computer eye - control by monitor screen

computer eye elektor june 1985 This photograph shows our prototype of the "computer eye" and, in the background, the LDRs fit- ted in shrink sleeves. control by monitor screen The circuit is based on an opto-electronic comparator as shown in figure 1. The "eye" proper is formed by two light-dependent resistors — LDRs — RI and R2. The voltage level at their junction is applied tc the inverting input of the comparator, IC1, via R4. The non-inverting input of ICI is held at a fixed reference voltage. The comparator toggles when the level at its pin 2 is lower than the reference voltage. Transistor Tl is then on, and the relay is actuated. At the same time, T2 conducts, so that the LED, DI, lights to indicate the state of the circuit visually. When the level at the inverting input of the comparator is higher than the refer- ence voltage, the relay is not energized, and DI is out. The idea is that the control program includes instructions which cause two light areas to appear on th...