Info on scan fail systems

[Banthai]

Greeny said

Absolutely. But having CE marking on a laser is no guarantee that it's being used safely!

In fact i was told by someone here on PL that imports a lot of high end gear from China that .... most of the Lowend DJ laser projectors have a CE mark on them when they come to the UK .... but if you ask the manufacturer what it stands for they tell you "CHINESE EXPORT"

that made me chuckle when i heard that


PS ....Greeny .... did your LW 50k scanset arrive are they ok .... i won a set on Ebay this week so im yet to find out

all the best ... Karl

[Lynx]

Mr Green Alien

Quote
The "CE" mark is now mandatory for regulated products sold in the European Union. This applies to prototypes and commercial freebies.


From the EU web site, they are bigger than us UK mortals, but EU law just the same !!

Regards


Kevin

[Lynx]

Hi Karl

Like it !!

You dead right no guaranty it it will be safe, I never said it would be



Regards

Kevin

[Lynx]

Hi All

You many have noticed that some characters are missing from my posts.

I have already mentioned that I am dyslestik, but I have just found a fault on my Mac Book Pro, apparatlly the kyboards have a fault So I have cotactd aple regarding this probem, but they may not reply as they may not undertand the Email

So, I now have a great excuss for poor spelling, wish I could have used this Appl computer in my school days.

Regarding CE marking

As long as you don't sell or transfer your DIY projector, you should be able to ignore CE legislation. If your DIY projector is a prototype intended for production or sale or even given as a commercial gift, you will need to go down the CE marking route. This does not negate the responsibility of the owner/creator of the DIY projector from legal duty of care on the safe use of the equipment.

So a suitable risk assessment is still required if used in public still referencing relevant standards for the product in this case a laser projector. Main areas of concern are low voltage directive, EMC, mechanical construction, BS 60825, labeling etc.

Also if you use this projector in public you will need to provide a
DSR (display safety record) for each display, even if you are not audience scanning.
The use of Class 3B Class 4 lasers requires the appointment of a LSO (laser safety officer appointed to manage the safety of the whole display and also to manage the full life cycle of the display (initial design , planning, installation, alignment, operation, maintenance, dismantling and transport)

The LSO is also responsible for the communication with relevant authorities examples:- local authorities, HSE, CAA, Maritime, police, ambulance, venue management, duty first aid staff and any other persons involved with the safe delivery of the display.

We (Lynx Laser UK) issue a general risk assessment (25 pages) for conventional audio visual equipment hire, together with a very detailed DSR (display safety record) which runs into approx 30 pages, not unusual if you think about all of the risks from a laser display (without audience scanning).

You may all think that this is a complete overkill and not necessary, but it is a requirement to ensure you have shown that you have reduced the risks as far as practically possible.

To give you all an idea of what is required, a master DSR (Display Safety Record) template is included within a document from John O' Hagen's doctoral thesis available on Pangolins web site.

I decided that the only way for our company to produce safe laser displays was to attend the Laser Safety Management Course at Loughborough University.

A full week intensive course with tutors Dr. John O' Hagen HPA (Health Protection Agency) and Dr. John Tyrer (Laser Safety Advisor Loughbrough). The course covers all aspects of laser safety not just for the entertainment industry, but also medical, industrial and communication lasers.
When I completed the course examinations and returned to our office, I immediately condemned my own dual scan 30mW laser system

You are all maybe thinking with all of that hassle I must be charging an absolute fortune for our Laser Displays. Here is the bottom line, we do charge a fortune to mainly three main clients who are prepared to pay more to ensure their clients safety or we build the costs into a complete production.

Some of you will probably do more laser displays than myself and I have seen costs in the UK for a laser display from £150 per night this is excellent value for money, considering even what I am paying for insurance. I would gladly give all of our Laser Display Work on a sub contract basis if they could convince me that they can provide a safe, insured and proffesional display Contact ME I AM Serious

I hope I have given enough information regarding laser safety, but if you need more, read John O' Hagens docs or attend a course.

IF YOU DONT UNDERSTAND AFTER ALL OF THAT, DON'T TAKE YOUR LASER OUT IN PUBLIC, ENJOY YOUR LASERS AT HOME !!!! AND BE SAFE


Regards


Kevin

[Pitts]

Adam... That was me telling you about it I got to see a draft version of it when I was with Greg at LSDI..

Looks like a basic one to get everyone on the basics of safety and a more professional one that you could upgrade to that had a possible examination based system.

The concept is great and what I saw of it there is plenty to look forward to.

