infra-red light barrier

Infra-red light barriers enjoy great popularity as timing devices at sports venues, as detectors in alarm instal- lations, as optoelectronic switches in counting equipment, and many others, because of their low cost and immunity to electrical interference. The present light barrier consists of a transmitter and a receiver. 2 R1 10 mA + 9V •470 ® 7-32 infra-red light barrier -ee - 111* 26 IC1 11 16 SL 486 RESET R7 BP 104 15 CLCS. CL3 10p 1673n 10076V 54 3 Ci7 4n7 7n C6 C12 C11 70n Tn2 7n T pB 2720 51.1 il 14 12 13 C9 *see text ¢o CiE ml C1CiR 4 men /29 10p 16V 16V D1 1N4148 R3 10 41,7 89 R2 IC2 rge/1 x" 2x 1N4148D2=I N1 ... N4 = IC2 = 4093 85449.2 03 Bz T1 elektor july/august 1985 3 Parts list (receiver) The transmitter, shown in figure 1, consists of an astable multivibrator (AMV), IC3. The output of the AMV, pin 3, consists of a pulse stream with a duty factor of about 30 per cent. The output is connected to a constant-current source, T 2. This source provides infra-red tra...