Hacking a Remote. Application Circuit 3


remote-5We construct different types of Infrared Receiver LED ( Rx) or IR Sensor ( TSOP 1738 ) based circuits. To test, the working of the circuit we have to use an IR Transmitter. Usually we use IC 555 based IR transmitter for this. But the frequency of the IR from the Transmitter should match with that of the Sensor, otherwise the circuit will not respond. Here is a simple solution to test the IR based circuits. Simply Hack a Mini Remote obtained along with low cost FM radio, Toys etc. You have such Remotes in your Junk box. Let us Hack one such Remote to make a Tester.
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Trick to test Remote


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Remote is now an inevitable part of our life to operate may electronic devices. Remote is an Infrared transmitter giving coded signals to the IR Sensor of the device. The circuit inside the device decodes the signals from remote and do the jobs accordingly. Remote fails due to 3 reasons. 1. Dead battery 2. Loose contact or Rust in the battery terminals. 3. Failure of Infrared LED. So before repairing or purchasing a new remote, just try this simple trouble shooting.
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Remote Tester using TSOP 1738. Sensor Circuit .16


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.

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IR Sensor Tester


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.

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