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Anonymous
 
Posted on Sunday, January 23, 2005 - 12:30 pm:   Edit PostDelete PostView Post/Check IPPrint Post   Move Post (Moderator/Admin Only)Ban Poster IP (Moderator/Admin only)

I got the communicator to work, but after a couple of tries the laser goes out. It dims then dies completely. I thought it was shorting out, but I have checked all connections. Can the amplifier be "blowing" the diode? At ten dollars a pop it is becoming expensive.
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Simon Quellen Field (sfield)
New member
Username: sfield

Post Number: 156
Registered: 12-2004
Posted on Sunday, January 23, 2005 - 1:36 pm:   Edit PostDelete PostView Post/Check IPPrint Post   Move Post (Moderator/Admin Only)Ban Poster IP (Moderator/Admin only)

The laser chips are sensitive to static electricity
and voltage spikes.

Be very careful when connecting the leads that you
do not have a static electric charge on your body.
Touch something grounded before touching the leads.

You can mitigate this by adding a 100 ohm resistor
between the laser and one of the test leads (either
one). This will limit the current getting to the
laser, and prevent the current surges from damaging
the laser chip.
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Geoff Howard
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Posted on Saturday, January 29, 2005 - 4:04 pm:   Edit PostDelete PostView Post/Check IPPrint Post   Move Post (Moderator/Admin Only)Ban Poster IP (Moderator/Admin only)

I have just witnessed the same rapid laser degradation. My observations below combined with this message from earlier this month: http://scitoys.com/board/messages/7/367.html?1100488298
lead me to believe that this could be related to the low quality of some lasers. Even with my degraded laser, I got very impressive results (i.e., kids were impressed, music very clear)

Here's a few details and pictures to feed discussion:

1) My disassembled laser looks significantly different than the one pictured in the article. It was far cheaper ($1 !!). Perhaps now I see why. As you can see in the scitoys.com picture, there appears to be a "real circuit" whereas the closeups in my pictures show there's not much going on. My picture showing the circuit board pulled out of the forward silver area reveals there was nothing much in there either. What the pictures probably don't show is that there seems to be a very loose (7-8 turns of over a half centimeter with roughly the same diameter) wire coil inside between the circuit board and the lens.
2) The wide angle view shows that my pointer appears to be roughly the same item as that for sale from the scitoys site. Could someone who has disassembled one of those report if it looks the same inside?
3) I haven't yet tried to use the 100 ohm resistor recommended here. I'll get another cheap laser pointer and try though.
4) After noticing this with the first laser, I was more careful to note what happened with my second (and last on hand). To eliminate damage to the board, I never disassembled the unit, but just connected the spring lead through the open back and clipped the positive lead to the tube. I first tested the connection with just my batteries (no transformer, etc.). This worked fine as expected. Then I connected up the whole circuit and noticed the light level immediately drop significantly. I then went back to the direct battery pack connection, and back to the original intended use with the button cells in the case with the back screwed on, and the light was still significantly lower (I can barely spot the light shining on a surface a foot away).
5) I didn't have a static ground lead connected, but I am skeptical that static charge was the problem with either of these, especially with the timing of my experience related in point 4 above.

I'd be very interested to hear if others have had better luck either with better quality lasers (is the one at scitoys.com store any better?), adding the resistor, being more careful about static, or more careful with the volume going into the 8ohm side of the transformer (incidentally, I used a Nintendo Game Boy headphone output for this because I had no small radio on hand with a 1/8" jack - perhaps it has odd output?)

Thanks!
Geoff
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Geoff Howard
Unregistered guest
Posted on Saturday, January 29, 2005 - 4:21 pm:   Edit PostDelete PostView Post/Check IPPrint Post   Move Post (Moderator/Admin Only)Ban Poster IP (Moderator/Admin only)

And here's the pictures:

Whole Pointer
Disassembled Front
Disassembled Back
Pulled Apart
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Simon Quellen Field (sfield)
New member
Username: sfield

Post Number: 168
Registered: 12-2004
Posted on Saturday, January 29, 2005 - 4:49 pm:   Edit PostDelete PostView Post/Check IPPrint Post   Move Post (Moderator/Admin Only)Ban Poster IP (Moderator/Admin only)

It looks like your laser lacks the internal chip
resistor. You will need an external resistor to
ensure that the current levels stay below 30
milliamps.

I have seen two different types of laser with similar
packaging. Ours have brass threads and brass
hologram holders. The others have plastic
hologram holders and the threads are cut into
the aluminum case instead of having a brass
insert. Either type should work, but the less
expensive ones may need extra current limiting
resistors. They may be counting on the high
internal resistance of the little batteries, and
when the Game Boy and larger batteries combine,
you get too much current.
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Geoff Howard
Unregistered guest
Posted on Saturday, January 29, 2005 - 5:43 pm:   Edit PostDelete PostView Post/Check IPPrint Post   Move Post (Moderator/Admin Only)Ban Poster IP (Moderator/Admin only)

Ok, that sounds reasonable. You're right about the plastic hologram holders. I'll buy a few more and monitor the current as I try different resistors.

Thanks, and thanks for this awesome site. This is the third or fourth "toy" we've tried and we've had a great time with all.
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Drew
Unregistered guest
Posted on Saturday, February 26, 2005 - 11:52 pm:   Edit PostDelete PostView Post/Check IPPrint Post   Move Post (Moderator/Admin Only)Ban Poster IP (Moderator/Admin only)

What is the rating of the internal resistor on your devices?
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Anonymous
 
Posted From: 192.153.23.100
Posted on Thursday, September 1, 2005 - 10:27 pm:   Edit PostDelete PostView Post/Check IPPrint Post   Move Post (Moderator/Admin Only)Ban Poster IP (Moderator/Admin only)

I had the same problem with the lasers I tried, except that they also burn out when powered by the same button cell batteries that came with them. I've used lasers from the local dollar stores and Target.
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christopher labreck (Chrysoprase)
New member
Username: Chrysoprase

Post Number: 1
Registered: 1-2006
Posted on Thursday, January 12, 2006 - 4:37 pm:   Edit PostDelete PostView Post/Check IPPrint Post   Move Post (Moderator/Admin Only)Ban Poster IP (Moderator/Admin only)

I am having trouble getting the laser communicator project to work. I made the transmitter and connected the output jack to my mp3 player. The laser works fine. I connected the receiver circuit using a photoresistor with the instructions on this site. I connected the output jack to a sterio. When the transmitter is turned on, and the speaker is brought within a range of about 5 inches of the transmitter, I can hear the music. But when I turn the laser on, the music stops playing. It seems that this is because of the radio waves the laser transmitter produces, and the sterio is just receiving them. What I don't understand is why the music will stop playing when the laser is turned on. Also, when the laser is shined upon the photresistor, there is still no music.

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