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Author Topic: Laser Pen. What resistor?  (Read 2245 times)
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Ive broken up an old Laser Pen i had laying around, and am appropriating it for a Cat annoyance turret.

(Currently a two axis turret, which moves randomly within a pre set range and the the laser dot irritates/entertains the cat.)

It ran of 3x 1.5v button cells (little tiny ones)

if i run it off the 3.3V rail on the duino, it is veeery Dull.
If i run it off the 5V, it is nice and bright.

Should i consider sticking a resistor in there to protect if from cooking itself, as the range of these things tends to be 3.5 - 4.5 V (apparently)
and if so, any suggestion as to what?
I cant find any indication of its power needs on the internet.
the only indication on the laser itself is <1mW (power output) 650nm (wave length)
sorry if its a dumb question.
Thanks in advance

Ol

P.S: the intention is to have some kind of simple sensor array, (two PIRs perhaps) covering two sectors, then set the turret to wave the laser dot around in the "sector" which the cat isnt in.
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Common red laser pointers I did a project with, usually require 35 mA.  For 3 button cell batteries, there is  should be a resistor close to diode/laser, I've seen 50 Ohm and sometimes 90 Ohm. You can measure a current, or just install 50 Ohm resistor for +5V power. Overcurrent above 40 mA degrade laser quite fast.
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Thanks Magician. I will have a fiddle and see what i come up with.
I have left the surface mount resistor on the PCB i took from the pen, so it should be ok with a 4.5v supply, but will run it at 3.3V for now rather than the full 5 to prevent wearing it out.
It runs for test purposes ok at the mo...
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Quote
Ive broken up an old Laser Pen i had laying around, and am appropriating it for a Cat annoyance turret.

Ha!  I remember doing that, too (and so, no doubt, does the cat).  Fry's had laser pens for 99 cents each so I bought several.  I powered mine with 5V from the Arduino and it worked fine.  And yes there was a surface mount resistor on it so I didn't add any more.
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the laser dot irritates/entertains the cat

P.S: the intention is to have some kind of simple sensor array, (two PIRs perhaps) covering two sectors, then set the turret to wave the laser dot around in the "sector" which the cat isnt in.

Even with the caveat of the dot being in the cat-free-zone, isn't this kinda dangerous? What about inadvertent reflections into the cat's eyeballs?
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Hey, i thought of this. No different than for you or I. as long as you dont stare at it, its only light.
Also, the device is up on the table, the dot is on the floor, so she is looking down at the dot. This way she cant really get it near her eyes. sometimes it hits her on the back of the head, but she just gets confused as it disappears as far as she is concerned
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