With the aim of making it more convenient for farmers to preserve their post-harvest agricultural products, Mr. Nguyen Dinh Phu, a teacher at the Xuan Lap junior high school in Long Khanh town and his partners have successfully built a sensor-based automatic roof system.

Based on the principle and application of sensors, the author has invented the device attached to the automatic roof system in families. The operating mode of this sensor system is as follows: using 220V AC power through two switches whose speed is controlled by two motors and through the adapter for two ends out: one with 24V DC power, which is used to control sensor pieces and relays and the other with 220V AC power attached to 2 power points supplying electricity for 2 motors with the current of 220V - 150W.

Accordingly, when it rains, a 24 V DC power source senses rain water that leads to the relay. When being exposed to rain water, the rain sensor affects the relay with a certain force. The power current continues to go through the normally-open switch of the relay 1 to the normally-closed switch of the relay 3, then supplies power for the relay 2 to act. During this time, AC power source is supplied to the motor via the relay 2 and causes the motor to work and pull the mica plate. When the mica plate is pulled out, it will act on switch 1, from which the 24 V DC power source supply power for relay 3 which will close normally. The relay 3 opens, which will result in no power to be supplied for relay 2 and the motor does not operate when the relay 2 is open.

When it is sunny, the rain sensor will dry, not supplying power the relay 1 from the normal switch. Due to no power sources, all relays 1, 2, 3 do not work. The DC 24 V power source runs through the normally closed switch of relay 1 and the normally closed relay 5 energizes the relay 4. When relay 4 is closed, the AC power supply for the motor operates via relay 4 to pull the mica plate into. When the mica plate is pulled in, there is no force on the switch 2, and the DC power source goes through the switch 2 and power is supplied for the relay 5 to cause it to close. The normally closed switch of relay 5 stops supply power for relay 4, and the motor stops working.

The entire process of the system is fully automatic, contributing to the reduction of human efforts and time. Importantly, thanks to the sensors’ ability to facilitate the outdoor drying of agricultural produce in changing weather, rain, and sunshine when farmers are not at home. The automatic rain roof can be assembled to meet such needs as drying clothes and agricultural products (pepper, cashew, coffee, corn, and so on).

Thanks to the power switch system, it is possible to prevent fires and explosions at night. In addition, the system is based on battery power, so it can still be used when power is cut. The design and installation of the system is very simple, which is easy to make with the popular tools on the market. In addition, the low assembly costs and the old machinery parts can be also taken advantage of.

The system has many applications to help save time as well as labor for users.