ElWire Control and Sequencing Questions

[malsyned]

I know there are some burners out there who know all there is to know about ElWire, and I'm going to try to pick your brains here for a minute.

I am designing a custom sequencer for some ElWire clothing for BM2k9. I'm an embedded programmer, so I'm looking forward to programming some interesting patterns, but my knowledge of circuit design, while growing quickly, is limited. I'm working with a friend who's an electrical engineer, but there are still some ElWire-specific questions that neither of us have answers to.

Question 1: If a driver says it is for "50-100 feet" or "20-100 feet", is it a problem to drive only 5 feet of ElWire with it?

My idea calls for 15 or 16 independently controlled channels, each driving 5 feet of ElWire. I would like to be able to power all 16 channels with a single driver, like CoolNeon's Big Boy or the 100ft driver from CooLight and use a microcontroller to turn different channels on and off through a transistor or triac, much like the setup in this Make Magazine article (schematic about 1/3 through the page).

This plan will only work if those drivers are actually capable of operating as little as 5 feet of ElWire without damaging the driver or the wire, since some sequences will only have one channel on at a time while other sequences may have all of them on at once.

Question 2: I thought I read somewhere that there was a problem with running an ElWire inverter with no ElWire attached. If I do any kind of a blinking sequence, that would effectively leave the inverter 12Vdc-powered with nothing connected for half of the blink cycle. For certain interactive sequences I'm dreaming of, the inverter may even be run with all output channels disabled for extended periods. Is this a real concern? And if so, is there anything that anyone can recommend to get around this problem?

Question 3: Does anyone know if ElWire responds well to attempts to control its brightness by Pulse Width Modulation of the power being applied to it? If so, what's a good frequency and range of duty cycles to use for a good range of brightnesses without a lot of flicker?

I know that it is possible to control the brightness of ElWire by varying the voltage of frequency of the AC power being fed to it. If I want independent brightness control for each channel, though, that becomes impractical since I would need 16 inverters instead of just one, so I'm considering using PWM control instead. The idea is to turn a strand of ElWire on and off rapidly, and change the ratio of on-time to off-time to achieve different brightnesses. For example, if I wanted low brightness I might turn the AC power on for 2ms and off for 18ms out of every 20ms, whereas if I wanted higher brightness I might use 18ms on and 2ms off. I know this technique works for LEDs, but I haven't been able to find any information about using it on ElWire.

Thanks,
--Sir Bunny

P.S. If there are other good places to post these kinds of questions to (or if this forum is inappropriate for this kind of question) please let me know. Thanks!

[Digital-Dragonfly]

Question 2: I thought I read somewhere that there was a problem with running an ElWire inverter with no ElWire attached. If I do any kind of a blinking sequence, that would effectively leave the inverter 12Vdc-powered with nothing connected for half of the blink cycle.

not quite sure I "see" your whole method... but could you not just build a "dummy load"/channel? Then bury/hide that dummy segment out of sight?

You might even use a hidden dummy load to bulk up a short lengths load.
like your 5' in view & 10" hidden from view.

Just a thought

[Dork]

Yes, there is a potential that you will damage the controller by leaving it unattached. Otherwise they would not publish a minimum amount of wire. It certainly won't burn out in seconds, because if it did they would burn out all of the time when something gets unplugged. It might take minutes, hours, or possibly never happen but it would be difficult to predict. The blinking would also concern me - they really aren't designed with that in mind. Usually people make them blink turning the power to the controller itself on and off. I'd suggest emailing coolneon to see if he's heard anything first hand about this kind of abuse causing problems.

It would definitely be worth investigating building your own controllers into the circuit, though, since you want to be able to vary the voltage and frequency anyway. All the wire needs is a little high voltage AC - you should be able to make that happen with a handfull of components.

I don't know how PWM would work with EL since they run on AC - it would be more like fast blinking. You'd have to experiment to see what the minimum length of time is for the wire to light before you turn it back off. Have you considered using LEDs with fiber optics or a piece of plastic instead? It may not be as bright, but you'd have infinite control over color and brightness of each strand. You could use an Arduino to control them directly.

[malsyned]

not quite sure I "see" your whole method... but could you not just build a "dummy load"/channel? Then bury/hide that dummy segment out of sight?
Just a thought

A dummy load of actual elwire for these drivers would cost upwards of 25 dollars for the inverter with the broadest range (20'-100'). Could I use a non-polarized capacitor with equivalent capacitance as a dummy load to protect the inverter?

It would definitely be worth investigating building your own controllers into the circuit, though, since you want to be able to vary the voltage and frequency anyway.

I'm trying to get this project done without breaking the bank on materials, so building 15 different inverters just so that I can get independent voltage or frequency control is pretty much out of the question - unless you know where I can get high frequency 8ish-to-1 transformers on the cheap. That's why I'm thinking about PWM instead.

