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Cummings
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http://www.eweek.org/site/DiscoverE/PDFs/middle/First you see it Then You Hear It.pdf
In my Photonics & Fibre Optics class today, our lecturer showed us a "Modern day photophone" he created for an easy $15 AUD (1AUD = 80US cents)
I did not have time to ask him how to make one myself, so I went home and emailed him but when waiting for a reply I found another version on the net - the link above.
Going down to the local electronics shop, I picked up a Diode Laser in place of a pointer, and in place of the batteries needed for the laser and receiving circuit, I used a computer power suply and a few resisters to try and get the right voltage.
Trying to set the lens for the diode laser was tough. Blu Tak (like plasticeine for sticking posters up) comes in very handy for minute adustments of the lens to achieve a pretty narrow beam.
After both the Modulator and Demodulator were complete, I tested it out. The speakers made a loud crackling sound when the laser was not pointed at the reciever, and went quiet when the laser was pointed directly at it.
Moving it around, sound eventually came out of the speakers..but it seemed that it would only be when part of the laser beam was incident on the receiver.
The link above sais to use a Photo Diode for the reciever but instead i used a Photo Transister, being the only component that said it worked with the visible spectrum as well as infared.
Also, the resisters used on the Reciever are for a 9V battery, where I am using a 12v DC power suply. The resisters on the Transmitter should be ok.
If someone could tell me the difference between a Photo Diode and Photo Transister, it would be great. The transister also has 3 prongs..a base a collector and an emmitor. I am using the Collector and Emitter..with the emitter connected to the positive coming from the power suply.
I am going to see the lecturer soon to see his idea that seemed to work flawlessly. But if anyone could tell me what might be going wrong with my version, i would be very appreciative.
Thanks heaps,
Cumming
BSc(Photonics) & BEng(Telecommunications & Internet Technologies)
In my Photonics & Fibre Optics class today, our lecturer showed us a "Modern day photophone" he created for an easy $15 AUD (1AUD = 80US cents)
I did not have time to ask him how to make one myself, so I went home and emailed him but when waiting for a reply I found another version on the net - the link above.
Going down to the local electronics shop, I picked up a Diode Laser in place of a pointer, and in place of the batteries needed for the laser and receiving circuit, I used a computer power suply and a few resisters to try and get the right voltage.
Trying to set the lens for the diode laser was tough. Blu Tak (like plasticeine for sticking posters up) comes in very handy for minute adustments of the lens to achieve a pretty narrow beam.
After both the Modulator and Demodulator were complete, I tested it out. The speakers made a loud crackling sound when the laser was not pointed at the reciever, and went quiet when the laser was pointed directly at it.
Moving it around, sound eventually came out of the speakers..but it seemed that it would only be when part of the laser beam was incident on the receiver.
The link above sais to use a Photo Diode for the reciever but instead i used a Photo Transister, being the only component that said it worked with the visible spectrum as well as infared.
Also, the resisters used on the Reciever are for a 9V battery, where I am using a 12v DC power suply. The resisters on the Transmitter should be ok.
If someone could tell me the difference between a Photo Diode and Photo Transister, it would be great. The transister also has 3 prongs..a base a collector and an emmitor. I am using the Collector and Emitter..with the emitter connected to the positive coming from the power suply.
I am going to see the lecturer soon to see his idea that seemed to work flawlessly. But if anyone could tell me what might be going wrong with my version, i would be very appreciative.
Thanks heaps,
Cumming
BSc(Photonics) & BEng(Telecommunications & Internet Technologies)