Light show project

jefm

Hi gang, I've been playing with Stamps and accessories for years but never took time to make anything worthwhile. Now a simple project with a hard deadline has been dumped in my lap and I want to come through! Here are the details as I know them and more as it comes in...

This project is a portable laser light show. The project will consist of these sections:
Beam: a minimized laser pointer with heat sync and fan for 100% duty cycle. Probably 5mW, hopefully bigger, but hard to find now thanks to kids pointing them at aircraft
Control: Basic Stamp II operating three small processor fans with home made front side mirrors glued to the hubs. Three pots will be read by the stamp and turned into PWM for each fan. The whole point for using a stamp is to have an optional "auto mode" that will consist of incrementing/decremating values influenced by random numbers.
Casing: Classic metal lunch box, pipe hanging strap and Plexiglas.
Power: Separate source for beam and control system. To be based on AA NIMH, field changeable, and fit in lunch box.

This is inspired by a laser lunch box tutorial in Make Magazine (which I lost, I'm making it up from here on) and various light show tutorials on instructables.com.

I think I can figure out a lot of this but the big stumper at the moment is what to do for PWM. I know the Stamp does it on board, but supposedly it will not consistantly run all three motors at once, especially when I'll be doing constant RCTIME polls for the pots. Seems like there are two ways to do it with Parallax parts, with similar costs:
PWMPal: can do all motors on one device, needs some external circuitry.
Micro Dual Serial Motor controller: would need two of them. does not seem to need external circuitry for small motors (me).

Anyone have a suggestion as to which route to take? I'm also all ears for laser sources, I was going to raid the office/electronics shops for laser pointers and maybe look at hardware stores for laser-level type equipment. But people seem to be saying that green lasers are brighter.

Thanks for any help gang, can't wait to play Stamp again!

metron9

"...all ears for laser sources"

Tons of lasers here up to 500mw and tiny red ones for 3 bucks that work great.
http://www.dealextreme.com/products.dx/category.911~page.2

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Think Inside the box first and if that doesn't work..
Re-arrange what's inside the box then...
Think outside the BOX!

jefm

Thanks for the link! Sadly, unless I'm missing something, they flat out do not ship >5mW lasers to the US due to the actions of irresponsible people. I did grab several 5mW pointers from shops around town, to try out. I'm generally pretty cautious but do not know much about laser safety, so for now it's probably for the best.

If I could tack on an electronics question... I want to run this laser off a larger bank of AA NIMH batteries for more runtime. Can I, say, build a 6vdc pack, and use a voltage regualtor to bring it down to 3v? I know that's probably wasteful but I don't know if it's any better to hook batteries up in parallel.

Thanks for any help :}

sumdawgy

Jef,

Your regulator·idea will work fine..

One of my biking projects included using a 3V regulator to power my new tandy walkmate cassette player. (Yeah so·I'm dating myself.)·I locked the player·into my biking vest that·would jack·into a backpack containing 12V amplified speakers & a 10Amp/Hr battery.· Plenty of ride time at full volume and no need to change out the AA bateries!

When the battery was low...I·controlled drag on the cassette by simply lowering the volume to reduce the drain from the speakers.· This is what you had in the back of your mind....right?

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Before you criticize someone, walk a mile in his shoes. That way if he gets angry, he'll be a mile away and barefoot. - unknown

Spiral_72

Hey, you want a 5mW laser???

You can purchase the green lower power units and "hack" them for up to and more than 5mW output. I know from personal, first hand experience. Google it.

A little note here: The button cells won't last very long anymore [noparse]:)[/noparse]

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"puff"...... Smile, there went another one.

mikediv

Jef Miller I just ran into that when I tried to order one, I am confused what about all those ebay ads for "balloon popping" Match lighting laser pointers are they phony??

jefm

The laser thing is pretty goofy. I didn't think the day would come where I long for a "pre-ban laser pointer". But, that's progress for you. I found a pretty scary FDA site having to do with (not) importing lasers, but I can't find it now and don't want to quote what I can't cite.
Apparently there is a whole fandom dedicated to popping ballons, lighting matches and etc with these things. Not my interest, I just want to make neat lights :}
I did get a couple 5mW units from shops around town. I haven't played with lasers much so these seem bright. I did order a 15mW unit from wickedlasers.com, along with optics and most important LASER SAFETY GLASSES. Somehow these are supposed to be legal to buy in US, if not, I'll just say I missed the memo :} The 5mW I have seems bright enough for a show, but I don't know how much it will dim after being bounced three times and shot through a plexiglass aperture. I'll have to look into the modding thing as well when I have a moment, I got a $2 red cheappie just to have something to ruin.

Nobody mentioned PWM so the two mini controllers are in the mail, we'll see what happens. Lunch boxes and acylic for front side mirrors are on the way. All these parts in the mail.. reminds me of fabrication gigs :}
Thanks for the help and for reading!

jefm

So far, I got basic PWM working via the PWMPAL and got the 3v laser to work off of the 12v Pro Dev Board. I used an adjustable voltage regulator from Radio Snack for this. It's needed since I'm hoping to run the whole system off of 12-15vdc. Laser works fine, but was I surprised when I touched the regulator, that puppy is hot!!! I worry about how much power I'm wasting in the conversion. I'm probably better off running the stamp/motors on their own pack and the laser on another. What do you think?

