March 29, 2024

led dot matrix writing display

This article introduces the LCD dot matrix writing display in detail, from the hardware schematic diagram to the applied chip and circuit.
The design hardware of LED display is mainly composed of the minimum system of STC89C58 single-chip microcomputer, 32 & TImes; 32 two-color dot matrix display array, light pen, buttons, LCD screen and so on. The red LED in the two-color dot matrix always works in a dim scanning state. The STC89C58 microcontroller uses a self-made light pen mid-infrared photoelectric transistor to detect the lighting of the red LED light at the position of the light pen, calculate the rank coordinates of the light pen position, and set according to the button The different working modes of the LED control LED display, so as to realize the functions of lighting, highlighting, reverse display, clearing the screen, dragging the strokes, and taking turns to display. The display screen can automatically adjust the display brightness of the display screen according to the ambient light intensity. When the light pen does not touch the display screen or the buttons are not pressed within the set time, all displays are turned off, and the system is put into a sleep state to reduce power consumption. The system resumes operation when pressed.
Keywords: STC89C58; LED two-color dot matrix; infrared photoelectric tri-plate light pen

0 Introduction In recent years, dot-matrix LED displays have used dot-matrix modules or pixel units composed of light-emitting diodes to form variable-area display screens with high reliability, long service life, strong environmental adaptability, high performance-price ratio, and cost of use. The low-level features have become an electronic tool for many display media and outdoor job displays, and are widely used in advertising such as stations, hotels, finance, securities, post and telecommunications, sports, or transportation and other industries. At present, there are many ways to realize the design of the LED display. This design is based on the STC89C58 microcontroller using a self-made light pen mid-infrared photoelectric transistor to detect the lighting of the red LED lamp at the position of the light pen, calculate the rank coordinates of the light pen position, and according to The different working modes set by the keys control the LED display, so as to realize the functions of lighting, highlighting, reverse display, clearing the screen, dragging strokes, and taking turns to display.

1 The system design scheme uses a two-color LED dot matrix (red and green) module to form a 32 & TImes; 32 LED dot matrix screen. Among them, the red LED is used for micro-bright scanning detection, the green LED is used for display, and the infrared optical transistor is used to make a light pen. Light up the red LEDs in sequence during detection. When a certain LED is lit, if the light pen is placed on the LED at this time, the resistance of the infrared phototransistor will change, and a high and low can be obtained through the corresponding detection circuit When the level changes, the single-chip microcomputer can judge the current position of the light pen when it detects the signal change.
The scheme is simple and easy to implement, with high sensitivity to the position determination of the light pen, and strong anti-interference ability. The use of two-color dot matrix and infrared phototransistor can effectively reduce the interference of ambient visible light and the light emitted by the display LED (green) on the phototransistor in the light pen.

2 System structure and unit module design
2.1 Overall block diagram of the system The system is mainly composed of microprocessor STC89C58, 32 & TImes; 32 two-color LED dot matrix display, light pen and detection circuit, external light intensity detection circuit, key input circuit, liquid crystal display module and other parts. The block diagram of the system hardware structure is shown in Figure 1.

Overall system block diagram


The single-chip microcomputer STC89C58 has 1 KB of off-chip RAM, which can meet the requirements of saving four-screen display information. The single-chip microcomputer has a high cost performance. The system schematic diagram is shown in Figure 2.


2.2 The light pen and the detection circuit use infrared phototransistors to make the light pen. The light pen detection circuit is shown in Figure 3. In the picture, Q2 is an infrared phototransistor, used to complete the detection of 32 & TImes; 32 dot matrix red LED lights on or off; R6, RP1 is used to limit the current of Q2, in addition, you can also adjust RP1 to increase or decrease the output The voltage value of R7, R8 is used to provide the reference voltage value to the non-inverting terminal of U3A (comparator), through which it is compared with the voltage value output from the collected information (U2> U3, U1 = Umin), R12 is U3A Output pull-up resistor. The working principle is as follows: when the red light shines on the infrared phototransistor, the resistance of the infrared phototransistor becomes smaller, and its emitter voltage rises. At this time, the voltage at pin 2 is higher than the voltage at pin 3, and the output of comparator 1 is low. When the capacitor C11 is charged for a period of time, the voltage at the pin 2 of the comparator is lower than the voltage at the pin 3, and the output of the comparator 1 is high. Thus, when an optical signal is detected, the circuit will generate a pulse signal. Since the coupling capacitor is added in the circuit, the effect of the environment on the light pen can be effectively prevented.

