So I bought a green laser on eBay...

Hello, new to the forums and just purchased my first REAL laser for a project. The laser won't be the only piece in this project, as it has to run alongside another circuit in parallel, both turning on at once via a momentary switch.

Here is the laser I purchased: http://i.imgur.com/hJH3U.png

Here are the stats:
Wavelength - 532nm
Power - 100mW 20% tolerance
Working Condition - < 300 mA at 3.0V DC
Duty Cycle - 60 seconds on and 5 seconds off
Life - >3500hours
Size - 12mmx60mm

I have a few questions, this being my first real laser. For one, the other circuit all but requires a 9-volt battery to run, and I'd like to run the laser off of the same battery. Is this possible in any way? Second, should I just use a current regulator, or have a voltage regulator as well? Basically, what can I do to make this laser put out at least 50-75% of its power while connected to this circuit? I'm not interested in burning things, I just want a very bright, showy green laser, so it doesn't have to run at max power.

The other circuit in this project is a tone generator using a 556 timer IC. I have no idea how much current it draws, and don't have a multimeter or anything to test it with. I don't want to blow up this laser, so any input would be greatly appreciated. If it comes down to it, I could always just run it separately with two AAAs or something, but I REALLY don't want to have to do that, as space is a definite concern with this project.

Also, before I forget, would these safety glasses do any good? HDE Safety Glasses for Lasers w/ Protective Case
I have no clue, this being the first time I've had to deal with a legitimate laser and all, but I definitely want to be safe. Problem is, I'm on a strict budget and can't afford much. Thanks in advance!

Hahah! ... BS duty cycle. That would mean you could turn it down 8% and run it without a duty cycle, and 8% isn't enough to make a difference.

9V is a bad idea. You either complicate things with DCDC converters, or create a lot of heat and drastically shorten battery life. You really should just run it at 3V.

Oh, and if drive current is any indication, I seriously doubt it will be 100mW.

Cyparagon said:

Hahah! ... BS duty cycle. That would mean you could turn it down 8% and run it without a duty cycle, and 8% isn't enough to make a difference.

9V is a bad idea. You either complicate things with DCDC converters, or create a lot of heat and drastically shorten battery life. You really should just run it at 3V.

Oh, and if drive current is any indication, I seriously doubt it will be 100mW.

Click to expand...

Damn. I was hoping there'd be a good solution. Having to run it off of 3V isn't impossible, just hard. I need to be able to activate both the laser AND the tone generator with a single trigger. This is going to be tough. I may need to build a switch from scratch.

So if it's probably not 100mW, what are we looking at then? I only paid about $30 for it, so I'm not too upset.

ever heard of a double pole switch ?

weeba2kv said:

ever heard of a double pole switch ?

Click to expand...

A DPST would work if I had more than about 1.5-2mm of space to work with and didn't have to rig things up to an actual trigger. This is all going inside of a plastic and metal gun casing, and the trigger is going to be the switch for everything. A momentary pushbutton was about the only thing that'd fit in the space I have to work with. Toggle switches are a no-go.

I'm not even sure if I've ever seen a momentary DPST, and if it would be the same size as the tiny momentary SPSTs that one would typically use for this application. I'm also not sure if I can even fit four wires in the trigger cavity of the gun. Probably, but I don't think they could fit down to where the button would need to go. This project just went from 'relatively painless' to 'a real headache' in no time.

that pic was an example

weeba2kv said:

that pic was an example

Click to expand...

I've still never seen a DPST momentary pushbutton. :/

Even Google is like ""

But, to answer your question specifically, YES, I have heard of a double pole switch. I'm a beginner to lasers, not to electronics overall.

In the case of this project, it would probably be easier to just build my own momentary double pole switch, from scratch, than to hunt one down like it was Bigfoot or the Loch Ness Monster. And no, I'm not being sarcastic. That's what I plan on doing, since you can't power an LD with 9V apparently. I have an LM317, can't I just use that? Is there some special reason why I wouldn't be able to?

Like I said, it can work with 9V, but you either introduce DCDC converters or you make lots of heat and drastically shorten battery life. The lm317 is the latter.

DPDT is more common and can be used as a DPST if you just leave two of the contacts disconnected.

Cyparagon said:

DPDT is more common and can be used as a DPST if you just leave two of the contacts disconnected.

Click to expand...

I have a similar problem here. I don't know if I can find a DPDT small enough. Space is a very big problem with this build. About the only switch that'd fit inside the trigger mechanism area is this little guy:


The barrel of the gun is metal, so I'm thinking heat dissipation would be, in the very least, alright. I don't plan on running the laser for any real lengths of time anyway.

Also, I've never really had to mess with a DC/DC converter. Doesn't seem like it'd be that much trouble, looking at schematics.

Whoops, sorry for the double post.

Well, I received my laser yesterday... I'm not sure it's 100mW, like someone mentioned. It didn't come with a collimating lens, so I can't test it on anything (correction: it did, just not a very good one, and the threads were glued on). It IS bright, though. The beam is visible (ever so slightly) in a light room, and in the dark, it's quite visible. I tried to take a picture of it working, but my camera doesn't really want to pick it up. It will probably do the trick. I may just go ahead and build a voltage regulating circuit, since I already have the LM317 and all. Quick question, though: I assembled the circuit using two resistors that were supposed to set the LM317 to 2.78 V, and tested it on an LED, which quickly burned out and died. I assume it was drawing too much current, but I can't know for sure. If someone with more knowledge of this chip could tell me an ideal circuit to step 9V down to 3V, I'd greatly appreciate it.

Update: I did manage to get this laser to focus properly. Put a hole through a strip of electrical tape at about a foot away.

What kind of LED? 2.78V is too much for most reds and yellows, and too little for blues, greens, and whites. Measure the voltage to be sure it is what you expect

Cyparagon said:

What kind of LED? 2.78V is too much for most reds and yellows, and too little for blues, greens, and whites. Measure the voltage to be sure it is what you expect

Click to expand...

It was a green one. I think I just need to find a multimeter. I'm sick of not having one.

A quick update, even though I'm fairly certain no one cares.

I've decided to not use the tone generator at all. Instead, I'm using a 3V piezo buzzer for noise. This way, everything can run off of two AAAs. The original concept was cool, but way more trouble than I have time for. I'll post pictures and video, maybe, when it's done.

Yeah, post some pics of your project for sure when you're done.

Well, I took some very bad-quality pictures of the laser working. I had to mess with settings quite a bit to get the beam to show up. This is all I have for now, there will be more to come.





Still not sure if it's 100mW or not, but here's some things it can do, when focused:
-Burn my skin where I have a tattoo
-Smolder and glare through electrical tape (doesn't actually punch directly through)
-Generate a plume of smoke off of the end of a cigarette
-Pop a black balloon with little effort

Here's a comparison between my laser and a standard store-bought red pointer:

(image linked because of huge.)

And I think the batteries for my laser are running low, too.