>I have been monitoring mail traffic for IIR, Laser diode or Ultrasonic suggestions that my be able to solve my problem. >I need to detect the speed of an object 2 - 5 feet from the sensor mount. >Sensor is mounted upward looking at the sky. Why not use the Sun's IR? I have no idea if this would work; but, adjust the bias on an IR detector until it just trips a Schmidt trigger in open sunlight. When the object passes overhead it will (presumably) obscure the sun. Putting a second detector in the line of travel will give a second pulse that confirms the validity of the first one and could be used for speed calculations if the geometry is right. Granted it's downright ugly, but it sure is cheap . Cheers, Win