How to Connect and Control 55 Individual LEDs with 8051 Microcontroller?

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#1 21660483 26 Dec 2011 00:32

Dharmik Brahmbhatt Dharmik Brahmbhatt

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Post #1
21660483 26 Dec 2011 00:32

hi i am making a digital clock made of led digits but what is the way to connect such large no. of leds and turn them on and off individually .... as the 8255 is not a completely bit addressable is their availablity of such kind of port with completely bit addressable feature.??? or any alternative by which i can perform the same ????
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#2 21660484 26 Dec 2011 04:38

Steve Lawson Steve Lawson

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Post #2
21660484 26 Dec 2011 04:38

You need to use multiplexing. Pieter explains this at:
http://www.eeweb.com/electronics-forum/is-it-possible-to-perform-parallel-looping-in-80511/
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#3 21660485 28 Dec 2011 17:23

Todd Hayden Todd Hayden

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Post #3
21660485 28 Dec 2011 17:23

I have also used these TI led segment drivers before. You can daisy chain the serial I/O between multiple devices if you are pin constrained on the microcontroller.

http://www.ti.com/lit/ds/symlink/tlc5921.pdf
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#4 21660486 28 Dec 2011 17:29

Todd Hayden Todd Hayden

Anonymous

Post #4
21660486 28 Dec 2011 17:29

I forgot to add this pics where I used the TI drivers. You can see the 3 ICs located between the large LED digits in this display I made for the local Snake River SCCA autocross club. I mounted the ICs on SMT/through-hole adapters and brought out stips of brass soldered to the IC thermal pad, for heat sinking. I built this back in 2004 and it is still in service.
#5 21660487 17 Jan 2012 15:20

Timothy Shuck Timothy Shuck

Anonymous

Post #5
21660487 17 Jan 2012 15:20

You could always use a few shift registers, cascaded together such as the 74595. This way, you would only use a few pins. Basically, you'd shift out each bit, corresponding to each LED and latch it out. There is no flicker because the LEDs only change when you latch the shift register outputs to the IC outputs.
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How to Connect and Control 55 Individual LEDs with 8051 Microcontroller?

How to Connect and Control 55 Individual LEDs with 8051 Microcontroller?

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