Infrared Beacon Circuit

This is the circuit for the IR beacon you will use to return to your home base for the Salvage Bots competition. WE WILL PROVIDE THIS DEVICE for the competition so you do not have to build one, but having your own will definitely be useful when you are debugging your IR receiver circuitry.

For a 50% duty cycle, Resistor values R1 and R2
are as shown.  The time period during which
the output high is, t1 = 0.693 R1C.  For the
output low it is,
     t2 = [ (R1R2)/(R1 + R2) ]C  ln[ (R2 - 2R1)/(2 R2 - R1) ]
 

*Note: R2 cannot be greater than ½ R1

D1 can be any Infrared LED, we will use  HSDL-4220 from Newark. Any visible red LED will be useful for debugging this circuit. If you want to check that your circuit works with an infrared LED, look at it through the viewfinder of a handheld video camera (which is sensitive to IR light).