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Battery Polarity - Make NO Assumptions

threeneurons

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I just bought a 405nm 5mW (blue/violet) laser pointer. It did not come with any batteries, which is fine. It requires 2 AAA batteries, of which I have plenty. The seller shipped no paperwork with it. I don't want to make the assumption (because "when you assume, you make an A out of U and ME), since I may damage the pointer if I guess wrong. Its eBay number 280445522110. It seems to be a common model. If anyone owns one, I'd like to know the proper battery polarity. Positive (+) pointing forward, or Negative (-) pointing forward ? Forward being the business end where the light comes out. PLEASE DON"T GUESS. Only respond as if your live depended on it. Does anyone believe in documentation anymore ?! If only to avoid returns, if it gets damaged, by inserting the batteries in wrong.
 

rpaloalto

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Most 405nm are all case - meaning positive in first, just like a normal flashlight.
It's the greens, the 532nm that are case positive.
Anyway most of those lasers have revers polarity protection. So if it wont work one way flip them around.
But I'm very sure it's + up
 

threeneurons

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Thank you for the quick replies.

I just tried it, and its the negative (-) towards the end where the light comes out from. That means the case does get the positive (+) as per the two responses I got back, as of the time I'm writing this.

Not to get into any arguments, but in normal incandescent flashlights, the positive (+) goes towards the light end. Even though, an incandescent bulb really doesn't care about polarity. In that type of device, its the mechanical constraints that really determine polarity.

As a follow up question, do these laser pointers (any or all) have any protection to prevent the user from killing the pointer by inserting the battery backwards ? It could be either electrical (diode), or mechanical (inhibiting contact).
 

rpaloalto

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That is strange, if it's case +.
I have never seen one like that, other then my green pointers.
 

Hemlock_Mike

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I got a cheap Blu pointer and was amazed when I found it case + !!! Like a green.
Many blu diodes aren't connected to the case so they use what driver they have.

HMike
 

threeneurons

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I'm new, to the finer points of laser pointers. The only other one I own, is a cheap red one, I picked up at the 99-cent-only store. It, too, has a positive (+) body. Its powered by 3 LR44 batteries.

I do have experience in both electronics, and bigger lasers. The State of California, issued me an Electrical Engineering Degree, but that was a while ago, and it is from California. However, I guess I know which end of a battery is positive (+). On a good day, anyways. I'm also a partner, in laser cutting service, for cutting metal. Cold roll steel up to 3/4" thick. I have no intention of getting a laser pointer to burn things. I already have one for that. 4000W of CO2 IR. Yes, it can burn. Cold roll usually uses O2 as the purge gas, which causes the molten slag to burn, similarly to an acetylene cutting torch. N2 is used for cutting stainless, so its used just to push the slag out of the way, and by not burning the metal, keeps it from being discolored.

Thank's again for everybody's help. Any thoughts on 'polarity inversion' protection, from my previous response ?
 

hakzaw1

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My 'e-time' overspec(52mWs) 5 mW BRs are pos to the spring like a greenie...HZ
 




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