Experimental Brightness Attenuator / Scan fail

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see I never understood the point of one of these scan fails

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I was simply responding to this, by giving you a reason for their existence. I think it is of immediate interest to most people outside of the US.

Although Mccarrott makes some good points about why it might of use in the US, I'd just use a beam mask and be done with it. Far cheaper and likely less prone to error than scanfail.

US scanfail:
http://www.sxc.hu/pic/m/i/iu/iuriata...etal_plate.jpg

EU scanfail:

http://www.pangolin.com/PASS/PASS0002.jpg

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Originally Posted by mccarrot

Now what if your galvo PSU breaks down.

Or one of the galvo's gets a melt down and get stuck (sometimes seen with chinese scanners)

Or some idiot drive over your ILDA cable shorting only the X Y wires

Or one of the Galvo drivers dies

Or one of the galvo cable comes loose due to the 10KW PA system next to the laser.

Or one of the galvo bearings gets stuk

or.....

or...

or....


I hope the scanfail will never have to do its job, but if something goes wrong you will be happy you have it.

Also if there is problem where a audiance member gives you a claim its good to proof you have a scanfail in place, this give you a advantage in court...

finaly the guidelines advise you to use a scanfail.



On only time you do not need to use a scanfail is when you mask of the audiance area with a cover, so in case of a problem there is zero chance a beam hits the audiance.

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OR, I could put a piece of metal as mccarrot so gracefully illustrated and even if the world explodes inside my projector theres absolutely no way (short of the lasers making a few KW to go through the aluminum) that I will get an unwanted beam in the audience...

audience scanning is a neat effect, but honestly, I personally find it annoying, and to do it legally here really isnt worth it... the resulting effect from a legal audience scanning show that complies with CDRH regs is about as awe-inspiring as shining a .1mW pointer into your face after spending endless amounts of blood sweat and tears trying to get it approved...

annoying because you can't do it properly over there ?

theres more to the world than the US you know ;)

Any updates to this project?

My scope just broke down, so I can't test it myself :mad:

Why use two npn transistors instead of a single pnp?

/Thomas

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Why use two npn transistors instead of a single pnp?
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Simply force of habit, I stock more NPN then I do PNP and it seems to survive better under stressful conditions.


No other updates.

Steve

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Originally Posted by aijii

annoying because you can't do it properly over there ?

theres more to the world than the US you know ;)

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Oh I have to agree - audience scanning is the height of bad taste. It says in moron speak, "Hey - he he he - look what I can do..." Roughly the equivalent of sticking your thumb in someone’s eye – and then doing it again and again. Dumb in the first place and F’n idiotic without first rate hardware and safeguards...

brian

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Originally Posted by aijii

theres more to the world than the US you know ;)

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lies! *retardo

15 characters

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Originally Posted by aijii

theres more to the world than the US you know ;)

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And it is all irrelevant... *retardo

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Originally Posted by mixedgas

Simply force of habit, I stock more NPN then I do PNP and it seems to survive better under stressful conditions.
Steve

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I see :p

I still think a PNP/PFET would be better - should the power to the scanfail disappear, the transistor will turn on and attenuate the modulation output.

/Thomas