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Hand Dryer Solution
After washing your hands, put your hands near the air outlet of the automatic hand dryer (hand dryer), and (hot) air will blow out to dry your hands. Once your hands leave during the blowing process, the automatic hand dryer will stop working quickly. And once it works continuously for a period of time, the automatic hand dryer will stop working, and if you try again later, it will continue to work. Due to the sanitation and convenience of automatic hand dryers, more and more public places have begun to use automatic hand dryers, and some families have also begun to use automatic hand dryers. According to the blowing speed, automatic hand dryers can be divided into two types: slow and fast; according to the installation method, automatic hand dryers can be divided into two types: wall-mounted and standing.
1. Working principle of automatic hand dryer
The automatic hand dryer works by far-infrared automatic induction. It is composed of an infrared transmitter, a receiver, a monostable delay switch, a solid-state relay and a hair dryer, etc., forming a simple self-excited multivibrator. Modulated infrared light with a frequency of about 40kHz. When the human hand reaches under the automatic hand dryer, part of the emitted infrared rays is reflected back by the human hand, and after being received by the photosensitive transistor, it is converted into an electrical signal of the same frequency, and then amplified, shaped, After the band-pass comparison, output a low-level pulse signal, and then trigger the formed monostable circuit to enter a transient state, make it output a high level, light up, and the AC solid state relay is turned on, so that the hair dryer can send out hot air when it is energized. When the hand is dried away, the infrared pulse signal is lost and the high level is restored, and the monostable circuit is quickly reset. Due to the delay effect, the hair dryer will automatically recover after working for about 10 seconds at most, and then stop working. In order to adjust and change the action sensitivity of the automatic hand dryer, a series network composed of resistors and capacitors can be added to the circuit to improve the frequency characteristics and gain of the preamplifier, so as to ensure that when the short-term signal disappears, such as when the hand shakes and deviates from the infrared detection range , the circuit power supply will not jump instantaneously, ensuring that the hair dryer can still work stably and continuously.
2. The key components of the hand dryer
The "heart" of the automatic hand dryer is mainly a single-phase different motor that drives the fan blades. Considering that the automatic hand dryer is used in a humid environment with a water source, the structure of the motor must adapt to the humid environment without early failure. For example, single-phase capacitive asynchronous motors often reduce the operational reliability of capacitive induction motors in humid environments due to capacitor failures. If a single-phase series motor is used, the commutator working in a humid environment is prone to moisture and short circuit, and the insulation performance of the dielectric will deteriorate, resulting in a shortened durability and service life of the motor. The noise of this motor is relatively large, and it seriously interferes with radio waves. During operation, multiple horizontal stripes will appear on the images of TVs and video recording equipment in and around the rooms, which will affect the clarity, so it is not suitable for use. The single-phase double-ring shaded pole asynchronous motor is more suitable for the above environment. It eliminates the shortcomings of the above two types of motors. The shaded pole motor has better durability in humid environments and a long service life. The stator pole of the motor is detachable, and the excitation winding is concentrated winding. , directly wound into the nylon coil frame and put it on the core pole, and then pressed the core pole into the stator yoke with a special fixture. This work is completed on a 49kV press. The electrical strength of the medium of this motor structure is greater than 4000V.1min without breakdown, which meets the requirements of GB4706.1-2005 Safety Technical Standard for Household Appliances, Class II electrical products. The electric strength is 3000V.1min without breakdown and no flashover. Smooth start, compared with the specified value that the rated voltage should be able to start smoothly, there is a larger safety margin.
3. Common quality problems of hand dryers
Due to the small sales volume of automatic hand dryers, large enterprises are unwilling to organize production, so that the current domestic automatic hand dryer manufacturers are generally small enterprises with small production scale, poor technical strength, and backward production equipment, and there are even some manual workshops. The quality of products produced by these enterprises is worrying. In recent years, the pass rate of automatic hand dryer type test spot checks is less than 50%, and the main quality problems are as follows:
(1) Product marking is incomplete or irregular: the marking should contain important information to guide users to use it correctly, and the correct marking of products is one of the basic measures to ensure the safety of users' personal and property. The marking is required to be durable and eye-catching, it should not fall off after normal use, and the content should be clearly identifiable. The common problems are that there is no manufacturer name, model number, no waterproof grade mark, no assembly drawing, manual, II appliance identification is not standardized, rated voltage, power identification is not standardized, and the identification is incomplete, etc.
