Is EL Lighting legal ?
 

electroluminescent (EL) lighting uses an inverter to raise the 12v voltage way up to drive the lights. The rules say custom circuits cannot have voltages over 24v relative to the battery ground. It is possible the inverter outputs are isolated from ground and might be legal.

Anyone know for sure ?

Re: Is EL Lighting legal ?
 

"Relative to battery ground" provides a reference since voltage is a measure of a difference in potential between two points. Under the 2014 rules, I don't see how a 100+V driver is under 24V and meets R40.

*I'm not an inspector or the GDC, and with the new control system, the electrical rules are expected to undergo significant revision for 2015.

Re: Is EL Lighting legal ?
 

As a robot inspector, I would not permit EL lighting at 100 V under the 2014 rules.

Re: Is EL Lighting legal ?
 

Isn't there a safety risk posed to humans in instances of contact with an EL lighting inverter?

Re: Is EL Lighting legal ?
 

Under which rule? Just for being unsafe?

R40 very specifically says 24V relative to the negative terminal on the battery, not earth ground, and not the ground of your EL thing.

If there's an isolation transformer, like de_ says, you wouldn't be able to measure any voltage between your robot's negative battery terminal and any point in the EL wiring because your EL thing is completely isolated from the rest of the robot's electrical system. There's no path for current to flow from the EL system to the rest of the robot's electrical system because of that transformer.

Re: Is EL Lighting legal ?
 

In the past I've seen a number of teams, including one we work fairly closely with, use EL wire without any issues at inspection. This is what they used on several different robots:

http://www.thatscoolwire.com/wizard/

Not sure if it's the same type of thing you're looking at, but this stuff, as far as I know, only requires a 12v input.

Re: Is EL Lighting legal ?
 

Well, now that's interesting.


Input voltage doesn't matter if the input voltage gets stepped up to 100+V. 100+V is not legal*, even in a non-functional decoration.

*2014 rules.

Re: Is EL Lighting legal ?
 

Guys,
100 volts is still 100 volts no matter how you slice it. It won't matter a bit if one side is tied to the robot frame or to the battery, when you get it across your arm, heart, or someone's pacemaker, we will convert a robot competition into something much different.
Sorry, but no.
BTW, is that spec 100 volts loaded or unloaded?

Re: Is EL Lighting legal ?
 

EL wire looks cool :( (and same with the EL flat stuff too) also, isn't EL Wire A/C current? Won't that cause interference with the radio too?.

Instead of EL wire, we used addressable LEDs and a smoked glass plastic diffuser. that produces the same effect as that flat EL stuff

Re: Is EL Lighting legal ?
 

Chad,
It depends on the frequency of the inverter.

Re: Is EL Lighting legal ?
 

100 volts is legal under the 2014 rules if you have an isolation transformer before the voltage is stepped up to 100 volts. It's only illegal if you can measure more than 100 volts between the negative terminal of the battery and some point on the EL thing.

It may be ruled illegal for being unsafe.

Re: Is EL Lighting legal ?
 

It's unsafe. See Al's post. If I was making the ruling, I would probably reference both rules - the limitation for 100V from the negative terminal of the battery provides good guidance on safety considerations, even if you try to lawyer it and say the 100V is isolated from the robot battery. This should not be ruled legal at any venue.

Re: Is EL Lighting legal ?
 

While it may be legal under reading just of R40, I think most inspectors would consider R40 as guidance for allowed differential voltage. Call it a combination of R40 & R8 if you want. Al made his opinion known. If pushed he is pretty much the final arbitrator of the robot rules on game day as for as the LRIs are concerned. I don't think you will get the FTA or Head Referee to take up your cause.

Re: Is EL Lighting legal ?
 

I checked with tech support at Sparkfun.com since they sell a lot of this stuff.

The 100v volts will only provide a mildly discomforting shock due to the very very small current available. Not remotely life threatening.

The rule says 24v relative to the robot common buss. It is possible to design inverters whose outputs are totally isolated from the inputs (think isolation transformers). So if you use a voltage meter between the common buss and any output HV wire on the inverter, it reads 0 volts. Lab power supplies should be an example where the outputs are completely isolated from any of the input power lines. Else its not usable in a situation that needs differential power.

Unfortunately according to Sparkfun, its 12v inverter input common wire input is connected to one of the output wires so if you measure the robot common to the other HV line you should see 100v AC.

Oh well. Back to robots

Re: Is EL Lighting legal ?
 

If you really wanted to, you can cut that wire, but you should be careful to keep things on either side of that isolation transformer completely isolated, but it would likely be ruled illegal still, due to violating the "magic safety rule".

You use isolation things like this all the time when measuring with an oscilloscope. Typically, the ground clip on a scope is grounded to earth ground. When you'd like to measure the voltage between two different signals, you'd short the one with the ground clip to earth ground. This can be a serious issue if the thing you're measuring is referenced to earth ground (as most wall-powered electronics are). If you put an isolation transformer on the equipment's power supply, the equipment is no longer grounded. Then, wherever you clipped the ground clip, you'd reference that point to ground.

