Testing Scheme for White Radiation OLED-matrix
DOI:
https://doi.org/10.31649/1997-9266-2020-153-6-115-120Keywords:
OLED-matrix, LED, test circuit, microcontrollerAbstract
The scheme of testing the organic LED-matrix is proposed, the size of which is 16´16 tricolour pixels, the voltage control range is 5…30 mA, the supply voltage has 16 discrete values that vary in the range from 2 to 6 V in steps of 0,25 V. The purpose of the device for which the scheme is developed is to study the reliability of the failure time in different modes of operation, dynamic and electrical characteristics in the range of the device, which is determined by the condition that the loss of luminosity is from 100 to 70 %.
The proposed testing scheme is designed on two boards (two modules) for flexible upgrades if necessary.
The main module is the controller of the LED panel. It is built on an eight-bit ATMega8515 microcontroller. Since the size of the test field of the panel is small, the speed of such a microcontroller is quite sufficient. The microcontroller dynamically controls the display driver, display voltage, and communicates with the computer via the USART interface using a USB-USART bus converter. The microcontroller's internal random access memory (RAM) is insufficient, so the data for display on the display panel is stored in the external memory type SRAM, which is connected to the microcontroller.
The slave module is the driver board of the LED matrix. The LEDs are powered by a separate adjustable voltage source, which additionally allows you to adjust the overall brightness of the display, explore its operation in different ranges of supply voltages, extend the service life during operation. Switching of supply voltage on lines is carried out through electronic keys on the TD62783 chip. The matrix row is selected by a 4-on-16 decoder 74HC4514.
To control the brightness of the LEDs on the columns used specialized chips WS2801. They provide bit control of 8 bits per color, a total of 24 bits, which is more than 16 million shades. The two-wire data recording circuit and the possibility of cascading reduces the number of wires in the circuit. The ability to connect reverse resistors (RFB, GFB, BFB) to the current stabilizer of the LED, allows you to compensate for the variance of the parameters of the LED matrix by selecting the values of these resistors.
A special power supply module provides stabilization of supply voltages of digital chips and LED matrix
References
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