I did get some mirrored acrylic, some processor fans that can spin pretty slow without stalling, combined that with the PWM and laser developments, and can draw circles on the wall now :} Baby steps, right? one thing at a time...

jefm

I did ultimately get the laser spirograph to work on a bench, with a computer telling the Stamp what to do. I did not make the system portable in time for the art show however, mostly because:
1) I have a lot to learn about electronics
2) I tried to build the whole thing on a BS2 carrier, which might have worked under better circumstances but generally cause me a lot of problems (too much stuff for a carrier)
3) I have a lot to learn about programming (how to do decimal math on the non-decimal stamp, for starters)

Most of the time spent on the project wound up being sunk in fabrication and a lot of the computer/electronics stuff wasn't messed with until the final day(s). Not a good way to work, but now I just have time to fix some of the mistakes I know I made and figure out various stuff I could not get going. I will probably try making a custom PCB (pad2pad.com?) as well, since I wasted a lot of time troubleshooting my horrible wiring job on the Carrier.

This project is not dead, it is resting. :}

Spiral_72

That's really cool nonetheless. Any chance we could see a video of the spirograph [noparse]:)[/noparse] I'd love it!

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"puff"...... Smile, there went another one.

jefm

Ok, enough of a break, time to get this going again :}

This time I will make my first custom PCB. I'm starting out with ExpressPCB and am doing the schematic right now; first schematic I've done in a computer. I love projects, always so many new firsts, just makes you wonder what previously "impossible" thing you will learn to do next.

A big problem I had with the Carrier based system (besides everything) was that the laser ran off a variable voltage regulator (wired for 3v). Although the laser only draws a few hundred mA, the regulator ate up almost an amp in the conversion, and put out a ton of heat. I've been trying to think another way to do this...

-dedicated batteries for laser: cool, but I'd prefer dealing with a single 15v battery bank
-use Stamp regulator to go from 15v to 5v, then regulate 5v to 3v: neat, but I'd have to test what amps it takes to go from 5 to 3v (what mA can the Stamp's regulator handle anyway?)

Perhaps I could do this trick with a Zener diode and a resistor?
http://www.reuk.co.uk/Zener-Diode-Voltage-Regulator.htm
If this is such a good, simple idea, why do people use regulators at all? (my guess is high current?)

Would love to breadboard it up but can't get to electronics shop until weekend, might have to eat crow and get some Zeners from Mouser.

Spiral_72: I'll post a video when it's done and working :} Right now things are all chopped up until I can get the board finished, and I only really bothered to take one picture of a "laser tunnel" which didn't even turn out too well.

mph

Hi jefm ~

let me tackle your last question about lasers and why green lasers appear to be "brighter". You should read up a little on the difference between "photometry" and "radiometry". Radiometry is about measuring power of the radiation (measured in Watts) while photometry is about measuring how bright a radiation source appears to the human eye (measured in lumens). The "sensitivity" of your eye depends on the wavelength of the light, that is for a constant radiant power (watts) you perceive different colors as having different "brightness" (lumens). This is what is called the "luminosity function" (see http://en.wikipedia.org/wiki/Photopic_vision), and it shows that the eye is most sensitive in the green (555 nm) and less sensitive in both the blue (~450 nm) and the red (~650 nm) for a fixed radiant intensity (watts). So for a fixed electrical power consumed by a light source (laser) green appears brighter than either red or blue. This is also called the "luminous efficacy" (http://en.wikipedia.org/wiki/Luminous_efficacy), which tells you how much "brightness" (lumens) you get per supplied electrical power (watts). Therefore, if color is not of concern and you need to get the most brightness per electrical watts, you would choose a green laser.

As for green lasers, you can get a whopping 200 mW laser at 532 nm (green) for $50-$80 (http://www.gadgettown.com/gg/Lasers--2604-241grid-Wavelength--532nm~635nm?gclid=CJ-rqomttaICFQ_yDAod2Sso6A). With a bit of searching you'll find higher powers and/or lower prices. It all depends on your specs and budget.

Good luck!
mph

jefm

wow, thanks for the info MPH! I'd always wondered about the red "save your night vision" filters for lights... sure, they might save your vision, but you could fall in a hole using them! lol

Ok guys so I've worked on the schematic for three weeknights and it's nearly done, here's a sneak peek attached. Not very complicated, it was easier to redo from scratch then to figure out what I'd done. It's not finished, the legend got changed, it doesn't pass netlist test yet, and is quite a mess, but take a peek if you like. It contains a couple experiments so the whole thing has to be breadboarded again before going to PCB.

One question is do I need diodes for protection with my processor-fan motors, or is the MOSFET isolation enough? I noticed in the PWMPAL documentation, there is no diode in the circuit.

I'm going to try using Zener diodes for voltage regulation, hopefully they will be more efficient then voltage regulators.

Post Edited (jefm) : 6/25/2010 12:11:11 AM GMT