IR Switch

Here is a Simple Infrared controlled Switch. It can be operated using the TV remote handset Load can be any AC operated device which can be connected to the relay. The load turns on for three minutes then goes off. It can be used to switch on the lamp in the TV room

The circuit uses the popular IR sensor module TSOP 1738 and the precision Monostable / Astable IC CD4538. TSOP 1738 IR sensor accepts 38 KHz infrared pulses from the remote. Its output is high at power on and gives 5 volts. When it senses pulsed IR rays, its output becomes low.

CD 4538 is the Precision Monostable /Astable Multivibrator IC that is free from false triggering .It is more reliable than the popular timer IC 555. Here the IC is wired as a short duration monostable timer using R3 and C1 as timing components. With the given values, output of IC1 remains low for three minutes. By changing the value of C1 or R3 various time intervals can be obtained. Unlike 555 IC in the monostable mode, here in CD4530, output of IC becomes high at power on and becomes low when the trigger pin5 gets a low-to-high transition pulse.

IR Switch Circuit

Normally, the output of the IR sensor remains high and T1 conducts. This keeps the trigger pin 5 of IC1 low. When the remote handset is focused on to the IR sensor and any of the button is pressed, output of IR sensor becomes low and T1 turns off. This makes the collector of T1 high and the low to high transition at pin 5 of IC1 triggers it and its output becomes high.T2 then turns on and relay triggers. The load connected between the common and NO contacts of the relay turns on for three minutes. Adjust VR to keep IC2 off in standby condition

Caution: Take extreme care while connecting AC load. Careless handling may cause lethal shock


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