Here is a simple tester to test the IR Sensor TSOP 1738. It is a highly sensitive device that damage easily if its input voltage rises above 5V. This Tester can be used to test TSOP 1738 before using in a circuit. It confirms the condition of the Sensor, whether it is functioning properly or not. It can also be used to check the IR Sensors kept in your junk box so that you can keep only the good one for use.
Remote hand sets of TV, VCD player, Home Theater system etc uses Infrared rays pulsating at 38 kHz. So in the receiver section, there is an Infrared receiver to receive the coded IR pulses. In most cases the 38 kHz IR module TSOP 1738 is used as receiver which is specific for 38bkHz IR rays. This module has a PIN photodiode and a pre amplifier stage enclosed in an epoxy case which acts as a filter and passes only IR rays. Its output is active low and gives + 5 V DC in the stand by state. The circuitry inside of the module amplifies the coded pulses from the IR transmitter. From the PIN Photodiode, the coded signals pass into an Automatic Gain Control (AGC) stage and then into a Band pass filter. Finally a Demodulator demodulates the signals and sends to the output transistor which forms the output. So when the module gets coded signals, the output transistor sinks current.
Most of the Remote control systems use TSOP 1738 IR Sensor module to control various functions. This IR Sensor is highly sensitive and may damage easily, if is supply voltage increases above 6 volts. This tester is useful to check the working of the IR Sensor. It gives audio-visual indications when the IR sensor is working properly.