First, some background. I'm turning an RC car into an autonomous vehicle with an Arduino. At the moment I have three IR sensors in order to detect/avoid obstacles (left, right & front). These sensors usually output 5v; when an object is detected, the output then drops to zero (or thereabouts). However these sensors have quite a narrow detection range and one sensor per side doesn't detect all objects in the way; the car is relatively large, compared to most simple robotics kits/chassis. Therefore I want to use two sensors for each side (2 front, 2 left, 2 right, etc). Problem is that I don't want to use too many pins on the Arduino, as I have other plans for it (such as controlling a parallel LCD). I had the idea of using logic gates so that the sensors can be "paired" - therefore still only using one Arduino pin per side. As far as I can tell, I'd first need to invert the output of both sensors (i.e. a NOT gate) and feed that into an OR gate; when either sensor detects an object, the output of the OR gate becomes active. Only trouble is, this involves using two ICs - one NOT and one OR. Is there a better/more efficient way to do this? I could of course use sensors with a wider detection range but I'd likely need ultrasonic sensors, and they aren't cheap. The sensors I'm using cost less than a fiver each, but ultrasonic sensors start at around £20 each. Plus I'm not really interested in range detection at the moment, just non-contact obstacle detection.