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Author Topic: brain storm an optimal human safety system for back line  (Read 102365 times)

Stephen Swaffer

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Re: brain storm an optimal human safety system for back line
« Reply #220 on: May 21, 2015, 10:01:47 am »

Tim's got a point-JR is expending a lot of brain power and energy primarily because other's don't wanna use theirs-but it seems like JR is enjoying this(or maybe he just wants an excuse to barricade himself in his basement?)
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Steve Swaffer

John Roberts {JR}

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Re: brain storm an optimal human safety system for back line
« Reply #221 on: May 21, 2015, 11:49:14 am »

It is never good business to allow the talent to get hurt even when it isn't our fault. I have seen examples of this and the lawyers will often stretch to blame anyone even peripherally involved if they look like they have deep pockets. (Look at all the sound equipment they own. ) 

=======

Back on topic. I connected the ground current sense and it trips the GFCI with no ground fault but only at start-up. If I re-connect my opto-shunt after it is started and latched, it doesn't trip the GFCI so that's what I need to fix today. There is something weird about the initial start-up conditions causing this.

My opto-triac has 400V of safe off voltage and only tens of nA leakage when off, so that should not trip the GFCI, and doesn't trip it after it is on and stable. Perhaps some capacitance not shown on the data sheet? (This is why we breadboard circuits.  8) )

JR

PS: Yes this is an exercise in mental masturbation. I will never manufacture these and frankly there aren't that many actual deaths specifically caused by this fault (while likely more than global warming). This is just a pet cause of mine and we have the technology to prevent death for 99.9%. In fact GFCI with stinger cap does that already. I plan to publish full schematics after I get it working.
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Don't tune your drums half-ass. Listen to what a properly "cleared" drum sounds like.   http://circularscience.com/

Tim McCulloch

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Re: brain storm an optimal human safety system for back line
« Reply #222 on: May 21, 2015, 12:50:36 pm »

It is never good business to allow the talent to get hurt even when it isn't our fault. I have seen examples of this and the lawyers will often stretch to blame anyone even peripherally involved if they look like they have deep pockets. (Look at all the sound equipment they own. ) 

=======

Back on topic. I connected the ground current sense and it trips the GFCI with no ground fault but only at start-up. If I re-connect my opto-shunt after it is started and latched, it doesn't trip the GFCI so that's what I need to fix today. There is something weird about the initial start-up conditions causing this.

My opto-triac has 400V of safe off voltage and only tens of nA leakage when off, so that should not trip the GFCI, and doesn't trip it after it is on and stable. Perhaps some capacitance not shown on the data sheet? (This is why we breadboard circuits.  8) )

JR

PS: Yes this is an exercise in mental masturbation. I will never manufacture these and frankly there aren't that many actual deaths specifically caused by this fault (while likely more than global warming). This is just a pet cause of mine and we have the technology to prevent death for 99.9%. In fact GFCI with stinger cap does that already. I plan to publish full schematics after I get it working.

Don't get me wrong - I'm not about people dying because of someone elses bad/unsafe decisions - but if some stupid twit thinks that using his precious vintage electrocution device is more important than his personal safety, WHO AM I to tell him no by using a device that interrupts power?  I'm being partly sarcastic and absolutely serious at the same time...

I believe it's our responsibility to provide stage power that is up to Code and meets or exceeds all generally recognized safe practices.  It's not our job to tell "An ARTISTE" that his stuff sucks and he can't use it on our stage because someone got electrocuted 5 years ago or on another continent.  Can you imagine the lawsuit from the promoter and ticket buyers when "ZXY sound company refused to provide power" and the show is cancelled in the ARTISTE's fit of pique?
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"Practicing an art, no matter how well or badly, is a way to make your soul grow, for heaven's sake. Sing in the shower. Dance to the radio. Tell stories. Write a poem to a friend, even a lousy poem. Do it as well as you possible can. You will get an enormous reward. You will have created something."  - Kurt Vonnegut

John Roberts {JR}

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Re: brain storm an optimal human safety system for back line
« Reply #223 on: May 21, 2015, 01:11:20 pm »

Don't get me wrong - I'm not about people dying because of someone elses bad/unsafe decisions - but if some stupid twit thinks that using his precious vintage electrocution device is more important than his personal safety, WHO AM I to tell him no by using a device that interrupts power?  I'm being partly sarcastic and absolutely serious at the same time...
Natural selection will always be in play. I saw a recent post where a GFCI was patched around due to unexplained tripping. In my judgement it is worse to bypass a safety device, than not use one in the first place. That said the "show must go on" mentality usually wins in the short term.
Quote
I believe it's our responsibility to provide stage power that is up to Code and meets or exceeds all generally recognized safe practices.  It's not our job to tell "An ARTISTE" that his stuff sucks and he can't use it on our stage because someone got electrocuted 5 years ago or on another continent.  Can you imagine the lawsuit from the promoter and ticket buyers when "ZXY sound company refused to provide power" and the show is cancelled in the ARTISTE's fit of pique?
As compared to said ARTISTE being killed? Choose your poison. I posted about liability issues, but there is also a strong component of just doing what is right.

JR
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Tim McCulloch

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Re: brain storm an optimal human safety system for back line
« Reply #224 on: May 21, 2015, 01:49:47 pm »

Natural selection will always be in play. I saw a recent post where a GFCI was patched around due to unexplained tripping. In my judgement it is worse to bypass a safety device, than not use one in the first place. That said the "show must go on" mentality usually wins in the short term. As compared to said ARTISTE being killed? Choose your poison. I posted about liability issues, but there is also a strong component of just doing what is right.

