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laser_transceiver

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Overview

The laser transceiver is a free space optical communication device that encodes audio on a laser beam using pulse width modulation (PWM). A single transmitter and receiver unit can be built for about $15-$20 in parts. We used to use this for a demonstration in ELEC 3030 (RF Systems Lab), but aligning the lasers took quite a bit of time to setup.

Design

This uses a laser pointer communicator designed by Ron Jones (K7RJ). We made no changes to it other than adding an on/off switch.

Materials List

Here's a list of the stuff you'll need to buy to build one. It runs off two 9V batteries, so you'll need to buy parts that are rated above 9V. Stuff in the 15V-20V range is good, but if you can find stuff for cheap that's rated higher than thats fine. The diodes we used were rated to 100V and the electrolytic capacitor was rated to 35V.

Buying extra parts is always a good idea, and due to price breaks and quantity discounts, sometimes an item will cost the same (or, rarely, less!) if you buy 10 instead of 8.

You can find the item by searching for the manufacturer part number. You don't have to by the one we used, but they are the ones we used in our transmitter. Where we haven't listed a part number (like resistors, switches, or battery clips), any will do.

Item Quantity Manufacturer Part Number
photo diode sensitive to 650nm 1 SFH 229
100k ohm resistor 1
0.01 uF ceramic capacitor 1
0.1 uF ceramic capacitor 2
10 uF electrolytic capacitor 2
LM386 opamp 1 LM386N-1/NOPB
3.5mm audio jack 2 ACJS-MV35-3
1N914 diode 1
0.001 uF ceramic capacitor 1
100k ohm resistor 2
15k ohm resistor 4
240 ohm resistor 1
4V zener diode 1 TZX3V9C-TAP
LM311 opamp 1 LM311N
741 opamp 1 LM741CN/NOPB
555 timer rated to at least 15V 1 NE555N
prototyping board 2
red laser 1
10k ohm potentiomter 1
9V battery clip 2
SPST switch 2

Other Materials

You will also need:

  • A microphone
  • Speakers
  • Cables to connect the microphone and speakers
  • Two 9V batteries

Photos

Transmitter

Receiver

Experiments/Demonstrations

laser_transceiver.1415741155.txt.gz · Last modified: 2014/11/11 15:25 by cwh0009