Homemade automatic dimming electronic curtains

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RF cable can be customized for other specifications

Photocoupler

The electronic curtains described in this article can automatically adjust the indoor lighting, which is convenient to use.

Circuit principle: Photodiode D and R1, R4, R5 form a balanced bridge. When the light is appropriate, the potentials of the two points A and B are the same. Both are 1/2EC, the KD28 two op amp output terminals 3 feet and 5 feet potential are also the same, the motor M does not turn, the curtains remain the same. When the outdoor light is enhanced, the indoor illumination is also enhanced, the internal resistance of the photodiode becomes smaller, the potential at point A rises, the potential of the 3 pin of the KD28 output rises, the potential of the 5 feet decreases, the motor M rotates forward, and the curtain slowly closes until the indoor illumination Decrease, the resistance of D rises until the bridge is rebalanced. Conversely, when the light is weakened, the motor M is reversed and the curtains are slowly opened. C1 and R6 act as delays, which can make the control process run slowly, and avoid the repeated starting of the motor caused by the wind blowing the curtains accidentally.

The intensity of indoor lighting can be divided into three categories: strong, medium and weak. At night, indoor lighting can not reach the weak position even if the lights are turned on, and the curtains will all open. If you want to close the curtain, you can switch the switch S to the "night" position. At this time, the potential at point A is always higher than the potential at point B. The motor rotates forward and the curtains close. In addition, there is still current when the motor is in the extreme position (the curtain is fully open or fully closed). For this purpose, an extreme position self-stop switch must be installed, which is done by contact point J and button AN. When the motor is running to the extreme position, J is disconnected and the power is cut off. When re-enabling, press AN, the circuit turns on the curtain to exit the extreme position, J is restored, and the control circuit can be controlled normally.