Solid state safety.

[keeperx]

FYI the laserboy forum is "anti-pangolin/anti-ILDA" in the same way that linux forums are anti microsoft..

as the admin of that forum, i can assure that the discussions over there are mostly about the free software and hardware that its members are developing. I will own a pango someday (when i can afford it).


That being said, i would really like to keep this discussion on track..




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Regarding SOlid state laser safety.

There are other things that i think solid state systems should use.. like some sort of protection circuit for the damn diodes.. something that will CLAMP the mA and voltage to a certain level.. i THINK the new FlexMod does this but im not sure..

The Lasorb is another GREAT invention that i will own, no so much for audience safety, but for diode safety...

I guess what i would like to see is some solid state 'monitoring' circuits that handle safety while also protecting the hardware (lasers/scanners/etc)

Am I completely off base here?

[sugeek]

Am I completely off base here?

I find it a bit funny you want a bunch of extra protection for the electronics, but don't want a shudder? I am actually waiting on my projector right now for the lasorb. I am stuck in the situation my solid state lasers do not modulate (DDL) so the shudder is very important! I will get some analog modulated drivers as soon as I can (anybody want an industrial camera for a couple lava drives )

-Adam

[mophead]

Keeperx, this isn't a jab, just something i found humorous from your ENTP link:

--ENTPs have been known to cut corners without regard to the rules

[keeperx]

Mophead.. no offense taken.. ENTPs have there good traits and there bad traits..

Sugeek.. im not against a shudder, but think that there are additional steps that can be taken to ensure both safety of the equipment and safety of the people around it, that are not part of the current "standard"

[mixedgas]

Regarding SOlid state laser safety.
begin

I'm gonna GET REAMED on this post. But the truth shall set you free.

There are other things that i think solid state systems should use.. like some sort of protection circuit for the damn diodes.. something that will CLAMP the mA and voltage to a certain level.. i THINK the new FlexMod does this but im not sure..
end quote

Diode drivers clamp current by definition.

Already exists , problem is most people here want a under 20$ driver to get going and don't want to pay for a clamped one. Professional diode drivers do not suffer from a lot of the faults the hobby drivers do. Ie the one in your CDROM is good for how many hours ??? The folks who make the cheap DPSS often do not put much into their driver circuitry, its often minimal function engineering, ie what do we have to do to ship a fairly reliable product that lives xxx hours. If you want a clamped module, you call up Analog Modules Inc or Diode Drive or the like and order one.

The issue here is PLers do not like to all buy the same standized gear, use the same switching power supplies, the same cabling, the same scanners etc. This makes it a bear to sell protective gear. I could lay out a board tomarrow, and produce it, but I'm only gonna sell 10 pieces if I'm lucky, and I'll have to support it to the same or better level that Ferrari does, or PLers wont be happy and I'll never sell another one. I'll also have to accomodate a wide range of standard and non standard hardware. PLers want minimum cost, maximum bang for their buck, whereas a bulk customer for a board agrees on performance standards and quality control. Its hard to make PLers happy. Look at how many posts DZ had to do over his recent breakout board. Most of what you ask for has existed for 10-20 years now.

This is why few products hold up to PLers "standards". One bad review in the sellers section and you loose business. There are lots of things I could sell on PL, but getting everybody around here to agree on anything is difficult at best.

begin quote:
I guess what i would like to see is some solid state 'monitoring' circuits that handle safety while also protecting the hardware (lasers/scanners/etc)
end quote

Already exists:

http://www.eyemagic.gr/laser-iris-colorsafe.html

Pangolin's PASS

See CAT-SAFE here:
http://www.medialas.de/documentation.html

Most cambridge amps have/had a coil temperature calculator, ie a CTC, and it seems to be the one part of the circuit the Chinese galvo makers do not copy, which is a pitty, because it only adds about 5$ to the cost of the board. CTCs pull down the scanner image size when driven too hard. One other problem is that analog multiplier chips are not readily available in China. Even though AD makes them there and exports them. I can sell a CTC board for cheap, but since no two LOW COST scanner amps come off the line with similar feedback levels, or even the same feedback connections, its gonna be a hard row to hoe to get them calibrated, as most PLers dont own oscilloscopes. YET if it was done at the factory or the distributer level, its TRIVIAL. A CTC doesnt catch everything, either!

Oh, wait , their main customers, the folks who make disco club toys, dont care...... That may be why we don't see them, demand.

Several people, myself included, have posted scanfail system schematics here, including one contest to get them down to the 3-4$ level in parts, that a few talented people submitted great ideas for.

The only true standard in this crowd is which is ironic, the ILDA file format and the ILDA connector. YET even at LEMs we find many different implementations of voltage levels and shutter circuits, and often have a soldering iron out to link up projectors. Not to mention the Chinese projectors that have wierd ILDA connector sense circuits. Most people would say their systems take 0-5V for color, but I've never seen two identical wiring harnesses at a LEM. PL is about INDIVIDUALS on often limited budgets having fun with lasers, and that makes it difficult to sell hardware for PLers because they WANT to be Individuals.
If we bought 500 or more lasers a year here, we could enforce standards on the manufacturers.


