Home Page.
A not too complicated photo cell detector circuit for up to 60cm (2 feet). This circuit has a degree of interference rejection to cope with flourescents and similar noisy light sources. The Infra-red output transistor is pulsed at about 13 kilo hertz with a short pulse of high current.
The detector photocell has a constant current supply which compensates for varying ambient light levels so the pulse is not swamped. The signal pulse is filtered, amplified and integrated by the comparitors to produce a constant output level which is used to drive the transistor or light the LED.
A not too complicated photo cell detector circuit for up to 60cm (2 feet). This circuit has a degree of interference rejection to cope with flourescents and similar noisy light sources. The Infra-red output transistor is pulsed at about 13 kilo hertz with a short pulse of high current.
The detector photocell has a constant current supply which compensates for varying ambient light levels so the pulse is not swamped. The signal pulse is filtered, amplified and integrated by the comparitors to produce a constant output level which is used to drive the transistor or light the LED.
LINK TO IMAGE - pcell-2.gif
Circuit Schematic
