This circuit was found in a Popular Electronics from the 90's. The CMOS integrated circuit used is not very common nowadays. The range depends on the infrared LEDs. R7 can be changed.
November 2016 - Texas Instruments' new TLV8802 nano-power operational amplifiers for wireless...
This sophisticated photometer that has a light comparator with LED indicator came out in an...
This is a version of the previous circuit that includes a tone modulator based on a Hartley...