LED monitor display

Introduction

As xmas is coming individuals have currently lightened their homes. I thought to do something different because of this Christmas time besides the festive Christmas time lights. We made a running message screen making use of LEDs, and thought of sharing it to you. That is an easy to use running message display task that presents the message ‘MERRY XMAS’, where each letter is done with 5mm diameter red-color LEDs. The 9 letters into the message tend to be separately switched on or down through a PIC16F688 microcontroller’s I/O pins. For that reason, a number of screen habits is created through the computer software inside the microcontroller.

Theory

LED Mathematics

The forward voltage of a Light-emitting Diode is dependent upon its type. If LED is red, the forward voltage is generally between 1.7 – 2.1 V. For green and blue LEDs, this worth is greater. An LED calls for a resistor in series to limit the present within the LED to a secure worth. Many 5mm LEDs work near to their peak brightness at a drive existing of 20 mA. In this task, i will be operating my LEDs at 15 mA and nonetheless glow pretty brilliant. So, each of my computations are based for 15 mA current through LEDs. We sized the forward current across my LEDs plus they are about 1.95 V. Calculating the worthiness regarding the show resistor for an LED is easy. Assume, if you'd like to drive a LED through a 5 V energy supply, you need a resistor of price (5-1.95)V/15 mA = 203 ? to limit the present to 15 mA. The closest readily available resistor (regarding the top end) is of 220 ?.

today, let’s observe which will make display letters with LEDs. The first page associated with message (MERRY XMAS) is shown below. 17 LEDs are utilized in generating the letter M. in the event that you drive each LED through a 5V offer, you're looking for 17 series resistors, and the current will sum up to 17×15 = 255 mA. In the event that you add the existing demands of other letters in message, the net up-to-date would go up to 2 A, which can be a lot of present and you also most likely need a bigger heat sink for your voltage-regulator. I didn’t wish to accomplish any of these. Thus I looked at doing it in a different way that would save yourself myself from soldering to many resistors and also reduce the internet existing requirement of the task. How do I do this? Yes, you are right, by utilizing higher supply voltage.

We continue to have my old printer’s external power supply which includes with 3 output pins for +15 V, +32 V, and Ground, and it can provide present around 800 mA. I was thinking of linking LEDs in show and drive all of them through 32 V. In this manner i will link at most 16 LEDs in show with just one current limiting resistor. So, here is how we arranged the 17 LEDs for page M. I can’t connect them all in series as that would require significantly more than 17×1.95 = 33.15V. And so I linked the very first 9 LEDs in series (cathode of 1 is connected to the anode of various other) to make a chain. The residual 8 LEDs are accustomed to form another sequence. For first chain, the worth associated with series resistor would be,