• This circuit can be used to detect the presence of modulated infrared signals in its vicinity from any electronic source, for instance, an IR hand held remote controller.
  • It can also be used for testing IR burglar alarm systems. It generates a musical sound produced with help of IC UM66 when a infrared signal falls on the IR sensor used in the circuit.

  • The circuit consists of an infrared signal detector-preamplifier followed by a melody generator and a tiny audio amplifier.



1. C1 10µF

2. C2, C3 0.1µF

3. C4 470µF

4.C5 220µF

5. R1 100 Ω

6. R2 470 Ω

7. R3 100K

8. R4 470Ω

9. R5 220Ω

10.R6 1K

11.R7 10 Ω

12. IR LED1



15.IC1 UM66

16.IC2 LM386


IC LM386-The LM386 is a power amplifier designed for use in low voltage consumer applications. The gain is internally set to 20 to keep external part count low, but the addition of an external resistor and capacitor between pins 1 and 8 will increase the gain to any value from 20 to 200.

The inputs are ground referenced while the output automatically biases to one-half the supply voltage. The quiescent power drain is only 24 milliwatts when operating from a 6 volt supply, making the LM386 ideal for battery operation



  • The UM66TXXL series are CMOS LSI designed for using in door bell, telephone and toy application.
  • It is an on-chip ROM programmed for musical performance produced by CMOS technology, the device results in very low power consumption.
  • Since the UTC UM66TXXL series include oscillation circuits a compact melody module can be constructed with only a few additional components.

Infrared (IR) LED:-

IR radiation is electromagnetic radiation with a wavelength between 0.7 and 300 micrometers, which equates to a frequency range between approximately 1 and 430 THz.


  • The circuit consists of an infrared signal detector-cum-preamplifier followed by a melody generator and a tiny audio amplifier.
  • The circuit, in principle, converts the IR signal pulse trains into noticeable aural notes. S1 is used to switch on/off mains power and LED1 indicates power- ‘on.’ Resistor R4 and zener diode ZD2 form a low-current voltage stabiliser for providing steady 5.1V DC to the small signal preamplifier circuit.
  • IR LED1 is the main sensing element.
  • The IR signal detected by IR LED1 is amplified by npn transistors T1 and T2. The amplified signal is fed to the melody generator via resistor R5. The output of the melody generator is fed to LM386 low-power audio amplifier (IC2) via variable resistor VR1, which works as the volume control.

  • The loudspeaker sounds to indicate the presence of IR signal near the circuit .IC LM386 is wired as a minimum-parts amplifier with a voltage gain of ‘20,’ which is sufficient for this application.
  • Capacitor C3 is used for decoupling of the positive rail and the R-C combination network comprising C4 and R7 bypasses high frequency to ground.


1) It can be used to detect IR rays ,which cannot be detect by naked eye.

2) It can also be used for testing IR burglar alarm systems.

3) It can be used as wireless switch.

4) It can be used in house security system.

1 comment:

  1. well done guys...nice blog,even more informative...all the best...improve more...its really nice & helpful for others...


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