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DIY Moving Message Display

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I need to do increase power suply for led display to +7V - 9V instead +5V wich is now. Row drivers is irf9530 (from mcu thru 1K on gate, +5V sors, drainon led row), and column driver is HC164 + ULN2803.
Instead of irf9530 I try with BD242 (and few others), but if I increase suply on emiter above 5.5V, transistor is fully conductive (colector - emiter), and every led is on. With +5V on emiter everything is ok, but leds are with verry poor light.
When I replace ULN2803 with 8xBS170 (n-fet), I have little better result but still not good enough.
All this is without current limiter ressistors.

Leds are red, 2 leds in series for 1 dot.


Regards
 

deniah said:
I need to do increase power suply for led display to +7V - 9V instead +5V wich is now. Row drivers is irf9530 (from mcu thru 1K on gate, +5V sors, drainon led row), and column driver is HC164 + ULN2803.
Instead of irf9530 I try with BD242 (and few others), but if I increase suply on emiter above 5.5V, transistor is fully conductive (colector - emiter), and every led is on. With +5V on emiter everything is ok, but leds are with verry poor light.
When I replace ULN2803 with 8xBS170 (n-fet), I have little better result but still not good enough.
All this is without current limiter ressistors.

Leds are red, 2 leds in series for 1 dot.
Click to expand...

Hi "deniah";

Seems the 5v (4.5V) doesn't enough to drive your 2 leds in series. Try and measure it as static!
Due the multiplexing method the current is theoretic 1/7 of the static current (for ex. if the static max. current is 40 mA, the average current is only 40/7 mA and it's too small). Of course only if you have seven rows...

But... this is the theoretic maximum, in your case it's far smaller I think. Please use for shift regs the hc595 instead of the 164, it has output latches too. This decreases drastic all the blank times.

To increasing of the led power for rows: simply use level shifter Zener diodes in serial on your 1K (from MCU). Use a 3v3 Zener. And apply also a B-E (G-S) resister (2k2...4k7) to all your row driver FETs or PNP darlingtons (!).

Use better leds (or NOT in serial but paralell)!

Hope this helps
zuisti
 

Hello zuisti
Thanks for reply

Unfortunately wont work. Now I need ~9v to get the same result, but when increase above 9V same thing is happening, all leds are on.

Regards
 

Hi , rojo , in your code

row<<=1;
if(row==0)
row=0x02;
delay_us(800);
porta=0;
if I do not use the porta=0 , can you redesign the program replace the code
porta=0 ??????
 

why dont you try to contact rojo through his private mail box
 

can i have d hardware diagram
 

Hi every one!
I am doing project which is display SMS on led dot matrix using AT89c51 microcontroller please help me
 

Hy everybody!

Could you help me with the command of a matrix of 72*72 LED's (or bigger)? I have the PCB with the LED's already done, but I don't have any ideea how to drive them. :cry:

This matrix must display animations and text (perhaps sent from a PC via COM port).
Any IDEEA?!?!?!

THANKSSS!!!

P.S. Please excuse my poor english...
 

Hi Friends,
Going too good.i am a user of ATMEL AVR using C.Is anyone doing work on dual color 8*8 matrix and shapes as well as text scrolling left,right,up,down.If someone have links or any work on this,plz send me.
 

IF i use a keyboard to enter text then send it out via any wireless to the display board. How i send out the date from keyboard using wireless......
Anyone can help??
 

do you guys have a program in picbasic for a moving message??

and what book do you suggest for me in studying how to program a moving message and how to create the circuit of the dot matrix display??

hope you guys can help me..
 

is there anybody here who has a picbasic code for pic16f877a???
or even for any pic micros??

a circuit for the dot matrix display would also be useful
and if you dont mind can you post a:
block diagram
schematic diagram

and what book do you guys recommend me to use because i'm trying to study how to program and how to build a moving message using picbasic.

i hope somebody here can help me...:D
 

how to send out the data from keyboard or PC (using any wireless) to the DOT-matrix display board with wireless connection??
 

hi,
any one can help me to write a program of moving message display with pic16f877a, such that row are scan with cd4017 and colums are scrol with 74ls595.:cry:
code in proton basic or c , will be highly helping.
regards
 

My newest 16 char MMD with a small PIC

My project is finished (for the present) :|

This is a new Moving Message Display with a PIC16F628A and 8(16) x 5x7 led matrix, working in Proteus but it's working as well also on the real hw.

It uses a new and fast algorithm, written in assembly too.

It is modular: it uses one or two same 8 char display unit(s).

Online commands (via rs232, in Proteus: in Virtual Terminal)

- scrolling by pixel or by character
- pause/continue scrolling
- on/off one pixel gap between fonts
- home function (back to the begin)
- append function (jump to the text end)
- max. 127 chars displayable text
- - - stored in the PIC's EEPROM
- - - last typed char is deletable (backspace function)
- scrolling speed up/down
- single step left/right
- ASCII char test
- multi language characters (also full Greek)
- default settings via switches
- get/store settings from/to PIC's EEPROM

I'm attached here the project (for 8 or 16 chars) with the hex firmware only, because I wrote the program in Proton but with many (70%) hard and hand optimalisation in assembly (for the speed).
I think it is not a human readable program, and sorry... it's not for public!

Please study also my previous posts at this thread if you want to build this!

Try it!

Edit:
About the source look at my next post here!
 

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