A design scheme for remote intelligent control system of fully automatic rice cooker

With the rapid development of the Internet of Things and software technology, easy and convenient ways of cooking are becoming more and more popular. Intelligent, environmentally friendly, energy-saving high-end rice cookers will become a highly anticipated product in the future, especially fully automatic intelligent rice cookers that can be remotely controlled will become the direction of future development.

At present, there are many technical studies on smart home at home and abroad, most of which are realized by wireless data transmission technology, but the system design cost is high. However, there are few studies on the full automation technology of electric rice cookers, which have not attracted people's attention. This paper transforms the traditional electric rice cooker, designs an electric rice cooker that can be fully automatically controlled, and uses GPRS modules, ordinary mobile phones and other simple and cheap devices to develop a remote electric rice cooker control system with good reliability, which can make the electric rice cooker cook for people in a timely, appropriate and accurate manner.

1. Hardware composition and principle of the system

The overall block diagram of the system is shown in Figure 1. The design adopts a modular design concept, which is conducive to the assembly and debugging of the system and shortens the development cycle.

Since the amount of data transmitted by the rice cooker information is small and the timeliness requirement is not very high, the system mainly uses the SMS service provided by the GSM network.

Its principle is as follows: the mobile phone sends a control text message to the GSM module through the GPRS network. The microcontroller obtains the control command word by reading the GSM module and parses it to obtain clear command information, controls the relay action, completes the control of the rice cooker, and feeds back the command execution status to the user's mobile phone through the GSM module in the form of a short message.

2 Hardware Implementation of the System

This system is mainly composed of a fully automatic rice cooker and an intelligent control circuit system. The fully automatic rice cooker is modified by adding mechanical devices to the traditional rice cooker, and the intelligent control circuit system consists of four main parts: power module, GSM module, single-chip module, and state detection and control module.

2.1 Design of fully automatic rice cooker

Traditional rice cookers, whether they are automatic heat preservation type, timed heat preservation type, or new microcomputer controlled type, have made great progress in real time, but there are still obvious defects and shortcomings, such as too long timing time will affect the taste of rice, etc. Effectively solving the various defects of current rice cookers is the direction of innovation and development. Among them, the full automation and remote intelligent control of rice cookers is a direction for the development of rice cooker technology in the future. To realize the full automatic control of rice cookers, a fully automatic rice cooker is a prerequisite. This paper combines the design idea of ​​fully automatic washing machines, and on the basis of traditional rice cookers, by adding appropriate mechanical devices, the fully automatic rice cooker designed is shown in Figure 2.

The design includes rice storage, rice taking, rice washing, rice placing and water adding devices. The top funnel is a rice storage device with a diameter of 25 cm and a height of 12 cm, which can store about 5 kg of rice at a time. The rice taking device is realized by the electromagnet at the bottom of the rice storage funnel. The electromagnet uses the DC electromagnet HCNE1-1039. The friction resistance of rice grains is reduced due to the inclined design of the card slot. The rice washing device consists of a rice washing motor and a rice washing funnel, and the rice washing motor uses TN-40.180/HC685G100618.

The rice placing device is composed of an electromagnet and a lever. The electromagnet is also HCNE1-1039. The lever is controlled by a reversible motor and can be raised and lowered. The limit switch is used to open and close the lid of the rice cooker. The water adding device is composed of a solenoid valve and a water inlet pipe. The solenoid valve is 2W160-15. The overall mechanical actions include storing rice, taking rice, washing rice, placing rice, and adding water. After receiving the control command, the single-chip microcomputer outputs high and low levels to control the relay to achieve this.

2.2 Design of intelligent control circuit system

2.2.1 Power module design

When GTM900C is powered on, logging into the GPRS network, sending data, etc., it usually consumes a high current [3], up to 2 A, so the power chip must meet the maximum current supply of at least 2 A. The power circuit is mainly composed of MIC29302-BT, whose chip generates 3.8 V voltage to power the microcontroller and GTM900C module. As shown in Figure 3, this circuit can basically meet the conditions. The other pin is the enable terminal, which can be connected to the microcontroller port to make the chip not work when not connected to the Internet, thereby reducing power consumption.

2.2.2 MCU module design

The system MCU uses the MSP430F149, a MSP430 series microcontroller produced by Texas Instruments. It is a low-voltage (1.8~3.6 V), high-performance 16-bit microcontroller with multiple interrupt sources, which can be nested arbitrarily and is very flexible to use. This microcontroller also has low-power idle and power-down modes, supports software settings for sleep and wake-up, and can meet the needs of this system.

2.3 GSM Module Design

Considering the production cost and compatibility, the system uses Huawei's GTM900C chip. Since the logic level of the I/O port of the single-chip microcomputer is 3.6 V, which is not much different from the 2.85 V logic level of the I/O port of the GTM900C, the hardware docking can be performed without level conversion. The connection between the GSM module and the single-chip microcomputer is relatively simple. After the serial ports of the two are connected, the serial port parameters can be set on the single-chip microcomputer side, and the corresponding AT commands can be sent to operate the module. The connection between the GSM module and the single-chip microcomputer is shown in Figure 4. The communication rate is 9600 Kb/s, using 8-bit asynchronous communication.