YOU WANT TO MAKE CHANGES< YOU"LL HAVE TO GET THE GEAR MANUFACTURERS TO PUT PROPER FEEDBACK OUTPUTS ON THEIR PRODUCTS!


We are blessed , however, with distributers here that do read PL, and do kick back ideas to the factory, God bless them for it.

Steve

[keeperx]

Steve,
While i do appreciate your input here, you seem to be completely missing the question.

Eyemagic is interesting but has nothing to do with circuitry protection and CAT-SAFE is listed under 'outdated products'

Im looking for monitoring circuits to protect the hardware and the people around the hardware.

-------------------


I had an interesting thought.. a hi tech shudder. Ever seen those windows that can go from clear to black in a split second? i believe they use polarization but i may be wrong.

The other thing to protect/monitor is the modulation signal. You do NOT want any outside signal controlling the laser modulation so how would you shield your scanner? Faraday cage?

[sugeek]

I have been wondering about building an optical interlock or replacing the entire ILDA port with a small fiber bundle. They are making some pretty neat stuff with a solar cell and fiber powering tiny devices. The high tech shutter would only pass the legal stuff if it was spring loaded.

I guess your high tech shutter makes me wonder is the damage threshold of all those photons pumping into it how long would a polarized filter last with 10 watts of q-switched 532? I am sure the rest of the filter would be fine around the hole through it...

-Adam

[keeperx]

Ahh good point... melted = bad

now what about shielding.

[mixedgas]

Look, other then the hopefully soon coming Lasorb, the hardware to protect the hardware is the hardware as sold. The scan fail devices I listed protect the people around the hardware. Otherwise the protection for the people around the hardware is to follow proceedures, and to make sure you have a properly grounded metal case, and good green wire grounds in the venue.

The way you protect the hardware is design the hardware to take a hit from the ground up. There are no add on boards that can protect a diode from being over driven, that is the function of the diode driver, you buy one with overcurrent shutdown and input clamping from the likes of the places I listed. The problem is nobody here wants to spend 99$ more to protect a 14$ diode. I dont blame them. But otherwise then the brilliant little Lasorb, the only way you can protect a DPSS is at the design phase. It takes a heck of a lot of engineering to do that, and there are limits on what you can do.

Take for example control loop bandwidth. If I add a board in series with the diode driver to protect the diode and the driver, I have to limit the fuctionality of the protected unit in terms of bandwidth. By definition, I have also doubled the chance of a component failure in terms of reliability. That is bad.


If you place a current limiter in series with the diode driver, as you seem to think is possible, all you get is a diode driver in series with a diode driver. From a electronics point of view, that is a bad thing. A diode pops far faster then any fuse and often far faster then the upstream protector could react. Pay the $$$ for a professional scientific driver, or buy a better grade laser. Its cheaper in the long run.

You can put a TVS (transient voltage supression device) on your signal inputs. Odds are it wont help you in the catastrophic failure of a misswire, or it will only protect until it fails itself. Or you can zener clamp the inputs, which results in a mushy clamp. It might deflect some static zaps, but if not done properly, it can distort your signals.

The traditional way to protect the hardware, if using single ended signals, is to add a series current limiting resistor to the opamp outputs of the show controller. Then add them to the inputs of the device being driven. This limits the length of the cable you can drive, and since there is no standardized input impedance for laser gear, although most of us hope its at least 600 to 1000 ohms minimum for a single ended input. Now you have a series circuit of the device's output resistance, two "limiting" resistors , and the devices input resistance. You gained a small amount of protection at the loss of signal amplitude in the resistors, and a limit of the cable you can drive. You may actually now need to drive your cable with twice the signal (google"Back terminated" video) Once the input voltage rises above the op-amps common mode voltage, the circuit will fail or latch up or the outputs will distort anyways. So this is a limited amount of protection.

But lets look at this another way, the traditional way that works for the audio industry and professional show company types. Laser show signals are DC to roughly twice the bandwidth of a audio signal.

Its a system of systems engineering point of view, aka design for reliabilty, safety, and long life.

Its called proper design and procedure. AkA do it right at the design stage and use a checklist in the field.

HERE IS YOUR REAL EQUIPMENT PROTECTION DEVICE:


First of all you check the grounds in the venue at both ends of the cable, and you use power cables with 3rd wire ground. Your projector has a metal case that is grounded, and you use shielded cables and connectors with grounded shields for control signals. At one end of the cable you may have to break the ground to prevent loops, but that is common practice in audio and well documented. You need to use a volt-ohm meter and a outlet tester pre show. The US three wire safety ground if used properly, will protect your equipment a great deal, provided your gear is designed to use it. Do not use cords or outlets without the third conductor, or with the grounding lug cut off.

Bill Benner published a free world class document on how to do projector wiring to prevent these problems.
It is here and elsewhere:
http://www.laserist.org/laserist2008...onnections.htm

Second. Don't connect and disconnect cables with the system energized and hot.

