I can't power a laser properly:( help me?

So I'm trying to make a laser trip switch, everything works besides my laser:( its a 50mW green laser that uses 2 1.5V AAA batteries. I took the batteries out and I'm trying to power it with a 12v battery working trough a 5v regulator with a few diodes in series to bring the volts down to 3v. I connected a 20ohm resister after the diodes to limit current but it doesn't even turn on. I then connected a 10ohm resister (10 parallel 100ohm registers) and then the laser comes on but goes dimmer and dimmer after about 30seconds or so. Why does it do this and how can I properly power it without using batteries. I did not remove the laser driver

Are you measuring 3V across the laser power terminals?
Did you look at powering it from Arduino 3.3V source with a transistor to make the ground connection?

CrossRoads:
Are you measuring 3V across the laser power terminals?
Did you look at powering it from Arduino 3.3V source with a transistor to make the ground connection?

I measured 3.4 volts across the positive and negative terminals that I connect to the laser. I don’t want to power it with the arduino because the laser will be about 10m away from my arduino. And it must be totally separate from the arduino circuit.

Get a 3V supply then
http://www.dipmicro.com/store/DCA-0310

CrossRoads:
Get a 3V supply then
Switching DC Wall Power Adapter 3V / 1A - dipmicro electronics

I would like to make due with what I have. I have LM317 regulators as well but the laser does not power on when I give it 3v from the regulator. I have a small 12v battery I want to power the laser with. There is no electricity where I'm going to use It so I need to use the battery. All I wana do is swop the AAA batteries with a 12v battery that will give more hours

Take out the current limiting resistor. It was designed to run off batteries, so any needed current limiting is done inside your device. An exception would be if you were drawing too much current for your regulator. Ideally, power the thing off your AAA batteries and measure the current before connecting up to your regulator.

arduinodlb:
Take out the current limiting resistor. It was designed to run off batteries, so any needed current limiting is done inside your device. An exception would be if you were drawing too much current for your regulator. Ideally, power the thing off your AAA batteries and measure the current before connecting up to your regulator.

When I drive it with 3volts with or without registers it doesn't switch on? I can't understand this because the batteries supply 3v. What I'm thinking is that I've wired the LM317 up incorrectly? I've heard that it can be wired up in two ways?

I hope you realise that the casing of the laser - the metal shell which connects to the shell of a pointer - is the positive terminal and the battery contact at the back is the negative?

Paul__B:
I hope you realise that the casing of the laser - the metal shell which connects to the shell of a pointer - is the positive terminal and the battery contact at the back is the negative?

Yes I do know that thanx for checking though

Have you read this:-
http://www.repairfaq.org/sam/laserdps.htm

Grumpy_Mike:
Have you read this:-
Sam's Laser FAQ - Diode Laser Power Supplies

that is way over my head, too advanced for me

calvingloster:

Grumpy_Mike:
Have you read this:-
Sam's Laser FAQ - Diode Laser Power Supplies

that is way over my head, too advanced for me

Maybe then the whole project is.

Grumpy_Mike:

calvingloster:

Grumpy_Mike:
Have you read this:-
Sam's Laser FAQ - Diode Laser Power Supplies

that is way over my head, too advanced for me

Maybe then the whole project is.

I don’t see why it has to be so complex to just exchange the AAA batteries with a 12v battery that is regulated to 3v for the laser while leaving the original driver in place. Why is this so difficult?

Why is this so difficult?

It told you on that web site that was over your head.
Now instead of throwing up your hands and giving up read it again and when there are bits you don’t understand ask about them.
Or are you not interested in learning anything for yourself?

If you find it overwhelming, at least look at the sections headed:
Substituting Batteries in Laser Pointers
Powering a Laser Pointer From an External Source

Ok thanx guys, ill stop being a baby and try figure it out

I've been trying to power a 50mW laser from a 12v battery for the past week. I use a 5v regulator and a heat sink amd it works but the heat sink gets hot and the laser dims until it barely lights up. I have not removed the laser driver circuit so wtf am I doing wrong

so wtf am I doing wrong

Missing out a stack of detail?

I use a 5v regulator and a heat sink

Have you checked the voltage out when it goes dimmer?

Yes there is not a lot to go on in your post. Do you have a constant current driver somewhere in the mix? A fixed voltage will not cut it. see:-

http://www.repairfaq.org/sam/laserdps.htm

calvingloster:
I've been trying to power a 50mW laser from a 12v battery for the past week. I use a 5v regulator and a heat sink amd it works but the heat sink gets hot and the laser dims until it barely lights up. I have not removed the laser driver circuit so wtf am I doing wrong

Perhaps your laser draws more current than the regulator wants to work with therefore thermo limiting itself.
So what is the volatge rating of you laser?
And what is the spec of your regulator? Do these "match"?