-★ 1. Only from the circuit diagram, the polarity of the receiving diode is reversed.

-★ 2. In the connection in the figure, the receiving diode is in direct voltage degradation, and it is not controlled whether it is lit or not.

-★ 3. Please see the attached drawing: When there is no light, the diode is turned off; When there is light, the reverse resistance value drops rapidly. ......