So ive bought a cheap laser pointer. I want to now power it using a wall adapter. The laser currently uses 3 LR44 batteries each giving 1.5 volts(4.5v total). Can i not tap into the laser solder wires and directly run it off a 4.5 v power supply? The problem is ive tried this before and after a few minutes the laser just dies, even though ive given it a constant 4.5v supply and ive soldered the wire before the resistor on the laser diode.
How can i make this work. :~
The Laser is probably not rated to run continually and that's why it dies. I have a pen laser that runs off 2x AAA batteries but the instructions say don't power for more than 10 seconds at a time else diode will overheat and life is shortened.
Ive heard abt tht too. But it has a metal casing so i guess with i can use a heat sink.. I think the power supply is the real problem for me. 
So how should i power the laser? would a simple resistor do the trick on a constant 4.5v supply? help? anyone pls?
You should be able to remove the batteries, connect the wires of a smoothed regulated DC supply of the same voltage to the battery terminals, and the laser won't see any difference. (Of course, not all wall warts are smoothed and regulated, and if you choose one that isn't then you could easily overload the laser.)
You will still have to deal with any duty cycle or temperature related restrictions imposed by the laser - just because you have an unlimited power supply doesn't mean the laser will tolerate being left on.
The laser module may indeed be utilizing the built=in internal resistance value of the LR44 batteries to keep the laser from drawing excessive current and burning up. What I would do would be to try and power the laser using 3 LR44 batteries in series and measure the current consumption that the laser draws. Then if you power the module with a fixed external regulated 4.5vdc power source, just add a series resistor that results in the laser drawing the same amount of current as it was while being powered by the batteries.
Lefty
retrolefty:
The laser module may indeed be utilizing the built=in internal resistance value of the LR44 batteries to keep the laser from drawing excessive current and burning up.
That's a thought, I hadn't considered that. I don't know what the internal resistance is, but What is a lr44 battery current rating? - Answers suggests around 20 Ohms. If it's powered off button cells, is it safe to assume that the current consumption must be very low, else the battery would flatten unreasonably quickly? I suppose the battery capacity is only around 100mAh, so it would be possible to guestimate the current draw if the battery life was known.
This link has some good advice on powering lasers
http://www.repairfaq.org/sam/laserdps.htm