(2) There are many problems with electrical safety performance: exaggerating technical indicators, deceiving and misleading consumers (mainly focusing on one-sided exaggeration of input power); disordered internal wiring, unreliable grounding connections, unqualified heat and flame resistance tests, and unqualified anti-shock protection. These unqualified items are mandatory items closely related to user personal safety and environmental safety. The main reasons for these unqualified products are: the small scale of the production enterprise and weak technical strength, which lead to the error in the parameter design of the electric heating element of the production enterprise, resulting in excessive deviation of the input power; the large opening of the air outlet, resulting in some products that can be touched with the test finger to the electrified body. Some internal wiring uses multi-strand wires and uses simple soldering connection methods, resulting in unreliable connections; the selected insulating materials do not have the ability to withstand 125°C heat resistance and inferior materials. Some enterprises lack the necessary detection means, and a few enterprises do not strictly control product quality.
4. Design idea of hand dryer
As a modern sanitary appliance, hand dryers are more suitable than traditional towels, and avoid cross-infection of diseases and bacteria. The hand dryer is a kind of circulating multi-directional air outlet equipment, and an air guide device is set up at the air outlet. There is a kind of wind guide leaf on its device. During the process of turning the air guide blades, the hand dryer starts to discharge air in a circular and non-directional manner. Most of the hand dryer products on the market are basically composed of very common digital devices. Whether it is debugging or installation, the circuit structure is not very convenient, and it presents a single function. If the internal circuit of the hand dryer fails, it is inconvenient to repair, and it is relatively difficult to replace it with other circuit components. However, the use of single-chip microcomputer technology in the production of hand dryers makes the entire circuit relatively simple. Single-chip microcomputer is an integrated circuit chip that integrates central processing unit CPU, read-only memory ROM, random access memory RAM, and various I/O ports and interrupt systems.
The single-chip microcomputer selected for the production of the hand dryer is the 89C52 single-chip microcomputer product of the MCS-51 series of INTEL company. The 89 (352 single-chip microcomputer is used as the controller of the entire circuit chip, and its electronic switch is mainly controlled by infrared rays. Generally speaking, ordinary hand dryers are equipped with infrared sensing devices, which can sense the temperature of human hands and control the switch. The electric hair dryer is turned on. The temperature of the hand leaves, and the switch is controlled to turn off the electric hair dryer. Therefore, the single-chip microcomputer technology is used in the production of the hand dryer, and the infrared control switch and the electric hair dryer are also installed inside it. Connect them with a line and use The effect is the same as that of the automatic hand dryers on the market. When making the hand dryer, you can also freely play, adding light effects or sound effects. You can also paste some decorations on the surface of the hand dryer to enhance the aesthetics. Using single-chip technology To make a hand dryer, only one integrated block is enough, which has the same function as the basic circuit.
5. The technical principle of hand dryer development
After the hand dryer with single-chip microcomputer technology is ready, it is connected to the power supply. The entire hand dryer has current passing through it, the i/o port is initialized, the main control program starts to mobilize the acousto-optic system, and the acousto-optic prompt appears. Program the internal setting, let the microcontroller output a small square wave at intervals of a short period of time. The 89C52 single-chip microcomputer has the ability of low-level driving, which can drive the transmitter to start emitting infrared rays. When installing the transmitter and receiver, pay attention to careful debugging and keep the best distance. Objects can be used to approach the emitter and receiver, and the infrared light will be emitted to the object and then reflected back to be received by the receiver. Once the receiving head receives the infrared light, its high level will change to a low level. Because the external pull-down is low, the P3 port of 89C52 will output current, causing the central processing unit to be disconnected. The entire service routine is shut down at this point. The lights, sound, and relays in the program are all connected to one line, causing the electric hair dryer to blow out hot air.
