Electric blanket program development and design
An electric blanket is a kind of low-temperature bed heating product that relies on electric heating wires to generate heat. It is especially suitable for indoor damp and cold environments without heating equipment, especially in winter. It is one of the necessary heating tools for every family. For the elderly, children, and people suffering from arthritis and asthma, using electric blankets to sleep can achieve very ideal physiotherapy results. The electric blanket is mainly composed of heating element, core, fabric, power cord, junction box (the connecting part of heating element and power cord), control switch (or thermostat), etc.
1. Classification of electric blankets
There are many brands of electric blankets on the market, and consumers must consider its safety, comfort, reliability, durability, and functionality when purchasing electric blankets. At present, there are two kinds of electric blankets commonly used in the market: single electric blanket and double electric blanket. The heating power for single use is mostly 40～60W, and the heating power for double use is mostly 60 IOOW. Depending on the voltage used, there are electric blankets powered by 220V and safe electric blankets below 24V.
(1) Ordinary electric blanket. Mainly rely on the plugging and unplugging of the power switch to realize power-on heating and power-off cooling, but it is not convenient to control the temperature.
(2) Manual temperature control type. Most of the market is of this kind. The switch is manually controlled. When the semiconductor diode is connected, the voltage is reduced to achieve the purpose of heat preservation.
(3) Automatic temperature control type. It uses a constant temperature control device, when the temperature rises to a certain rated value (such as 40 ~ 6Oqc), it can automatically reduce the voltage or power off, and it can automatically increase the temperature when the temperature is too low. Constant temperature electric blankets belong to higher-end electric blankets.
(4) Safety electric blanket. There is a high-voltage type, directly connected to 22Ov alternating current; a low-voltage type, usually through a power transformer, the voltage is reduced from 220 volts to tens of volts, which can be adjusted within a certain range.
(5) Multifunctional low-voltage health electric blanket. This kind of electric blanket has the following advantages: First, it is safe, energy-saving and electricity-saving. The heating element adopts a new type of alloy heating wire, which has low resistance value, high conductivity, high thermal efficiency and fast heating. The second is temperature control. The temperature switch adopts dual-channel dual-temperature dual-control. The electric blanket on the same bed can be controlled in two different temperature zones according to different needs to realize the control function of the temperature difference between two persons. The temperature rise of the temperature control switch can be controlled within the range of 15～45℃, and it has the functions of adjusting temperature, controlling temperature, keeping warm and removing cold to meet human needs.
(6) Electric blanket with magnetic therapy and health care function. The conversion of this kind of electric blanket from 220V to 24V low voltage is completed by magnetic field frequency conversion and voltage reduction. The working frequency is within the range of 25k Hz. Due to the special structure of the heating element, the electric blanket produces suitable magnetic flux during operation. The magnetic fluxes of some magnetic therapy or pulse health products are consistent with each other. They are designed according to the physiological structure of the human body, which can adjust the acupuncture points of the whole body, relax the tendons and activate the collaterals, encourage the joints of the body to relax easily, improve blood circulation, promote cell metabolism, and make endocrine vigorous.
Second, the working principle of the electric blanket program
The power supply of the electric blanket is directly connected to the electric heating wire via a switch and a fuse. When in use, plug in the power plug, turn on the power switch, the heating wire heats up, and the temperature adjustment can only be done by switching and plugging the power plug. The fuse among them should play the role of overcurrent protection.
The electric blanket currently mainly uses heating elements to work, and the main function of the heating components is to convert electrical energy into thermal energy. Nowadays, the main heating element used in many electric blankets is thermistor.
Thermistors are made using the property of semiconductor materials that change in resistivity with temperature. The commonly used semiconductor materials are iron, nickel, cobalt, molybdenum, titanium magnesium copper and other oxides or other oxides. Thermistor has the advantages of high sensitivity, larger resistance temperature coefficient than metal, small size, low thermal inertia, good structure, strong mechanical properties, low price, and long life. But there are also poor reciprocity and complexity, serious nonlinearity, and narrow temperature measurement range.
