A simple IR beam to over 3 feet.

[Robert Frey]

The circuit for inexpensive infrared train detector was first published in MR in the October 2009 issue.  A QRB1114 IR Reflective Sensor was used.   (When IR photo transistor puts about 2 uAmp into a 470K resistor, the Darlington Transistor can turn on a 10 mAmp LED.) 

 

You could also check out the thread Dave started prior to this thread on the simpler version of the circuit with both the emitter and receiver were mounted in the track.  (When IR photo transistor puts out about 4 uAmp into a 220K resistor, the Darlington Transistor can turn on a 10 mAmp LED.)

 

http://cs.trains.com/mrr/f/744/t/213706.aspx

 

 

The Inexpensive infrared train detector two circuits.  (When IR photo transistor puts out about 10 uAmp into a 100K resistor, the Darlington Transistor can turn on or turn off a 10 mAmp LED with two different circuits)

 

http://cs.trains.com/mrr/f/744/t/219552.aspx

 

 

“A simple IR beam to over 3 feet” is basically using two IR emitters in series to produce a bright IR light beam to a photo transistor to put out about 10 uAmps. To start the operation. A 22 uF capacitor forms a delay in turnoff for the Bob Frey’s IR Cover Box Circuit.

 

http://cs.trains.com/mrr/f/744/t/219552.aspx?page=2

 

 

Bob Frey