Building EL Displays On A PCB

ELElecrolumiscent displays have seen a huge swing in popularity recently, but only in limited forms like EL wire or flat EL panels. You can, of course, cut and bend these wires and panels to suit any purpose, but custom shaped EL displays are just the bee’s knees. They’re not hard to fabricate, either: with cheap custom PCBs, all it takes to make custom EL panels is just a few chemicals.

[Nick]‘s method of fabricating custom EL displays uses an exposed copper layer on a PCB you’d pick up from OSHpark or any of the random board houses in China. The process consists of designing a display – be it a few letters, pixels, or a seven-segment arrangement. The display ‘stack’ is a layer of painted-on dialectric, a phospor, and finally a translucent conductive ink that connects the display segments to ground. It looks like an extremely easy process, and from the pictures it looks like [Nick] is making some EL displays of reasonable quality.

[Nick]‘s work was inspired by the grand poobah of homebrew electrolumiscent displays, [Jeri Ellsworth], who managed to make a similar EL pixel on a PCB. [Nick]‘s display looks great, though, and with a little work some custom segment displays should be very possible.

Electronic wedding attire for a geeky wedding

In the past we featured many projects that were used at [Bill] and [Mara]‘s wedding. However we forgot the most important thing: their electronically enhanced clothes.

As you can see from the picture above, the wife opted for LEDs while the husband preferred Electro Luminescent (EL) wires/panels. The ATtiny based platform LilyTiny was picked to control all the LEDs, and charlieplexing was implemented as only 4 IO pins were available. Animations were made using Vixen and exported via a python script.

To power the EL wires, [Bill] hacked a Sparkfun EL battery pack/inverter. He removed the shell and took out the inverter part, reverse engineered the design enough to figure out how to bypass the onboard microcontroller that generated the on/off/blink function. Finally, he 3D printed enclosures to pack the electronics with one Li-Ion battery pack. A boost regulator was used to supply the 12v required by the EL panel power supply.

Don’t forget to also check out their centerpieces and wedding invitations that we previously featured.

Months of failure lead up to this EL panel dimmer that pulses to the music

el-panel-dimmer

Way back in March [Ch00f] took on a for-hire project to make a suit that lights up to the music. He decided to build something based around a pulsating EL panel. He’s put a lot of time and tried of a few different techniques, but he finally has a working EL panel dimmer.

This is a saga we’ve kept our eye on. The fall seems to have been good to him, after a failure using TRIACS he managed to adjust the brightness of some EL wire by messing with the current going to the driver’s oscillator. Standing on the shoulders of that success he designed the board seen above by getting serious about audio signal processing. There’s a microphone on the board which picks up sound which is then processed into a signal responsible for the brightness of the EL panel.

There’s a demo video after the break, but you’ll want to dig into his article to get all the gritty details.

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How TO dim EL wire: Current limiting the oscillator!

[Ch00f] finally made a breakthrough with his efforts dimming EL wire.  He’s been at it for months and the last we heard his TRIAC idea had sputtered out. Not to be discouraged and with an determination we have to admire he has been hard at work reverse engineering others’ and developing his own methods. He put all of this knowledge to task helping a friend of his with a sleeping disorder, and made a dream-catcher that pulses at the approximate rate of an average person’s breathing (as determined by Apple for their pulsing power button lights).

Essentially the whole thing boils down to simply using a transistor to limit the current to the oscillator. A 555 timer is used to pass a triangle wave to the current limiting transistor at approximately the same rate as the Apple button (1/5 Hz). [Ch00f] notes that this isn’t the sinusoidal wave that apple uses, but it’s good enough. Finally a timeout power off is built in to the night light using a decade counter to monitor the number of triangles from the 555. This should keep the EL wire from wearing down faster, though we are hard pressed to  think of a project we used EL on that has lasted anywhere near the 7 year service life of the wire.

Check out [Ch00f]‘s page as he walks us through the process, or just watch his circuit in action after the jump!

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How not to dim EL panels, TRIACs!

We’ve all been there: an exciting brilliant idea, scratched onto a napkin, hastily plugged into a breadboard, all for naught.  Even the best ideas sometimes suffer from a heavy dose of reality.  [Ch00f] over at ch00ftech recently had a similar experience dimming an EL panel of his using a TRIAC and some clever waveform manipulation. Instead of tossing the parts across the room in a fit aside and moving on he goes into a detailed analysis of what went wrong.

This method differs from the way most EL drivers dim output loads, instead of chopping the output like a PWM controlled LED the TRIAC snips the ends of the waveform and makes an ugly but less powerful output. The issue with this method is that when you cut the waveform during non-zero crossings it causes massive current spikes. These can wreak havoc on a cheap EL inverter and generally cause headaches all around.  [Ch00f ] speculates that his woes may be due to the fact that EL wire is a capacitive load, causing voltage to fall out of phase with the current. This is one of those engineering problems with a thousand and one answers, we can’t wait to see what he comes up with.

Check out the writeup for all the “deets” (as [ch00f] would say) as it is a pretty good primer on TRIAC operation. If there isn’t enough glowy wire in this post you can also check out this sound reactive panel or an informative guide on EL or even more from [ch00f] in general.

High Voltage Hacks: All About Electroluminescence

Although many might not know it, electroluminescent materials use high voltage, and thus qualify for our featured topic. Many may assume that these sheets work in the same way as LED lights, using low-voltage DC power.  This, however, is not the case, as they need around 100 volts of AC current to allow them to light up.

For a battery-powered solution, this means converting the battery’s DC power to AC. Adafruit has a good tutorial about working with EL wire and powering it up using a portable inverter. One should obviously be careful to properly insulate any clothing using this material as being shocked is generally not fun.

The video after the break is pretty long, but is well produced and will give you a good background of EL use. If you don’t have 30 minutes to dedicate to this, be sure to at least skip to 2:43 to see one of the coolest EL shirts we’ve seen. [Read more...]

More EL chemistry: Luminescent ink

[Jeri Ellsworth] continues her experiments with electroluminescence, this time she’s making EL ink. The ink she’s looking for is Zinc Sulfate in a solution. The process she chose is to re-dope some glow powder so that it can be excited by the field around an AC current. In her video (embedded after the break) she talks about the chemical properties she’s after by detailing a cubic lattice of zinc and sulfur atoms with an added copper atom (adding that atom is a process called doping).

The quick and dirty synopsis of the experiment starts by washing the glow powder with dish soap to acquire zinc sulfide crystals. Then she combined copper sulfate and zinc shavings from the inside of a modern penny to yield copper metal and zinc sulfate suspended in solution. That was mixed with the zinc sulfide from the glow powder washing and doped with a little more copper sulfate. The excess liquid is poured off, the test tube is capped with glass frit, and the whole thing hits the kiln to start the reaction. The result glows when excited by alternating current, but could have been improved by adding chlorine atoms into the mix.

We’re excited every time we see one of [Jeri's] new chemistry hacks. We’d love to see more so if you’ve come across interesting chemistry experiments during your Internet travels, please let us know about them. Just make sure you have some idea of what you’re doing when working with chemicals… safety first.

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