So for a 4-digit display we’ll have 7 pins of the 7 segments, 4 pins of the 4 digits (common terminals) and 1 pin for the decimal point (DP) which means a total of 12 pins.In 14 pin display we have extra 2 pins for : between 4 digit 7 segment display pin 7 is com of these : and pin 8 should be connected to a GPIO pin of Arduino. The following diagram shows the internal. To use this display, we need to connect GROUND to pin 3 and pin 8 and, and connect +5V to the other pins to make the individual segments light up.
You can use common cathode but for that you have to invert the data displaying instructions in the code. 4 x PNP transistor ( 2SA1015, 2S9015, 2N3906 …)I am using common anode 7 segment display in this project/tutorial. Multiplexing helps in reducing the power consumption of any battery operated device significantly, with the power consumption of single 7 segment display we can power an array of 7 segment displays. In case of common cathode keep it LOW in your code.All the commercial products which employees 7 segment display are multiplexed and are either common cathode or common anode type.
Proteus 7 Segment Common Cathode Display Code Free Software With
This means each common pin has to be connected to +5V in order to turn on its related digit.The NPN transistor type allows current flows from collector to emitter when base-emitter voltage is greater than threshold voltage (about 0.7V).The PNP transistor allows current flows from collector to emitter when base-emitter voltage is lower than threshold voltage (about -0.7V).In this project if we use a NPN type then its collector will be connected to +5V and its emitter to the common pin of 7-segment display. In this project we’ve a common anode 7-segment display. For that I used Timer1 module interrupt with the following configuration:* Interfacing Arduino with common anode 7-segment display* This is a free software with NO WARRANTY.// common pins of the four digits definitions// Timer1 module overflow interrupt configurationTCCR1B = 1 // enable Timer1 with prescaler = 1 ( 16 ticks each 1 µs)TCNT1 = 0 // set Timer1 preload value to 0 (reset)TIMSK1 = 1 // enable Timer1 overflow interruptISR(TIMER1_OVF_vect) // Timer1 interrupt service routine (ISR)Disp(count / 1000) // prepare to display digit 1 (most left)DigitalWrite(Dig1, LOW) // turn on digit 1Disp( (count / 100) % 10) // prepare to display digit 2DigitalWrite(Dig2, LOW) // turn on digit 2Disp( (count / 10) % 10) // prepare to display digit 3DigitalWrite(Dig3, LOW) // turn on digit 3Disp(count % 10) // prepare to display digit 4 (most right)DigitalWrite(Dig4, LOW) // turn on digit 4Basically, choosing a transistor type of NPN or PNP depends on circuit design. That means each transistor supplies one digit segments.The 4 transistors are used to supply the display LEDs with sufficient current because Arduino microcontroller ( ATmega328P) may not be able to do that (maximum output current is 40mA).Each transistor emitter pin is connected to +5V that comes from the Arduino board and each transistor base is connected to the Arduino through 4.7k resistor.Each 100 ohm resistor is used for limiting the current that passes through the segment LED.Interfacing Arduino with 7-segment display code:Since the 4 digits are multiplexed we need to refresh the display very quickly (display one digit at a time, others are off).
If there’s a 5V at base and 5V at emitter how will the transistor turn on?You can use NPN type but the 7-segment display will not be supplied correctly with 5V (about 4 Volts) which yields low brightness.If you have a common cathode 7-segment display then you should use NPN type.
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