Automatic corridor lights with self-locking function

The author installed an automatic lamp in the corridor at the door of his house. It can automatically light up when someone passes by, and automatically turn off after the person leaves. It stops working during the day. It is convenient and energy-saving and has anti-theft and deterrent functions. In the production practice, the author found that there are some shortcomings in the ordinary light control circuit. The ordinary light control circuit has certain requirements for installation. The photoresistor needs to be separated from the lamp by a long distance. Otherwise, the light will interfere with the light control circuit and make the light flicker. Therefore, in actual use, the power of the bulb cannot be too large, and the sensitivity of the debugged circuit is always too high. For this reason, the author made some changes to the light control circuit so that the lamp will automatically lock in the light state once it is lit, and will no longer be interfered by the lamp itself.

Working principle: The power supply part is composed of C1, C2, R1, DW, D, which is a typical capacitor step-down circuit, providing a stable +11V DC voltage. TX982 is a microwave induction control module. It uses microwave Doppler technology to establish a micro-electric field in a certain space. When a person or moving object enters the electric field, it will reflect the echo. After mixing by the electronic circuit, a very weak frequency shift signal is detected. After intelligent processing, this signal can output a control signal. Due to the use of a dedicated microprocessor for microwave detection, it is able to process the pulse frequency and pulse width of the input signal, thereby eliminating interference from small animals, distant trees, high-frequency communication signals, distant lightning and electrical switches. This is incomparable to the detection circuit composed of infrared, ultrasonic, pyroelectric elements and conventional microwave circuits in the past. In actual use, the false alarm rate is extremely low. When the microwave circuit detects that someone is active within the monitoring range, the output end of the microwave induction control module outputs a pull-down level, which cuts off the T1 tube, and point A changes from a low level to a high level, and the light control circuit composed of the 555 circuit starts to work. When the ambient light is very weak, the voltage dividing point between the photoresistor and R4 is lower than 1/3VCC, the third foot of the 555 circuit outputs a high level, the thyristor BCR is turned on, the light bulb lights up, and at the same time, the high level of the third foot turns on the T2 tube, and point B is forced to be pulled to a low level. Only after the person in the monitoring range leaves, the transistor inside the output end of the microwave sensing control module is cut off, the T1 tube is biased in the on state by R2, the potential of point A is at a low level, the 555 circuit is reset, the third foot becomes a low level, the light goes out, the T2 tube is cut off, the circuit exits the self-locking state, and prepares to enter the next working cycle.

Because the improved circuit has superior anti-interference performance, the control can be installed in the common ceiling corridor light cover, leaving no trace on the outside and has anti-vandalism function.