Light pen and detection circuit


In this system, the light pen is a very important link, in order to better stable work, you must add appropriate anti-interference measures. In terms of signal transmission, shielded soft coaxial copper wire is used, and a black heat shrink tube is added to the periphery of the infrared phototransistor. The infrared phototransistor has a smaller diameter than a single LED lamp to ensure less interference from outside infrared.
2. 3 LED two-color dot matrix display and drive circuit There are many types of LED two-color (red, green) dot matrix, of which the most commonly used are 4 × 4, 8 × 8, 16 × 16 type modules, this design requires a 32 × 32 dual-color display, the display brightness and volume are defined by the designer. Taking into account the factors of purchase, the 32 × 32 dot matrix display screen composed of 16 8 × 8 two-color dot matrix modules is selected. The display is driven by 74HC154 and 74HC595 chips. The serial port works in mode 0 (fast speed). The information is quickly sent to 74HC595.
LED is a non-linear component, when the voltage across it reaches a certain value, the current through it will rise sharply. Consider that the 32 × 32 dot matrix consists of 1,024 light-emitting diodes. When they light at the same time, the current is large, and the power supply capacity must be considered. The current value of the general LED is 5-20 mA, the maximum value is 20 mA, and two lines are lit at the same time, there are: I = 20 × 64 = 1 280mA.
2. 4 external light detection circuit The external light detection circuit is shown in Figure 4. The circuit uses a photoresistor RP in series with a fixed resistor R9 to convert the light change into a voltage change. After the analog-to-digital conversion (A / D) of this voltage signal is passed through the chip AD833, it is sent to the single-chip processor by pin 5 to control the brightness adjustment.

d.jpg


According to the principle of partial pressure, there are:
e.jpg
It can be seen that choosing a different value of R9 can change the size of Vin, so that the input signal is within a suitable range. The resistance value of the photoresistor RP changes with the light change is 3 ~ 4 kΩ. From the above formula, R9 can be calculated as 3 ~ 4 kΩ, and R9 = 4 kΩ.
2.5 Time-out low-power design Time-out low-power design is implemented by software, using the button to set the time constant, when the light pen does not touch the display or the button is not pressed within the set time, all displays are turned off, and the system enters the sleep state , To reduce power consumption, the system resumes operation when a button is pressed.

Electric Kettle

 

Electric Kettle are made by food grand stainless steel and Polypropylene. It helps you to have a 1.8L bottle of boiled water in 5 minutes. Type 201 Stainless stell is the main material for the electric kettle housing. sometimes called a tea kettle or teakettle, is a type of pot, typically metal, specialized for boiling water, with a lid, spout, and handle, or a small kitchen appliance of similar shape that functions in a self-contained manner. Kettles can be heated either by placing on a stove, or by their own internal electric heating element in the appliance versions.

 

Features:

360-degree swivel base: Great way with cordless pouring; kettle lifts off base for cord. Separate base to move kettle conveniently, 360°rotation design.The cord can be wrap neatly into the base bottom for easy storage. The concealed stainless steel heating element brings fresh hot water with no metal Taste.

Soft Handle for easy using: Comfortable stay-cool handle; brushed stainless steel finish. Cool-touch buttons and ergonomic stay-cool handle.

Large Capacity for Multiple Cups: 1.8 L large capacity, with Max. water level inside the kettle. almost 1.5x the size of most tea makers. Brew up to 6oz at once! Perfect for small gatherings & parties!

Fully Stainless Steel Faster Boils: Stainless Steel Interior cover with no plastic taste. Boils water rapidly, save more time and energy. Faster than the microwave & safer than your traditional stovetop teapot.

On/off switch with LED light.: Automatic On/Off switch makes life easier. No need standing by for hot water. It shuts down when reaches a full rolling boil. Boil-dry and overheat protection to ensure the safety use.

Time Saver & Higher Safety: 1500 watts energy efficient for quick heat-up time brings water to a boil, Fast boil, auto shut off and boil dry protection technology with three-prong plug.

Brushed stainless steel housing

 

Applications

Making hot water for tea brewing.

Making Coffee.

Cool milk-tea.

Steaming eggs.

Any occation if you need hot water in short time.

Any color of plastic is available to produce but in big quantity. Its

Electric Kettle

Electric Kettle,Stainless Steel Electric Kettle,Electric Boiler,Big Capacity Electric Kettle

Guangzhou Taipeng Electrical Appliances Technology CO., LTD. , https://www.kettles.pl