I have received a number of emails requesting schematics for infa-red remotes. So here is one. This remote transmits a tone using an infa-red LED. This tone is decoded by the receiver. Since the receiver only switches when it "hears" the tone, there are no accidental activations.
Schematic For Transmitter
Schematic For Receiver
Parts:
R1
22K 1/4W Resistor
R2
1 Meg 1/4W Resistor
R3
1K 1/4W Resistor
R4, R5
100K 1/4W Resistor
R6
50K Pot
C1, C2
0.01uF 16V Ceramic Disk Capacitor
C3
100pF 16V Ceramic Disk Capacitor
C4
0.047uF 16V Ceramic Disk Capacitor
C5
0.1uF 16V Ceramic Disk Capacitor
C6
3.3uF 16V Electrolytic Capacitor
C7
1.5uF 16V Electrolytic Capacitor
Q1
2N2222 NPN Silicon Transistor
2N3904
Q2
2N2907 PNP Silicon Transistor
Q3
NPN Phototransistor
D1
1N914 Silicon Diode
IC1
LM308 Op Amp IC
IC2
LM567 Tone Decoder
LED1
Infa-Red LED
RELAY
6 Volt Relay
S1
SPST Push Button Switch
B1
3 Volt Battery
Two 1.5V batteries in series
MISC
Board, Sockets For ICs, Knob For R6, Battery Holder
RELAY
6 Volt Relay
Notes:
1. To adjust the circuit, hold down S1 while pointing LED1 at the receiver. Adjust R6 until you hear the relay click.
2. You can increase range by using a high output LED for LED1.
3. Bright light will stop the receiver from responding to the transmitter.
Source: Electronics Lab
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