I want to design a IR proximity sensor

[nikhil arora]

I have TSop1738 ir sensor which has good sensitivity
it sense signal from my remote even after reflecting from wall which 5-7 feet above.

Now i want to make such ir proximity sensor but it should not give false alarm due to my tv remote.
I want to do it using 89c2051 controller.
I have developed code for sending ir which is working and giving me similar range now i want to recieve and validate the ir recievd pattern matching with my transmitted pattern for this i know we have to do heavy multitasking.
I have tried this using timer but success was partial.

I would like to know your ideas and suggestions

 

[akg]

what i understood -> u transmits a custom pattern , and the TSOP receives it . but r u using the same micro for Tx and Rx? my idea is that u can do this by reading timer along with low-high and high-low interrupt ( i donno 2051 supports edge selection for interrupts)

 

[nikhil arora]

yes i did the same way and succeded
and 2051 supports edge triggering
i start timer at a negative edge and then stop timer at next negative edge
i repeat this for 5-8 times and ensure a valid reflected signal.
this ckt is totally free of any false triggering.

 

[nikhil arora]

but one problem which i am facing is i am not still getting good range,
as i am increasing current range is increased and after 2.5feets it suddenly jump to very large values upto 5feet

i am making ir on for 1.5ms and then of 1.5ms and this is repeated 24 times and then 50-80ms of pause is there

Is there any other means to make a proximity detector with good range and no false detection

 

[nikhil arora]

this is very nice product how i can i made one