IR Receiver

[lord_von]

Can anyone please explain this attached circuit circuit?

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
Q2____________2N2907 PNP Silicon Transistor
Q3____________NPN Phototransistor
D1____________1N914 Silicon Diode
IC1____________LM308 Op Amp IC
IC2____________567 Tone Decoder
LED1__________Infa-Red LED
RELAY_________6 Volt Relay
S1_____________SPST Push Button Switch
B1_____________3 Volt Battery
MISC.__________Board, Sockets For ICs, Knob For R6

 

[semiconductor]

First, you have to verify that the transmitter send out signal at which frequency (you can check this by calculating central frequency of LM567, refer to LM567 datasheet).

Because, received signal is week so that, after detect the signal, we have to amplify it, then the LM567 do this task, if the main frequency of the signal is the same as the central frequency of LM567, then the output pin is grounded (or high, I don't remeber), this causes the relay be on or off.

The above is the main idea of your circuit. You can simulate it using Circuit Maker or some similar softwares.

Any question?

 

[Nigel Goodwin]

Apologies to Semiconductor, but his English was a little confusing :?

As he already mentioned, the incoming signal needs to be a modulated IR signal, at the same frequency the PLL is tuned to.

The first IC is a simple non-inverting amplifier, amplifying the incoming signal by about 100 times - this increases the range greatly.

The second IC is a PLL tone detector, it looks for a specific frequency on it's input pin, when it finds this frequency it switches it's output - so it's important that it's tuned to the correct frequency, the variable resistor is to trim the centre frequency for maximum range.

The circuit is a simple IR remote receiver, you can buy ready made 3 pin IC's which do this, tuned to about 38KHz, commonly used in almost everything with IR remote control.