This set of two circuits from the basis for a very simple light wave transmitter. A LASER beam is modulated and then aimed at a receiver that demodulates the signal and then presents the information (voice, data, etc..). The whole thing is very easy to build and requires no specialized parts execpt for the LASER itself.
Parts:
C1,C2_______0.1uf Ceramic Disc Capacitor
C3__________100uf 25V Electrolytic Capacitor
R1__________100K Ohm 1/4W Resistor
R2__________1M Ohm 1/4W Resistor
R3__________10K Pot
Q1__________NPN Phototransistor
U1__________741 Op Amp
U2__________386 Audio Amp
SPKR1_______8 Ohm Speaker
T1___________8 Ohm:2K Audio Transformer
MISC_________Wire, Board, Knob For R3, LASER and Power Supply
1. In the transmitter schematic, no ballast resistor is shown because most small LASER power supplies already have one built in. Yours may differ, and a resistor may be needed.
2. The receiver should be kept away from bright lights. You may want to put a piece of wax paper infront of Q1 to keep the LASER from swamping it.
3. In order to get any decent amount of modulation, you may need to drive T1 with more then a watt.
4. The circuit can be made to transmit computer data with the use of two modem chips.