100 volts is not some magic number to be feared. A balloon rubbed on your head (or a robot driving on carpet) will have 10's of times the voltage to ground, but is not dangerous because the amount of charge on the balloon is too small to produce any significant current.

This is one of those judgement call rulings. Obviously, the high voltage from a balloon rubbed on a head is safe, but the high voltage transformer for your CRT display isn't. Al, who is the lead robot inspector, has said that it is illegal, not be because it is over 24 volts to the negative terminal of the battery, but because it's just unsafe.

Re: Is EL Lighting legal ?
 

But if it can't supply enough current to do any harm, what's the worry?

Re: Is EL Lighting legal ?
 

Good question.

Re: Is EL Lighting legal ?
 

Won't the isolation transformer output float with respect to the input? (If there was a predictable potential difference, even 0 V, they'd be coupled, not isolated.) And if it's floating, than you don't know if there's 1 V or 1 000 V with respect to the PD ground at any given instant, so verifying compliance with R40 would be impractical.

(I realize there's some degree of coupling in an isolation transformer, but is that reliable enough to pin down the voltage between them? I doubt it.)

Re: Is EL Lighting legal ?
 

As for being unsafe, most small hobby-style electroluminescent kits wouldn't usually be unsafe, unless you pierced your skin with the wires, and perhaps not even then. But the question did not specify the kind of electroluminescent equipment, and it's definitely possible to design a system to have high enough current to do harm, in addition to high enough voltage to arc dangerously.

But that's why we have R8. (R40 supplements it in this case.) And as a result, there's no need for a ruling on electroluminescent systems in general.

Re: Is EL Lighting legal ?
 

EL systems are very safe (unless you are running a *very* long strand/lots of EL lights). Adafruit.com always show people how they can use it in costumes and decorations. They have masks with glowing EL eyes and costumes with the EL wire sown in. I don't think that they would do that if it wasn't safe. A big advantage to EL over LED is that it takes up a relatively low amount of energy. This also is a reason why it is safe. Also, EL tape/pads can be cut to whatever shape you want.

For me, though, I would not put it on anywhere but a protected part of the robot. I wouldn't want to have it get smashed and shorted out. I would definitely place it inside logo cutouts and around the inside of the frame for a glowing look.

I feel like it should be allowed, but only if it is inside the frame (not running along the outside). Hopefully they can change this for next year!

Re: Is EL Lighting legal ?
 

I think we generally agree. I'm mainly pointing out that it's not the technology that's the problem, it's the implementation. (For example, this might be problematic on an FRC robot, though you'd presumably need a whole lot of panels to justify its capacity.) Fortunately, we have procedures in place to deal with stupid implementations.

That may be a fair assumption, but it's hard to make rules on the basis of their commitment to avoid killing their customers.

Re: Is EL Lighting legal ?
 

Dave and magnets,
In order for 100 volts to provide only a mild sensation the current would have to be severely current limited to something in the microamp range. According to this site... http://elbestbuy.com/elwitein.html 1 meter of wire could require 10 mamp at 2kHz. So when we look at an inverter that is making 100 v RMS (that is 288 volts peak to peak) at 2kHz (as the 12 volt model on the Sparkfun site that is capable of running 15 feet of wire does) you are talking some seriously high and dangerous voltage. To give you an idea, the GFI in your bathroom must operate to open the circuit at 4 mamp or above. So even if the inverter did float the input and output, a simple failure of the wiring, a piece of heatshrink that is not capable of holding off 288 volts, a pinched wire, a robot hit, could potentially put the robot frame at high voltage. This not only puts participants at risk, it puts robot systems and control devices at risk. The 24 volts on the current PD when put across the robot frame in contact with another robot with an wiring issue will take out both cRIOs. I find it unsettling that a tech support guy at a firm like Sparkfun would say that the inverter will only produce a mildly discomforting shock. It is information like that that gets people dead. While a balloon may make a couple of microamps at several thousand volts of discharge, that is enough to take out electronics, permanently. LEDs are so much nicer, take a look at ours.
BTW, most DVMs cannot accurately read RMS voltage at 2kHz as that exceeds the input frequency response of the meter.

Re: Is EL Lighting legal ?
 

That's actually a very good point. If you accidentally send 100v through your roboRIO, I don't think it would like it very much... (I know that you can short any pin on the roboRIO and it will be fine, but I don't think they intend for 100v going across something)::ouch::

Re: Is EL Lighting legal ?
 

Something else for the beta teams to test...

Re: Is EL Lighting legal ?
 

Chad,
Knowing that NI is one of those great industrial controls companies, one of the things they do in design and then testing is to plan for electrostatic discharges near and to their equipment. There are actually electric "guns" that cause a discharge that is repeatable for testing. In the industry we call these "lightning strikes" but the equipment is designed to survive most of those and keep on ticking. That is one of the reasons that the case of the cRio is at power supply common. In the field it is intended to be "grounded" to power line ground or building ground to prevent electrical issues and to drain the high voltage spikes away from the sensitive controller.