The photoelectric controller takes 555 time-base integrated circuit as the core, the control method is relatively simple, reliable in use, and long in life. It is a photoelectric control switch circuit with low price, small size and easy to make. It can be used in the control of industrial production and household appliances, etc.
1. The working principle of the circuit
The circuit principle is shown in Figure 18.
When there is no light, the resistance of the photoresistor RG is very large (above 1MΩ), the voltage of pin 2 and pin 6 of the 555 time base integrated circuit is about 1/2 (6V) of the power supply voltage, and the output of pin 3 is low, KA The coil is de-energized and the relay releases. When light shines on the photoresistor RG, the resistance of RG will drop significantly (less than 10KΩ), the voltage of pin 2 and pin 6 of 555 will drop below 1/3 (4V) of the power supply voltage, pin 3 will output high level, When the KA coil is energized, the relay is closed, even if the light disappears, KA remains in the closed state.
Later, if there is light shining on the photoresistor RG, the voltage stored in capacitor C1 will be added to pin 6 of 555 through RG, so that the voltage of pin 6 is greater than 2/3 (8V) of the power supply voltage, and pin 3 will output low power. Ping, the KA coil loses power, the relay releases, and the circuit returns to its original state. Every time the photoresistor RG is irradiated by light, the switch state of the circuit is changed once.
2. Components Selection and Fabrication
NE555 integrated circuit for debugging IC, RG should choose photoresistor with bright resistance value ≤10KΩ; dark resistance value ≥1MΩ. There are no special requirements for other components. See the circuit diagram for the parameters of each component. After the circuit is installed, put it into a small plastic box, expose the photoresistor RG, and it can work normally without debugging.