[SOLVED] 100 LED line control

Hi
I have a question, please to help answering.

I have 100 LED ( LEDs are separated I mean that every LED has it ON or OFF separately , everyone of the LEDs has its own +5 Vdc )

I need to control these LEDs either ON or OFF using vb.net software.

can any one tell me how to interface PC to this 100 LED line ?

timing is important issue for me, I mean once I trigger the LEDs line ON or OFF , they must be ON or OFF on the exact timing ( no delay allowed even for 2 milli seconds ) , parallel port is only capable of managing 8 LEDs maximum , but i need to control 100 LED !

Thanks alot

Hi,

you want all LEDs to be switched ON or OFF at the same time?

Or dou you want to control each of the 100 LEDS independently?

Are they connected in common anode or common cathode style?
Is there a current limiting resistor at each LED?

Klaus

Parallel port has >50kB/s bandwidth easily.

Your design requires a refresh rate spec and allowed latency, supply power source and LED Vf @If specs.

If 0.5ms is allowed then refresh rate is 2kHz then parallel rate is 25kHz x8bit /

Serial encoder/decoder would require 100 x 2kHz rate. If you need to latch the LED state, a serial clock and data port with a start trigger would seem to be the best approach.

You may want to think about using parity or error detection.

A 3.3V supply would be more efficient.

You need to define the allowed latency from time to display and if sync error from 1st to last LED if permitted. e.g. raster update mode or parallel load.

There are quite a few multi channel LED driver chips around that may be of interest;
https://www.google.com.au/search?cl...oe=utf-8&gfe_rd=cr&ei=hOhYVtT2NqLu8weWmoHIAg#

Serial input will load all the inputs (software + serial which all takes time) then a common strobe latches all LEDs together so they all change together at the exact same instant.

KlausST said:

Hi,

you want all LEDs to be switched ON or OFF at the same time?

NO ( independent LED patterns) , each LED behaves independently regardless of the status of other LEDs

Or do you want to control each of the 100 LEDS independently?
Yes , independent control

Are they connected in common anode or common cathode style?

Yes , Common Cathode ( common GND)

Is there a current limiting resistor at each LED?
( for this project the most important thing is to trigger the LED ON or OFF , so resistor and current limitation is not in important issue ) , please to give your output if you have recommendations

Klaus

Click to expand...

*** SunnySkyGuy and Wrapspeed thanks a lot I will study your advice and come back .

SunnySkyguy said:

Parallel port has >50kB/s bandwidth easily.

Your design requires a refresh rate spec and allowed latency, supply power source and LED Vf @If specs.

If 0.5ms is allowed then refresh rate is 2kHz then parallel rate is 25kHz x8bit /

Serial encoder/decoder would require 100 x 2kHz rate. If you need to latch the LED state, a serial clock and data port with a start trigger would seem to be the best approach.

You may want to think about using parity or error detection.

A 3.3V supply would be more efficient.

You need to define the allowed latency from time to display and if sync error from 1st to last LED if permitted. e.g. raster update mode or parallel load.

Click to expand...

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Hi
thanks alot
what you wrote sounds interesting, but I did not fully get it and I would like to explain more
HardWare : I have LED matrix (100 LED ( width) X 100 LED (height))
SoftWare: on hard disk I have many random size colored images files and using vb.net I converted one of these images into an image file of black and white pixels only - why ? in order to send this image into the LED matrix, the final image size is always ( 100 pixel width X 100 pixel height), I did image processing to convert any image on harddisk into 100 pixel X 100 pixel to send it to the LED matrix.

what I need to do is to send this image file of black and white dots into the corresponding LED and make this image scroll down on the LED matrix. for example pixel (0,0) should be sent to LED(0,0) and make it ON -if pixel is WHITE or OFF-if pixel is BLACK, pixel(1,0) should be sent to LED(1,0) until I reach pixel ( 100,100) should be sent to LED(100,100)

I need a method either parallel or serial to send these pixels(either black which is 0 or white which is 1 ) to its corresponding LED to make it ON or OFF , also I need to crawl down the image , what I mean I need this image to move from up of the LED matrix and crawl down to the end of the LED matrix.
and how I can control the speed of crawling ?
would you please explain more ? or a book or example
Thanks alot

You still need to define how you intend to map 8 bits and bytes to the display like a memory map.
You will need software to map from an array to serial then hardware to map from serial to an array.

With 10k pixels, if you decide your latency to fill the map is 50ms then you need a 200kbps minimum flow to fill the memory array.

This can be a serial port or a 8b parallel port, depending on your skill level.
Raster scan is most common from left to right, top to bottom like all monitors.

This memory would be rather inefficient in serial with 10k bit shift registers chain.
But then at most you can only MUX 4 LEDs at 4x the desired current and probably less if you do not violate the ABS MAX urrent.

https://trmm.net/Cubescroller

good luck.


Hardware is going to get ugly interfacing 10K ports unless you accept less than avg max current.

You can see how to cascade these for every 96 LEDs

https://www.maximintegrated.com/en/products/power/MAX6974EVKIT.html#popuppdf