[erbgins]

I was interested in the suggestion to use a capacitor as a dummy load to protect the invertor when less than the minimum amount of el-wire is attached. Does anyone know how to select the correct capacitor? Does el-wire have a certain amount of capacitance per foot, so that if you knew the minimum feet of el-wire required for an inverter you could supply a dummy load with a capacitor? I don't know much about capacitors, except that they are rated in microfareds. Any information would be appreciated.

[gyre]

This information should be in the technical sheet or provided by the supplier.

There are different types of capacitors.
Make sure to use the appropriate type, such as polarized or non-polarized and so on.

[erbgins]

Thanks for the reply, Gyre. If only it were true that information is supplied on technical sheets! I've ordered el-wire and inverters from a number of different on-line suppliers, and they never come with even instructions let alone technical specifications!

Does anyone know how to actually test a strand of el-wire to see what its capacitance is? Also, does anyone know what the correct type of capacitor is to simulate the load?

It seems like this could help design more interesting circuits, where an inverter is left on with a base load supplied by a capacitor, and then connected via a relay or other type of switch to different stands of el-wire to make a pattern. The other option of having a separate inverter for each strand and turning the inverters on and off to make the pattern seems clumsy.

Thanks for any information you may have.

[gyre]

A capacitance tester would be the easy way to do this.
Seems like there is a way to rig up something to give you derived values, but i never did it and I don't remember details.

The inverters are supposed to be very rapid response, so it doesn't seem to hurt them to be switched.
They make special controls for loads that make before breaking contact.
I don't know if this is called for.

I found an el wire forum.
Maybe there is useful info for this?
http://www.thatscoolwire.com/forum/

[malsyned]

Thanks for the reply, Gyre. If only it were true that information is supplied on technical sheets! I've ordered el-wire and inverters from a number of different on-line suppliers, and they never come with even instructions let alone technical specifications!

ElWire is sold through several distributors, but is only manufactured by one company, LyTec. Their website is at http://www.elam.co.il/ and they have PDF data sheets for all of the various thicknesses of elwire.

There is a data sheet for each type, specifying electrical characteristics like resistance, capacitance, current consumption, and power consumption per for for different frequencies and voltages, and a data sheet for each color describing its illumination properties.

For example, the data sheet for general purpose elwire lists the capacitance for 120V, 2 kHz as 6.1nF per meter. The data sheet for general purpose blue-green (sometimes called aqua) elwire lists its initial brightness for 120V, 2 kHz as 146.2 cd/m^2.

The only thing to watch out for is that the color names that LyTec uses are not always the same as the names used by the distributors. "ultramarine" for example, is usually called "blue" by distributors, and most distributors sell only one of "red" or "hot red". They all seem to use the same product clip art though, so those are actually the best way to match up products to data sheets.

ElWire appears to have a very low capacitance, but the data sheets also list their "equivalent ohmic resistance" at 100 kOhm for 120 V, 2 kHz, so does that mean that to replace elwire with a dummy load would require a relatively big resistor in series with a tiny capacitor?

[gyre]

One supplier tells me that they don't think their drivers are harmed by running without a load.
It never hurts to check.
The issue may be that too short a run will burn out the elwire, rather than an issue with the inverter.

[dragonfly Jafe]

Have you tried calling and talking to one of the Distributors with your questions? I have had good luck talking with Cool Light (Joel) and World-A-Glow (Pat or Mike or Tim) when I needed tech help (phone, not email). I have also used a Cat-9 sequencer with some channels not hooked up without any apparent issues. YMMV.

edit: another idea, double core wire counts as twice the length, so 5' of double core is like 10' of regular ELwire. Double core is brighter also, so may work better for your PWM idea. Good luck! Sounds interesting....

[erbgins]

Thanks for all the great replies about el-wire tehnical specs and inverters. I just got my BM tickets and am more psyched than ever!

[Mister Jellyfish Mister]

edit: another idea, double core wire counts as twice the length, so 5' of double core is like 10' of regular ELwire. Double core is brighter also, so may work better for your PWM idea. Good luck! Sounds interesting....

Good one, Jafe. I understand the same goes for "high bright" el wire which is mostly what folks are buying these days.

[malsyned]

I just spoke to Ryan at WorldAglow, and he says that it is in fact bad for an inverter to give it significantly less el-wire than it is expecting, and that it's bad for the inverter to have no el-wire connected as well. He suggests switching either a power resistor or a cap into the circuit when less than the inverter's rated minimum wire is being used.

As far as PWM brightness control goes, Russ Hensel has an ElWire project that, according to his wiki, is successfully controlling brightness using a PWM. More info here: http://www.opencircuits.com/Russ_Hensel ... re_Project