Third, design your system so it sequences power, ie the projector doesn't power up until the remote signal source or cpu is powered up. Scanner amps need to have a relay on them that waits until both the plus and minus rails are energized and stable before connecting the galvo amps. This way your galvos don't oscillate on the startup and you have no common mode problems on the inputs.

Fourth, the shutter is there and can't open until commanded. A key must be turned and a button pressed, and its designed to fail shut if the power fails or the control cable is disconnected. Make sure it is designed in such a way that it doesn't surge open on powerup. It also must use current loop control to insure its failsafe from induced voltages. That protects the people from wayward beams.

Fifth, you use differential signaling. I could spend a week explaining how that works and so can Bill, So you read Bill's projector wiring document to get that. Suffice it to say it has many advantages. Instead of being really cable impedence dependent for image size, it has a high impedence by definition and design, and cancels noise. Diff inputs can be made to take a hit way outside the common mode voltage of the opamp. The problem is , everybody runs differential for the X and Y and not for the color. This makes the color circuits really vunerable. Few controllers support color diff outputs. Pangolin is one of the few that do. And almost no Chinese lasers support diff signaling.

Sixth, the weak TTL signaling needs to go if you use it. It needs replaced by DMX, or a differential protocol like RS485.

Seventh, Dont be in a situation where you have to adjust projector electrical settings on the field. If everything is not on outside knobs, something is wrong. This includes stuff like color gains, and image size, and image flips. And these knobs should be in grounded, enclosed boxes.

Eigth, cables need latches or latching connectors, so they cant fall out hot.

Nineth, if your in a situation where static electricity can form, you shouldnt be touching your diode drivers, which should have been metal enclosed and shielded in the first place. Same for the laser heads.

Tenth, dont use cabling systems with screw terminals outside the projector. Bare wires during setup are asking for trouble.

eleventh, if you use ion lasers, special grounding procedures must be taken with respect to the laser head and projector.

Twelth, Dont buy cheap controllers that use wall warts for power, as they are floating and can be a source of evil. If you do buy them,add the proper ground bonding at their connector.


And last, outlet strips are evil, go to the hardware store, buy a metal "new construction box" , three prong cords , and wire your own outlets.


Next up is the part that takes DISCIPLINE.

1. Dont swap cables with the system hot.
2. Follow a preshow checklist with the cabling on it.
3. Follow the 2 and 3 meter rules.
4. Control access to your equipment. The law and good practice requires it, and prevents people from hot swapping cables or pulling power cords.
5. Secure the auditorium or whatever during setup
6. Dont make up connections in the field.
8 Gaff tape or cable tie your cables for security an piece of mind.
9. Sequence your power.
1o actively seek out sources of electrical noise in your venue preshow, and kill or neutralize them. Some of these sources can include intelligent lighting, arc lamp or metal halide based fixtures, and two way radios.
11. Use a predeparture checklist so you are using your cables, dont borrow a unknown possibly or miswired cable or adapter.
12. Add the physical layer needed to protect your show, ie saftety cables on bounce mirrors, projector masking, bolt down projectors to the scaffold, lock scaffold wheels, erect Danger signs, and Brief all persons who will share the stage with you on laser safety, procedures, and things like cooling water for Ions. Security is everyone's business and it should be part of your contract.
13. Make sure you have time for a systems check and a rehearsal.
14. Bring spare everything, like projectors, controllers, lasers, fuses, tools and cooling gear. Doubly redundant is very nice.
15 The definition of doubly redundant is two setups, but one is not in use and is off and electrically cold.
16. Follow the CDRH guidelines and your safety checklist.

One big way to get help is show up at a major lem and have your gear looked over, and to check compatability , join in the linked projector shows that happen at LEMs.


See, protecting your people and projector is based on planning, and state of mind, and procedure. NOT GADGETS !!!!

Steve

[mixedgas]

I had an interesting thought.. a hi tech shudder. Ever seen those windows that can go from clear to black in a split second? i believe they use polarization but i may be wrong.

The other thing to protect/monitor is the modulation signal. You do NOT want any outside signal controlling the laser modulation so how would you shield your scanner? Faraday cage?[/quote]


It is spelled SHUTTER.

The lcd does not physically stand up to the power , and ferroelectric lcds retain the the last state they were set to, NOT failsafe.

Everything is Faraday Caged in the field. A good projector is a FARADAY CAGE, by design. Plastic sides are out, unless they are metal lined inside or individual parts are shielded by their own cage.

People are protected from laser by the failsafe shutter design specified by CDRH, and Projector Masking, and Physical placement/mounting of the projector and bounce mirrors in such a way that IT cannot endanger people.

You do not set up in a theatre or club with people and staff in the club, its part of your preshow checklist, which is required by law if you have a variance. You seal the damn place off, and kick out the Roadies, the Lighting Director , The Clients, The Sound Guys. Oh HELL, I even kicked out Fire Marshals in two different cities. They appreciated the guesture, especially since its a condition of my show contract and variance that I can. Heck, I can even kick out another varienced laserist, and have done so, when that person's setup technique endangered him and myself.

You then test where the beams go and cut a custom metal mask for your projector to prevent deviations. You also align at low power, something you cannot do with a TTL laser without special optics.

Steve