Ah... we're now in our third thread category.
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You may not be getting many answers because I suspect most people here are not using SD cards and trying to trigger built in cues so, they may not know the answer. Most go with a laser software and hardware solution which, I still maintain that you should be considering. Particularly since this is for the public and you have an obligation to the safety of your patrons to not run a laser at them with a cobbled together hobbyist experiment to save money. I'm glad to see you're considering the Venus II though.
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The answer to 3, I already gave you. http://www.ebay.com/itm/SUNY-Stage-L...0AAOSwNSxU9p-f and, you are far better off with the Venus.
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The answer to 4 is (assuming you mean the touchscreen built into the Venus) is yes, you can reduce the brightness with the built in touchscreen.
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Sorry to sound so harsh but, it needs to be emphasized again that, your plan is to put this in a public club that you operate. As a business owner especially, you have an obligation for your patrons safety. The effect of having lasers is not a cheap endeavor. I know it's a lot of rubles but, please make sure you are buying a good projector and using proper laser software since you are using it with the public. Just because the laser is "only going to be used a little bit on Friday and Saturday night so it doesn't have to be reliable" is a bit of a scary proposition. As is trying to experiment with making it work with a solution other than something designed for lasers.
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Just want to see you doing things safely and not find yourself in any trouble. If this were just for your own enjoyment at home, I'd say rock on and experiment, learn and have fun but, since this is in a very small bar, and you've admitted to being confused and somewhat new to everything, you really want to do this the right way.