’t exactly new, but they stem from a time when their predecessors had to bathe under ultraviolet light in order to make space for something new. [Taylor Schweizer] recently came across some of these quartz-window decorated chips, and was curious to find out what is stored in them. Inspired by the BIOS reverse engineering scene in Halt and Catch Fire, he ended up building his own simple reader to display the EPROM’s content.

The 2732 he uses is a standard EPROM with 32kbit memory. Two pins, Chip Enable and Output Enable, serve as main control interface, while 12 address pins select the data stored in the chip’s internal 4K x 8 arrangement, to output it on the 8 data output pins. You could of course hook up the EPROM to a microcontroller and send what you read via serial line, but [Taylor] opted for a more hands-on approach that lets him read out the data in a manual way. He simply uses a bank of DIP switches to set the address and control pins, and added a row of LEDs as display.

As you can see from the short demonstration in the video after the break, reading out the entire EPROM would be a rather tedious task this way. If you do have more serious intentions to read out the content, you could have a look at one of those microcontroller based solutions sending data via serial line after all.

Continue reading “Reading out an EPROM – with DIP switches”

A Mini Stacker Arcade Cabinet

For [LumoW], what started as a school project turned into a passion project. He and his team made a hardware implementation of an arcade game called Stacker. Never heard of it? It’s pretty fun, kind of like an inverse Tetris. You can play the flash version here and see their mini arcade version after the break.

The game is based around the Mojo FPGA which the class required, and it’s programmed entirely in bitwise operators. It uses WS2812 RGB LEDs to represent the individual tower building blocks, and these are mounted on plywood in a matrix and separated into cells by a grid of foam board. After some trial and error, the team found the perfect shade of acrylic to diffuse the bright dots into glowing squares.

Since the game only needs one input, we don’t think [LumoW] should apologize at all for using the biggest, baddest button they could find. Besides, the game has that edge-of-your-seat action that can turn panic into heavy-handedness and cool DIY arcade games into shards of sadness.

Looking for something more advanced to do with an FPGA? Try your hand at vector games.

Continue reading “A Mini Stacker Arcade Cabinet”

Joule Thief Steals in Favor of Christmas

A lot of things tend to get stretched during the holiday season, like shopping budgets and waistbands and patience. This year, [Chris] is stretching the limits of both the mini breadboard and the humble 1.5 V LR44 coin cell with his joule thief-driven LED mini Christmas tree.

With the push of a micro momentary, the joule thief circuit squeezes enough power from an LR44 to boot an MSP430 microcontroller, which needs 1.8 V – 3.6 V. After boot, the micro takes control of the joule thief circuit and milks it whenever the voltage falls below 3.2 V. This tree may be small in stature, but it’s feature-rich. A push of the same momentary button cycles through four different light shows, ending with a medley of all four. Be dazzled after the break.

The code for this tiny tree, which features an awesome ASCII breadboard layout and schematic, is up on GitHub. [Chris] has it listed among a few other manageable bare-metal ‘430 projects that would be great for beginners at pure C. If that sounds like you, why not give yourself the gift of learning a new language?

We’ve seen some spirited ways of lighting LEDs, but doing it with candle power takes the fruitcake.

Continue reading “Joule Thief Steals in Favor of Christmas”

Spice up your dice with Bluetooth

There’s no shortage of projects that replace your regular board game dice with an electronic version of them, bringing digital features into the real world. [Jean] however goes the other way around and brings the real world into the digital one with his Bluetooth equipped electronic dice.

These dice are built around a Simblee module that houses the Bluetooth LE stack and antenna along with an ARM Cortex-M0 on a single chip. Adding an accelerometer for side detection and a bunch of LEDs to indicate the detected side, [Jean] put it all on a flex PCB wrapped around the battery, and into a 3D printed case that is just slightly bigger than your standard die.

While they’ll work as simple LED lighted replacement for your regular dice as-is, their biggest value is obviously the added Bluetooth functionality. In his project introduction video placed after the break, [Jean] shows a proof-of-concept game of Yahtzee displaying the thrown dice values on his mobile phone. Taking it further, he also demonstrates scenarios to map special purposes and custom behavior to selected dice and talks about his additional ideas for the future.

After seeing the inside of the die, it seems evident that getting a Bluetooth powered D20 will unfortunately remain a dream for another while — unless, of course, you take this giant one as inspiration for the dimensions.

Continue reading “Spice up your dice with Bluetooth”

Raspberry Pi Tracks Office Happiness

It’s always great to see people who haven’t had the opportunity to work with hardware like the Raspberry Pi before come up with a great project and have fun putting it together.  [Katja]’s company has a two-day hackfest where employees can work on some cool non-work-related projects. [Katja]’s team decided to use a Raspberry Pi and some buttons and LEDs to create a ‘happiness tracker‘ for the company.

The resulting project is mounted near the entrance to the office and when they come in or leave, an employee can push one of four buttons to indicate their mood at the time, ‘bad,’ ‘not so good,’ ‘good’ or ‘super.’ The result is tracked and an overall impression of the office’s happiness is the result.

The project consists of the aforementioned Raspberry Pi, four push buttons, five LEDs that animate when a button is pressed and another LED that shows the system is currently up and working. When a user presses a button, the five LEDs animate in the shape of a check mark to show that the button press was successful. A Python script running at startup on the Pi takes care of detecting button pressing, lighting LEDs and sending a message to the server which monitors the level of happiness.

It’s a simple project, but that’s exactly what you need when you start with hardware you haven’t worked with before. It seems like [Katja]’s team had fun building the project and they hope that this can help gauge the overall wellbeing of the office. [Katja]’s blog post has an embedded video of the project in action. In the meantime, check out this bit of facial recognition software that determines how happy you are based on your smile, or this project that lets you know how happy your plant is.

Using a Decade Counter to Make LEDs Flash

[Andrea De Napoli] created a LED display consisting of a half-dozen LEDs connected to the inverted signals of a CD4017 decade counter, giving the effect that a dark LED is running back and forth. The CD4017 works by activating 10 outputs, one at a time, as controlled by a clock signal sent to pin 14.

The first and last LEDs are lit by outputs 0 and 5 with the help of a PNP transistor and a 12K resistor. The middle four LEDs are switched by two outputs each and go dark when one of them goes high. [Andrea] really delves into the CD4017 and he shares a lot of detail in the project page.

Hackaday publishes a lot of posts about obscure ICs: Project 54/74 aims to create a database of die images of 5400 and 7400 series ICs. In a remix of a classic, the Baby 10 uses a 4017 to make a music sequencer. Continue reading “Using a Decade Counter to Make LEDs Flash”