Ir transmitter and receiver circuit suply problem

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hakansefau

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Hello everyone,

I designed ir beam sensor. When i try to work this circuits:





Its dosnt work stabil about 1-2 hours later. This circuits work 24V AC and i realized this circuits are too hot. This works outdoors, and maybe sun light can interfered this signal. But i 've to slove this heating problem, i guess our voltage dividers resistor values are wrong?Maybe for transmit circut BC547 bias problem? i dont know. Can everyone help this problem?
 

You forgot to tell us which parts get hot. I think the resistors R2 and the 7805 voltage regulators because the 24VAC from the transformer is much too high. 24VAC produces a rectified and filtered 32VDC. The 7805 works fine with an input of 7V so you have 25V times the current of heat to throw away.

Did you calculate the heat in the BC547 transmit transistor? Its current is only about (5V - 1.2V - 0.1V)/100 ohms= 37mA and its saturated voltage is only 0.1V so its heating is only 37mA x 0.1V= 3.7mW which is nothing.
 

What's the exact HK23F type? There are versions with different coil resistance.

I presume the voltage regulator is the only hot part. You can either provide a sufficient heat sink for it, or use a lower AC input voltage. C1 capacitance may be need to increased a bit then.
 

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