Light control delay on

Principle: Connect two resistors (one is a photoresistor) in series between the power supply and the ground to form a voltage divider, use an op amp (used as a voltage comparator in this application) to detect the voltage at the dividing point, and use TL431 to set the reference voltage (threshold) ), when the voltage division value is greater than the threshold, the op amp outputs a high level to charge the capacitor through current limiting, and enters the next stage op amp. When the capacitor voltage value is greater than the second stage op amp (the threshold of the second stage op amp is divided by a resistor, Because the op amp outputs a high level when the threshold is used (no need to change for special applications), it drives the transistor to cause the relay to operate.

Application: Commonly used for lighting control, not subject to the general time control switch time limit (can also be used with the time control switch), the lights will automatically turn on as long as the sky gets dark at any time, with a delay function to avoid accidental lighting or frequent occlusion Action burns out the load. Turning off the delay function during on-site debugging will get twice the result with half the effort. The delay function has a delay of about one minute when it is turned on or off. Changing the capacitance or current limiting resistor can change the delay time.

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