SER Pin 14: At this pin we give data to be shifted in the shift register. It has eight outputs Q A to Q H, Operating supply voltage is from 2 to 6V, we connect Vcc (Pin 16) to 5V. Let’s understand pins of 74HC595 8-bit shift register. From the figure 3.2 you can clearly understand that bargraph displays are simply LED’s connected in a row. For 12V supply use 4.7K Ohm current limiting resistor. Pin no 1 can be identified by the bevel, normally 330 Ohm to 1 K Ohm resistor is used for current limiting at 5V supply. Circuit Connections of Bargraph Display with Arduinoīefore we move to bargraph display connection with arduino, Lets understand Bargraph display pin connections. Third line we need is “Latch” when we are putting data in shift register it will not affect previous status of its output until we give latch pulse. Shift register take input in serially Data, Clock. We need only three IO lines to control this shift register output. Refer its datasheet for more information. For this example we use low cost 74HC595 8-bit shift register with latch. As we know that to operate 10 LED’s we need 10 IO Lines but in all our examples we focus on minimum IO lines utilization. Zero volt corresponds to all led off and 5V to all LEDs on. In this example we use 10 LED bar-graph to show voltage level from 0 to 5V. It is available in common cathode and common anode, with different color and size options. One terminal is common and other terminals are used for giving supply. Bar-graph display has multiple LEDs 8 or 10 LEDs in a column. With reference to above application we are showing voltage level on LED bar-graph display. As we have seen in previous application we used only one LED to indicate battery level. Most of the inverter units have LED bar-graph display on its front panel. LED bar-graph displays are much popular in battery level indication, water level indicator applications.
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