Subject:
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Re: Lego Laser
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Newsgroups:
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lugnet.robotics.rcx
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Date:
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Wed, 12 Apr 2000 01:45:10 GMT
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Viewed:
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1622 times
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"Mike W. Burger" wrote:
> Using pointers (pun) from a previous post, I have been building a laser
> for my robots. I used a miniature laser pointer from Sam Goody which
> was only $10. The hardest part so far was chopping up the pointer to
> get out the guts. It turned into a major piece of butchery with a hack
> saw. The module will mount in a 2x3 stud brick with the brass case of the
> diode itself sticking out a bit. The surface mount board is about the same
> size as the diode brass housing. The whole thing is 5/16 inch wide
> (very "Lego") and 1.25 inches long.
>
> It runs on three batteries producing a total of about 4.5 volts. I
> measured the output of the RCX ports and found them to be 7.8 volts.
> I measured the current drain of the laser with its original batteries
> and found it to be about 37.5 ma, so I selected a 100 ohm resistor.
> The module has quite a few surface mount parts on a tiny attached board.
> It is definately protected in a number of ways, including reverse polarity.
> So I just unsoldered the switch with a very fine point iron and magnifier
> lamp and replaced it with a 100 ohm resistor. I unsoldered the spring
> and was left with two nice plated holes for the wires to the brick to
> mount. Without fancy diodes it should just refuse to work if hooked up
> backwards. Heaven knowns in fiddling with it I have powered it backwards
> many times. If I had tried to start with a diode I would have blown things
> for sure 10 times over. But these modules seem to assume people are going
> to put the watch batteries in backwards 50% of the time. One could I suppose
> mount two of these with different polarities to the same output and select
> which one to power with the motor direction.
>
> So far things appear to work. What is left is to mount the unit into a
> brick. In truth, for $10, scrapping a laser pointer is definately the
> way to go! Reverse voltage protection (apparently), all the photodiode
> stabilizationfeedback circuitry, and even a microscopic pot to set the
> voltage threshold.
>
> The pointer produces an intense spot of red light. I found a cute heat
> sink that exactly fits over the diode brass housing. Probably not required
> but does make it look neater. I hope I do not break anything in the final
> mounting, or immediately fry the diode when I try to power it with the
> brick directly after making it "pretty".
>
> Usual disclaimers about playing with laser pointers apply...
One thing to make sure of is that the RCX outputs are not constant. If you power
the pbrick with external power it can shoot to over 9.5 volts.
Something to keep in mind.
Dean
--
Coin-Op's For Sale!: http://www.akasa.bc.ca/tfm/coin-op.html
Dean's Lego Workshop: http://www.akasa.bc.ca/tfm/lego_wr.html
Vancouver Lego Club: http://www.akasa.bc.ca/vlc
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 | | Lego Laser
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| Using pointers (pun) from a previous post, I have been building a laser for my robots. I used a miniature laser pointer from Sam Goody which was only $10. The hardest part so far was chopping up the pointer to get out the guts. It turned into a (...) (25 years ago, 11-Apr-00, to lugnet.robotics.rcx)
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