The four base terminal of the four transistors are connected to four pins of Arduino through current limiting resistors.Īll the connections are shown in the circuit diagram. The emitter terminals of four transistors are connected to ground. The four common pins from four displays are connected to collector terminals of four different transistors through current limiting resistors. We assume that the selected 7 – segment module is of common cathode type. These eight pins are connected to eight pins of Arduino. Hence, only 8 pins will be sufficient to control all the eight segments of all four displays. Respective segment pins (A to G and DP) of all the 7 – segment displays are connected with each other. The following figure shows four multiplexed 7 – segment LED displays.
We can use a compact 4 – digit module or use four individual 7 – segment displays and multiplex them to make a 4 – digit display. In this project, we are using a 4 – digit 7 – segment LED display.
ARDUINO LED MULTIPLEX CODE
It is important to determine whether the display is of common anode or common cathode type as the code for Arduino (or any microcontroller) will depend on it. If the segment doesn’t glow, reverse the polarity of the supply and then it glows. If the segment glows, then it is common anode display. The resistor is given positive voltage and any of the segments (A to G) is connected to ground.
The common terminal of the display is connected to a current limiting resistor. To determine whether the 7 – segment display is common anode or cathode, a small test circuit can be built. The equivalent circuit of a 7 – segment display in common anode and common cathode configuration is shown below. The following figure shows the pattern of digits displayed by a 7 – segment LED display.Īs mentioned earlier, in a 7 – segment display, the LEDs can be arranged in common anode or common cathode mode. The following figure shows a general representation of 7 – segment LED display with dedicated names to each segment.Įach segment can be powered separately to display digits from 0 to 9. Each LED bar is in the form of a hexagon and the overall arrangement will be in the form of ‘8’. Working of 4 – Digit 7 – Segment LED DisplayĪ 7 – Segment LED display, as the name indicates, is an assembly of LED bars, where each bar can be powered individually.
4 – Digit compact 7 – segment LED display - 1(Or)7 – Segment LED display - 4.Working of 4 – Digit 7 – Segment LED Display.
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