Church Project, Help Needed

I'm working on a project for church for our bible school this year, and I'm needing some help. I've been asked to make a laser maze. I don't think it will be bad, but I've got several cheap red diodes that I'm going to try to use.

I'm going to run everything from an arduino. What I'd like to know, is there somewhere I could buy some cheap diodes that are in a module cheaply. I've got some 5mw reds, but I'd like to get either some stronger reds 50+mw or greens in the same range. I'm going to give them a pair of safety glasses to wear through just the same, and as soon as the beam is interrupted, the power will be cut off from the laser, using a photoresistor. I've kind of gotten out of lasers, and was wondering where would be the best place to get these diodes without spending a fortune.

DX
DHGate
Kaidomain
FocalPrice
others?

How will they see a low powered beam if they are wearing goggles?

Peace,
dave

You should prolly get the maze done at ankle height.

My initial thought was to use 5mw lasers all coming from one side, and have them move through facing the opposite side without goggles.

I'm actually hooking up 3 sets of lasers to a seperate switch. for younger kids, it'll be ankle high where they simply step over, then progressively more difficult (Level 1,2,3).

How critical would goggles be for a 50mw green or red if the power is removed as soon as the beam is interrupted?

zeramant86 said:

My initial thought was to use 5mw lasers all coming from one side, and have them move through facing the opposite side without goggles.

I'm actually hooking up 3 sets of lasers to a seperate switch. for younger kids, it'll be ankle high where they simply step over, then progressively more difficult (Level 1,2,3).

How critical would goggles be for a 50mw green or red if the power is removed as soon as the beam is interrupted?

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This sounds like a pretty cool idea! I want to play this game!

Obviously goggles are recommended for anything >5mW. However, if the beam is around waist hight and cuts off as soon as it's interrupted, I don't think goggles are critical.
Again, goggles would probably be best, but then the game becomes more of a "guess-where-the-beam-is-and-try-to-avoid-it" game.

Overall I'd just say to keep it at waist height and MAKE SURE it's aligned correctly so that it cuts off when interrupted. Plus give the kids a strict warning not to look into the beams!

Hope that helps,
Adam :yh:

May also want fog if I understand what you are doing correctly.

petters said:

May also want fog if I understand what you are doing correctly.

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Good suggestion. This will actually allow you to use lower powered lasers yet still see the beam.

Also, as for where to get the modules, I'd say probably DX. It's cheap, and although they'll be under spec, you don't need on-spec modules for this project.

Kids and lasers that could harm the eyes in an instant. Honestly man this sounds like a recipe for liability lawsuites. If a kid gets rowdy and is playing around and pushes another kid into a beam and it strikes their eye....you have very mad parents. 500mW is a Class 3b laser product and is able to cause damage. Even if it cuts off when interrupted you still have a split second of exposure. That can be enough.

I used to work at a church and my dad was a pastor all my growing up years and I can count on a few things from church people and kids.
1. Kids will be roudy. ESPECIALLY the little shits.
2. Parents will always side with the kids. Even the little shits.
3. Everyone is always quick to point fingers. Always.


If you do this you are risking so much for so little. I have worked many many VBS years and we saw lots of results without laser mazes. If it was for the sole use of a youth group and would involve liability waivers I would say baller, let me give you some pointers. Not for kids though man.

Good luck with the bible school, show the kids the light(that won't leave permanent retinal damage).

Edit: if you stick to truly 5mW or below then no problem. Use fog to see the beam. 5mW cannot damage the eye unless long periods of direct exposure occur.

What you really ought to do is use low-powered red lasers and just have a lot of fog. Even 50mW reds aren't going to be very visible without some sort of fog, and it'll be pretty dangerous too.

You should also drop the output power of your lasers to about the 0.5-2mW range (Class I or II). 5mW is the upper limit on blink-reaction power, but "eyesafe" is really in the Class I or II range. It should be as eyesafe as supermarket barcode readers. With fog you won't need to worry so much about visibility anyway.

If you need cheap low-power red modules, get some on eBay. They only need 3V or something.

Wannaburn, you misread there, that was 50mw, not 500mw.

I thought about the fog machine, I just need to see if the photo resistors will still pickup through the fog. I've already ordered some cheap 5mm red diodes, just wondering what the visibility will be like.

I've actually kicked the idea around for using two horizontal green beams instead of the push buttons, and use the break of those beams to be the start/stop buttons instead.

I hope it works out as well as in my head.

500mW would be Class IV. Class IIIb lasers still pose a danger to the eye. Anything more than 5mW can harm even with the blink reflex.

Warning: If you end up buying 5mW modules, BE CAREFUL! They won't be 5mW - they're almost guaranteed to be overspec. Check around the forums to find a trusted supplier who offers a "5mW or less" guarantee. Even then, it might be a good idea to get the modules metered before you use them.

Better safe than sorry.

EDIT: About the photo resistors picking up the beam through the fog.. I'm almost positive that will still work. The fog just enhances the visibility of the beam, so the laser dot will still be visible at the end of the line.

Yeah theyll all be regulated with the circuit I'm going to use.