Laser pointer...

[TaDa]

Hi!

For better or worse, I've been using a laser pointer for teasing my cat.
Before you ask, yes, I'm very careful not to point it at its eyes.

Now, the continuous use has done two things, broken the press switch
and cost me a fortune in the little watch batteries it takes (3 at a time).

I've not opened it up, yet, but is it likely I could rehouse this in a small torch
and run it off cheaper AA orAAA batteries (ideally rechargeable).

Actually, I'm pretty sure I can but are there any gotchas I should bear in mind?

Thanks

 

[Sceadwian]

Nope, none really, match the voltage and you should be okay. Personally I own three laser pointers, all of them use AA or AAA batteries, you should never buy ones that use the button cells unless you need one on a keychain for some reason. If you replace it with AA batteries I'd just use alkalines, a set of decent alkalines will last forever. I have a non-contact IR thermometer that has a laser pointer built in which I use to play with my cats from time to time, not frequently though, I just had to replace the batteries and I bought it a year and a half ago.

 

[TaDa]

Well, I bought it on impulse years ago - and only now have a 'real' use for it

I'm glad to hear it should be a matter of matching up the voltage but is that the whole story?

Thinking about it a little more I wonder would the button cells have a higher internal resistance to would limit the current?
A nice new set of alkalines would, I'm sure, have a lower internal resistance -it'd be a shame to see the laser go phut!

Am I just worrying needlessly?

 

[Sceadwian]

So put a small resistor in series with it if it makes you feel better.

 

[HarveyH42]

Those key chain lasers only cost a couple of bucks, usually less than a set of batteries. Real pain to take a part too. I used a small pipe cutter, which only used once before, installing a water heater. Cut just above where the button protrudes. This exposes a small circuit board, where you can access the button and battery connections. Probably best to either short the existing switch (solder blob), or solder to it, and add a switch inline to your batteries. Make sure the polarity is correct, these are cheap and minimal protection. Best not to do much more, leave the laser mounted to the remaining housing, and the lens as well.

 

[TaDa]

Thanks everyone - I'll give it a go now.
Thanks for the warning about keeping laser and lens together - that hadn't crossed my mind.
As they are so cheap and its already broken I'll just go with the alkalines - without the resistor.

Once again - thanks!

 

[HarveyH42]

They usually have a resistor already, little SMD on the few I've taken a part. Since three button cells are 4.5 volts, you could probably use 4 rechargeables, a diode in series could drop 0.6 volts, if you are worried about the little extra.

There are a bunch of cheap, if not free (if you don't mind advertising printed on the side), LED flashlights, which run off 3 AAA batteries. Mine has an aluminum housing, with plenty of room in the head for the laser portion, but even if it protruded a little, wouldn't matter. It came to mind, because the LEDs are cheap and flicker, but the rest of the flashlight is pretty nice, and kind of fits your needs, battery holder, button, enclosure. Just remove the LED circuit board, solder the two wires to the laser board, bypassing the switch, little hot glue...

 

[TaDa]

In the end, I mounted the hole of the laser pointer in a cordless toothbrush - I ripped out the oscillating drive gears and cut the hole bigger where the brushes fitted on and fixed it all in place. Perversely I had to leave the motor in it as it was an integral part of the switch.

The funny thing is, as yet, I've not actually recharged it - we're looking at 4months of usage from one charge - nice

Thanks everyone