The external interrupter began to become the I/0 port, and the peripheral level was detected irregularly. When the P3 port writes "1", they are internally pulled up to a high level, and then return, the central processing unit is connected, and the system is on standby. Be prepared for a delay during this time. Human hands will keep shaking in the hand dryer. If the receiving head is not ready for delay, it will continuously send out signals, making the relay open and close again, and the beating will not stop. Be prepared for delays and be prepared for people to respond. The delay time set by this self-made hand dryer is 3 seconds, which basically solves the shaking phenomenon. The method of playing audio sound is an oscillation method, which takes a long time, and the relay will be turned off suddenly every time it is interrupted. The beating frequency of the relay is high, which affects the service life. If you want to avoid a large beating frequency and prolong the pull-in time of the relay, you can use a capacitor to store energy. The P2 port in the 89C52 microcontroller is an 8-bit bidirectional I/O port with an internal pull-up resistor, which can limit the input current, reduce the charging reaction of the capacitor, and avoid damage to the I/0 port.
6. The power supply circuit of hand dryer MCU
(1) Power circuit: The power circuit part of the single-chip microcomputer uses the current of the transformer rectifier diode to obtain direct current, and then obtains 5V direct current through the three-terminal voltage regulator integrated circuit, which can be used by the single-chip microcomputer. The internal hair dryer uses AC 220V.
(2) Infrared detection circuit: Infrared detection consists of an infrared emitting component and an infrared receiving component. The infrared emitting member is composed of an infrared light emitting diode IRLED. The infrared receiving component is a receiving circuit, which mainly includes infrared monitoring diodes, limiters, amplifiers, integrating circuits, band-pass filters, etc., and a receiving head to receive infrared information.
(3) Working circuit of the electric heating hair dryer: the relay adopts the specifications of 5V voltage and 5A current, and the IN4007 diode is connected in parallel with the relay port. The coil of the relay is connected in series with a PNP transistor. A resistor should be added to the line port, and a resistor should be connected between the electrode and the electrode.
7.Hand dryer (hand dryer) installation and commissioning procedures
To apply single-chip microcomputer technology to the production of hand dryers, it is necessary to debug the homemade hand dryers. Debugging can measure the sensitivity of the received signal. The use of an integrated receiving head can fix the sensitivity of the received signal and adjust the transmission frequency. The most sensitive frequency of the receiving head is about 36kHz-40kHz, and the sensing distance will often be extended to about 7 meters, which exceeds the pre-sensing distance. Therefore, for infrared diodes, a frequency of 500kHz can be used for debugging. Adjusting the level change in the timer interrupt program can change the frequency of transmission. Through debugging, it is found that the sensing distance should be between 15cm-20cm.
Summarize
The hand dryers on the market have single function, complex structure and high price. Applying single-chip microcomputer technology to the production of hand dryers has more stable and reliable performance, convenient maintenance, and low price. The circuit of single-chip microcomputer technology is relatively simple, and the program is simple and flexible, so there are no major circuit problems in the process of making the hand dryer. The single-chip microcomputer integrates the central processing unit CPU, read-only memory ROM, random access memory RAM, and various I/O ports and interrupt systems. Because of its obvious advantages in the production of hand dryers, it will be more widely used in future life. middle.
The above are the details of the hand dryer solution introduced by Shenzhen Zuchuang Microelectronics Co., Ltd. for you. If you have electronic function development needs for hand dryers, you can trust us. We have rich experience in customizing and developing electronic products. We can evaluate the development cycle and IC price as soon as possible, and can also calculate PCBA quotations. We are a number of chip agents at home and abroad: Songhan, Yingguang, Jieli, Ankai, Quanzhi, realtek, with MCU, voice IC, Bluetooth IC and module, wifi module. Our development capabilities cover PCB design, single-chip microcomputer development, Bluetooth technology development, software customization development, APP customization development, WeChat official account development and other hardware and software design. It can also undertake the research and development of smart electronic products, the design of household appliances, the development of beauty equipment, the development of Internet of Things applications, the design of smart home solutions, the development of TWS earphones, the development of Bluetooth earphone speakers, the development of children's toys, and the development of electronic education products.
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