Laser voltage

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Sherrylynn
 
Posts: 4
Joined: Fri Jul 26, 2013 8:36 am

Laser voltage

Post by Sherrylynn »

Hi all,
Complete newbie here.
I'm building a laser tripwire using an off the shelf kit. It uses the common laser pointers (green in my case) that need 3v. I'm wondering if anyone know whether they will tolerate 3.6v without blowing up or really reducing the lifespan. I want to build this as a remote device so the plan is to have it in a waterproof enclosure and use the 3.6v lipoly batteries and adafruit charger together with the larger solar panel. The charger has take-off points for 3.6v built in so I was planning on powering the laser from that point (and maybe get some additional power output from the laser) but I don't want to damage t be applying too much voltage. So I was hoping someone here would know if I need to add a 3v regulator between the charger power take off and the laser to keep the voltage down or if it will tolerate a steady 3.6v without significant damage/reduction in life (and I avoid having to add another component). Thanks in advance.

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adafruit_support_rick
 
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Joined: Tue Mar 15, 2011 11:42 am

Re: Laser voltage

Post by adafruit_support_rick »

Actually, current will likely be a bigger problem than voltage. Your laser pointers were designed to run off a couple of coin cells. Offhand, I don't know what sort of current they will supply, but coin cells typically have quite a bit of internal resistance. For instance, you can connect an LED directly to a coin cell without the need for a current-limiting resistor to prevent the LED from burning out.

If you did the same thing with a LiPo, you would be treated to the delightful spectacle of a bright flash of light, followed immediately by a small puff of smoke.

To run a laser pointer from a LiPo, you're going to have to find out how much current the pointer can tolerate, and you'll have to add a resistor in series with the battery to limit the current flow accordingly. That same resistor will probably also take care of the voltage problem.

If you have a multimeter, you ought to be able to measure the current flow to the pointer from its regular batteries. To do that, you need to arrange to have the meter connected as part of the battery circuit - Set up the meter to measure milliamps, remove the batteries from the pointer, connect a wire from the negative pole of the batteries to the pointer's ground (probably the case), connect the black lead of the meter to the positive pole of the batteries, and then connect the red lead to the positive battery contact in the pointer.

Sherrylynn
 
Posts: 4
Joined: Fri Jul 26, 2013 8:36 am

Re: Laser voltage

Post by Sherrylynn »

Thanks. I'm a real newbie and just starting out but you advice is really appreciated and I'll try it the way you suggested. I'm ordering the laser module from adafruit as well as the solar panel, charger board and lipo battery so I thin I have everything I need, I just don't want to blow up the laser module :).

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adafruit_support_rick
 
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Joined: Tue Mar 15, 2011 11:42 am

Re: Laser voltage

Post by adafruit_support_rick »

If you have an iOS device, like an iPhone or iPad, you can download our free Circuit Playground app. It features an LED Resistor calculator, which can help you choose the correct current-limiting resistor for your laser diode.
http://www.adafruit.com/circuitplayground

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