Edge-lit Pendants Show Two Layers are Better Than One

Engraved acrylic lights up nicely with LED lighting. Simply engrave clear acrylic with a laser engraver, then edge-light the acrylic and watch the engraving light up. This badge made by [Solarbotics] shows how they used this principle when creating some pendants for an event that performed particularly well in the dark.

The pendants they created have two engraved acrylic panels each, and that’s about it. Two LEDs and a CR2032 battery nestle into pre-cut holes, and the engraved sides are placed face-to-face, so the outer surfaces of the pendant are smooth. By using some color-cycling RGB LEDs on one panel and blue LEDs on the other panel, the effect is that of an edge-lit outer design with a central element that slowly changes color separately from the rest of the pendant.

The design stacks the LED leads and coin cells in such a way that a simple wrap of tape not only secures things physically, but also takes care of making a good electrical connection. No soldering or connectors of any kind required. [Solarbotics] found that CR2032 cells would last anywhere between a couple of days to a week, depending on the supplier.

This design is great for using a minimum of materials, but if that’s not a priority it’s possible to go much further with the concept. Multiple layers of edge-lit acrylic were used to make numeric 0-9 display modules as well as a full-color image.


Heart-shaped project takes no shortcuts


If all [Blake] wanted to do is scroll “Blake loves Kim” on some LEDs he could have stopped with the breadboard version of the project. Or hastily craft a cardboard heart around the marquee. But he really just used this heart-shaped electronics project as an excuse to get his feet wet with several different types of manufacturing.

The project started as a simple scrolling message pendant. Something along these lines. His very small LED module was being driven by an ATtiny85. He planned to run it from battery which is a perfect excuse to learn how to use the sleep functions built into the chip.

The initial design worked so well he decided to lay out his own circuit board. This made it quite simple to add in a side-positioned button to wake from sleep, and a coin cell battery holder on the back. He used OSH Park for board manufacturing — good thing they allow creative board outlines. To protect the circuitry he also ordered laser-cut acrylic plates that work in conjunction with stand offs to form a case.

He mentions he missed his Valentine’s Day delivery date by a long shot. But that’s how these sort of things go, right?

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Super-cap powered blinky jewelry charged by the sun or USB


We don’t see ourselves wearing these pendants around, but we still enjoyed taking a look at the design. These are just two from a wide range of offerings meant to be worn around and recharged by the sun. But a cloudy day won’t ruing the fun; they can be topped off via USB as well. Parts lists and schematics are included in the assembly Instructables for both the Owl and the Heart.

[Marty] and [Robin], a brother and sister developement/design team, were showing them off at the Sector67 hackerspace in Madison, WI. The single integrated circuit used in both is an OpAmp responsible for managing the blinking. The heart board has a calculator-style solar cell which charges that 0.5F supercap. The Owl has just a 0.022F coin-type capacitor and features a different style of solar harvester. The six components around the cap are each individual solar cells. [Marty] told us that they pump out a ton of juice in direct sunlight, outperforming the calculator-style cell. The opposite is true indoors. But as we’ve seen before, indoor solar harvesting is a tough game.

Need even more bling around your neck? Check out these LED matrix pendants.

8×8 LED matrix pendant sealed in a block of epoxy


This is the back side of [Dmitry Grinberg’s] 8×8 LED matrix pendant. He had seen the other projects that used a 5×7 grid but wasn’t really satisfied with the figures that can be drawn in that confined area when each pixel has only the option of being on or off. His offering increases the drawing area and includes the ability to display each pixel at several different levels.

He’s using an ATmega328 microcontroller soldered directly to the pins on the back of the LED module. He mapped out the IO in his firmware to make the soldering as easy as possible. To protect the hardware he fashioned a mold around the edges of the LED package using duct tape. The tape held epoxy in place as it hardened, encasing the microcontroller and holding the power wires and ICSP header tightly.

After the break you can see about six seconds of the device in action. The four levels of brightness for each pixel really do make quite a difference!

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TinyMatrix derivative uses PIC instead of AVR

[Stu] has a teenage niece whose birthday is coming up and he wanted to give her something unique as a gift. He’s working on an LED matrix pendant that can display pixel graphics, play animations, and scroll messages.

He began the work after drawing inspiration from the TinyMatrix project. That clever design uses a DIP AVR chip soldered directly to the legs of a 5×7 LED matrix. It was powered by a coin cell with the power and ground wires acting as the necklace for the pendant. [Stu] is more comfortable developing using PIC chips, so he based his project on a 16F88. It will not run from a 3V source so he’s got a few issued to work out before the final design is finished.

One thing that’s quite interesting is his side project. After growing weary of hand coding the arrays for each frame of an animation he wrote a GUI in C# that let him design the image and output the code with a few clicks of the mouse.

Wireless controller operates your CNC mill

[Darrell Taylor] wanted to add a CNC control pendant to his mill but didn’t want to foot the bill which can often run several hundred dollars. These pendants are basically a physical remote control that operates the CNC software that controls the machine. Since he was already using a Linux box running EMC2, it wasn’t too hard to figure out how to operate the mill with a PlayStation controller.

To get the controller talking to his Linux machine he uses a package called QtsixA. The package identifies and loads the control through Bluetooth pairing. From there it can be used to map the buttons and joysticks as keys on the keyboard or as a mouse. In the video after the break [Darrell] demonstrates how he has his shortcuts set up. He’s able to move the machine head, and even start or step through the programmed routine. As he mentions, this is pretty nice if you’ve got dirty hands; just throw the controller in a zipper bag and you’re set to go.

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