• 40KHZ LIGHT RECEIVER AMP
  This circuit is similar to 30KHZ LIGHT RECEIVER AMP but provides more gain and operates up to 40KHz.  However it draws more power supply current.

• 40KHz LASER BURST DETECTOR
  This circuit was originally designed to detect weak flashed of laser light bounced off of a fabric video projection screen. It was used as part of a firearm training system. It generates a 100mS output pulse whenever it detects a 3ms to 5ms laser burst, modulated at 40KHz. It is very sensitive and could be modified for long range laser communications.

• 40KHZ LED TEST SIGNAL GENERATOR
  This 40KHz crystal controlled oscillator circuit drives an infrared LED with powerful 40ma pulses.  The circuit can be used to test optical communications circuits, designed to receive 40KHz modulated light signals.

• 40KHz Light Detector with Sunlight Immunity  NEW
  The circuit below was designed to turn on an external 12v relay, whenever it detects light from a nearby LED light source, modulated at 40KHz to 50KHz.  This circuit was originally designed to operate from a fast moving vehicle. The light transmitter was positioned at a stationary position, while the matching receiver was mounted on the vehicle.  The circuit has high ambient light immunity and in most cases, can operate in direct sunlight.

• 40KHz LIGHT RECEIVER IS IMMUNE TO AMBIENT LIGHT
  If you want even more sensitivity than the above circuit, try this design. When used with a one centimeter square photodiode, you can achieve a range of several hundred feet with a standard TV or VCR remote control module.

Free Space Communication circuits #'s continued