Third, the design safety plan of the electric blanket
The electric blanket is mainly composed of heating wire, blanket material, controller, connector and wire, and the heating wire, controller and connector play a key role in safety. In several random inspections conducted by relevant national departments, it was found that all unqualified electric blankets mainly have the following problems. One is that the heating wire of the electric blanket is unqualified, which is easy to break and cause ignition; the other is that the temperature control is not up to Standard requirements; third, the leakage current indicators of live parts are unqualified. The safety electric blanket must have the following four elements:
1) The heating wire must use a pressure-resistant heating wire with a double-layer spiral structure. 2) The controller must have anti-arc, anti-leakage and automatic protection functions. 3) The connector must have a high pressure resistance and a closed insulation connection function. 4) Must have a strict test environment to ensure 100% safety.
1. Design of heating wire for electric blanket
The biggest safety hazard of electric blankets is fire. Therefore, it is necessary to consider how to prevent fire accidents caused by local high temperature of electric blankets, overheating of blankets, and broken wires. Compared with the ordinary single-layer heating wire, the double-layer spiral heating wire structure is able to detect temperature signals and fault signals throughout the circuit due to the addition of the spiral detection wire layer, and these abnormal signals can be quickly transmitted to Controller for safety control.
2. Design of electric blanket controller
The controller is also commonly referred to as a switch. In the design of a safety electric blanket, it can not only switch and adjust the temperature, but also needs to cut off the power supply to protect the electric blanket. Therefore, compared with the ordinary two-wire switch, the safety electric blanket must adopt a three-wire structure. In addition to the power cord, an independent temperature and fault signal feedback channel needs to be added, and a high back pressure rectifier tube and a high-precision temperature fuse device are used. And current fuse devices, etc., to achieve effective monitoring of the safety status of the electric blanket during use. Once an accident occurs, the power supply can be cut off in time to achieve multiple safety protections.
Through investigation, it is found that the burning of many electric blankets is not caused by excessive temperature, but by the arc spark of the controller. Therefore, the controller of the safety electric blanket must be able to prevent arc sparks. The controller of the electric blanket must use a flame-retardant PCB board and be equipped with a PA self-lubricating sliding contact sheet. In the manufacturing and process, automatic wave soldering and power cords must be used Hook welding can effectively prevent arc sparks and prolong the service life of the switch.
3. Connector design
The connector is the device that connects the heating wire and the controller. Although this is a very important device, it is also a device that many electric blanket manufacturers ignore. Some manufacturers of inferior electric blankets directly use low-grade glue to connect the heating wire and the controller through wires, and some even use insulating tape to connect. These have great safety hazards, and it is easy to cause electric blankets in a humid environment. Leakage hurts people. The connector of the safety electric blanket must have a high compressive strength, use flame-retardant PCB board and automatic constant temperature welding technology to ensure absolute safety between the heating wire and the controller. Ensure the insulated and airtight connection of the heating wire and the controller to prevent potential safety hazards.
4. Design of electric blanket temperature control system
Electric blanket is a kind of low power consumption and economical heating equipment. At the same time, it also has the heating effect and economic effect that cannot be replaced by air conditioner during sleep. It is widely used among urban and rural residents in my country, especially in winter and spring. The phenomenon of heating is very common. However, ordinary household electric blankets have only two gears, high and low temperature. When used in severe winter, the temperature in the high temperature gear is often too high, and the temperature in the low temperature gear is too low. The user is often awakened by heat or freezing in winter nights and wakes up to the gear. To adjust, seriously affect people's sleep quality. This not only makes people feel uncomfortable, but also wastes energy. Therefore, the research and development of a new type of electric blanket and its control system to improve the comfort, reliability and convenience of the electric blanket has become the common expectation of users and electric blanket manufacturers, and it is also an important issue that needs to be resolved in the development of the entire electric blanket industry.