After the system is powered on, the MCU starts GTM900C, queries the SIM card status, and then controls GTM900C to complete module initialization and the MCU enters sleep mode.

When a new short message arrives, the GTM900C module sends a command to the MCU to wake it up. The MCU reads the content of the short message and decodes it. The I/O port outputs high and low levels to control the relay to complete the control of the rice cooker. After processing, the short message is deleted from the SIM card using a command, and then the above process is repeated. 2.4 Design of status detection and control module

This module mainly includes a state detection circuit and an intelligent control circuit. The state detection circuit mainly collects the fault information and completion status information of the rice cooker, including "start cooking", "end cooking", "fault", etc. The data collected by each module is transmitted to the single-chip microcomputer through a unified SPI bus, and the single-chip microcomputer encodes the data according to each state and sends it to the mobile phone through the GPRS network. The intelligent control module includes two parts: mechanical control and cooking control. Mechanical control is mainly achieved by outputting high and low level control relays through the I/O port of the single-chip microcomputer. The system uses HF32FA/005-HS type relays. The interface between the single-chip microcomputer and the solid-state relay is shown in Figure 5. The driving circuit in the figure is to improve the driving ability and anti-interference ability of the single-chip microcomputer.

Rice cooking control is mainly used to realize the selection of rice cooking methods of the rice cooker, including "fine cooking", "fast cooking", "porridge", "steaming", "congee" and other methods. This system is based on the control circuit and heating circuit of the "Midea FD302" intelligent rice cooker, and an external relay is added to realize the selection of cooking methods. The microcontroller outputs high and low levels from the corresponding I/O port to control the corresponding relay to turn on. After a short time, the relay is disconnected to realize the fully automatic button function of selecting the cooking method of the rice cooker.

3 System software design

The main task of software design is to write application programs. The application program of this system focuses on the program of the microcontroller, and its main functions include the following aspects:

(1) Initialization of the GSM module;

(2) Intelligent control;

(3)Data communication.

The GSM module is one of the most critical components in the system, so its initialization operation must be very careful [6]. The MCU writes the corresponding AT setting command to the GTM900C module through the serial port to initialize it, so that the module can successfully adhere to the GPRS network, obtain the dynamic IP address assigned by the network operator, and establish a connection with the target terminal. The initialization of GTM900C mainly includes the following instructions:

(1)ATE, turn off the echo;

(2) AT+CPIN, check whether the SIM card is normal;

(3) AT +CGREG sets the module registration prompt;

(4) AT + CREG tests the network connection status, etc. In addition, the program also includes CPU initialization, incoming SMS detection, external power failure detection, etc. The software system adds a watchdog program [7] when initializing the CPU, which can automatically reset the system when a problem occurs. Figure 6 is a flow chart of the main program.

4 System Testing

After the hardware and software design of the remote intelligent control system of the fully automatic rice cooker is completed, the system needs to be tested to verify the effectiveness of the design. After the system is powered on, the GPRS network indicator light suddenly goes out and the module automatically shuts down. After the capacitor is connected to the output terminal of the power supply voltage to remove the ripple, the module works normally. The wireless module is debugged with the Socket Tool software, and the GPRS can be successfully connected and return the correct data. The Coolpad 8050 mobile phone is selected to edit and set the information of the amount of rice and the cooking method "300 g, fast cooking" and send it. After receiving the command, the microcontroller completes the entire process of taking rice, washing rice, putting rice, adding water and cooking, and feeds back the cooking status to the mobile phone. After 4 tests, after the cooking is completed, the mobile phone receives feedback information within 7 s, 9 s, 11 s, and 10 s respectively, which can basically meet the requirements. The system measures the amount of rice and water according to the selected cooking method and controls the electromagnet and solenoid valve by the single chip microcomputer. During the test, the amount of rice is set to 300-500 g, the interval is 50 g, and the “fast cooking” mode is used. The amount of water is set to 1.8 times the amount of rice, that is, when the amount of rice is 300 g, the amount of water is 540 mL, and so on. The amount of rice and water are tested 3 times each. The test values ​​and set values ​​are shown in Table 1.

As can be seen from Table 1, the set values ​​of rice and water are close to the test values, indicating that the measurement using timing control is basically accurate. Through multiple experiments on the remote control system of the rice cooker, the system can complete all actions as required, and the measurement of rice and water is also relatively accurate, indicating that the system has good remote communication, the rice cooker works stably, and the measurement is accurate.

From the experimental results, the scheme of the fully automatic rice cooker remote control system designed in this paper is feasible. The measurement of rice and water volume uses single-chip timing control to replace the complex flow control device, making the operation simpler, improving the stability of the system, and also making the system cost lower.

5 Conclusion

This article introduces a design scheme for a system that uses ordinary mobile phones to remotely control rice cookers. The system uses GTM900C to send and receive text messages, and uses the single-chip MSP430F149 to control the rice cooker. No other equipment is required. Users can use ordinary mobile phones to conveniently send Chinese command text messages to remotely control the rice cooker, and can receive timely feedback information on the rice cooker's execution of user commands in the form of text messages. This system has been used in the "Energy Saving and Remote Control Technology Research and Development of Rice Cookers" project. If expanded with RF chips, all household appliances can be connected to the Internet to realize the intelligence of the home, and the application is very wide.