proximity obstacle detection sensors problems

Hi,
I am trying to built a presence detection device with a small microcontroller and sensors which is located on the ceiling and could alert on whether an object (non moving) is present within the radius of 1 meter in all directions. It should be very small and cheap (less than 5$) so any solutions like radar or laser scanning is out of the question, so I have left with the ultrasonic and infrared possibilities, but due to budget and size limitations i need to use as few sensors as possible.
I have tried to make some measurements with infrared transmitter and receiver in the same housing but so far I've been able to detect only objects in the range of about 20 cm, and pretty much only if it is perpendicular to the sensor. I have used TSOP1838 as a receiver and TSHF5210 as an emitter and supplied it with different current values but I could not significantly increase the range and the beam detection angle
1) 2)3)4)
Thank you very much in advance 
Shahar

Hi Shahar, I think everything depends on the size of the object and what the background is reflecting to create a meaningful signal to noise ration. For low cost application your can check-out also LED-triangulation like it is used to detect a person in front of an elevator or automatic door. How triangulation work you can check-out here: https://www.ichaus.de/FB5_en . By using HB-LEDs distance can be easy extended.

Enjoy your design work!

Thanks HTA for your reply. I am checking your suggestions.
The purpose of this is to serve as an add-on to a smoke detector and alert when large objects as a wardrobe for example is located near the detector and could undesirably affect the detectors sensitivity. Small objects would not simnifically affect the detectors sensitivity and therefore, the objects to be detected are rather large, but should be detected at any direction under the detector at about 1 meter radius.

what I don't get is how a normal tv remote control, which for my understanding does not use some high power or high brightness IR led emitter, but rather a normal 960nm one, is bale to transmit to a range of about 10 meters and with such high angle. why can't i get more than 40 cm detection? what am I missing here?

Hi Shahar, the optical design of the sensor is key to spread the beam. Example for automatic door opener: **broken link removed** . In 3D monitoring systems for elevators a time of flight approach is also used(see: **broken link removed** ).

Enjoy your design work!