JR

Some ARTISTEs would rather die than play a safer rig or at a lower volume or... or... make ANY change whatsoever.  In any confrontational aspect of artistic relations, the production company will be voted off the island.  Can you tell I've been down this road recently?
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"Practicing an art, no matter how well or badly, is a way to make your soul grow, for heaven's sake. Sing in the shower. Dance to the radio. Tell stories. Write a poem to a friend, even a lousy poem. Do it as well as you possible can. You will get an enormous reward. You will have created something."  - Kurt Vonnegut

John Roberts {JR}

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Re: brain storm an optimal human safety system for back line
« Reply #225 on: May 21, 2015, 02:13:20 pm »

OK back on topic, I just got the ground sense circuit working. I had to increase the series resistance in my shunt circuit from GFCI output line-hot, to GFCI input neutral, to intentionally trip the GFCI. according to spec this only needs to be 6mA max, but I worry if there are multiple faults going on at the same time. Right now my shunt is delivering 8 mA nominal so should work even with low line and high tolerance GFCI.

My initial speculation was that the shunt opto-triac had enough terminal to terminal capacitance when off to trip the GFCI. The GFCI sensitivity may be different during start up too. Another data point is that the opto-triac has something like an up to 1000V/uSec rise time limit... So thyrister probably conducts if hit with really really fast edge rates. Perhaps an added C across the triac working with the series R could slow it down enough to not turn on.. but that C would conduct current too.  :o  arghh another trapeze act. Making the shunt R larger probably already forms a RC with the intrinsic triac body capacitance (pF?) . Add a cap to slow it down below 1000V/usec but don't sink so much current it trips the GFCI.    8)


JR


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Don't tune your drums half-ass. Listen to what a properly "cleared" drum sounds like.   http://circularscience.com/

John Roberts {JR}

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Re: brain storm an optimal human safety system for back line
« Reply #226 on: May 21, 2015, 02:20:26 pm »

Some ARTISTEs would rather die than play a safer rig or at a lower volume or... or... make ANY change whatsoever.  In any confrontational aspect of artistic relations, the production company will be voted off the island.  Can you tell I've been down this road recently?
Even a lowly musician probably doesn't really want to be killed by his amp, while I can appreciate being loyal to a legacy amp tone.

My simple cheap and dirty GFCI with stinger cap, has been tested to actually be quieter than a hard grounded outlet for some pedal applications, and never noisier or negatively affecting tone.

The GFCI will protect an unwashed musician from his faulty amp, and the stinger cap will protect against the hot mic scenario.

If the musician really needs killin, don't do it on stage in front of witnesses.

JR
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Mark Cadwallader

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Re: brain storm an optimal human safety system for back line
« Reply #227 on: May 21, 2015, 04:31:35 pm »

<snip>

If the musician really needs killin, don't do it on stage in front of witnesses.

JR

Yeah, unless the lampie is in on the deal and can pull off the complete blackout and restore trick (as done in the murder mystery shows).
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Scott Holtzman

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Re: brain storm an optimal human safety system for back line
« Reply #228 on: May 21, 2015, 11:56:14 pm »

I think it more humane for music and art to simply let the AC flow.... and if some numb-nuts muso wants to run dangerous equipment that results in his death or injury, that's his personal decision.  Kind of the libertarian approach to safety...  /satire, sort of but not really

Tim "still cynical after all these years" Mc

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John Roberts {JR}

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Re: brain storm an optimal human safety system for back line
« Reply #229 on: May 22, 2015, 03:32:44 pm »

I will try to ignore the dark humor this thread has engendered and I appreciate many of you are bored. I would be bored too if i wasn't still learning.

The last squirrely part was the GFCI tripping during start up... It appears that this is in fact related to the edge rate of the initial waveform  (apparently more than 1000V/uSec ). One of the reasons I take this much time to refine the design is because I have my over-night team of design engineers (my sub-concious) always working at solving difficult design problems in the back ground. 

To restate the problem If I added a RxC across the shunt load, the current drawn by the cap would contribute to tripping the GFCI. Making the shunt resistor larger was a POOGE (not a real fix). The fix that my overnight team came up with, and shared with me yesterday while i was out riding my bike, is to connect the C of the RC shunt to the output side neutral, so at start up the RxC current is all in the output side circuit and does not imbalance the GFCI. When the circuitry senses ground current and turns on the opto-triac, it connects the output resistor to the input side neutral... It now works like a charm (with .01uF cap) and I have returned to my original value R so I can be confident that my ground trip does not interfere with a marginal GFCI fault at low current.

Once this trips the 3 pole relay opens up and nobody will be at risk from this outlet.  8)

To be determined still is optimum ground current sense circuit, but i no longer need to worry about keeping max ground current under 12mA so you can't get stuck to it... since it will open circuit almost immediately getting stuck is not a concern.

Finally...

PS: After i clean this up, I will send the working proto along to Mike to double check my work on his bench that simulates sundry power faults. My bench is a little dicey, with an RPBG wired outlet on purpose to reverse polarity back correct again, and provide a ground path, so I can test the ground current trip...  I don't have a real grounded outlet in my whole house.
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Don't tune your drums half-ass. Listen to what a properly "cleared" drum sounds like.   http://circularscience.com/

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Re: brain storm an optimal human safety system for back line
« Reply #229 on: May 22, 2015, 03:32:44 pm »


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