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Topic: Laser Harp Help? (Read 2 times) previous topic - next topic

majenko

15 on the 200mA range means 15mA.  The 200mA range can measure between 0 and 200mA.

So, you have 15mA per laser - multiply that by the number of lasers, and you have the total current.

But at 15mA for a laser you are inside the ratings for an Arduino IO pin.  You just need to drop 0.5V at 15mA - which is R=V/I = 0.5/0.015 = 33? resistor.  It looks to me like you can treat it just like an LED.

However, I am no expert on lasers, so I for one would feel happier if someone else could corroborate this before you go and blow up your Arduino :)
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jnighlight

And if that's the case, and I connect them them all in series with the Arduino ground at the end, they'll all just pull what they need and it'll just work all fine and dandy?
Also, does it matter where in the circuit I place the resistor?

Chagrin

What are our assets? Do you have any adjustable voltage regulators or transistors?

What are you using to power the Arduino? What specific model of Arduino are you using?

jnighlight

Our assets consist of my Arduino Uno, 8 laser pointers (In varying stages of being taken apart), varying photoresistors, and a breadboard to put them all on (I'll move onto an actual board when I'm done with the planning). I would power the Arduino with a 9-volt battery, and I don't believe I have any regulators or transistors at my house. I could pick some up at Radioshack though...

Chagrin

Powering everything with a 9V battery will mean you'll be going through batteries every couple hours. A 9V is ~600mah, meaning it can provide 600ma for one hour, or 300 for two, etc. You'd be best off locating a 9V power supply and plugging it into the wall, but I can understand that if you're on the road with the harp that it would be handier powering it from a 9V.

With a 9V supply you can put a pair of lasers in series and four pairs in parallel.

It might also be worth a test to see if the lasers illuminate well enough at 3V; 2 AA batteries (~2000mah) would give you >8 hours powering all eight lasers and would be a lot cheaper than 9Vs. I suggest 3V because I don't think the 'shack stocks 3xAA holders.

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