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12V 7 Segment LED Display Driver (ATmega8 Based)

12V 7 Segment LED Display Driver (ATmega8 Based)
SKU SKU17826  
Weight 200.00 grams
 
Our price: Rs649.00 ($13.52)
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Seven segment driver for token display and counter

One of the most common place where small MCUs are used is to drive big seven segment displays in public area. For example the bank token number, flight or train schedule, train coach number, production volume (in factories), current forex(in banks) or gold rates etc. Since these are public display they should be big (and bright) enough to be seen from a distance of few meters. And due to their bigger size(and high brightness) they require 12V supply for each segments. Current requirement is also high. All these call for a sophisticated circuit, since these type of circuit is very common we have developed a compact board with integrated high voltage driver circuit coupled with an AVR 8 bit CPU.

Typical Connection

4 inch 4 digit LED display

At the hearth of this circuit is ATmega8 28 PIN microcontroller IC that can be programmed in C language for various types of application. The MCU is clocked from its internal 8MHz RC oscillator, thus does NOT require any external crystal. The microcontroller is connected to ULN2003 IC and few transistors that helps in driving large size 12 volt LED digit displays. The control board has a 10 PIN FRC cable that is used to download programs using a AVR programmer.

Few i/o ports of the microcontroller are available on the male headers. They are listed below.

  • PC0
  • PC1
  • PC2
  • PC3
  • SDA
  • SDL

These are used to connect various other things likes buttons, sensors or RTC module as per requirement.

Main board is powered by a 12V transformer and the board has onboard rectifier diodes and filter capacitor to convert this to DC current required for the display. Additionally the board also has 7805 voltage regulator to generate stable 5v supply required for the microcontroller.

Preparing a multiplex display

In this part we will discus how to prepare a multiplexed connected display to use with this board. You need a 4 inch or 2.3 inch common anode displays. Let us say we want to make a four digit counter, so we will require four such displays.

The segments of a 7 segment displays are named like this ...

seven segment names

their is one corresponding pin for each segment as shown in the image below ...

seven segment pin

in multiplexed wiring we place four such displays side by side and then connect segment A of each display together as shown in the image below.

wiring multiplex display

similarly we connect other segments (B,C,D,E,F,G) together. These are then connected to the segment connector pin of the main control board. You can see the segment connector at the top left hand side of the PCB.

In the PCB, pins are also labeled as a,b,c,d,e,f to make it easy for you to do the connection.

Then the common (COM) pin of right most display is connected to the green screw terminal (bottom of the PCB) labeled 1

THE COMMON PINS (COM) ARE NOT CONNECTED TO EACH OTHER LIKE SEGMENT PINS!

In the same way next display's COM pin is wired to terminal labeled 2 and so on.

To do this connection you may use our readymade PCB which you can buy from this link.

This board comes with a preloaded program that displays digits 0-9 in all modules one by one thus helping you easily check the working.

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