infrared proximity sensor

[inetquestion]

I've been working on an ir proximity sensor, but am having problems with its sensitivty. With the emitter and detector side by side, the approaching object has to be about 3 inches away before any objects are detected. Is there a way to get more sensitivity out of these systems?

One other question I have is about the emitter circuit. Right now the best output i've found is any tv remote. The ones i've build tend to burn out the emitter or are way to weak. Is there something really simple I'm missing?

Regards,

-Inet

 

[hjames]

A schematic of what you currently use to test would be useful.

Proximity sensors aren't very sensitive in general. The reflectivity of the surface tends to vary a lot, and any focusing lenses would definitely help.

The other thing to do is to worry about the electronics side - how much the electrical gain is there, and how much rejection of background noise is there. Bandpass filtering at a minimum, synchronous detection if you want to go all-out. Also AGC (automatic gain control) is sometimes used in order to deal with background environments that are too bright.

One thing that you might already know is that usually IR transmitters operate pulsed - 500mA - 1A for a few tens/hundreds of microseconds, followed by a lot of cool down time in between. The duty cycle should keep the average current in the ~50mA range for IR leds, but this depends heavily on the actual LED (i.e. check the datasheet).

 

[audioguru]

Parts burn out when the datasheet's important ratings and spec's are ignored.
A receiver's sensitivity is related to its amplifier's gain.

 

[Hero999]

The ones i've build tend to burn out the emitter or are way to weak. Is there something really simple I'm missing?

Probably a resistor in series with the IR LED.

 

[hafi2_07]

hi......i need some explanation....i use the ir tranceiver as the pic attached....but my problem is, this ir sensor is too sensitive...even though i have blocked both the ir transmitter and receiver, the receiver circuit still can detect the ir tranmitted..???any suggestion..???


**broken link removed**

 

[audioguru]

If you blocked the emitter and the resiever then how can it detect the IR?
Through a common power supply that does not have a supply bypass capacitor??
Add a 100uF capacitor across the power supply connectins of the transmitter and receiver. Try separate 9V batteries.

The 555 oscillator causes huge supply current spikes that are picked up by the receiver.

 

[lord loh.]

I had similar experiences. My problem was solved by increasing the IR strength from the LED. This was done by a low resistor value in series with the IR LED. -> 33ohm for 5v VCC... And there were two LEDs in series.