What is up with polarity??

[B Mann2]

New guy figuring out things. I have used 18650 LED flashlights practically since they came out. I picked up a couple cheap laser pointers and seeing some have case positive polarity and some case negative polarity. OK I can understand the different design. Then toss in most of these do not come with instructions, or show polarity on the case. Then find out (on some) if you insert battery backwards (reverse polarity) you can blow the laser. Greeeeaaaaat.

Are there tricks to figure out polarity? Last thing I want to to swap a battery and toast a driver. I have never heard of problems like that with the drivers on LEDs.

 

[Gryphon]

Unfortunately there is no standard. Back in simplier times it was quite easy, red diodes are always case negative so unless someone goes through the trouble of isolating the module, all home made red lasers and store bought red lasers were case negative. Green lasers were also all dpss, considering all the IR pump diodes were case positive all home made and store bought greens were case positive. Now that the majority of direct green and blue diodes are case neutral any this is possible.

There have only been a handful of times when I've come across a case negative direct green or blue, but if I'm ever in doubt I'll ask the seller.

 

[paul1598419]

Most DPSS lasers are case positive still. I just got a new 591 nm laser recently and because it is DPSS it too is case positive.

 

[B Mann2]

Maybe I will engrave on the case what it is. At least the positive case.

BTW how many lasers can be damaged by reverse polarity? Is it rare or very common? Battery style.

 

[paul1598419]

You will damage any laser by reversing the battery polarity.

 

[Gryphon]

I've let the smoke of out many laser driver with accidental reverse polarity, did just that today in fact. Some are protected but definitely not all.

 

[paul1598419]

I've let the smoke of out many laser driver with accidental reverse polarity, did just that today in fact. Some are protected but definitely not all.

Yes a diode in series with the driver's input will stop that from happening. But, you do have a 0.7 voltage drop.

 

[B Mann2]

So I don't do any more damage... If I didn't already. Any clue on this laser? Guessing case positive. Cheap one anyway.

OK, not enough posts to post a link.

If you want to look, go to aliexpress and put in 3256805200471401 in the search. Thx

 

[ZRaffleticket]

The listing includes a photo of the battery going in positive end first. So case negative.

 

[B Mann2]

The listing includes a photo of the battery going in positive end first. So case negative.

View attachment 77791

Well thank you for that. I just went over the listing and still cannot find the picture you posted. Maybe because I am using a desktop?? Every picture I see shows assembled ones.

 

[ZRaffleticket]

Odd. I got it from desktop after expanding the description to show more images

 

[Encap]

Well thank you for that. I just went over the listing and still cannot find the picture you posted. Maybe because I am using a desktop?? Every picture I see shows assembled ones.

Scroll down onthe listing to the description section to the picture with 3 small images at the bottom. click on "view more"-- scroll down through the images, it is the last picture in the group.

 

[B Mann2]

Thanks, I found it. I am new to Aliexpress. Didn't notice the view more in the description. Always learning something.

Now if I can figure out why I don't get email alerts when new replies are posted. It does show Watched at the top. (actually a button to unwatch)

 

[GSS]

Thanks, I found it. I am new to Aliexpress. Didn't notice the view more in the description. Always learning something.

Now if I can figure out why I don't get email alerts when new replies are posted. It does show Watched at the top. (actually a button to unwatch)

Isn't hitting the Watch button just a way to see what you were looking at Aliexpress or any sight so you won't have to re look at tons of items you were interested in??

There has to be another way to get Email notifications.

 

[GSS]

I didn't even register but i'm seeing a notification tab for updates.
I'm sure when you register there are Email notifications. I think your just missing it.