Please Help w/Laser Communicator

Hi all,

I'm trying to replicate the 'Laser Communicator' project that can be seen on youtube and other internet sites. I bought all the necessary parts and followed all the schematics, and I still cannot get it to work.:cryyy:

Here is what I am using:

The Transmitting Side
1. 405 nm 100mw laser powered by 9v (HighTechDealz)
2. Radio Shack audio transmitter
3. CD player (w/ U2 cd inside)
4. Audio cable w/jack
5. Alligator clip leads

The Receiving Side
1. .55V 500uA Photovoltaic solar cell ( 7/16 x 7/16 in.)
2. Mini-Amplifier Speaker w/ mono 1/4" plug to 1/8" jack adapter
3. Audio cable w/jack
4. Alligator clip leads

I couldn't find a video of someone using a blu ray for this project - only red & green lasers. Is the wavelength the problem?

If that isn't the problem, then lets get to the problem by process of elimination. I know the CD player, laser, and amplifier are working. I have 2 solar cells, and have tried both. The chances that both are faulty is slim, so I will eliminate them as the culprit. Audio cables & clip leads are new. Maybe the transmitter is faulty? Maybe the solar cell doesn't like U2? I'll put something else in if that's the case!

Does anyone have any suggestions? Any help is greatly appreciated.

Thanks,

Tim

Your questions are not clear....
It like me asking you... the car I built isn't working... why???

We have no idea what you built...
We have no idea of your schematic/drawings...
We have no idea what doesn't work...
You have not linked to the YouTube video you reference...

You will need to try to put the images you have in your
head... into ours first...


Jerry

A thousand pardons laserbee. I posted 3 pics at home-and-garden.webshots.com/album/576755373fNOYbh. I removed http:// from it because I'm not supposed to post links unitl I reach 10 posts. Also, if you do a search for 'laser communicator' on youtube, it should be the first video by Make Magazine. If you need any further info, I'm sure you won't hesitate to speak up.:yh:

I just looked at the KipKay video... he is a little vague in his details...
I also looked at your Photos...

Webshots - Page Not Found

Your problem seems to be your Solar Cell... It is too small...
It is probably not putting out enough current (the bigger the
Solar Cell surface the higher the current for the same voltage)
Look at the size of the Solar Cell they use...

I can't tell by your photos.... Make sure the Audio Transformer is
connected to the correct side.. they are NOT the same...

I found a .PDF file of the "Simple Laser Communicator"...
This should help you more than the Video...

http://cdn.makezine.com/make/lasercomm.pdf

BTW....

welcome to the Forum...


Jerry

It might take an hour or so for those pics to be updated on Webshots.

The solar cell I use might be smaller in size, but is actually a little better than the one in the video. Mine is .55v and .5 amp. The Radio Shack cell they use is .55v and .3 amp. So, that shouldn't be the problem.

The Audio Transformer connections are correct. The CD player is connected to the 8 ohm side, and the 1,000 ohm side is connected to the battery & laser. The laser's - is connected to the battery's +, and the laser's + is connected to the transformer green wire. The transformer blue wire is connected to battery's -.

Has anyone else out in laserland done this project before?... Anyone?... Anyone? ...Buehler?

Tim

Update: the link you have for Webshots is missing the letter 'h' at the end - that is why you were getting the 'Page not found' message.

And thanks for the welcome.

Tim

Tim ---
1. Is the laser putting out any power at all? You should see a beam.
2. What driver are you using to limit the "idle" current? That 1K ohm transformer is IMPEDANCE, not resistance. The 9V cell may have toasted your diode.
3. If you have a driver, It may, by design, level out the audio modulation.
4. What is the spectral responce curve of the solar cell? It may not respond to BLU or be too slow in its responce to "see" the modulation. Many projects like this use a photo diode as the receiver.

SEE -- It's all so simple !!!!

HMike

5. It may require an O'scope to read the laser diode current under modulation. Modulation peaks can also toast the laser diode.

Hi HMike,

The laser is fine - puts out a good beam. I'm thinking you're on to something with either points #2 & #3, or #4. The driver is a Rkcstr Micro-Drive V3 adjustable driver set at 100ma. I'm not technical enough to know whether this driver is interfering with the sound modulation or not. Any thoughts?

I don't know the answer to #4. I was thinking of getting a cheap 650 nm to see if that would work instead of the blu ray.

Tim

Put your O'scope on the output of the solar cell and see if your hand cutting the beam makes a difference. Also, That cell should be hit with a diffused beam to get more surface area involved with the detection. It isn't a thermal detector.

HMike

The rkstar driver uses a type of LM317 current source. It may be reacting too quickly to modulation current peaks and causing a null condition.

Keep us informed. Good to see an experimenter here for a change.......

If there is a capacitor across the Laser Diode, that will stop the modulation by absorbing the peaks of the input wave.

Tim71 said:

It might take an hour or so for those pics to be updated on Webshots.

The solar cell I use might be smaller in size, but is actually a little better than the one in the video. Mine is .55v and .5 amp. The Radio Shack cell they use is .55v and .3 amp. So, that shouldn't be the problem.

The Audio Transformer connections are correct. The CD player is connected to the 8 ohm side, and the 1,000 ohm side is connected to the battery & laser. The laser's - is connected to the battery's +, and the laser's + is connected to the transformer green wire. The transformer blue wire is connected to battery's -.

Has anyone else out in laserland done this project before?... Anyone?... Anyone? ...Buehler?

Tim

Click to expand...

I thought your Laser did NOT work at all...

If you quickly scan the laser's beam back and forth across you Solar Cell..
do you get any sound out of your amplifier... if not the problem is at the
receiving end...

I would like to see the data sheet for the Solar Cell you are using in the
photo... I'm having a hard time swallowing that the little 1/2" square
Solar Cell is outputting 1/2 watt at 1/2 Volt...:undecided:
I may be wrong... The data sheet will tell...


BTW... I fixed the link to the Photos...


Jerry

Thanks HMike for the help. I'll definitely post my results here when I get a chance to try out some of those suggestions.

Tim

I just updated mt last post...

Jerry

Great project, used to do that with a modulated HeNe and a CDS cell ages ago.

Good luck, Laserbee and Mike seem to have you on the way.

Welcome aboard.

No solar cell .5" square outputs .5 Amps. Also, You need only milivolts output not current to drive a high impedance input audio amp. Look into a photo diode for a sensor. Much faster detection rate for audio.

HMike

@Wayne -- Hard to believe that a CdS cell could react fast enough for audio! That IS old technology !!! However, it reacts in a similar fashion to a photo diode. Just need to apply a little excitation voltage (bias).

Mike, it was crude voice only, left the physics class in awe (1982)

Those white metrologic HeNe self contained units had a 1/4" jack on the rear.

the CDS was hooked to a small 8 pin op amp, then an audio amp.

Sounded kind of funny, but it worked for transmitting a voice or simple oscillator tone from one end of the lab to the other.

man I feel old.

I bought the solar cell off eBay. If you type 'Photovoltaic Solar Cell' it will be the ones that are blue with the wires pre-soldered selling for $1.32 each. I think I found the problem...at least one of the problems. On the auction listing, it states the solar cell is 500uA. That's microamps, right? So it's only .0005 amps! My bad.

Tim