Remote Tester. Home Utility Circuit 31


2BEvery Home requires a Remote Tester because we are now using a number of Remote controlled Gadgets like TV, Home theater system etc. The Remote handset emits invisible pulsed Infrared rays which controls the functions of gadgets based on the pulsed data arriving. The Infrared Receiver LED (Rx) or a Photo module in the gadget senses this pulsed IR rays and makes the gadgets function accordingly. The Infrared Emitter LED (Tx) in the remote handset is similar to an ordinary LED but emitting Infrared rays in the wavelength around 900 nanometres. This wavelength is beyond our Spectral response, so we can’t see it. So what will do to confirm whether the Remote handset is working or not. If this tester is not available, we have to go to the shop to purchase a new one. Sometimes, it may be due to battery problem. Let us make one tiny Remote tester. It blinks an LED if the Remote is good. Its cost is only Rs.25.
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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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