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Unread 08-10-2014, 18:04
de_ de_ is offline
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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 ?
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Unread 08-10-2014, 18:12
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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.
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Unread 08-10-2014, 18:16
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Re: Is EL Lighting legal ?

As a robot inspector, I would not permit EL lighting at 100 V under the 2014 rules.
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Unread 08-10-2014, 19:48
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Re: Is EL Lighting legal ?

Isn't there a safety risk posed to humans in instances of contact with an EL lighting inverter?
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Unread 08-10-2014, 20:04
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Re: Is EL Lighting legal ?

Quote:
Originally Posted by DonRotolo View Post
As a robot inspector, I would not permit EL lighting at 100 V under the 2014 rules.
Under which rule? Just for being unsafe?

Quote:
Originally Posted by cgmv123 View Post
"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.
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.
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Unread 08-10-2014, 22:02
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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.
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Unread 08-10-2014, 22:45
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Re: Is EL Lighting legal ?

Quote:
Originally Posted by cbale2000 View Post
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.
Well, now that's interesting.


Quote:
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.
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.
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Last edited by cgmv123 : 08-10-2014 at 22:53.
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Unread 08-10-2014, 23:23
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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?
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Unread 09-10-2014, 00:14
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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
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Unread 09-10-2014, 07:50
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Re: Is EL Lighting legal ?

Chad,
It depends on the frequency of the inverter.
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Unread 09-10-2014, 07:56
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Re: Is EL Lighting legal ?

Quote:
Originally Posted by cgmv123 View Post
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.
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.
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Unread 09-10-2014, 08:47
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Re: Is EL Lighting legal ?

Quote:
Originally Posted by Jared View Post
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.
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.
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Unread 09-10-2014, 09:01
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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.
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Unread 09-10-2014, 16:24
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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
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Unread 09-10-2014, 16:49
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Re: Is EL Lighting legal ?

Quote:
Originally Posted by de_ View Post
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
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.

Last edited by magnets : 09-10-2014 at 16:53.
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