How to Transmit Audio With a Laser Pen

You can make a simple laser communicator that converts a sound source into light that travels across a room and back into sound with very little quality loss using a simple laser pen pointer, a few miscellaneous parts, and about 15 minutes.


1. Read Things You’ll Need

2. Remove all batteries from the laser.

3. Connect a clip lead to the inside of the laser pointer where the battery came into contact. There is usually a small spring to which the clip lead can be attached. The other end of the battery is usually connected to the laser’s case. Because laser pointers come in a variety of styles, you may need to experiment with clip lead placement to get the laser to work with the new external battery pack. You may also need to wrap a rubber band or some wire around the laser’s push button switch to keep it in place. To ensure that the laser works with the new battery pack, test the connection before attaching the transformer. If it still doesn’t work, try reversing the battery. The laser will not be harmed by battery reversal.

4. Connect the transformer’s 1,000 ohm side to the battery and the laser. Three wires are connected to the transformer’s 1,000 ohm side. We only use the two wires on the outside. The inside wire is known as a centre tap, and it is not used in this circuit. Attaching the battery allows you to test the laser. At this point, the laser should be operational normally.

5. Connect the earphone jack to the 8 ohm side of the transformer. The schematic of the transmitter looks like this:

6. The receiver is the most basic component. Simply plug the solar cell into the amplifier’s or stereo phono input and connect it to the microphone jack. It makes no difference which way the wires are attached to the solar cell. The receiver’s schematic is as follows:

7. Check that the transistor radio is turned off and the laser is turned on. Connect the laser’s earphone jack to the radio’s earphone socket.

8. Connect the solar cell to the amplifier or stereo and increase the volume until you hear a hissing noise, then decrease the volume slightly until the hiss is no longer audible. If it were playing music, the volume control should be set fairly high, corresponding to an ear splitting level.

9. Aim the laser across the room so that it lands on the solar cell. As the laser beam passes over the solar cell, you may hear clicks or pops from the stereo or amplifier. This indicates that everything is functioning normally at this time.

10. Turn on the radio and gradually increase the volume until you hear radio station voices or music coming from the amplifier across the room. If you pull out the earphone jack, the radio should be barely audible, not loud. If you can’t hear the sound from the amplifier across the room, make sure the laser is shining on the solar cell, and then try turning up the amplifier volume before turning up the radio volume.

11. At this point, you should be able to hear the radio station clearly in the amplifier across the room. Break the connection by putting your hand in front of the laser beam, and the music will stop.

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