I have built an IR proximity sensor using a normal 940nm IR LED, Tsop 4856 kHz IR photodiode. I have used 555 timer to generate pulses to the IR led. the circuit is working correctly as far as I know.
Using an oscilloscope, I can see 5V straight line without obstacle, a 0V straight line when there is a obstacle and a square wave between 0 and 5 V when the obstacle distance varies. But the range is only 8 - 10 cms.
I have tried the circuit with a transistor in the output of 555 timer. But the range remains same.
I have to detect an obstacle at a distance of 1.5 meters. How could I achieve this range.
Major problem: I have projected normal IR source on the Tsop sensor. the output LED blinks even for that source which shouldn't be going on. As per my knowledge the sensor should not give output when is subjected to other IR frequencies except for 56 kHz.
What do you think is wrong and what should I do to eliminate other frequencies?
I have attached my circuit diagram.
This is my first project in electronics. I want to learn by doing. It would be very helpful if you could explain in detail.