The temperature control system of the electric blanket should generally meet the following requirements: (1) Stable constant temperature control. After the temperature is set, the temperature should be stable near the set value, and there should be no large fluctuations. (2) Strong applicability. There are many types of electric blankets, and the temperature control system should be suitable for different types of electric blankets. (3) Easy to operate. The adjustment of the temperature control system should be easy to operate and easy to master. (4) Simple structure. The temperature control device should be simple in structure and easy to manufacture and install. (5) Good economic benefits. The temperature control system should save electricity as much as possible. (6) Good safety. The temperature control system must have an upper temperature limit to prevent excessive temperature and prevent unsafe accidents.
There are two commonly used electric blanket temperature control systems: a temperature control system based on thyristor and a control system based on intelligent detection. The working characteristics of the two systems are different in principle.
The thyristor-based temperature control system can manually adjust the potentiometer to adjust the heating power of the electric blanket. Its working mode is continuous heating, that is, the heating wire of the electric blanket is always working. The user can adjust the heating power to control the temperature of the electric blanket, which is a stepless temperature adjustment. However, due to the lack of an indicating device, the resistance value of the potentiometer can only be adjusted based on experience. The adjustment accuracy depends entirely on the user's experience. When the temperature adjustment is high, it may An unsafe accident occurred.
The temperature control system based on the controller collects the actual temperature through the temperature sensor, and can display the current temperature of the electric blanket in real time. The user can conveniently set the temperature. After reaching the set temperature, it will automatically stop heating. The working mode is intermittent heating. The method can effectively save energy under the premise of meeting temperature control; and with corresponding protection measures, the safety is high.
5. Recommendations for purchasing electric blankets
In order to ensure the safety of using electric blankets at home and the service life of electric blankets, and to prevent and avoid unsafe factors in the process of using electric blankets, it is necessary to purchase electric blankets correctly:
(1) When purchasing electric blankets, choose products that have passed the inspection of the national quality inspection department. Identify the safety mark (OS) of the electric blanket, indicating that the safety product that has passed the national quality and safety inspection is firmly not to buy the three-no product produced by the small manufacturer, otherwise the safety of use cannot be guaranteed;
(2) Purchase at a regular shopping mall. The product must have the name of the factory, the factory logo and the address, the year and month of the factory, the inspector's stamp and the certificate of conformity; there must be a clear and clear mark, which should reflect the specifications of the electric blanket, Manufacturer and necessary reminders;
(3) The area of the electric blanket is different, and the heating area is also different. Usually divided into single, double or triple electric blankets. Where possible, choose electric blankets with a larger area as much as possible;
(4) Choose fabrics with good texture as much as possible, and choose thicker ones than thinner ones; the power should not exceed 6oW for a single person, and 120W for two persons;
(5) Power-on inspection, put it in the high-temperature position, about 3-5m in by hand, there should be a temperature rise in the middle of the electric blanket, which proves that the file is intact. If the thermostat is of other types, the test time can be extended:
(6) The power controller of the electric blanket should be complete, smooth, free of defects, flexible in use, with clear switch marks, and the power cord used should be double-sheathed.
6. Precautions for the use of electric blankets
(1) Before using the electric blanket, you should read the instructions carefully and strictly follow the instructions: (2) Do not insert needle pins; (3) Do not use if wet; (4) Do not dry clean or wash; (5) Avoid using the appliance (6) Do not allow people who cannot take care of themselves, infants or people who are not sensitive to use it; (7) Store in a dry place when not in use. Do not fold and use; (8) Check the appliance frequently for signs of wear or damage. If there are such signs, or if the appliance has been misused, it should be returned to the supplier before the next use; (9) If the power cord is damaged, in order to avoid danger, it must be replaced by the manufacturer or its maintenance department or similar full-time personnel; (1O) Using the high temperature setting position for too long may cause skin burns.