Hair dryer control panel development and design

In the past, fires caused by improper use of hair dryers have occurred frequently, seriously damaging collective and individual lives and property. Departments and schools at all levels have attached great importance to the use of hair dryers in student dormitories. Most schools prohibit students from using hair dryers in dormitories. . According to relevant statistics, the fire caused by the hair dryer is mainly because the user did not turn off the hair dryer in time when he left.

1. The overall scheme design of the hair dryer

The hair dryer designed in this paper includes a human body induction module, a signal acquisition module, a signal processing module, an execution module, a main circuit, a switch, a casing and a power cord, etc.; the human body induction module and the signal acquisition module are connected through a detection resistor, and the output terminal of the signal acquisition module is The input terminal of the signal processing module is connected, the output terminal of the signal processing module is connected with the power supply terminal of the execution module, and the contacts of the execution module are connected in series with the main circuit of the hair dryer. The main circuit is composed of motor, thermal resistance wire, switch and other components.

2. Design of induction module of hair dryer

The human body induction module is composed of a high-resistance resistor, a detection resistor, a metal body, a human body, a fuse, a signal line, and the ground; the high-resistance resistor, a detection resistor, a fuse, and a signal line are built into the hair dryer, and the high-resistance resistor , detection resistor, and fuse are connected in series through the signal line, and one end is connected to the power line, and the other end is connected to the metal body; the metal body is a metal sheet with good conductivity, and is embedded in the groove on the handle of the fan. The thickness of the metal body is consistent; when the user holds the hair dryer, the palm and the metal body will be in good contact, making the human body and the ground a part of the induction circuit; if the power line is connected to the power supply, the current will flow through the power line, high resistance Resistors, detection resistors, metal bodies, human bodies, and fuses flow into the ground to form a loop. Since the resistance value of high-value resistors is very high (generally 2 to 3 megohms), even if a conductive loop is formed, the line resistance is extremely high. The high current makes the current very weak and has minimal impact on the human body. Although the current in the loop is weak, it can output electrical signals. The signal acquisition module can collect weak electrical signals, indicating that the hair dryer is in the hands of the user; in order to prevent the resistance from aging and prevent the decrease , A fuse is added in the induction circuit, and its fusing value is very small. Once the current exceeds the set value, the fuse will blow immediately, cutting off the circuit and protecting the user.

3. Design of hair dryer signal acquisition module

The signal acquisition module is built in the hair dryer and consists of a detection resistor and a sampling circuit; the detection resistor is a common part of the acquisition module and the human body induction module, and its function is to convert the current signal in the human body induction module into a voltage signal; the sampling circuit is to convert the collected The voltage signal becomes a voltage signal of appropriate size and sent to the STM32 processor; if there is current flowing through the human body induction circuit, the current will generate a voltage difference at both ends of the detection resistor (although the current is very weak, according to Ohm's law, increasing the resistance value can improve Voltage value), the detection voltage is amplified and stabilized by the sampling circuit and sent to STM32. At this time, STM32 receives an open electrical signal.

4. Design of hair dryer signal processing module

The signal processing module consists of an STM processor and a rectification and filtering circuit. The two parts are built into the handle of the hair dryer. The function of the rectification and filtering circuit is to provide power to the STM32. The rectification and filtering circuit is a circuit board, and the STM32 processor can be embedded on the circuit board. This makes the signal processing module small in size and can be placed in the narrow and long handle of the hair dryer; when the signal acquisition circuit sends a signal voltage to the STM32, the STM32 will control the relay to be energized.

5. Design of executive module of hair dryer

The executive module is a small relay, the relay has four pins, two pins are the relay power port, one end of the power port is connected to the STM32 pin, and the other end is connected to the neutral line, which is controlled by STM32 to power on or off, and the other two pins are The relay contacts are connected in series to the main circuit of the hair dryer; when the relay is energized, its contacts are closed, and the hair dryer can only work when the switch is pressed at this time; when the relay is powered off, its contacts are disconnected, and the hair dryer stops working. The relay cannot be energized, and its contacts are in a disconnected state. No matter how the switch is controlled, the hair dryer will not work.

6.Hair dryer main circuit design

The main circuit of the hair dryer is composed of a motor, a thermal resistance wire, a fuse, a switch and a circuit. The motor and the thermal resistance wire are connected in parallel. Each branch circuit is equipped with a switch. Different switch state combinations can realize various working states. The dryness of the main circuit The relay contacts are connected in series on the road, so that the relay can directly cut off the power of the line, and the set fuse can prevent the main circuit from aging or failure caused by other reasons. Once the current is too large, the fuse will be disconnected immediately.

7. Working process of hair dryer

When the user uses the hair dryer, the palm will be in contact with the metal body. At this time, a current will flow through the human body and lead to the earth. When the current flows through the resistor, a voltage will be generated at both ends of the resistor. The signal acquisition module can receive the voltage at both ends of the resistor. Signal, if there is no user or the user does not touch the metal body, since there is no current flowing, no voltage will be detected at both ends of the resistor; the signal acquisition module will amplify and stabilize the voltage signal after collecting the voltage signal, and finally output a suitable The voltage signal, the voltage signal is sent to the signal processing module, and the signal processing module sends a signal to the execution module, the relay operates, and the relay contacts connected in series in the main circuit are closed, which meets the prerequisite for the hair dryer to work. On the basis of satisfying this condition Press the switch on and the hair dryer will work. When the user does not touch the metal body, the signal collector will stop sending signals to the STM32 if it cannot receive the voltage signal, and the STM32 will immediately send a disconnect signal to the relay to realize power failure.

The above is the development example of the safety hair dryer control board introduced by Shenzhen Zuchuang Microelectronics Co., Ltd. for you. If you have the development needs of hair dryer module solutions, you can trust us. We represent a variety of single-chip microcomputers, voice chips, dual-mode Bluetooth ICs, and wifi chips. Brands include Songhan MCU, Yingguang MCU, Jerry Bluetooth, Ankai Bluetooth, Allwinner, and Realtek. Our technical services include: PCB design, microcontroller development, Bluetooth solutions, software and hardware custom development, APP development, small program development, WeChat official account development, etc. It can also undertake the design of intelligent electronic products, the development of living appliances, the research and development of beauty equipment, the application of Internet of things platform, the smart home control system, the development of TWS earphones, Bluetooth earphone speakers, the development of children's educational toys, the design of electronic education products, etc.