Cheers

Ray

[greenalien]

Lynx - thanks for finally agreeing that homebuilt laser projectors don't need CE approval before use! Safe operation, risk assessment, method statements, operator training and experience, figure measurement, radiation exposure calculations and all other aspects of laser use in public are all topics which most of us can benefit from learning more about, especially when it comes to sharing industry best practice, so I'm not going to argue about the rest of your posts!

Banthai - 50k Laserworld scanset arrived OK, this is the second one I've bought - the original was a 45k one but looks the same; that set works fine. Not had time to try the new ones yet but they were well packed and look OK.

MODS - A while ago, I put forward the suggestion that we should have a separate Safety forum - looking at the way this topic has diverged since it started, and the number of useful and informative comments, perhaps now would be a good time to start.

[mixedgas]

To get things started on a freeware photon lexicon NO liability shutdown system, the recommended 1980's safety circuit from a certain now dead, very big, laser show company "cruise ship safety system" consisted of a fast analog devices analog multiplier chip being fed the scanner amp velocity signal, into both inputs. This squared the input , which was ran into a precision rectifier circuit based a on a very fast (for its day) opamp and schottkey diodes. A CMP-05 or similar fast comparator was fed the PRs output on one side and a level setting pot on side. the comparator output drove a AO cell (fast shutter) and the mechanical master shutter (no where near fast) for the cut off on failure to have a certain velocity. No lowpass filters or anything, to ensure some modicum of speed.

Now thats all well and good, but if anyone ever asked me to show them that drawing, ( part of a CDRH approved manufacturers report and owners manual no less!)it is now unobtainium. It was (1996 or so) setting on a dusty bookshelf in a car dealership that bought the projector and a 13 watt laser ionics, then installed modern coated energy saving windows a few months after they got the laser installed. The install required the beams to go through the show room windows to the bounce mirrors outside. A year later they were not talking to laser whatever and I got a service call to fix the ionics. You can guess how dissapointed they were when I measured 70% reflection @ 514 off the window coatings, plus they had installed megawatts of metal halide and sodium lighting outside. They were NOT happy campers after this. So I dont think they would still have the system or the book, dispite paying some 50K$ to laser something or another.

So I bet that drawing is now trashed.

jeeze, WARNING< I may have forgot some details here and there,last time I saw that manual was 1995 or 1996, so dont hold me liable if you build this thing.

AD now makes some very fast analog multipliers, much faster then the 534 that was used in that board, I dont know if AD633 (low cost)is fast enough. Note the above scheme nowhere near covers all the contingencies needed for safe scanning, but its a good start.

Steve

[Pangolin]

Hi Steve,

I know the circuit of which you speak, and might even have the schematic around. I wasn't aware it was used on cruise ships (but it makes perfect sense). This company also had an installation at Disney's Epcot center, but it wasn't used for audience scanning per se...

One thing. I think that circuit is actually more complex than is needed for these guys. Also, at least some of the Chinese scanner manufacturers do not put a velocity test point on the scanner amp, but most do have access to the position test point, therefore a position-based system would be more useful and applicable.

Note that some Chinese amps don't even make the position signal available (such as the older DT-40), and some amps have a kind of "fake" position signal called "Safety" (such as the newer DT-40 PRO). In my examination of these amps, I personally would not use the "safety" signal for a scan-fail board. I honestly don't know what this signal is, but I know that it's not Position, and Jian also can't tell me what it is. It's like going to the store and buying something called "lunch meat", but nobody -- not even the person behind the meat counter will tell you what it is... Would you eat it?

Anyway, I can tell you guys where you can tap off the scanner amp to get position. I have to do that when I am doing the mods...

Bill

[dave]

As Adrian mentioned before, I did a bit of playing round with a analogue design, but it has been shelved for a while now.. At the moment we are using a digital safety board, and toying with the idea of putting PASS into our projectors...

Anyway, where I got to was a safety board in 3 parts I guess.

2 parts were circuits to compare x input and x feedback, and y input and y feedback. Output would be shut down if error went outside a preset margin.

The third part was integrating the position signals from x input and y input and summing them. They were then squared with a AD633. I think Steve has mentioned this technique on here, as well as on Alt.lasers.

By sensing the velocity on the DAC output, then comparing the scanners input signals to feedback signals avoided the issues associated with the galvos inertia.

Anyway, we probably got it 70% of the way there. To the point where it was taking out hotspots on some effects quite nicely...

I would be more than happy to share what I have done, get something that works well, then perhaps design up a board people could build up.

David

[greenalien]

I see that Medialas also do a safety board, the 'Safe-Guard II'. Does anyone have experience of using this?

http://www.medialas.de/data/Safe_Guard_II_eng.pdf