1. Design requirements and goals
This product adopts single chip microcomputer + minimum system + digital tube display module + digital tube drive module + temperature acquisition module + human body induction module + fan module + button module, etc.;
Function description:
(1) The DS18B20 temperature sensor is used to measure temperature, and the human body sensor module detects whether there is a person.
(2) A total of 3 buttons: 1 button to switch/set, 2 buttons to add, 3 buttons to decrease.
(3) There are three modes in this design: automatic mode, manual mode and natural wind mode.
(4) In automatic mode, press the 1 button to set the upper limit of temperature, and then press to set the lower limit of temperature, both can be adjusted by buttons. The first digit of the digital tube is not displayed, and the last three digits display the temperature value. When the human body sensor module detects a person, the fan does not rotate when the temperature is lower than the lower limit, and rotates 50% between the upper and lower limits. When the temperature is higher than the upper limit, the fan rotates at full speed. After the person leaves, the fan stops rotating after a few seconds delay, which plays the role of energy saving and environmental protection.
(5) In manual mode, the first digit of the digital tube displays the fan position, and the last three digits display the temperature. Press the 2 key/3 key to increase or decrease the fan position (1, 2, 3).
(6) Natural wind mode, the first digit of the digital tube displays "b", and the last three digits display temperature. In this mode, the fan rotation is independent of temperature. As long as the human body sensor module detects a person, it will simulate natural wind to rotate the fan. The time is slow, and the blowing is more comfortable; after a person leaves, the fan stops rotating after a few seconds delay.
2. Design ideas and plans
(1) Control chip selection
Using the single-chip microcomputer as the controller, not only can the temperature sensed by the sensor be displayed through the display circuit by writing a program, but the user can freely set the upper and lower limit action temperature values through the keyboard interface to meet all-round needs. And the temperature is judged by the program with extremely high accuracy, which can accurately grasp the small changes in the ambient temperature.
(2) Selection of temperature sensor
The digital integrated temperature sensor DS18B20 is highly integrated, which greatly reduces the error factors of external amplification and conversion circuits. The temperature error is very small, and because the principle of sensing temperature is essentially different from the principle of the above two solutions, its temperature High resolution. The temperature value is converted into a digital quantity and output directly inside the device, which simplifies the system programming. In addition, because the sensor adopts advanced single-bus technology (1-WRIE), the interface with the single-chip microcomputer becomes very simple and has strong anti-interference ability.
(3) Display circuit selection
Using five-digit common anode digital tube to display temperature, dynamic scanning display mode, the display temperature is clear and eye-catching, and can be seen at night, the power consumption is extremely low, and the programming of the display driver is relatively simple. This display mode is widely used.
(4) Speed regulation method
Use thyristor to form stepless speed regulation circuit. The conduction angle of the thyristor is controlled by a potentiometer, which can realize stepless speed regulation from maximum wind speed to closed, and the wind can be adjusted to any wind power between closed no wind and maximum wind to realize "free wind".
(5) Control method
Using a relay, whether the relay's access circuit with a resistance to control the conduction angle of the thyristor is controlled by the single-chip microcomputer, according to the current temperature value, sends a high/low level at the corresponding pin to determine whether the conduction angle control resistance of a certain relay is Access the circuit.
3. Hardware circuit
