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FrozenGate by Avery

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Alchemist

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I have a a cheap E-Bay Green laser pointer that normally runs on two AAA batteries. It uses a driver with an LM358 chip. I have separated the laser and pointer from the housing and want to use them in a Lumia projector, but I don't want to use batteries.

I have an old Nokia phone charger that puts out 3.7V DC. If I put a 1N4007 diode in series with the positive lead to drop the voltage will it be safe to run the laser without burning anything out?
 





I would suspect that you will need some sort of heatsink amd/or fan to keep the module from overheating if you want it to be on for longer than ~30sec.
 
Ash said:
I would suspect that you will need some sort of heatsink amd/or fan to keep the module from overheating if you want it to be on for longer than ~30sec.
Click to expand...

Even with no modification to the driver itself? The laser diode still has the large brass tube with the threaded lens assembly attached that acted like a heat-sink in the pointer.

Correct me if I'm wrong, but aren't the drivers supposed to provide a constant current to the diode? That current shouldn't change as long as the voltage is kept to the ~ 3V provided by the batteries correct? (1n4007 has a bout a .7V voltage drop so putting one in series should get me back to 3V)

I have played around with this particular pointer where I've had it on for over an hour in almost continuous operation and the pointer never even warmed up.

I will, however, be mounting the entire module to a large block of aluminum as the projector is constructed and I can add a fan if needed, so I guess the point is a bit moot.

I just wanted to be sure I wasn't going to smoke the driver if I hooked it up to the charger. (Charger is rated 350ma BTW)
 
The thing is those are cheap drivers and remember using a 3.5 volt cr2 battery in a 2x AA 50mw and it made it look brighter, but it would run a little bit hotter after awhile. Just have to watch it. ( it measured around that when fully charged.)
 
Why not build build a 3 Volt Regulated Power
supply using an LM317... It's would be good
up to 1 Amp...


Jerry
 
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Well, I found some LT1875 3.3V regulators in my supplies so I cobbled together a 3.3V supply out of an old 5V supply and a the regulator. Tested everything with a meter to be sure I was actually getting 3.3V and everything looked OK. Ran the laser for about 20 minutes off the new supply and it ran reasonably cool. Spent the rest of the afternoon building the lumia projector, got it finished, came inside powered it up and it worked for about 30 seconds and a couple of either resistors or capacitors on the driver board decided to blow. *sigh* Ah well. That's why I bought 4 of the pointers. Back to the drawing board. Maybe the diode is salvageable.
 
Well, found the problem... During my last soldering bit shortening a wire, apparently a big blob of solder went trundling off on it's own and decided to sort of short the output pin of the regulator to the input, so I just threw 5V at my driver board without realizing it. That's what I get for soldering while exhausted.
 
You would be fine using the output straight from the charger. A lot of people here run them on single li-ions that are fully charged to 4.2V and dont have any issues. Heatsinking might be needed.
 
You reasoning is "if 1 volt over works, 2 volts over will surely work"? Hell, why stop there? :) "if 2 volts over works, 3 volts over will surely work." "If 3 volts over works, 4 volts over will surely work." ad infinitum
 
Cyparagon said:
You reasoning is "if 1 volt over works, 2 volts over will surely work"? Hell, why stop there? :) "if 2 volts over works, 3 volts over will surely work." "If 3 volts over works, 4 volts over will surely work." ad infinitum
Click to expand...


I basically said "if 4.2V works and 3V works than 3.7V should work"

I dont see any flaw in that logic. Is it ideal to run it with 3V? sure, probably, but will it work with 3.7V and is the risk of losing a $6 laser pointer that big of a deal? You have to decide that for yourself I guess.
 
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