IR Infrared Obstacle Avoidance Sensor (2pcs) IR Transmitting and Receiving Tube Photoelectric Switch 3-pin Compatible with Ar-duino Smart Car Robot

By simply placing an Infrared Sensing Stickers, the range is much greater than 12 inches.

There are equivalent offerings available at a much lower price. The divergence of the IR LED beam - like most 5 mm LEDs - is about +- 30 degrees. Consequently, the detection range is limited to about 5-6 inches, as advertised. (Note: Polishing the LED flat increases the beam divergence to about +- 60 degrees.) Also, black objects tend not to reflect well at the wavelength (0.9 um) of the IR LED, and so are not seen. I converted this product into a broken-beam sensor by demounting and remoting the LED and photodiode facing each other. The broken-beam sensor I made works at a separation up to roughly 11-12 inches.

Total waste of money. Doesn't really work and if you see some reviews stating how good it is and works, be weary. I sent it back.

So... they do work. and will likely work well for you if you don't mind the max sense distance to be around 3CM not 30CM. I tested this at 5V. The pot is only really useful in about 40% of the range and set any higher will just cause a full on state even with out any light from the emitter. Yes in a dark room too. I also covered both sides with electrical tape. Its just not a good pot or maybe the circuit is sub optimal.

The units I got were assembled using 1-turn potentiometers which don't have nearly enough resolution to allow you to adjust the sensitivity correctly. Working units of this design will use 10-turn potentiometers.

The product description on the Amazon site is unintelligible. It would be useful to have a link to the data sheet.