A practical method for driving LED Bargraph display

LED Bargraph display because with intuitive display, brightness uniformity, high reliability and low cost, vibration, impact resistance and other characteristics have been used for a variety of display control instrument, as well as the process variable or control the amount of analog indication of valve position, has become a contemporary International Panel Meters latest trends. But in the past to see the complexity of the driving method, needed a lot of integrated circuits, it is difficult to achieve high reliability and simple and practical.
Drive Circuit Design
LED light beam lattice structure determines its display segment must be scanned and the scan shows dot display. The basic principle is that the drive circuit of the input analog signal into a digital signal, and outputs the dynamic scanning method of the digital transformation. LM3914 is 10 light-emitting diode driver, it can convert the analog input to digital output driver 10 light-emitting diodes for display or dot column display.

4 feet and 6 feet 10 is connected between the precision resistor divider, 7 feet and 8 feet between a reference voltage source, 9 feet for the point / column mode selection, five feet for the signal input. 128x32 oled LM3914 voltage reference output is approximately 1.2V, ie between 7 feet and 8 feet to maintain a 1.2V reference voltage Vref, the reference can be directly used for internal divider, so that when Vin (5 feet) input a 0 to 1.2 V voltage, the comparator can be lit via 0 ~ 10 light-emitting diodes.
8 feet can also be adjusted according to the appropriate potential, the time required eight feet on the ground connection resistor R2 (not shown), the 8-foot potential:. Using this relationship can be designed as an 8-foot floating potential, that segment scan while changing R2, you can generate an 8-foot ladder in potential, 6 feet and 4 feet, you can generate a ladder basis, so that when scanning to N (N = 1 ~ 10) segment, the segment that determines the reference voltage of the light beam that paragraph the number of lines.
The design of the drive circuit shown in Figure 3, the figure means that the 101 line GV TFT Lcd Modules beam. 555 and R1, R2, C1 composition oscillator provides the clock signal for the 4017, 4017 is a decimal counter / pulse divider, at every clock cycle, Q0 ~ Q9 sequentially outputs a high level, T1 ~ T10 followed by conduction, for light beam scanning section, while T11 ~ T20 is turned on in order to change each of the reference voltage point through the LM3914 for display, so be constantly scanning and point display section, when the scanning frequency is greater than 50Hz, the human eye will not feel display blinks.