Improving Cheap Green Laser Pointers @ JWC.blog

I own several cheap green laser pointers and I’ve noticed that some of them behave very differently from others.

I bought my first green laser pointer back in September for a little over $20. It was this one. At that time, I had no clue of what a typical 5mW pointer looked like, but I expected that I received somewhat of an overpowered unit since it could burn through trash bags and had a clearly visible beam (as it turns out, the pointer is about 50-80mW based on a few readings I took).

I then purchased a few more pointers for my family for Christmas a few months later. The units I received were nothing like what I had originally bought. First of all, they had different stickers on them and the size of the apertures was much smaller. Secondly, not only were they extremely weak, but on rechargeable (NiMH) batteries, they needed about 30-45 seconds of warm-up in order to produce a decent dot. With alkaline batteries, they were a bit better.

A few months ago, I purchased a 50mW pointer from LEDshoppe. It was also bright on alkalines but miserable on rechargeables. It occurred to me that the driver seemed to be the problem. Alkaline batteries probably allow the driver to just cross the threshold voltage required by the IR pump diode. So, rechargeables, which have a nominal voltage of about 1.2-1.3V, cannot quite reach this barrier and as a result, the laser will barely lase.

The driver used in the first laser I purchased clearly had to be a boost driver; i.e. it boosts the voltage output to compensate for low voltage input. The other drivers were just linear constant-current drivers.

So, since I don’t really want to pay for new alkalines constantly, I decided to look into another method that was already being used by a few members of LaserPointerForums.com. 10440 batteries are 3.6V lithium cells that are the same size as standard AAA batteries. Therefore, if I use a single 10440 with a spacer in my laser pointer, the output should be at its intended maximum.

There are a few downsides to this:

Assuming that the driver is linear and outputs constant current, a significantly higher input voltage will result in excess heat dissipation.
These batteries are typically only around 300mAh, so lots of recharging will be needed, as a typical ~100mW pointer will draw up to 600mA.

While discussing these issues on LPF, member Warske recommended using a diode to lower the voltage going to the driver so that heat would be dissipated in the spacer instead of on the driver board.

I got my 10440s and charger today, so I quickly built a spacer with some cardboard, wire, and a diode.

The results were spectacular. The laser is drawing its full 600mA or so and is definitely over 100mW (I’ll test it on my LPM when I get home).

Here’s a comparison between my improved laser (on the left) and one that’s doing roughly 50-60mW.

This picture was taken in broad daylight with a limited exposure time, so that's why the lasers aren't particularly bright.

So here’s what you can do if you want to make your green laser pointer more powerful:

Buy a pack of 10440s. I know it’s tempting, but don’t put both batteries into the pointer because you’ll fry the driver.
Buy a charger. I used this one, which seems to be the best. Be careful though, if you’re using your own lithium charger, make sure it is designed to charge 10440s. They need a significantly lower charging current than CR123As or 18650s.
Buy a regular-ol’-diode from Radioshack or anywhere cheaper.
Get some ~22 gauge wire and make two little coils like I did in the first picture.
Solder the ends of the coils to each end of the diode. Make sure that the total length is about the same as a standard AAA battery, but err on the side of making it a little longer.
Get some cardboard or thick paper and wrap it around the wire/diode setup so that just the coils stick out on either end.
Finally, make a little paper tube so that you can connect the positive end of the 10440 battery with the coil without the chance of that coil touching the side walls (otherwise, the diode is useless!). Make sure that the diode is in the correct way; i.e. the white painted stripe should be connected to the coil that touches the end of the barrel.
Put it all together, and enjoy!